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Hydroxynitrile glucosides
Abstract
beta- and gamma-Hydroxynitrile glucosides are structurally related to cyanogenic glucosides (alpha-hydroxynitrile glucosides) but do not give rise to hydrogen cyanide release upon hydrolysis. Structural similarities and frequent co-occurrence suggest that the biosynthetic pathways for these compounds share common features. Based on available literature data we propose that oximes produced by CYP79 orthologs are common intermediates and that their conversion into beta- and gamma-hydroxynitrile glucosides is mediated by evolutionary diversified multifunctional orthologs to CYP71E1. We designate these as CYP71(betagamma) and CYP71(alphabetagamma); in combination with the classical CYP71(alpha) (CYP71E1 and orthologs) these are able to hydroxylate any of the carbon atoms present in the amino acid and oxime derived nitriles. Subsequent dehydration reactions and hydroxylations and a final glycosylation step afford the unsaturated beta- and gamma-hydroxynitrile glucosides. This scheme would explain the distribution patterns of alpha-, beta- and gamma-hydroxynitrile glucosides found in plants. The possible biological functions of these hydroxynitriles are discussed.
... There is evidence of a close biosynthetic relationship between cyanogenic glucosides and β-and γ-hydroxynitrile glucosides. With the single exception of 53, α-, β-and γ-hydroxynitrile glucosides have common amino acid precursors (Nielsen et al., 2002;Bjarnholt and Møller, 2008;Knoch et al., 2016). Especially after the insights gained over the past decade, a quote from a review by Dirk Selmar from 2010 is more valid today than ever (Selmar, 2010): 'The biosynthesis of cyanogenic glucosides represents one of the best-understood examples for complex biosyntheses, and doubtless will serve as a model for the elucidation of the biosynthetic pathways of other natural products'. ...
... The monocots are mainly characterised by cyanogenic glycosides from Phe/Tyr group, but members of the Val-/Ile and Leu groups also occur. As an example, Leu-derived compounds are present in barley (Hordeum vulgare, Poaceae): five different cyanoglucosides (=β-and γ-hydroxynitrile glucosides) co-occur with the cyanogenic glucoside epiheterodendrin (25) (Nielsen et al., 2002;Bjarnholt and Møller, 2008;Knoch et al., 2016). ...
... In sapindaceous plants, seed germination leads to loss of cyanolipids (found in the seed oil) without the release of cyanide but with concomitant accumulation of 30 in the developing seed. Thus, cyanolipids might be the storage and/or transport forms of nitrogen and of the hydroxynitrile glucosides (Seigler and Brinker, 1993;Bjarnholt and Møller, 2008). ...
Cyanogenesis describes the ability of living organisms to liberate hydrogen cyanide from stored cyanogenic glycosides upon tissue damage by hydrolysis and/or decomposition. It has been described for more than 3000 species of higher plants. Chemically, cyanogenic glycosides are glycosides of α-hydroxynitriles (cyanohydrins). Cyanogenic glycosides together with plant glycosidases and hydroxynitrile lyases form a preformed defence system. The structures are biogenetically related to only a few precursor amino acids. In the biosynthetic pathway, two multifunctional P450 enzymes and a glucosyltransferase act in a sequence. Biogenetically, glucosides of β- and γ-hydroxynitriles are closely related.
Cyanogenic glycosides and their related nitriles also may serve as storage forms for reduced nitrogen. A recycling pathway has been proposed to recover reduced nitrogen for primary metabolism. Many food plants are cyanogenic, and great efforts are made to optimise their detoxification. The presence of cyanogenic glycosides in the animal kingdom appears to be restricted to arthropods. Some insects, often aposematically coloured, synthesise cyanogenic glycosides de novo and/or sequester them from their host plants.
• Cyanogenic glycosides are secondary metabolites known from more than 3000 different higher plant species.
• Cyanogenic plants are able to liberate hydrogen cyanide from their cyanogenic glycosides upon disruption of plant tissue.
• Cyanogenic glycosides and their corresponding degrading enzymes are part of a preformed defence system. Thus, they can be regarded as phytoanticipins.
• Cyanogenic glycosides are glycosides of α-hydroxynitriles, derived from five proteinogenic amino acids (Phe, Tyr, Val, Ile and Leu) and from the nonproteinogenic amino acid cyclopentenyl glycine. Acalyphin is apparently derived from nicotinic acid.
• A biogenetically related class consists of β- and γ-hydroxynitrile glucosides, apparently derived from the aliphatic amino acids (Val, Ile and Leu).
• Up to now more than 100 different glycosylated α-, β- and γ-hydroxynitriles are known from higher plants and arthropods.
• Additional roles and functions of cyanogenic glycosides include storage of reduced nitrogen, transportation of nitrogen and the turnover of nitrogen into primary metabolism.
• The presence of cyanogenic glycosides in animals appears to be restricted to arthropods.
• Some insects are strongly associated with their cyanogenic host plants. They sequester the cyanogenic glycosides from these plants and additionally carry out de novo biosynthesis of these compounds.
• Convergent evolution in plants and insects has resulted in two identical biosynthesis pathways: two multifunctional P450 enzymes and a glucosyltransferase, acting sequentially.
... Cyanogenesis, defined as HCN release, occurs from plants following β-glucosidase-catalyzed hydrolysis of cyanogenic glucosides ( Figure 1A) (Morant et al., 2008;Gleadow and Møller, 2014). These α-hydroxynitrile glucosides are widespread defense compounds found in ferns, gymnosperms, and angiosperms, in some cases co-occurring with the structurally related noncyanogenic β-and γ-hydroxynitrile glucosides (Bak et al., 2006;Bjarnholt and Møller, 2008). Amino acid-derived oximes are key intermediates in the biosynthesis of hydroxynitrile glucosides as well as glucosinolates, a group of sulfur-and nitrogencontaining specialized metabolites produced almost exclusively in the Brassicales (Halkier and Gershenzon, 2006;Bjarnholt and Møller, 2008;Takos et al., 2011). ...
... These α-hydroxynitrile glucosides are widespread defense compounds found in ferns, gymnosperms, and angiosperms, in some cases co-occurring with the structurally related noncyanogenic β-and γ-hydroxynitrile glucosides (Bak et al., 2006;Bjarnholt and Møller, 2008). Amino acid-derived oximes are key intermediates in the biosynthesis of hydroxynitrile glucosides as well as glucosinolates, a group of sulfur-and nitrogencontaining specialized metabolites produced almost exclusively in the Brassicales (Halkier and Gershenzon, 2006;Bjarnholt and Møller, 2008;Takos et al., 2011). Extensive chemical diversity exist among glucosinolates and their degradation products produced upon hydrolysis of the thioglucosidic bond by myrosinases and subsequent conversion of the aglucon into isothiocyanates, simple nitriles, epithionitriles, or thiocyanates ( Figure 1B) (Burow and Wittstock, 2009;Wittstock and Burow, 2010;Agerbirk and Olsen, 2012). ...
... The variation is presumably caused by a combination of a strong variation in initial alliarinoside content as previously demonstrated (Frisch et al., 2014) and our inability to completely quench all enzymatic activity in the t = 0 samples, possibly causing β-glucosidase mediated conversion of some of the alliarinoside pool in these control samples. The possible product formed from further metabolism of the alliarinoside aglucone remains unidentified, but may be the derived furanone (γ-lactone) formed by hydrolysis of the nitrile group and subsequent cyclization of the hydroxyacid as previously suggested, resulting in antifungal and antimicrobial defense (Bjarnholt and Møller, 2008;Frisch and Møller, 2012;Saito et al., 2012). ...
Alliaria petiolata (garlic mustard, Brassicaceae) contains the glucosinolate sinigrin as well as alliarinoside, a γ-hydroxynitrile glucoside structurally related to cyanogenic glucosides. Sinigrin may defend this plant against a broad range of enemies, while alliarinoside confers resistance to specialized (glucosinolate-adapted) herbivores. Hydroxynitrile glucosides and glucosinolates are two classes of specialized metabolites, which generally do not occur in the same plant species. Administration of [UL-¹⁴C]-methionine to excised leaves of A. petiolata showed that both alliarinoside and sinigrin were biosynthesized from methionine. The biosynthesis of alliarinoside was shown not to bifurcate from sinigrin biosynthesis at the oxime level in contrast to the general scheme for hydroxynitrile glucoside biosynthesis. Instead, the aglucon of alliarinoside was formed from metabolism of sinigrin in experiments with crude extracts, suggesting a possible biosynthetic pathway in intact cells. Hence, the alliarinoside pathway may represent a route to hydroxynitrile glucoside biosynthesis resulting from convergent evolution. Metabolite profiling by LC-MS showed no evidence of the presence of cyanogenic glucosides in A. petiolata. However, we detected hydrogen cyanide (HCN) release from sinigrin and added thiocyanate ion and benzyl thiocyanate in A. petiolata indicating an enzymatic pathway from glucosinolates via allyl thiocyanate and indole glucosinolate derived thiocyanate ion to HCN. Alliarinoside biosynthesis and HCN release from glucosinolate-derived metabolites expand the range of glucosinolate-related defenses and can be viewed as a third line of defense, with glucosinolates and thiocyanate forming protein being the first and second lines, respectively.
... A wide chemical diversity of bioactive compounds has evolved in plants, and one of their functions is to provide protection against herbivores or microbial pathogens. The amino acid-derived hydroxynitrile glucosides are a large class of such specialized metabolites found in many plant species (Nielsen et al., 2002; Bjarnholt and Møller, 2008). The a–hydroxynitrile glucosides in this class are known as cyanogenic glucosides. ...
... In the legume model Lotus japonicus, the two most abundant hydroxynitrile glucosides are the isoleucinederived cyanogenic glucoside lotaustralin and the non-cyanogenic c–hydroxynitrile glucoside rhodiocyanoside A (Forslund et al., 2004; Figure 1). Also present are linamarin, a valine-derived cyanogenic glucoside, and the isoleucinederived b–hydroxynitrile glucoside rhodiocyanoside D. Although the precise role of rhodiocyanosides in plant chemical defence remains to be established, the aglycone of rhodiocyanoside A is able to cyclize and form a furanone with potentially antimicrobial properties (Bjarnholt and Møller, 2008; Saito et al., 2012). In L. japonicus, a gene cluster on chromosome 3 contains most of the biosynthetic genes required for the production of hydroxynitrile glucosides , and includes members of one glucosyltransferase and two cytochrome P450 gene families (Forslund et al., 2004; Takos et al., 2011; Takos and Rook, 2012). ...
... Linamarin and lotaustralin are the main cyanogenic glucosides found in other legume species such as Trifolium repens (white clover) and Phaseolus lunatus (lima bean) (Butler, 1965). In contrast, rhodiocyanosides have only been reported to occur in two Lotus species, apart from their presence in the unrelated genera Ribes and Rhodiola, and are thought to have evolved more recently from the Lotus cyanogenic glucoside pathway, as some of the biosynthetic enzymes are shared (Bjarnholt et al., 2008; Takos et al., 2011). The b–glucosidases (b–D–glucoside glucohydrolase, EC 3.2.1.21) ...
Lotus japonicus, like several other legumes, biosynthesizes the cyanogenic α-hydroxynitrile glucosides lotaustralin and linamarin. Upon tissue disruption these compounds are hydrolysed by a specific β-glucosidase, resulting in the release of hydrogen cyanide. L. japonicus also produces the non-cyanogenic γ- and β-hydroxynitrile glucosides rhodiocyanoside A and D using a biosynthetic pathway that branches off from lotaustralin biosynthesis. We previously established that BGD2 is the only β-glucosidase responsible for cyanogenesis in leaves. Here we show that the paralogous BGD4 has the dominant physiological role in rhodiocyanoside degradation. Structural modelling, site-directed mutagenesis, and activity assays establish that a glycine residue (G211) in the aglycone binding site of BGD2 is essential for its ability to hydrolyse the endogenous cyanogenic glucosides. The corresponding valine (V211) in BGD4 narrows the active site pocket, resulting in the exclusion of non-flat substrates such as lotaustralin and linamarin but not of the more planar rhodiocyanosides. Rhodiocyanosides and the BGD4 gene only occur in L. japonicus and a few closely related species associated with the L. corniculatus clade within the Lotus genus. This suggests the evolutionary scenario that substrate specialization for rhodiocyanosides evolved from a promiscuous activity of a progenitor cyanogenic β-glucosidase resembling BGD2 and required no more than a single amino acid substitution.This article is protected by copyright. All rights reserved.
... Cyanolipids (CL) are a class of rare phytochemicals restricted to the Sapindaceae plant family [1][2][3][4][5]. Seed oils from these plants contain, in addition to acylglycerols, cyanolipids that consist of different hydroxynitrile fatty esters derived from amino acid metabolism [1,6]. Four types of CL structures, namely type I, 1-cyano-2-hydroxymethyl-prop-2en-1-ol-diester, type II, 1-cyano-2-methyl-prop-1-en-3-ol-ester, type III, 1-cyano-2-hydroxymethyl-prop-1-en-3-ol-diester and type IV, 1-cyano-2-methyl-prop-2-en-1-ol-ester ( Fig. 1), with fatty acids esterified to a mono-or a dihydroxynitrile moiety, have been reported from several species, [4,5,[7][8][9][10]. ...
... It suggests that these phytochemicals may serve in vivo as a major nitrogen source for developing seedlings [13]. Nevertheless their co-occurrence with hydroxynitrile glucosides in some species [6] has suggested that they represent a biosynthetic variation of hydroxynitrile glucosides with esterification to lipids possibly serving specific functions related to storage and transport. Moreover, some structural types are involved in cyanogenesis. ...
... ; Figs.4,5,6). This is demonstrated, for example, by the characterization of CL 3 I and 4 I CL of A. dregeanus and P. cupana which comprise combinations of less-abundant ...
As a continuation of our investigation on unusual lipids, in the present work we describe a method based on GC–FID and GC–EI-MS to analyze the molecular composition of intact cyanolipids (CL) from selected Sapindaceae plants. We applied our method to the study of CL of type I (1-cyano-2-hydroxymethyl-prop-2-en-1-ol-diester) from Paullinia cupana var. sorbilis and Allophylus dregeanus and CL type III (1-cyano-2-hydroxymethyl-prop-1-en-3-ol-diester) from A.
natalensis and Nephelium lappaceum. Our analytical approach allowed us to obtain useful mass spectra to identify individual isomeric molecular species composing the CL mixtures and resulted in the very sensitive detection and identification of minor CL. Defined CL mass spectra resulted in suitable detection of these phytochemicals in complex plant oil mixtures containing acylglycerols. To the best of our knowledge GC–EI-MS spectra of cyanolipids have never been reported before. Moreover, this study improved previous knowledge of the lipid chemistry of Sapindaceae plants.
... The hydroxynitrile glucosides produced by members of the order Saxifragales including Ribes are different from those produced by plants grouped in Rosales including Urtica. The difference arises from the type of amino acid used as a precursor for the synthesis of hydroxynitrile glucosides, with leucine used in Rosales and isoleucine in Saxifragales (Bjarnholt & Moller 2008). Hydroxynitrile glucosides can be classified in two groups: those that release toxic cyanide upon plant cell disruptionthese are known as cyanogenic glucosidesand those that are noncyanogenic, namely band c-hydroxynitrile glucosides. ...
... Hydroxynitrile glucosides can be classified in two groups: those that release toxic cyanide upon plant cell disruptionthese are known as cyanogenic glucosidesand those that are noncyanogenic, namely band c-hydroxynitrile glucosides. Cyanogenic glucosides may deter those insects that casually try to feed on plants that contain this type of hydroxynitrile glucosides but do little against insects that specialize on cyanogenic plants (Zagrobelny et al. 2004;Bjarnholt & Moller 2008). In fact, the production of noncyanogenic hydroxynitrile glucosides in plants may reduce their nutritious value to herbivores that have evolved the ability to exploit cyanide (Bjarnholt & Moller 2008). ...
... Cyanogenic glucosides may deter those insects that casually try to feed on plants that contain this type of hydroxynitrile glucosides but do little against insects that specialize on cyanogenic plants (Zagrobelny et al. 2004;Bjarnholt & Moller 2008). In fact, the production of noncyanogenic hydroxynitrile glucosides in plants may reduce their nutritious value to herbivores that have evolved the ability to exploit cyanide (Bjarnholt & Moller 2008). For example, larvae of Zygaena filipendulae performed better on a Lotus species containing only cyanogenic glucosides than on a Lotus containing both cyanogenic and noncyanogenic hydroxynitrile glucosides (Zagrobelny et al. 2007). ...
Transcriptome studies of insect herbivory are still rare, yet studies in model systems have uncovered patterns of transcript regulation that appear to provide insights into how insect herbivores attain polyphagy, such as a general increase in expression breadth and regulation of ribosomal, digestion- and detoxification-related genes. We investigated the potential generality of these emerging patterns, in the Swedish comma, Polygonia c-album, which is a polyphagous, widely-distributed butterfly. Urtica dioica and Ribes uva-crispa are hosts of P. c-album, but Ribes represents a recent evolutionary shift onto a very divergent host. Utilizing the assembled transcriptome for read mapping, we assessed gene expression finding that caterpillar life-history (i.e. 2nd vs. 4th-instar regulation) had a limited influence on gene expression plasticity. In contrast, differential expression in response to host-plant identified genes encoding serine-type endopeptidases, membrane-associated proteins and transporters. Differential regulation of genes involved in nucleic acid binding was also observed suggesting that polyphagy involves large scale transcriptional changes. Additionally, transcripts coding for structural constituents of the cuticle were differentially expressed in caterpillars in response to their diet indicating that the insect cuticle may be a target for plant defence. Our results state that emerging patterns of transcript regulation from model species appear relevant in species when placed in an evolutionary context.
... Cyanogenic glucosides are a-hydroxynitrile glucosides, and they co-occur with b-and c-hydroxynitrile glucosides in several plant species (Figure 1). These may accumulate in similar amounts to the a-hydroxynitrile glucosides, are biosynthetically linked to cyanogenic glucosides, and are also quickly degraded upon tissue disruption, but do not release HCN (Bjarnholt and Møller, 2008; Takos et al., 2010, 2011). The functions of these non-cyanogenic hydroxynitrile glucosides are unknown, but they are also assumed to be dependent on BGD activation to exert their activity. ...
... + , which is a diagnostic ion for glucosides. In addition, cyanogenic glucosides display a characteristic fragment of [cyanogenic glucoside-HCN + K] + (Franks et al., 2005; Bjarnholt et al., 2008), which identified the molecular ions m/z 286 as [linamarin + K] + , m/z 300 as [lotaustralin + K] + (L. japonicus and cassava, Figure 2a,b,e,f) and m/z 350 as [dhurrin + K] + (sorghum, Figure 2d). ...
... japonicus and cassava, Figure 2a,b,e,f) and m/z 350 as [dhurrin + K] + (sorghum, Figure 2d). In addition, L. japonicus contains minute amounts of the b-hydroxynitrile glucosides ribesuvanins (Figure 1), which are isomeric to lotaustralin and therefore also give rise to molecular ions of m/z 300, but contribute very little to this peak (Bjarnholt et al., 2008). The three isomeric rhodiocyanosides (Figure 1) found in this plant give rise to molecular ions of m/z 298, which produce the [Glc-H 2 O + K] + fragment. ...
In comparison to the technology platforms developed to localize transcripts and proteins, imaging tools for visualization of metabolite distributions in plant tissues are less well developed and lack versatility. This hampers our understanding of plant metabolism and dynamics. In this study we demonstrate that Desorption Electrospray Ionization Mass Spectrometry Imaging (DESI-MSI) of tissue imprints on porous Teflon can be used to accurately image the distribution of even labile plant metabolites such as hydroxynitrile glucosides, which normally undergo enzymatic hydrolysis by specific β-glucosidases upon cell disruption. This fast and simple sample preparation resulted in no substantial differences in the distribution and ratios of all hydroxynitrile glucosides between leaves from wildtype Lotus japonicus and a β-glucosidase mutant plant lacking the ability to hydrolyze certain hydroxynitrile glucosides. In wildtype, the enzymatic conversion of hydroxynitrile glucosides and the concomitant release of glucose was easily visualized when a restricted area of the leaf tissue was damaged prior to sample preparation. The gene encoding the first enzyme in hydroxynitrile glucoside biosynthesis in L. japonicus leaves, CYP79D3, was found to be highly expressed during the early stages of leaf development, and the hydroxynitrile glucoside distribution in mature leaves reflected this early expression pattern. Direct DESI-MSI of plant tissue was demonstrated using cryo-sections of cassava (Manihot esculenta) tubers. The hydroxynitrile glucoside levels were highest in the outer cell layers, as verified by LC-MS analyses. The unexpected discovery of a hydroxynitrile derived di-glycoside shows the potential of DESI-MSI to discover and guide investigations into new metabolic routes. © 2013 The Authors. The Plant Journal © 2013 Blackwell Publishing Ltd.
... Upon tissue disruption, cyanogenic glucosides are degraded by specific b-glucosidases, resulting in the release of hydrogen cyanide, which provides a defence mechanism against generalist herbivores (Morant et al., 2008). Cyanogenesis is often regarded as an evolutionarily ancient plant defence mechanism with a single evolutionary origin implied due to the fact that all presently identified enzymes for the first committed step, the conversion of an amino acid into an oxime, are cytochrome P450s belonging to the CYP79 family (for reviews, see Bak et al., 2006; Bjarnholt and Møller, 2008). The first genes encoding enzymes for cyanogenic glucoside biosynthesis were identified in Sorghum bicolor using biochemical approaches (Koch et al., 1995; Bak et al., 1998a; Jones et al., 1999), which provided the basis for the identification of genes in other plant species by sequence homology . ...
... The model legume Lotus japonicus contains two genes, CYP79D3 and CYP79D4, that encode cytochrome P450 enzymes involved in the production of linamarin and lotaustralin and related non-cyanogenic b-and c-hydroxynitrile glucosides called rhodiocyanosides (Forslund et al., 2004). Rhodiocyanoside biosynthesis is thought to diverge from cyanogenic glucoside biosynthesis at the level of the hydroxynitrile intermediate , and natural variation for the presence or absence of rhodiocyanosides involves a genetic locus that we refer to here as Rho (Figure 1) (Bjarnholt et al., 2008). In white clover (Trifolium repens), an adaptive defence polymorphism ...
... In L. japonicus, the isoleucine-derived ahydroxynitrile glucoside lotaustralin co-occurs with the non-cyanogenic compounds rhodiocyanoside A (a c-hydroxynitrile glucoside) and rhodiocyanoside D (a b-hydroxynitrile glucoside) (Forslund et al., 2004). We previously reported natural variation in rhodiocyanoside content in L. japonicus, and a diversification of the hydroxynitrile glucoside biosynthetic pathway at the level of the nitrile intermediate was suggested based on biochemical considerations (Bjarnholt et al., 2008). ...
Cyanogenic glucosides are amino acid-derived defence compounds found in a large number of vascular plants. Their hydrolysis by specific β-glucosidases following tissue damage results in the release of hydrogen cyanide. The cyanogenesis deficient1 (cyd1) mutant of Lotus japonicus carries a partial deletion of the CYP79D3 gene, which encodes a cytochrome P450 enzyme that is responsible for the first step in cyanogenic glucoside biosynthesis. The genomic region surrounding CYP79D3 contains genes encoding the CYP736A2 protein and the UDP-glycosyltransferase UGT85K3. In combination with CYP79D3, these genes encode the enzymes that constitute the entire pathway for cyanogenic glucoside biosynthesis. The biosynthetic genes for cyanogenic glucoside biosynthesis are also co-localized in cassava (Manihot esculenta) and sorghum (Sorghum bicolor), but the three gene clusters show no other similarities. Although the individual enzymes encoded by the biosynthetic genes in these three plant species are related, they are not necessarily orthologous. The independent evolution of cyanogenic glucoside biosynthesis in several higher plant lineages by the repeated recruitment of members from similar gene families, such as the CYP79s, is a likely scenario.
... In the body, cyanide acts by inhibiting cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes (Bjarnholt, 2008) [6] . ...
... In the body, cyanide acts by inhibiting cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes (Bjarnholt, 2008) [6] . ...
Vegetables are an important source of protective food and a part of healthy diet. They contain chemical compounds, such as carbohydrates, sugars, proteins and vitamins, which are essential to human growth and health. In fact they make up for about 20% of an average Indian meal. However, plants generally contain toxic and anti-nutrients acquired from fertilizer and pesticides and several naturally occurring chemicals. Some of these chemicals are known as secondary metabolites or anti-nutritional factors and they have been shown to be highly biologically active. Anti-nutritional factor is known to interfere with metabolic processes such that growth and bioavailability of nutrients are negatively influenced. They include saponins, alkaloids, protease inhibitors, oxalates, haemaggluttinins (lectin), cyanogens, lethogens, and goitrogen. The list is inexhaustible, some of these plant chemicals have been shown to be deleterious to health or evidently advantageous to human health, if consumed in appropriate amounts.
... In the body, cyanide acts by inhibiting cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes (Bjarnholt, 2008) [6] . ...
... In the body, cyanide acts by inhibiting cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes (Bjarnholt, 2008) [6] . ...
Vegetables are an important source of protective food and a part of healthy diet. They contain chemical compounds, such as carbohydrates, sugars, proteins and vitamins, which are essential to human growth and health. In fact they make up for about 20% of an average Indian meal. However, plants generally contain toxic and anti-nutrients acquired from fertilizer and pesticides and several naturally occurring chemicals. Some of these chemicals are known as secondary metabolites or anti-nutritional factors and they have been shown to be highly biologically active. Anti-nutritional factor is known to interfere with metabolic processes such that growth and bioavailability of nutrients are negatively influenced. They include saponins, alkaloids, protease inhibitors, oxalates, haemaggluttinins (lectin), cyanogens, lethogens, and goitrogen. The list is inexhaustible, some of these plant chemicals have been shown to be deleterious to health or evidently advantageous to human health, if consumed in appropriate amounts.
... Linamarine et lotaustraline sont souvent concomitantes car une même enzyme permet d'achever la biosynthèse des deux (Hahlbrock & Conn, 1971;. Au contraire, les glucosides cyanogènes cyclopentenoïques sont restreints à peu quelques familles de plantes proches incluant Achariceae, Malesherbiaceae, Passifloraceae, Salicaceae, Turneraceae et Violaceae, capables de métaboliser le précurseur L-2-cyclopentenyl-glycine (Bjarnholt & Møller, 2008;Zagrobelny, de Castro, et al., 2018). ...
... Certains glucosides cyanogènes comme la tétraphylline B ou l'épivolkenine sont censés être retrouvés dans six échantillons testés, or ils n'apparaissent ici que dans l'échantillon d'H. (Nakamura et al., 2007;Bjarnholt & Møller, 2008 (Marshall et al., 1998). ...
De nombreuses espèces de papillons aposématiques possèdent des défenses chimiques associées à des patrons de coloration vifs constituant un signal d’alerte visuel pour les prédateurs. En population naturelle, il est fréquemment observé des convergences évolutives de ces motifs colorés entre espèces phylogénétiquement distantes. Ainsi, des « cercles mimétiques » formés de plusieurs espèces à l’apparence similaire émergent localement. Ces interactions de mimétisme Müllerien sont positives pour les papillons. En effet, plus le nombre d’individus et/ou d’espèces partageant le même motif est grand, plus ce signal d’alerte est efficacement appris par les prédateurs qui subissent les effets des défenses chimiques. Bien que l’évolution de l’aposématisme ne soit pas totalement élucidée, l’évolution des défenses chimiques au sein des lignées de lépidoptères a probablement joué un rôle important dans l’émergence de la convergence évolutive pour le signal d’alerte coloré entre espèces mimétiques. Dans le cadre de cette thèse je m’intéresse à des papillons mimétiques, principalement de la tribu des Heliconiini mais aussi de la tribu des Ithomiini (Nymphalidae). Ces deux clades ont divergé il y a 82 millions d’années. Si des espèces de ces deux tribus ont convergé vers un même patron de coloration, elles présentent en revanche des défenses chimiques très différentes dont les voies d’acquisition sont contrastées, ce qui peut causer d’importantes variations intra et interspécifiques qui à leur tour ont des conséquences sur le comportement des prédateurs et la dynamique du mimétisme. Les Heliconiini séquestrent des glucosides cyanogènes au stade larvaire à partir des feuilles de passiflores (Passifloraceae) mais synthétisent aussi de façon endogène ces métabolites secondaires tout au long de leur vie. En revanche, chez les Ithomiini, les défenses chimiques proviennent d’alcaloïdes pyrrolizidiniques acquis principalement au stade adulte à partir de fleurs ou végétaux en décomposition de la famille des Asteraceae, des Boraginaceae et des Apocynaceae. Les origines végétales variées et la possibilité d'une voie endogène des défenses chimiques ainsi que la différence dans les stades développementaux où elles sont acquises (chenille ou adulte) suggèrent une évolution différente des défenses chimiques dans ces deux tribus. Au cours de cette thèse j’ai pu montrer que la considération du mimétisme Müllerien est cruciale pour l’implémentation de modèle théorique visant à comprendre les boucles de rétroaction entre mimétisme, aposématisme et spécialisation sur les plantes hôtes. L’analyse des variations qualitatives et quantitatives des glucosides cyanogènes d’Heliconiini sauvages a mis l’accent sur l’influence des relations phylogénétiques mais aussi de facteurs écologiques : interaction mimétique, spécialisation à la plante hôte et micro-habitat, sur l’évolution des défenses chimiques. Elever des Heliconiini en conditions contrôlées précisa les variations des défenses chimiques au cours du développement et le contrôle génétique sur les glucosides cyanogènes synthétisés. Les papillons de ces deux tribus peuvent séquestrer un très grand panel de molécules candidates aux vues de la diversité des molécules produites par les plantes. Pourtant, la diversité des molécules de défenses connues des Heliconiini est assez restreinte contrairement à celle des Ithomiini. En exploitant des techniques de chimie analytique j’ai pu explorer la diversité des glucosides cyanogènes des Heliconiini et des alcaloïdes pyrrolizidiniques des Ithomiini pour tenter de découvrir de nouvelles molécules de défenses. La combinaison d’approches méthodologiques : de modélisation, de chromatographie liquide couplée à la spectrométrie de masse en tandem, de signal phylogénétique, d’élevage de papillon, d’imagerie par spectrométrie de masse et de réseau moléculaire a permis d’explorer des questions évolutives en alliant biologie, chimie des substances naturelles et phylogénie.
... 9 The nitriles are noncyanogenic β-glucosides of βor γ-hydroxynitriles, which do not release toxic hydrogen cyanide upon hydrolysis as a plant defense mechanism, as opposed to α-hydroxynitrile β-glucosides. 10 HCAs have been demonstrated to possess various biological activities in vitro and in vivo, such as antioxidative, antiinflammatory, antimutagenic, antibacterial, and anticancer properties. 2,11 The antioxidant capacity of free HCAs is shown to be higher than their corresponding glucose esters. ...
... The contents of free (E)-caffeic (8) and (E)-ferulic acids (12) increased at room temperature by a factor 3−4 during 12 months, regardless of the light conditions. Free (E)-and (Z)-coumaric acids (10,11) were released in even higher degree. The very special feature was that formation of Z-isomer was dominant. ...
Stability of phenolic compounds was followed in black currant juice at ambient temperature (in light and in dark) and at + 4 °C for a year. Analyses were based on HPLC-DAD-ESI-MS(-MS2) and HPLC-DAD-ESI-Q-TOF-MS methods supported by NMR after selective HPLC isolation. Altogether 43 phenolic compounds were identified, of which 2-(Z)-p-coumaroyloxymethylene-4-β-D-glucopyranosyloxy-2-(Z)-butenenitrile, 2-(E)-caffeoyloxymethylene-4-β-D-glucopyranosyloxy-2-(Z)-butenenitrile, 1-O-(Z)-p-coumaroyl-β-D-glucopyranose, (Z)-p-coumaric acid 4-O-β-D-glucopyranoside and (Z)-p-coumaric acid were novel findings in black currant juice. Hydroxycinnamic acid derivatives degraded 20–40% at room temperature during one-year storage, releasing free hydroxycinnamic acids. O-Glucosides of hydroxycinnamic acid compounds were the most stable followed by O-acylquinic acids, acyloxymethyleneglucosyloxybutenenitriles and O-acylglucoses. Light induced isomerization of (E)-coumaric acid compounds into corresponding Z-isomers. Flavonol glycosides stayed fairly stable. Flavonol aglycones derived mainly from malonylglucosides. Over 90% of anthocyanins were lost at room temperature in a year, practically independent on light. Storage at low temperatures, preferably excluding light, is necessary to retain the original composition of phenolic compounds.
... The MS2 spectrum of petiolatamide showed intense fragment ions at m/z =201 and m/z =108 corresponding to [Glc-H 2 +Na] + and [C 4 H 7 ON+Na] + , i.e., sodium adducts of an oxidized Glc fragment and a reduced aglucon (Fig. 2). The often observed m/z =185 fragment ion ([Glc-H 2 O+Na] + ) from glucosides was detected as expected (Bjarnholt et al. 2008), and a minor fragment with m/z =124 likely represents a sodium adduct of the aglucon, [C 4 H 7 O 2 N+Na] + (Fig. 2). The yield of isolated petiolatamide was approximately. ...
... The defensive activity of other hydroxynitrile glucosides have been established for the α-hydroxynitrile glucosides (cyanogenic glucosides), which release toxic hydrogen cyanide (HCN) from the aglucon after hydrolysis of the β-glucosidic bond, but the biological functions of β-and other γ-hydroxynitrile glucosides are yet to be resolved (Frisch and Møller 2012; Morant et al. 2008b). The aglucons of γ-hydroxynitrile glucosides have been suggested to rearrange to furanones with antifungal and antimicrobial properties (Bjarnholt and Møller 2008; Saito et al. 2012). This also may apply to alliarinoside, and thus may contribute to the inhibition of mycorrhizal fungi by A. petiolata (Frisch and Møller 2012). ...
Specialized metabolites in plants influence their interactions with other species, including herbivorous insects, which may adapt to tolerate defensive phytochemicals. The chemical arsenal of Alliaria petiolata (garlic mustard, Brassicaceae) includes the glucosinolate sinigrin and alliarinoside, a hydroxynitrile glucoside with defensive properties to glucosinolate-adapted specialists. To further our understanding of the chemical ecology of A. petiolata, which is spreading invasively in North America, we investigated the metabolite profile and here report a novel natural product, petiolatamide, which is structurally related to sinigrin. In an extensive study of North American populations of A. petiolata, we demonstrate that genetic population differences as well as developmental regulation contribute to variation in the leaf content of petiolatamide, alliarinoside, sinigrin, and a related glycoside. We furthermore demonstrate widely different metabolic fates of these metabolites after ingestion in the glucosinolate-adapted herbivore Pieris rapae, ranging from simple passage over metabolic conversion to sequestration. The differences in metabolic fate were influenced by plant β-glucosidases, insect-mediated degradation, and the specificity of the larval gut transport system mediating sequestration.
... Cyanogenic glycoside biosynthesis from Tyr, Val, and l-isoleucine in S. bicolor and M. esculenta is catalyzed by two membrane-bound multifunctional cytochrome P450s and soluble UGTs (Zagrobelny et al. 2008;Bjarnholt and Møller 2008;Jørgensen et al. 2011;Kannangara et al. 2011). However, the molecular basis of the cyanogenic glycoside biosynthesis presumably derived from Phe in P. mume has not been elucidated. ...
... These results indicate that the CYP79s were functionally expressed in S. cerevisiae. The narrow substrate specificity of CYP79D16 is reasonable, to limit the substrate available for the CYP71s in the subsequent conversion of aldoximes to hydroxynitriles, and is in agreement with that of known CYP79s identified in other cyanogenic plants (Bjarnholt and Møller 2008). These results suggest that CYP79D16 expressed in the seedling (Fig. 1) plays a pivotal role in catalysis of Phe into PAOx in the first step of cyanogenic glycoside biosynthesis in P. mume. ...
Japanese apricot, Prunus mume Sieb. et Zucc., belonging to the Rosaceae family, produces as defensive agents the cyanogenic glycosides prunasin and amygdalin, which are presumably derived from l-phenylalanine. In this study, we identified and characterized cytochrome P450s catalyzing the conversion of l-phenylalanine into mandelonitrile via phenylacetaldoxime. Full-length cDNAs encoding CYP79D16, CYP79A68, CYP71AN24, CYP71AP13, CYP71AU50, and CYP736A117 were cloned from P. mume ‘Nanko’ using publicly available P. mume RNA-sequencing data, followed by 5′- and 3′-RACE. CYP79D16 was expressed in seedlings, whereas CYP71AN24 was expressed in seedlings and leaves. Enzyme activity of these cytochrome P450s expressed in Saccharomyces cerevisiae was evaluated by liquid and gas chromatography–mass spectrometry. CYP79D16, but not CYP79A68, catalyzed the conversion of l-phenylalanine into phenylacetaldoxime. CYP79D16 showed no activity toward other amino acids. CYP71AN24, but not CYP71AP13, CYP71AU50, and CYP736A117, catalyzed the conversion of phenylacetaldoxime into mandelonitrile. CYP71AN24 also showed lower conversions of various aromatic aldoximes and nitriles. The K
m
value and turnover rate of CYP71AN24 for phenylacetaldoxime were 3.9 µM and 46.3 min−1, respectively. The K
m
value and turnover of CYP71AN24 may cause the efficient metabolism of phenylacetaldoxime, avoiding the release of the toxic intermediate to the cytosol. These results suggest that cyanogenic glycoside biosynthesis in P. mume is regulated in concert with catalysis by CYP79D16 in the parental and sequential reaction of CYP71AN24 in the seedling.
... In this work, the phytochemical investigation of P. utilis seeds led to isolation and identification of five new c-hydroxynitrile glucosides (1-5, Fig. 1) and 11 known (6-16) compounds. This work provides new examples to support the mechanisms for furanone formation from c-hydroxynitrile glucosides as suggested by Bjarnholt and Møller (2008). Herein, the isolation, structural elucidation, and evaluation of the antibacterial activity of these compounds as reported. ...
... Interestingly, except for compounds 4 and 16 isolated from the seeds, 4-methyl-5H-furan-2-one was also identified by GC-MS, while studying the composition of its volatile oil from seeds of P. utilis. Bjarnholt and Møller (2008) has already summarised the proposed mechanisms of furanone formation from c-hydroxynitrile glucosides. The research results here further support the possibility of this metabolic pathway (Supporting information: Scheme 1) given that the relevant metabolites were observed (Table 3). ...
γ-Hydroxynitrile glucosides (prinsepicyanosides A-E) were isolated alongside 11 known compounds from seeds of Prinsepia utilis Royle. Their structures were determined by detailed analysis of NMR and MS spectroscopic data. The relative configuration of prinsepicyanoside C was established by Cu-Kα X-ray crystallography. Prinsepicyanoside A, osmaronin, and 4-(hydroxylmethyl)-5H-furan-2-one exhibited borderline antibacterial activity against Salmonella gallinarum, Vibrio parahaemolyticus, and Vibrio cholera with MIC values of 30.1, 20.7, and 22.8μg/mL, respectively.
... When tissue of these plants is disrupted, HCN gas is enzymatically released from cyanogenic glucosides, which thus act as phytoanticipins affording an immediate chemical defense response to herbivores and pathogens (Møller, 2010). Despite the importance of cyanogenic glucosides to a wide array of plants, they constitute a very small class of bioactive natural products with only 60 or so different structures identified (Bjarnholt and Møller, 2008). This contrasts with terpenoids, for example, where in excess of 40,000 different structures have been elucidated (Bohlmann and Keeling, 2008). ...
... As a consequence, much of the structural diversity of cyanogenic glucosides is achieved simply by modification of the sugar moiety by additional glycosylation(s) or galloylation (Fleming, 1999;Ling et al., 2002). Another factor that is relevant to understanding the diversification in structure of cyanogenic glycosides is their possible additional roles in primary metabolism (Møller, 2010), particularly in nitrogen storage and transport (Bjarnholt and Møller, 2008;Jenrich et al., 2007;Jones et al., 2000). For example, when Prunus serotina seedlings germinate, the cyanogenic diglucoside amygdalin is transported from the seeds and metabolized to supply nitrogen to the developing seedling without release of HCN to the surroundings (Swain and Poulton, 1994). ...
... Ribes is not used as a host by any other nymphalid butterflies outside of Polygonia, suggesting that it is challenging to colonize (Celorio-Mancera et al., 2013). One possible reason is that leaves contain a rare form of hydroxynitrile glucosides with isoleucine as a precursor, including cyanogenic glucosides in at least some species, like the two tested here (Bjarnholt & Moller, 2008;Celorio-Mancera et al., 2013;Hegnauer, 1990). Also present are more common compounds such as, e.g., quercetin and kaempferol (Hegnauer, 1990). ...
In this study, we investigated whether patterns of gene expression in larvae feeding on different plants can explain important aspects of the evolution of insect-plant associations, such as phylogenetic conservatism of host use and re-colonization of ancestral hosts that have been lost from the host repertoire. To this end, we performed a phylogenetically informed study comparing the transcriptomes of 4 nymphalid butterfly species in Polygonia and the closely related genus Nymphalis. Larvae were reared on Urtica dioica, Salix spp., and Ribes spp. Plant-specific gene expression was found to be similar across butterfly species, even in the case of host plants that are no longer used by two of the butterfly species. These results suggest that plant-specific transcriptomes can be robust over evolutionary time. We propose that adaptations to particular larval food plants can profitably be understood as an evolved set of modules of co-expressed genes, promoting conservatism in host use and facilitating re-colonization. Moreover, we speculate that the degree of overlap between plant-specific transcriptomes may correlate with the strength of trade-offs between plants as resources and hence to the probability of colonizing hosts and complete host shifts.
... In the following study, along with visualisation, the enzymatic conversion of hydroxynitrile glucosides was also imaged in a Teflon imprint of Lotus japonicus leaf with indirect DESI MSI [118]. Hydroxynitrile glucosides are very sensitive phytochemicals that undergo degradation by specific β-glucosidases upon cell disruption [119]. Following damage to a restricted area in the plant, DESI was able to visualise the enzymatic degradation and localisation as well as the concomitant release of glucose. ...
The detection of chemical species and understanding their respective localisations in tissues have important implications in plant science. The conventional methods for imaging spatial localisation of chemical species are often restricted by the number of species that can be identified and is mostly done in a targeted manner. Mass spectrometry imaging combines the ability of traditional mass spectrometry to detect numerous chemical species in a sample with their spatial localisation information by analysing the specimen in a 2D manner. This article details the popular mass spectrometry imaging methodologies which are widely pursued along with their respective sample preparation and the data analysis methods that are commonly used. We also review the advancements through the years in the usage of the technique for the spatial profiling of endogenous metabolites, detection of xenobiotic agrochemicals and disease detection in plants. As an actively pursued area of research, we also address the hurdles in the analysis of plant tissues, the future scopes and an integrated approach to analyse samples combining different mass spectrometry imaging methods to obtain the most information from a sample of interest.
... Excess cyanide inhibits the cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis and so tissues suffer energy deprivation and death follows rapidly. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes [64]. High level of HCN has been implicated for cerebral damage and lethargy in man and animal. ...
... Cyanide is an extremely toxic compound that often leads to death by inhibiting cytochrome oxidase that acts at the final step in the electron transport chain, and thus blocks ATP synthesis. Other symptoms may include faster and deeper respiration, disfunction of the central nervous system, faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, bright red mucous membranes, and cardiac arrest (Bjarnholt and Møller, 2008). Apart from exhibiting toxic effects, cyanogens also serve as mobile nitrogen storage compounds in seeds, which is important at the time of germination. ...
... Rapid decreases in cyanogenic glucoside content following light spikes suggest an additional function as scavengers of reactive oxygen species 3,10 . Cyanogenic glucosides may co-exist with structurally related, non-cyanogenic βand γ-hydroxynitrile glucosides, which may also have defence functions 2 . ...
Barley (Hordeum vulgare L.) produces five leucine-derived hydroxynitrile glucosides, potentially involved in alleviating pathogen and environmental stresses. These compounds include the cyanogenic glucoside epiheterodendrin. The biosynthetic genes are clustered. Total hydroxynitrile glucoside contents were previously shown to vary from zero to more than 10,000 nmoles g−1 in different barley lines. To elucidate the cause of this variation, the biosynthetic genes from the high-level producer cv. Mentor, the medium-level producer cv. Pallas, and the zero-level producer cv. Emir were investigated. In cv. Emir, a major deletion in the genome spanning most of the hydroxynitrile glucoside biosynthetic gene cluster was identified and explains the complete absence of hydroxynitrile glucosides in this cultivar. The transcript levels of the biosynthetic genes were significantly higher in the high-level producer cv. Mentor compared to the medium-level producer cv. Pallas, indicating transcriptional regulation as a contributor to the variation in hydroxynitrile glucoside levels. A correlation between distinct single nucleotide polymorphism (SNP) patterns in the biosynthetic gene cluster and the hydroxynitrile glucoside levels in 227 barley lines was identified. It is remarkable that in spite of the demonstrated presence of a multitude of SNPs and differences in transcript levels, the ratio between the five hydroxynitrile glucosides is maintained across all the analysed barley lines. This implies the involvement of a stably assembled multienzyme complex.
... The aminoacid-derived hydroxynitrile glucosides are a large class of bioactive metabolites found in many plant species, some of which may have a role in plant defense against herbivores (Bjarnholt and MØller, 2008). In the legume model L. japonicus, four different hydroxynitrile glucosides have been reported: lotoaustralin, linamarin, and the non-cyanogenic rhodiocyanosides A and D (Forslund et al., 2004). ...
The symbiosis between Lotus and rhizobia has been long considered very specific and only two bacterial species were recognized as the microsymbionts of Lotus: Mesorhizobium loti was considered the typical rhizobia for the L. corniculatus complex, whereas Bradyrhizobium sp. (Lotus) was the symbiont for L. uliginosus and related species. As discussed in this review, this situation has dramatically changed during the last 15 years, with the characterization of nodule bacteria from worldwide geographical locations and from previously unexplored Lotus spp. Current data support that the Lotus rhizobia are dispersed amongst nearly 20 species in five genera (Mesorhizobium, Bradyrhizobium, Rhizobium, Ensifer, and Aminobacter). As a consequence, M. loti could be regarded an infrequent symbiont of Lotus, and several plant–bacteria compatibility groups can be envisaged. Despite the great progress achieved with the model L. japonicus in understanding the establishment and functionality of the symbiosis, the genetic and biochemical bases governing the stringent host-bacteria compatibility pairships within the genus Lotus await to be uncovered. Several Lotus spp. are grown for forage, and inoculation with rhizobia is a common practice in various countries. However, the great diversity of the Lotus rhizobia is likely squandered, as only few bacterial strains are used as inoculants for Lotus pastures in very different geographical locations, with a great variety of edaphic and climatic conditions. The agroecological potential of the genus Lotus can not be fully harnessed without acknowledging the great diversity of rhizobia-Lotus interactions, along with a better understanding of the specific plant and bacterial requirements for optimal symbiotic nitrogen fixation under increasingly constrained environmental conditions.
... A second CNglc producing species, Lotus japonicus, was used to verify the developed technique. This species produces both linamarin and lotaustralin and the noncyanogenic hydroxynitrile glucosides rhodiocyanosides A (4) and D (5) (Bjarnholt and Møller, 2008). A non-cyanogenic L. japonicus mutant (cyd1) harboring a non-functional CYP79A1 enzyme was also included in the present study and provided an experimental negative control system (Takos et al., 2011). ...
Mass spectrometry based imaging is a powerful tool to investigate the spatial distribution of a broad range of metabolites across a variety of sample types. The recent developments in instrumentation and computing capabilities have increased the mass range, sensitivity and resolution and rendered sample preparation the limiting step for further improvements. Sample preparation involves sectioning and mounting followed by selection and application of matrix. In plant tissues, labile small molecules and specialized metabolites are subject to degradation upon mechanical disruption of plant tissues. In this study, the benefits of cryo-sectioning, stabilization of fragile tissues and optimal application of the matrix to improve the results from MALDI mass spectrometry imaging (MSI) is investigated with hydroxynitrile glucosides as the main experimental system. Denatured albumin proved an excellent agent for stabilizing fragile tissues such as Lotus japonicus leaves. In stem cross sections of Manihot esculenta, maintaining the samples frozen throughout the sectioning process and preparation of the samples by freeze drying enhanced the obtained signal intensity by twofold to fourfold. Deposition of the matrix by sublimation improved the spatial information obtained compared to spray. The imaging demonstrated that the cyanogenic glucosides (CNglcs) were localized in the vascular tissues in old stems of M. esculenta and in the periderm and vascular tissues of tubers. In MALDI mass spectrometry, the imaged compounds are solely identified by their m/z ratio. L. japonicus MG20 and the mutant cyd1 that is devoid of hydroxynitrile glucosides were used as negative controls to verify the assignment of the observed masses to linamarin, lotaustralin, and linamarin acid.
... Cyanogenic glucosides (hydroxynitrile glucosides) are a-hydroxnitrile glucosides structurally related to the band g-hydroxynitrile glucosides; however, the latter two do not release toxic hydrogen cyanide upon degradation (Bjarnholt and Møller, 2008). Studies on cyanogenic glucoside (a-hydroxnitrile glucoside) biosynthesis were initiated in 1967 with linen flax (L. ...
Oximes (R1R2C = NOH) are nitrogen containing chemical constituents which are formed in species representing all kingdoms of life. In plants, oximes are positioned at important metabolic bifurcation points between general and specialized metabolism. The majority of plant oximes are amino acid-derived metabolites, formed by the action of a cytochrome P450 from the CYP79 family. Auxin, cyanogenic glucosides, glucosinolates and a number of other bioactive specialized metabolites including volatiles are produced from oximes. Oximes having the E-configuration have high biological activity compared to Z-oximes. Oximes or derivatives thereof have been demonstrated or proposed to play roles in growth regulation, plant defense, pollinator attraction and plant communication with the surrounding environment. In other cases, oxime-derived products may serve as quenchers of reactive oxygen species and storage compounds for reduced nitrogen that may be released on demand by the activation of endogenous turnover pathways. As highly bioactive molecules, chemically synthesized oximes have found versatile uses in many sectors of society, especially in the agro- and medical sector. This review provides an update on the structural diversity, occurrence and biosynthesis of oximes in plants, and discusses their role as key players in plant general and specialized metabolism.
... Since the first report of cyanogenesis in T. repens in 1912, plenty of studies have investigated the inheritance and polymorphism of cyanogenesis. Cyanogenesis is an ancient, stable, and heritable plant defense system with a single evolutionary origin because all presently identified enzymes responsible for the transformation of an amino acid into an oxime belong to the CYP79 family (Bak et al. 2006;Bjarnholt and Møller, 2008;Takos et al. 2011). Cyanogenesis polymorphism is common among the cyanogenic plant species, including T. repens L. and Lotus corniculatus L. (Aikman et al. 1996). ...
The natural products cyanogenic glycosides (CNglcs) are present in various forage plant species including Sorghum spp., Trifolium spp., and Lotus spp. The release of toxic hydrogen cyanide (HCN) from endogenous CNglcs, which is known as cyanogenesis, leads to a serious problem for animal consumption while as defensive secondary metabolites, CNglcs play multiple roles in plant development and responses to adverse environment. Therefore, it is highly important to fully uncover the molecular mechanisms of CNglc biosynthesis and regulation to manipulate the contents of CNglcs in forage plants for fine-tuning the balance between defensive responses and food safety. This review summarizes recent studies on the production, function, polymorphism, and regulation of CNglcs in forage plants, aiming to provide updated knowledge on the ways to manipulate CNglcs for further beneficial economic effects.
... Cyanogenesis has been well documented in plants and insects. Cyanogenic plants accumulate glycosides of hydroxynitriles called cyanogenic glycosides (CNglcs) as stable cyanide precursors [3]. ...
Specialized arthropods and more than 2500 plant species biosynthesize hydroxynitriles and release hydrogen cyanide as a defensive mechanism. The millipede Chamberlinius hualienensis accumulates (R)‐mandelonitrile as a cyanide precursor. Although biosynthesis of hydroxynitriles in cyanogenic plants and in an insect are extensively studied, (R)‐mandelonitrile biosynthesis in cyanogenic millipedes has remained unclear. In this study, we identified the biosynthetic precursors of (R)‐mandelonitrile and an enzyme involved in (R)‐mandelonitrile biosynthesis. Using deuterium‐labelled compounds, we revealed that (E/Z)‐phenylacetaldoxime and phenylacetonitrile are the biosynthetic precursors of (R)‐mandelonitrile in the millipede as well as other cyanogenic organisms. To identify the enzymes involved in (R)‐mandelonitrile biosynthesis, 50 cDNAs encoding cytochrome P450s were cloned and coexpressed with yeast cytochrome P450 reductase in yeast, as cytochrome P450s are involved in the biosynthesis of hydroxynitriles in other cyanogenic organisms. Among the 50 cytochrome P450s from the millipede, CYP3201B1 produced (R)‐mandelonitrile from phenylacetonitrile but not from (E/Z)‐phenylacetaldoxime, whereas plant and insect cytochrome P450s catalysed the dehydration of aldoximes and hydroxylation of nitriles. CYP3201B1 is not phylogenetically related to cytochrome P450s from other cyanogenic organisms, indicating that hydroxynitrile biosynthetic cytochrome P450s have independently evolved in distant species. Our study will shed light on the evolution of cyanogenesis among plants, insects and millipedes.
Database
Nucleotide sequence data are available in the DDBJ/EMBL/GenBank databases under the accession numbers LC125356–LC125405.
... These phytochemicals may serve in vivo as a major nitrogen source for developing seedlings (Selmar et al., 1990). Nevertheless, their co-occurrence with hydroxynitrile glycosides in some species (Bjarnholt & Møller, 2008), has suggested that they represent a biosynthetic variation of hydroxynitrile glycosides with esterification to lipids possibly, serving specific functions related to storage and transport (Tava & Avato, 2014). ...
The chemical composition of the oil extracted from the seeds of Sapindus saponaria L., (Sapindaceae), was investigated. Cyanolipids constituted 5% hexane extract of the seeds, whereas triacylglycerols (TAG) accounted for 90%. The oil contains type III cyanolipids (CL) 1-cyano-2-hydroxymethylprop-1-en-3-ol-diesters. Structural investigation of the oil components was accomplished by chemical, chromatographic (TLC, CC, GC-MS), and spectroscopic (IR, NMR) means. GC-MS analysis showed that fatty acids were dominant in the CL components of the oil from S. saponaria L., with cis-11-eicosenoic acid, cis-11-octadecenoic acid and eicosanoic acid as the only esterified fatty acyl chains respectively. This being the first report of this kind of natural products (CL), located in the seeds of this plant..
... Excess cyanide inhibits the cytochrome oxidase, the final step in electron transport, and thus blocks ATP synthesis and so tissues suffer energy deprivation and death follows rapidly. Prior to death, symptoms include faster and deeper respiration, a faster irregular and weaker pulse, salivation and frothing at the mouth, muscular spasms, dilation of the pupils, and bright red mucous membranes [44]. High level of HCN has been implicated for cerebral damage and lethargy in man and animal. ...
... In general, CNglcs are synthesized from specific amino acids in a series of reactions catalyzed by cytochrome P450s and a soluble UDP-glucosyl-transferase, with an oxime and a cyanohydrin as key intermediates. As for non-CNglcs, recent investigations suggested that their production was induced by diversification of the cyanogenic glucoside biosynthetic pathway at the level of the nitrile intermediate, wherein the evolutionary diversified multifunctional cytochrome P450s could hydroxylate different carbon atoms (α, β, and/or γ) present in the oxime derived nitriles [28][29][30][31]. Subsequently, dehydration reactions and/or further hydroxylations and a final glycosylation step afford the unsaturated β-and γhydroxynitrile glycosides. ...
... Because of the striking structural similarities of α -, β -and γhydroxynitrile glucosides and a high frequency of co-occurrence it has been proposed that the compounds are biosynthetically related [15]. Some biosynthetic relationships between acyclic α -, β -and γhydroxynitrile glucosides have been set up [16][17]. ...
Objective: Campylospermum oliverianum and C. sulcatum (Ochnaceae) are considered conspecific by some reports.
... This would be followed by β-cyanoalanine synthase and nitrilase mediated production of ammonia and incorporation into amino acids according to the general plant pathway for detoxification of HCN concomitant with ethylene at Monash University on October 30, 2015 http://pcp.oxfordjournals.org/ Downloaded from formation (reviewed by Bjarnholt and Møller 2008). This is supported by a recent genome wide association study showing that dhurrin content is associated with single nucleotide polymorphisms in regions where the closest genes are the two dhurrinases (β-glucosidases) responsible for dhurrin bioactivation (Hayes et al. 2015). ...
Many important food crops produce cyanogenic glucosides as natural defence compounds to protect against herbivory or pathogen
attack. It has also been suggested that these nitrogen based secondary metabolites act as storage reserves of nitrogen. In
sorghum three key genes, CYP79A1, CYP71E1 and UGT85B1 encode two cytochrome P450s and a glycosyltransferase, respectively, the enzymes essential for synthesis of the cyanogenic
glucoside dhurrin. Here, we report the use of Targeted Induced Local Lesions in Genomes (TILLING) to identify a line with
a mutation resulting in a premature stop codon in the N-terminal region of UGT85B1. Plants homozygous for this mutation do not produce dhurrin and are designated tcd2 (totally cyanide deficient 2) mutants. They have reduced vigour, being dwarfed, with poor root development and low fertility.
Analysis using LC-MS shows that tcd2 mutants accumulate numerous dhurrin pathway-derived metabolites, some of which are similar to those observed in transgenic
Arabidopsis expressing the CYP79A1 and CYP71E1 genes. Our results demonstrate that UGT85B1 is essential for formation of dhurrin in sorghum with no co-expressed endogenous UDP-glucosyltransferases able to replace
it. The tcd2 mutant suffers from self-intoxication because sorghum does not have a feedback mechanism to inhibit the initial steps of
dhurrin biosynthesis when the glucosyltransferase activity required to complete the synthesis of dhurrin is lacking. The LC-MS
analyses also revealed the presence of metabolites in the tcd2 mutant, which have been suggested to be derived from dhurrin via endogenous pathways for nitrogen recovery, thus indicating
which enzymes may be involved in such pathways.
... Alliarinoside is a γ-hydroxynitrile glucoside, structurally related to cyanogenic glucosides that are α-hydroxynitrile glucosides. The latter exert their biological activity by release of cyanide, but the mechanism by which γ-hydroxynitrile glucosides may participate in plant defense is not understood (Bjarnholt and Møller 2008). Recent work reveals that alliarinoside can be completely degraded, sequestered, or passed through the digestive system by P. rapae caterpillars, but comparative chemical work across other Pieris species has not been done (Frisch et al. 2014). ...
As it pertains to insect herbivores, the preference-performance hypothesis posits that females will choose oviposition sites that maximize their offspring's fitness. However, both genetic and environmental cues contribute to oviposition preference, and occasionally "oviposition mistakes" occur, where insects oviposit on hosts unsuitable for larval development. Pieris virginiensis is a pierine butterfly native to North America that regularly oviposits on an invasive plant, Alliaria petiolata, but the caterpillars are unable to survive. Alliaria petiolata has high concentrations of the glucosinolate sinigrin in its tissues, as well as a hydroxynitrile glucoside, alliarinoside. We investigated sinigrin as a possible cause of mistake oviposition, and sinigrin and alliarinoside as possible causes of larval mortality. We found that sinigrin applied to leaves of Cardamine diphylla, a major host of P. virginiensis that does not produce sinigrin, had no effect on oviposition rates. We tested the effect of sinigrin on larval performance using two host plants, one lacking sinigrin (C. diphylla) and one with sinigrin naturally present (Brassica juncea). We found no effect of sinigrin application on survival of caterpillars fed C. diphylla, but sinigrin delayed pupation and decreased pupal weight. On B. juncea, sinigrin decreased survival, consumption, and caterpillar growth. We also tested the response of P. virginiensis caterpillars to alliarinoside, a compound unique to A. petiolata, which was applied to B. oleracea. We found a significant reduction in survival, leaf consumption, and caterpillar size when alliarinoside was consumed. The 'novel weapon' alliarinoside likely is largely responsible for larval failure on the novel host A. petiolata. Sinigrin most likely contributes to the larval mortality observed, however, we did not observe any effect of sinigrin on oviposition by P. virginiensis females. Further research needs to be done on non-glucosinolate contact cues, and volatile signals that may induce P. virginiensis oviposition.
... Interestingly, most of these plants form part of the human diet. [37][38][39] For the AtHNL, XfHNL, BmHNL, PsmHNL and BpHNL no natural substrates are known 26 and the cupin based HNLs are much better catalysts for the synthesis than the breakdown of cyanohydrins. 36 For six of these structurally diverse HNLs X-ray structures have been reported (Fig. 1) and many of them are commercially available. ...
Hydroxynitrile lyases are a versatile group of enzymes that are applied both in the laboratory and on an industrial scale. What makes them particularly interesting is that to date five structurally unrelated categories of hydroxynitrile lyases have been discovered. Given their great importance they have often been immobilised utilising many different methodologies. Therefore the hydroxynitrile lyases are ideally suited to compare different immobilisation methods and their dependence on the structural features of the enzyme in question, since the activity is the same in all cases. This review examines all the different immobilisation methods applied to hydroxynitrile lyases and draws conclusions on the effect of the approach.
... As in indole glucosinolate biosynthesis, a CYP79 catalyses conversion of tryptophan to indole-3-acetaldoxime, which is the branching point between camalexin and indole glucosinolates biosyn- thesis [89,90]. A number of cyanogenic glucoside-containing plants also contain so-called non-cyanogenic hydroxynitrile glucosides [91] . While cyanogenic glucosides are a-hydroxynitrile glucosides, non-cyanogenic hydroxynitrile glucosides such as the rhodiocyanosides A and D in Lotus japonicus are g-and b-hydroxynitrile glucosides, respectively. ...
The irreversible nature of reactions catalysed by P450s makes these enzymes landmarks in the evolution of plant metabolic pathways. Founding members of P450 families are often associated with general (i.e. primary) metabolic pathways, restricted to single copy or very few representatives, indicative of purifying selection. Recruitment of those and subsequent blooms into multi-member gene families generates genetic raw material for functional diversification, which is an inherent characteristic of specialized (i.e. secondary) metabolism. However, a growing number of highly specialized P450s from not only the CYP71 clan indicate substantial contribution of convergent and divergent evolution to the observed general and specialized metabolite diversity. We will discuss examples of how the genetic and functional diversification of plant P450s drives chemical diversity in light of plant evolution. Even though it is difficult to predict the function or substrate of a P450 based on sequence similarity, grouping with a family or subfamily in phylogenetic trees can indicate association with metabolism of particular classes of compounds. Examples will be given that focus on multi-member gene families of P450s involved in the metabolic routes of four classes of specialized metabolites: cyanogenic glucosides, glucosinolates, mono- to triterpenoids and phenylpropanoids.
Barley produces several specialized metabolites, including five α‐, β‐, and γ‐hydroxynitrile glucosides (HNGs). In malting barley, presence of the α‐HNG epiheterodendrin gives rise to undesired formation of ethyl carbamate in the beverage production, especially after distilling. Metabolite‐GWAS identified QTLs and underlying gene candidates possibly involved in the control of the relative and absolute content of HNGs, including an undescribed MATE transporter. By screening 325 genetically diverse barley accessions, we discovered three H. vulgare ssp. spontaneum (wild barley) lines with drastic changes in the relative ratios of the five HNGs. Knock‐out (KO)‐lines, isolated from the barley FIND‐IT resource and each lacking one of the functional HNG biosynthetic genes ( CYP79A12 , CYP71C103 , CYP71C113 , CYP71U5 , UGT85F22 and UGT85F23 ) showed unprecedented changes in HNG ratios enabling assignment of specific and mutually dependent catalytic functions to the biosynthetic enzymes involved. The highly similar relative ratios between the five HNGs found across wild and domesticated barley accessions indicate assembly of the HNG biosynthetic enzymes in a metabolon, the functional output of which was reconfigured in the absence of a single protein component. The absence or altered ratios of the five HNGs in the KO‐lines did not change susceptibility to the fungal phytopathogen Pyrenophora teres causing net blotch. The study provides a deeper understanding of the organization of HNG biosynthesis in barley and identifies a novel, single gene HNG‐0 line in an elite spring barley background for direct use in breeding of malting barley, eliminating HNGs as a source of ethyl carbamate formation in whisky production.
Cyanogenic glycosides are a large group of secondary metabolites that are widely distributed in the many plants commonly consumed by humans, birds, and other animals. Thiosulfate sulfurtransferase (TST) and 3-mercaptopyruvate sulfurtransferase (MPST), are two evolutionary-related enzymes that constitute the defense against cyanide toxication and participate in the production of sulfane sulfur-containing compounds. The expression and activity of TST and MPST as well as the level of sulfane sulfur in chicken tissue homogenates of the liver, heart, and gizzard were investigated. The highest expression/activity of TST and MPST was noticed in liver homogenates which was associated with the high sulfane sulfur level. Both the expression and activity of TST as well as the sulfane sulfur level in chicken gizzard homogenates were significantly lower than in the liver and heart. Both TST and MPST enzymes can play an important role in cyanide detoxification in chicken tissues. Maintaining appropriate sulfane sulfur level together with the high activity of these enzymes is essential to protect tissues from the toxic effects of cyanide, released from certain nutrients.
Lotus japonicus is a leguminous model plant used to gain insight into plant physiology, stress response, and especially symbiotic plant-microbe interactions, such as root nodule symbiosis or arbuscular mycorrhiza. Responses to changing environmental conditions, stress, microbes, or insect pests are generally accompanied by changes in primary and secondary metabolism to account for physiological needs or to produce defensive or signaling compounds. Here we provide an overview of the primary and secondary metabolites identified in L. japonicus to date. Identification of the metabolites is mainly based on mass spectral tags (MSTs) obtained by gas chromatography linked with tandem mass spectrometry (GC-MS/MS) or liquid chromatography-MS/MS (LC-MS/MS). These MSTs contain retention index and mass spectral information, which are compared to databases with MSTs of authentic standards. More than 600 metabolites are grouped into compound classes such as polyphenols, carbohydrates, organic acids and phosphates, lipids, amino acids, nitrogenous compounds, phytohormones, and additional defense compounds. Their physiological effects are briefly discussed, and the detection methods are explained. This review of the exisiting literature on L. japonicus metabolites provides a valuable basis for future metabolomics studies.
The nitrate and peptide transporter family (NPF) is one of the largest transporter families in the plant kingdom. The name of the family reflects the substrates (nitrate and peptides) identified for the two founding members CHL1 and PTR2 from Arabidopsis thaliana almost 30 years ago. However, since then, the NPF has emerged as a hotspot for transporters with a wide range of crucial roles in plant specialized metabolism. Recent prominent examples include 1) controlling accumulation of antinutritional glucosinolates in Brassica seeds, 2) deposition of heat-stress tolerance flavonol diglucosides to pollen coats 3) production of anti-cancerous monoterpene indole alkaloid precursors in Catharanthus roseus and 4) detoxification of steroid glycoalkaloids in ripening tomatoes. In this review, we turn the spotlight on the emerging role of the NPF in plant specialized metabolism and its potential for improving crop traits through transport engineering.
β‐cyanoalanine synthase (β‐CAS) is an enzyme involved in cyanide detoxification. However, little information is available regarding the effects of β‐CAS activity changes on plant resistance to environmental stress. Here, we found that β‐CAS overexpression improves the resistance of tobacco plants to salt stress, whereas plants with β‐CAS silencing suffer more oxidative damage than wild type plants. Notably, blocking respiration by the alternative oxidase (AOX) pathway significantly aggravates stress injury and impairs the salt stress tolerance mediated by β‐CAS overexpression. These findings present novel insights into the synergistic effect between β‐CAS and AOX in protecting plants from salt stress, where β‐CAS plays a vital role in restraining cyanide accumulation, and AOX helps to alleviate the toxic effect of cyanide.
Cyanogenic glucosides are ancient and widespread defence compounds that are used by plants to fend off non-adapted insect herbivores. After insect herbivory and plant tissue damage, cyanogenic glucosides come into contact with compartmentalised plant β-glucosidases, resulting in the release of toxic hydrogen cyanide. Such a binary system of components that are chemically inert when separated is also referred to as two-component plant defence. Since the co-evolution of cyanogenic plants and insect herbivores has continued for several hundred million years, some specialised herbivores have adapted and gained the ability to feed on cyanogenic plants. Moreover, a few
specialists are even able to sequester cyanogenic glucosides into specialised tissues, often for use in their own defence. However, insect counter-adaptations to overcome plant cyanogenic glucosides are largely unknown.
This thesis presents evidence that larvae of the sequestering lepidopteran specialist Zygaena filipendulae have evolved diverse behavioural, morphological, physiological and metabolic adaptations to keep cyanogenic glucosides from its food plant (Lotus corniculatus, Fabaceae) intact and thus non-toxic during feeding and digestion (Chapter II). These adaptations are a prerequisite to sequester intact cyanogenic glucosides quickly from the gut into the haemolymph and other larval tissues (Chapter III). Finally, cyanogenic glucosides deposited in defence droplets are used in the insect’s own defence either due to the bitter taste of intact cyanogenic glucosides (typically
against vertebrates) or in combination with stickiness (typically against arthropod predators). In the case of severe damage, causing integument rupture, defence droplets release high amounts of hydrogen cyanide, because they mix with exuding haemolymph containing β-glucosidases (Chapter IV). Moreover, the generalist lepidopteran Spodoptera littoralis was shown to have similar adaptations to overcome cyanogenic glucosides as reported from Z. filipendulae (Chapter V). Thus, lepidopterans as well as some herbivorous species from other insect orders, including generalists and specialists, seem relatively well-adapted to cyanogenic glucosides and various other classes of
two-component plant chemical defence (reviewed in Chapter I, 2).
The results obtained in this thesis provide unique insights into the co-evolution and adaptation of insect herbivores to cyanogenic plants. It raises several research questions regarding herbivory of cyanogenic plants that need to be examined in more detail, and offer observations which could be extrapolated to other two-component plant-insect defence systems.
Chemical defences are key components in insect–plant interactions, as insects continuously learn to overcome plant defence systems by, e.g., detoxification, excretion or sequestration. Cyanogenic glucosides are natural products widespread in the plant kingdom, and also known to be present in arthropods. They are stabilised by a glucoside linkage, which is hydrolysed by the action of β-glucosidase enzymes, resulting in the release of toxic hydrogen cyanide and deterrent aldehydes or ketones. Such a binary system of components that are chemically inert when spatially separated provides an immediate defence against predators that cause tissue damage. Further roles in nitrogen metabolism and inter- and intraspecific communication has also been suggested for cyanogenic glucosides. In arthropods, cyanogenic glucosides are found in millipedes, centipedes, mites, beetles and bugs, and particularly within butterflies and moths. Cyanogenic glucosides may be even more widespread since many arthropod taxa have not yet been analysed for the presence of this class of natural products. In many instances, arthropods sequester cyanogenic glucosides or their precursors from food plants, thereby avoiding the demand for de novo biosynthesis and minimising the energy spent for defence. Nevertheless, several species of butterflies, moths and millipedes have been shown to biosynthesise cyanogenic glucosides de novo, and even more species have been hypothesised to do so. As for higher plant species, the specific steps in the pathway is catalysed by three enzymes, two cytochromes P450, a glycosyl transferase, and a general P450 oxidoreductase providing electrons to the P450s. The pathway for biosynthesis of cyanogenic glucosides in arthropods has most likely been assembled by recruitment of enzymes, which could most easily be adapted to acquire the required catalytic properties for manufacturing these compounds. The scattered phylogenetic distribution of cyanogenic glucosides in arthropods indicates that the ability to biosynthesise this class of natural products has evolved independently several times. This is corroborated by the characterised enzymes from the pathway in moths and millipedes. Since the biosynthetic pathway is hypothesised to have evolved convergently in plants as well, this would suggest that there is only one universal series of unique intermediates by which amino acids are efficiently converted into CNglcs in different Kingdoms of Life. For arthropods to handle ingestion of cyanogenic glucosides, an effective detoxification system is required. In butterflies and moths, hydrogen cyanide released from hydrolysis of cyanogenic glucosides is mainly detoxified by β-cyanoalanine synthase, while other arthropods use the enzyme rhodanese. The storage of cyanogenic glucosides and spatially separated hydrolytic enzymes (β-glucosidases and α-hydroxynitrile lyases) are important for an effective hydrogen cyanide release for defensive purposes. Accordingly, such hydrolytic enzymes are also present in many cyanogenic arthropods, and spatial separation has been shown in a few species. Although much knowledge regarding presence, biosynthesis, hydrolysis and detoxification of cyanogenic glucosides in arthropods has emerged in recent years, many exciting unanswered questions remain regarding the distribution, roles apart from defence, and convergent evolution of the metabolic pathways involved.
Controlling the reaction selectivity of a heterobifunctional molecule is a fundamental challenge in many catalytic processes. Recent efforts to design chemoselective catalysts have focused on modifying the surface of metal nanoparticle materials having tunable properties. However, precise control over the surface properties of base-metal oxide catalysts remains a challenge. Here, we show that green modification of the surface with carboxylates can be used to tune the ammoxidation selectivity toward the desired products during the reaction of hydroxyaldehyde on manganese oxide catalysts. These modifications improve the selectivity for hydroxynitrile from 0 to 92% under identical reaction conditions. The product distribution of dinitrile and hydroxynitrile can be continuously tuned by adjusting the amount of carboxylate modifier. This property was attributed to the selective decrease in the hydroxyl adsorption affinity of the manganese oxides by the adsorbed carboxylate groups. The selectivity enhancement is not affected by the tail structure of the carboxylic acid.
The new iron(IV) nitride complex PhB(ⁱPr2Im)3Fe≡N reacts with two equivalents of bis(diisopropylamino)cyclopropenylidene (BAC) to provide PhB(ⁱPr2Im)3Fe(CN)(N2)(BAC). This unusual example of a four-electron reaction involves carbon atom transfer from BAC to create a cyanide ligand along with the alkyne ⁱPr2N-C≡C-NⁱPr2. The iron complex is in equilibrium with an N2-free species. Further reaction with CO leads to formation of a CO analogue, which can be independently prepared using NaCN as the cyanide source, while reaction with B(C6F5)3 provides the cyanoborane derivative.
Barley (Hordeum vulgare L.) produces five leucine derived hydroxynitrile glucosides (HNGs), of which only epiheterodendrin is a cyanogenic glucoside. The four non-cyanogenic HNGs are the β-HNG epidermin and the γ-HNGs osmaronin, dihydroosmaronin and sutherlandin. By analyzing 247 spring barley lines including landraces and old and modern cultivars, we demonstrated that the HNG level varies notably between lines whereas the overall ratio between the compounds is constant. Based on sequence similarity to the sorghum (Sorghum bicolor) genes involved in dhurrin biosynthesis, we identified a gene cluster on barley chromosome 1 putatively harboring genes which encode enzymes in HNG biosynthesis. Candidate genes were functionally characterized by transient expression in Nicotiana benthamiana. Five multifunctional P450s including two CYP79 family enzymes and three CYP71 family enzymes, and a single UDP-glucosyltransferase (UGT) were found to catalyze the reactions required for biosynthesis of all five barley HNGs. Two of the CYP71 enzymes needed to be co-expressed for the last hydroxylation step in sutherlandin synthesis to proceed. This observation, together with the constant ratio between the different HNGs, suggested that HNG synthesis in barley is organized within a single multi-enzyme complex. This article is protected by copyright. All rights reserved.
Plants produce a wide spectrum of specialized metabolites that function in plant chemical defense against pathogens and herbivores or have signaling roles in the interaction with other organisms. The plant-specialized metabolites that have received most attention in legumes in general, and in Lotus japonicus as a legume model species, are proanthocyanidins, isoflavonoids, cyanogenic and non-cyanogenic hydroxynitrile glucosides, and triterpenoids. Here, we review these four classes of plant-specialized metabolites in terms of the specific compounds produced by L. japonicus, the biosynthetic genes responsible, and the genomic organization of the genes. We previously reported that in L. japonicus, the non-homologous genes encoding the complete biosynthetic pathway for the cyanogenic glucosides lotaustralin and linamarin are organized in a gene cluster. Here, we additionally describe gene clusters in the L. japonicus genome for triterpenoid and isoflavonoid biosynthesis. A model explaining how selection for reduced recombination results in gene cluster formation is presented.
A variety of novel natural products with significant bioactivities are produced by the basidiomycete Boreostereum vibrans. In the present study, we describe 16 novel natural oximes and oxime esters with a vibralactone backbone, vibralactoximes, which were isolated from the scale-up fermentation broth of B. vibrans. Their structures were determined through extensive spectroscopic analyses. These compounds represent the first oxime esters from nature. The hypothetical biosynthetic pathway of these compounds was also proposed. Seven compounds exhibited significant pancreatic lipase inhibitory activity, while ten compounds exhibited cytotoxicities against five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480), with IC50 values comparable with those of cisplatin.
The biosynthetic pathway for the cyanogenic glucoside, dhurrin, in sorghum has previously been shown to involve the sequential production of (E) - and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the E-oxime to the Z-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the E-oxime into an S-alkyl-thiohydroximate with retainment of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79 derived E-oximes may play an important role in plant defense. This article is protected by copyright. All rights reserved.
The allelochemical alliarinoside present in garlic mustard (Alliaria petiolata), an invasive plant species in North America, was chemically synthesized using an efficient and practical synthetic strategy based on a simple reaction sequence. Commercially available 1,2,3,4,6-penta-O-acetyl-β-d-glucopyranose was converted into prop-2-enyl 2',3',4',6'-tetra-O-acetyl-β-d-glucopyranoside and subjected to epoxidation. In a one-pot reaction, ring-opening of the epoxide using TMSCN under solvent free conditions followed by treatment of the formed trimethylsilyloxy nitrile with pyridine and phosphoryl chloride, afforded the acetylated β-unsaturated nitriles (Z)-4-(2',3',4',6'-tetra-O-β-d-glucopyranosyloxy)but-2-enenitrile and its isomer (E)-4-(2',3',4',6'-tetra-O-β-d-glucopyranosyloxy)but-2-enenitrile. Deacetylation of Z- and/or E-isomers afforded the target molecules alliarinoside and its isomer.
Cyanogenic glycosides (CNglcs) are bioactive plant products derived from amino acids. Structurally, these specialized plant compounds are characterized as α-hydroxynitriles (cyanohydrins) that are stabilized by glucosylation. In recent years, improved tools within analytical chemistry have greatly increased the number of known CNglcs by enabling the discovery of less abundant new CNglcs formed by additional hydroxylation, glycosylation, and acylation reactions. Cyanogenesis-the release of toxic hydrogen cyanide from endogenous CNglcs-is an effective defense against generalist herbivores but less effective against fungal pathogens. In the course of evolution, CNglcs have acquired additional roles to improve plant plasticity, i.e., establishment, robustness, and viability in response to environmental challenges. CNglc concentration is usually higher in young plants, when nitrogen is in ready supply, or when growth is constrained by nonoptimal growth conditions. Efforts are under way to engineer CNglcs into some crops as a pest control measure, whereas in other crops efforts are directed toward their removal to improve food safety. Given that many food crops are cyanogenic, it is important to understand the molecular mechanisms regulating cyanogenesis so that the impact of future environmental challenges can be anticipated. Expected final online publication date for the Annual Review of Plant Biology Volume 65 is April 29, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Secondary metabolites are essential plant fitness within the natural environment by providing defense against attacking and competing organisms including bacteria, fungi, insects, animals and other plants. These compounds' defensive function is frequently intertwined with specific accumulation in novel developmental structures. While, the biochemical community is making great strides in identifying the genetic and biochemical mechanisms that allow these chemicals to be synthesized there is vastly less progress on understanding the developmental mechanisms that is equally key to their defensive function. In this review, I briefly delve into several novel developmental structures and provide evolutionary hypothesis for how they may have evolved and how they could be unique systems for studying key developmental processes that have heretofore been recalcitrant to study.
Carbon monoxide (CO) and cyanide (CN–) can act as potent inhibitors of enzymes necessary for primary biochemical processes, however they also play important roles in biological systems. Well-studied cases include CN– biosynthesis in plants to act as a defense against herbivores and pathogens, CN– biosynthesis in certain species of bacteria to remove excess glycine, and CO biosynthesis by microbes for energy metabolism in the Wood–Ljungdahl pathway. The utilization of CO and CN– as essential metal ligands in biology is even more limited, with the only known examples being at the active sites of hydrogenase enzymes. This class of enzymes catalyzes the reversible oxidation of hydrogen, a reaction that in biology appears to be entirely dependent on the presence of CO and/or CN– ligands. To date, synthetic mimicsof hydrogenase active sites have not reproduced hydrogen production rates observed in some hydrogenases; it is thus of considerable interest to understand how biology has solved the intriguing problem of biosynthesizing efficient hydrogen catalysts. Of the hydrogenase enzymes discussed herein, recent advances in the [FeFe]-hydrogenase family has provided important insights into the synthesis of the CO and CN– ligands for its active site (H-cluster). Biosynthesis of the complex [FeFe]-hydrogenase active site requires only three iron–sulfur cluster-containing maturation proteins, where two act as radical S-adenosylmethionine (AdoMet) enzymes (HydE and HydG) and the other as a GTPase (HydF). In this review, biological CO and CN– genesis mechanisms will be assessed with specific focus on [FeFe]-hydrogenase maturation.
A revised and updated classification for the families of the flowering plants is provided. Newly adopted orders include Austrobaileyales, Canellales, Gunnerales, Crossosomatales and Celastrales. Pertinent literature published since the first APG classification is included, such that many additional families are now placed in the phylogenetic scheme. Among these are Hydnoraceae (Piperales), Nartheciaceae (Dioscoreales), Corsiaceae (Liliales), Triuridaceae (Pandanales), Hanguanaceae (Commelinales), Bromeliacae, Mayacaceae and Rapateaceae (all Poales), Barbeuiaceae and Gisekiaceae (both Caryophyllales), Geissolomataceae, Strasburgeriaceae and Vitaceae (unplaced to order, but included in the rosids), Zygophyllaceae (unplaced to order, but included in eurosids 1), Bonnetiaceae, Ctenolophonaceae, Elatinaceae, Ixonanthaceae, Lophopyxidaceae, Podostemaceae (Malpighiales), Paracryphiaceae (unplaced in euasterid II), Sladeniaceae, Pentaphylacaceae (Ericales) and Cardiopteridaceae, (Aquifoliales). Several major families are recircumscribed. Salicaceae are expanded to include a large part of Flacourtiaceae, including the type genus of that family; another portion of former Flacourtiaceae is assigned to an expanded circumscription of Achariaceae. Euphorbiaceae are restricted to the uniovulate subfamilies; Phyllanthoideae are recognized as Phyllanthaceae and Oldfieldioideae as Picrodendraceae. Scrophulariaceae are recircumscribed to include Buddlejaceae, and Myoporaceae and exclude several former members; these are assigned to Calceolariaceae, Orobanchaceae and Plantaginaceae. We expand the use of bracketing families that could be included optionally in broader circumscriptions with other related families; these include Agapanthaceae, and Amaryllidaceae in Alliaceae s.l., Agavaceae, Hyacinthaceae and Ruscaceae (among many other Asparagales) in Asparagaceae s.l., Dichapetalaceae in Chrysobalanaceae, Turneraceae in Passifloraceae, Erythroxylaceae in Rhizophoraceae, and Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae and Valerianaceae in Caprifoliaceae s.l. (C) 2003 The Linnean Society of London.
Auxins are growth regulators involved in virtually all aspects of plant development. However, little is known about how plants synthesize these essential compounds. We propose that the level of indole-3-acetic acid is regulated by the flux of indole-3-acetaldoxime through a cytochrome P450, CYP83B1, to the glucosinolate pathway. A T-DNA insertion in the CYP83B1 gene leads to plants with a phenotype that suggests severe auxin overproduction, whereas CYP83B1 overexpression leads to loss of apical dominance typical of auxin deficit. CYP83B1 N-hydroxylates indole-3-acetaldoxime to the corresponding aci-nitro compound, 1-aci-nitro-2-indolyl-ethane, with a Km of 3 μM and a turnover number of 53 min–1. The aci-nitro compound formed reacts non-enzymatically with thiol compounds to produce an N-alkyl-thiohydroximate adduct, the committed precursor of glucosinolates. Thus, indole-3-acetaldoxime is the metabolic branch point between the primary auxin indole-3-acetic acid and indole glucosinolate biosynthesis in Arabidopsis.
The long-known cyanogenic glucoside acacipetalin,
confirmed to be 2- (b-D-glucopyranosyloxy-)3 -methylbut-2-enenitrile, can be produced from a natural
b-D-glucopyranoside of 2-hydroxy-3-methylbut-3-enenitrile, which is distinguished from its epimer and named proacacipetalin.
Organisms that produce hydrogen cyanide gas to protect themselves against predators can do so by the enzymatic breakdown of a class of compounds known as cyanogens (such as cyanogenic glycosides)1, ². Here we show how a neotropical butterfly, Heliconius sara, can avoid the harmful effects of the cyanogenic leaves of Passiflora auriculata (passion vine), on which its larvae feed exclusively. To our knowledge this is the first example of an insect that is able to metabolize cyanogens and thereby prevent the release of cyanide. The mechanistic details of this pathway might suggest new ways to make cyanogenic crops more useful as a food source.
The major cyanogenic glycoside of Guazuma ulmifolia (Sterculiaceae) is (2R)-taxiphyllin (>90%), which co-occurs with (2S)-dhur-rin. Few individuals of this species, but occasional other members of the family, have been reported to be cyanogenic. To date, cya-nogenic compounds have not been characterized from the Sterculiaceae. The cyanogenic glycosides of Ostrya virginiana (Betulaceae) are (2S)-dhurrin and (2R)-taxiphyllin in an approximate 2:1 ratio. This marks the first report of the identification of cyanogenic compounds from the Betulaceae. Based on NMR spectroscopic and TLC data, the major cyanogenic glucoside of Tiquilia plicata is dhurrin, whereas the major cyanide-releasing compound of Tiquilia canescens is the nitrile glucoside, menisdaurin. NMR and TLC data indicate that both compounds are present in each of these species. The spectrum was examined by CI-MS, 1 H and 13 C NMR, COSY, 1D selective TOCSY, NOESY, and 1 J/ 2,3 J HETCOR experiments; all carbons and protons are assigned. The probable abso-lute configuration of (2R)-dhurrin is established by an X-ray crystal structure. The 1 H NMR spectrum of menisdaurin is more com-plex than might be anticipated, containing a planar conjugated system in which most elements are coupled to several other atoms in the molecule. The coupling of one vinyl proton to the protons on the opposite side of the ring involves a 6 J-and a 5/7 J-coupling pathway. A biogenetic pathway for the origin of nitrile glucosides is proposed.
Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.
Whereas high activities of -glucosidase occur in homogenates of leaves of Hevea brasiliensis Muell.-Arg., this enzyme, which is capable of splitting the cyanogenic monoglucoside linamarin (linamarase), is not present in intact protoplasts prepared from the corresponding leaves. Thus, in leaves of H. brasiliensis the entire linamarase is located in the apoplasmic space. By analyzing the vacuoles obtained from leaf protoplasts isolated from mesophyll and epidermal layers of H. brasiliensis leaves, it was shown that the cyanogenic glucoside linamarin is localized exclusively in the central vacuole. Analyses of apoplasmic fluids from leaves of six other cyanogenic species showed that significant linamarase activity is present in the apoplasm of all plants tested. In contrast, no activity of any diglucosidase capable of hydrolyzing the cyanogenic diglucoside linustatin (linustatinase) could be detected in these apoplasmic fluids. As described earlier, any translocation of cyanogenic glucosides involves the interaction of monoglucosidic and diglucosidic cyanogens with the corresponding glycosidases (Selmar, 1993a, Planta 191, 191–199). Based on this, the data on the compartmentation of cyanogenic glucosides and their degrading enzymes in Hevea are discussed with respect to the complex metabolism and the transport of cyanogenic glucosides.
The Arabidopsis GA3cDNA was expressed in yeast (Saccharomyces cerevisiae) and the ability of the transformed yeast cells to metabolizeent-kaurene was tested. We show by full-scan gas chromatography-mass spectrometry that the transformed cells produceent-kaurenoic acid, and demonstrate that the single enzyme GA3 (ent-kaurene oxidase) catalyzes the three steps of gibberellin biosynthesis from ent-kaurene toent-kaurenoic acid.
A cytochrome P450, designated P450ox, that catalyzes the conversion of (Z)-p-hydroxyphenylacetaldoxime (oxime) to p-hydroxymandelonitrile in the biosynthesis of the cyanogenic glucoside [beta]-D-glucopyranosyloxy-(S)-p-hydroxymandelonitrile (dhurrin), has been isolated from microsomes prepared from etiolated seedlings of sorghum (Sorghum bicolor L. Moench). P450ox was solubilized using nonionic detergents, and isolated by ion-exchange chromatography, Triton X-114 phase partitioning, and dye-column chromatography. P450ox has an apparent molecular mass of 55 kD, its N-terminal amino acid sequence is -ATTATPQLLGGSVP, and it contains the internal sequence MDRLVADLDRAAA. Reconstitution of P450ox with NADPH-P450 oxidoreductase in micelles of L-[alpha]-dilauroyl phosphatidylcholine identified P450ox as a multifunctional P450 catalyzing dehydration of (Z)-oxime to p-hydroxyphenylaceto-nitrile (nitrile) and C-hydroxylation of p-hydroxyphenylacetonitrile to nitrile. P450ox is extremely labile compared with the P450s previously isolated from sorghum. When P450ox is reconstituted in the presence of a soluble uridine diphosphate glucose glucosyltransferase, oxime is converted to dhurrin. In vitro reconstitution of the entire dhurrin biosynthetic pathway from tyrosine was accomplished by the insertion of CYP79 (tyrosine N-hydroxylase), P450ox, and NADPH-P450 oxidoreductase in lipid micelles in the presence of uridine diphosphate glucose glucosyltransferase. The catalysis of the conversion of Tyr into nitrile by two multifunctional P450s explains why all intermediates in this pathway except (Z)-oxime are channeled.
Acetone extracts of the leaves of 16 plants known to have toxic effects when ingested by livestock were screened for biological activity, on the basis that toxic plants have proven pharmacological activity. The plants were tested for antibacterial effects against two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive (Enterococcus faecalis and Staphylococcus aureus) bacteria. Anthelmintic activity against the free-living test nematode Caenorhabditis elegans was assessed. The potential cytotoxicity of the extracts was investigated using the brine shrimp lethality assay. Gossypium herbaceum, Lantana camara, L. rugosa, Thevetia peruviana and Sorghum bicolor inhibited the growth of all test bacteria with MIC values ranging from 0.39mg ml-1 to 6.3mg ml-1. A few plants, namely Gossypium herbaceum, Hertia pallens, Jatropha multifida and Lantana rugosa, showed notable effects against the nematodes at a concentration of 1mg ml-1. Only Hertia pallens (LC50 = 0.54mg ml-1) and Lantana rugosa (LC50 = 0.69mg ml-1) exhibited cytotoxic activity as indicated by the brine shrimp assay. These results establish the limited applicability of the brine shrimp assay to determine the toxicity of plant extracts.
In the Gramineae, the cyclic hydroxamic acids 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one
(DIMBOA) form part of the defense against insects and microbial pathogens. Five genes,Bx1 through Bx5, are required for DIBOA biosynthesis in maize. The functions of these five genes, clustered on chromosome 4, were demonstrated
in vitro. Bx1 encodes a tryptophan synthase α homolog that catalyzes the formation of indole for the production of secondary metabolites
rather than tryptophan, thereby defining the branch point from primary to secondary metabolism.Bx2 through Bx5 encode cytochrome P450–dependent monooxygenases that catalyze four consecutive hydroxylations and one ring expansion to form
the highly oxidized DIBOA.
Linamarase (EC 3.2.1.21) is a specialized β-glucosidase that hydrolyses the cyanogenic glucoside linamarin. Two clones of Trifolium repens L. derived from natural populations, of which one clone exhibited linamarase activity, were used in a comparative study to try to establish the localization of linamarase and other β-glucosidases. Two methods were used: the first one was vacuum infiltration of intact leaf cells, followed by centrifugation. A significant amount of linamarase and β-glucosidase activity could be extracted from intact tissue by a 0.25 M NaCl solution, indicating that these activities are localized in the apoplast. The second method, immuno-cytofluorescense of microtome sections, confirmed this. It was found that linamarase and other β-glucosidases are present in the cell walls, especially those of the epidermal cells, and in the cuticle. However their presence in the cell walls of other tissues i.e. walls of the vessels, could not be excluded. No difference in distribution could be detected between linamarase and other β-glucosidases.
Lotaustralin, (R)-2-(β-d-glucopyranosyloxy)-2-methylbutanenitrile, was isolated from Berberidopsis beckleri (F. v. M.) Veldkamp. The presence of valine/isoleucine-derived cyanohydrin glycosides in plants belonging or closely related to Flacourtiaceae is a primitive character as compared to the ability to produce cyanohydrin glycosides derived from 2-cyclopentenyl-1-glycine, typical of this plant family. The stereochemical aspects of biosynthesis of cyclopentenoid cyanohydrin glycosides and fatty acids are discussed.
The structure of a new cyanogenic glucoside, dihydroacacipetalin has been established, primarily on the basis of NMR and mass spectral data. This compound co-occurs with acacipetalin and is also derived from l-leucine in the plant Acacia sieberiana var. woodii (Leguminosae).
The cyanogenic glucosides of four Latin American species of Acacia (Fabceae: Mimosoideae) have been isolated and characterized. Acacia atramentaria (Argentina) contains proacacipetalin, A.aroma (Argentina) linamarin and lotaustralin, A. tortuosa (Venezuela) proacacipetalin and a second presently uncharacterized glycoside, and A. globulifera (Guatemala) epiproacacipetalin which has not previously been reported as naturally occurring.
The biosynthesis of deidaclin in Turnera angustifolia and of linamarin in Passiflora morifolia were investigated using intact plant tissues. Radiolabelled precursors, 2-(2′-cyclopentenyl)[2-14C]glycine and l-[U-14C]-valine were fed to freshly harvested shoots either alone or together with the presumed nitrile intermediates, 2-cyclopentenecarbonitrile and 2-methylpropanenitrile. The cyanohydrin glucosides were isolated and purified, and the incorporation of the radioactive labels was determined after enzymatic degradation of the glucosides to cyanide. The labels from the amino acid precursors were incorporated into the nitrile group of their corresponding cyanohydrin glucosides, and the incorporation was in each case strongly inhibited by simultaneous feeding with either of the two nitriles. Turnera angustifolia was able to synthesize linamarin when fed with 2-methylpropanenitrile, even though linamarin could not be demonstrated to be present in this plant naturally.
A new cyanogenic compound, sarmentosin epoxide, was isolated from the aerial parts of Sedum cepaea. Its structure was established mainly by 1H
The structure of acacipetalin isolated from Acacia sieberiana var. woodii has been revised, primarily on the basis of NMR spectra. Biosynthetic studies on the compound show that l-leucine is the most effective precursor of the aglycone. The isolation of a second cyanogenic glycoside closely related to acacipetalin is reported.
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Five cyanoglucosides have been isolated from extracts of the epidermal layer of barley and the structure of their trimethylsilyl derivatives have been elucidated spectroscopically (UV, NMR, MS). Three of these, namely 3-β- d-glucopyranosyloxy-3-methylbutyronitrile, 1-cyano-3-β-d-glucopyranosyloxy-2-methylpropene and 4-β-d-glucopyranosyloxy-3-hydroxy-3-hydroxymethyl-butyronitrile, are novel compounds.
Barterin, a classical cyclopentenoid cyanohydrin glucoside, was shown to be (1S,4S)-1-(β-d-glucopyranosyloxy)-4-hydroxy-2-cyclopentene-1-carbonitrile, being thus identical with tetraphyllin B, contrary to previous statements in the literature. Cyanohydrin glycosides from Adenia dinklagei, A. epigea, A. firingalavensis, A. frutescens, A. hastata, A. letouzeyi, A. spinosa, Passiflora coriacea, P. subpeltata, P. warmingii and Smeathmannia pubescens were isolated and identified. A summary of the present knowledge of distribution of cyanohydrin glycosides in Passifloraceae shows clear differences between the two chief genera, Adenia and Passiflora. Thus, the former genus appears to be dominated by β-d-glucopyranosides of 2-cyclopenten-1-one and 4-hydroxy-2-cyclopenten-1-one cyanohydrin; the glycosides generally occur as pairs having enantiomeric aglycones and the cyclopentene ring is usually trans-1,4-dioxygenated. By contrast, the pattern of cyanohydrin glycosides of Passiflora appears to be highly diversified, comprising valine or isoleucine-derived glycosides as well as cyclopentenoid glycosides, including more elaborate forms than those found in Adenia. The origin of epilotaustralin, possibly arising from the (3R)-epimer of l-isoleucine, is briefly discussed.
In addition to cardiospermin-5-(4-hydroxy)benzoate previously isolated from Sorbaria arborea, two further leucine-derived cyanogenic glucosides hav
A new cyanogenic glucoside, isolated from pods of Acacia sieberiana var. woodii, was shown to be (2R)-2- (β-d-glucopyranosyloxy)-3-hydroxy-3-methylbutanenitrile by spectroscopic and chemical methods. The absolute configuration of this glucoside was correlated with that of proacacipetalin by oxymercuration of the latter, followed by borohydride reduction of the product.
Over 90% of the cyanogenic precursors ofHevea seeds is stored in the endosperm tissue. During seedling development most of the cyanogenic material is consumed to form noncyanogenic compounds. No gaseous HCN is liberated in the course of this process. The ß-glucosidase, responsible for the cleavage of cyanogenic glucosides and the key enzyme for cyanogenesis is widely distributed over all tissues. The highest enzyme activity of the HCN-metabolizing ß-cyanoalaninesynthase is found in young seedling tissues. It is concluded, that the cyanogenic glucosides must be transported and metabolized in the young, growing tissues.
Two new glucosides, 3-β-d-glucopyranosyloxy-4-methyl-2(5H)-furanone and 4-β-d-glucopyranosyloxy-3-hydroxymethyl-butyronitril-2-en, were isolated from the hemolymph of adult Leptocoris isolata (Heteroptera). Besides these two compounds, the cyanogenic glucoside cardiospermin was found in whole adult bug extracts. The larvae contain the last two named compounds and a mixture of cyanolipids. Only the latter was found in the fruit of Allophylus cobbe, the host-plant of the insect. The possible relationship between the insect glucosides and the host-plant cyanolipids as well as their biological role is discussed.
This review will discuss several new drugs which were discovered and developed in recent years from traditional Chinese medicines by the Shanghai Institute of Materia Medica. Huperzine A was isolated from Huperzia serrata, a plant used for the treatment of contusion, strain, haematuria, and swelling in Chinese folk medicine. Pharmacological studies have indicated that huperzine A has powerful and reversible anticholinesterase activity. Y-maze methods have shown that huperzine A improves learning and retrieval processes, and facilitates memory retention. Huperzine A is used to treat patients with myasthenia gravis and Alzheimer's disease in China. Sarmentosin, a cyanogenic glucoside was isolated from the whole plant of Sedum sarmentosium. This plant has long been used to treat hepatitis by folk medicine. Sarmentosin significantly lowers the SGPT level of patients suffering from chronic viral hepatitis, and shows a suppressive effect on cell-mediated immune responses in mice. The root of Aconitum is well known in traditional Chinese medicine. Many Aconitum alkaloids have been isolated. Most show potent bioactivities, but with severe toxicity. Recently, some alkaloids such as 3-acetylaconitine, lappaconitine, have shown significant anesthetic activity and exhibit a higher therapeutic index. Guan-fu base A was isolated from the tuber root of Aconitum coreanum. Guan-fu base A has antiarrhythmic action and is now in clinical trials. Drug Dev. Res. 39:147–157. © 1997 Wiley-Liss, Inc.
[GRAPHICS] Leaves of the edible passion fruit plant, Passiflora edulis, contain benzylic beta -D-allopyranosides 1 and 2, representatives of a rare class of natural glycosides with D-allose as the only sugar constituent. The glycoside 1 is the first known cyanogenic glycoside containing a sugar different from D-glucose attached directly to the cyanohydrin center, Asymmetric perturbation of the L-1(b) transition of the benzene chromophore was shown to be useful for determination of absolute configuration of the cyanohydrin center of aromatic cyanogenic glycosides.
Five cyanohydrin glycosides with a cyclopentene ring, tetraphyllin A, tetraphyllin B, tetraphyllin B sulphate, deidaclin and volkenin, were isolated from Passiflora foetida grown from seeds collected on the Galápagos Islands. By contrast, P. foetida collected on Réunion Island contained the valine-derived glycoside linamarin, along with the cyclopentanoids tetraphyllin B, volkenin and tetraphyllin B sulphate. The chemical differences between the two populations were accompanied by pronounced morphological differences. This is the first report of two populations of the same species, having different patterns of cyclopentanoid and valine-derived glycosides.
A novel non-cyanogenic cyanoglucoside, 1-cyano-3-β-d-glucopyranosyloxy-(Z)-1-methyl-1-propene, was isolated from the latex of Jatropha multifida. The compound was named multifidin.
The effects of extracts ofRhodiola rosea radix on blood levels of inflammatory C-reactive protein and creatinine kinase were studied in healthy untrained volunteers before and after exhausting exercise.Rhodiola rosea extract exhibited an antiinflammatory effect and protected muscle tissue during exercise.
A microsomal fraction from Trifolium repens L. shoots of genotype Ac Ac has been used in the study of the biosynthesis of the two glucosides, linamarin and lotaustralin. It was demonstrated that it is likely that one set of enzymes is responsible for the biosynthesis of both hydroxynitriles from their respective amino acid precursors. The nitrile precursor of linamarin, 2-methylpropane nitrile appears to be used much less effectively than the oxime precursor. The results are discussed in relation to the role of the Ac/ac locus in the genetic control of cyanogenic glucoside biosynthesis, and in relation to results obtained with Linum usitatissimum.
When [2-14C]cyclopentenylglycine was synthesized and fed to seedlings of Turnera ulmifolia, the label was incorporated into the nitrile group of the cyanogenic glycoside deidaclin. The amino acid cyclopentenylglycine was also found to occur naturally in Turnera ulmifolia. These findings indicate that cyclopentenyl cyanogenic glycosides are synthesized from the corresponding amino acids by the same pathway utilized in the biosynthesis of other cyanogenic glycosides.
Two cyano-glucosides have been isolated from leaves of Acacia sutherlandii. One is the previously described cyanogenic glucoside proacacipetalin and the other is the novel, non-cyanogenic, glycoside 1-cyano-2-β-D-glucopyranosyloxymethyl-(Z)-prop-1-en-3-ol which has been given the trivial name sutherlandin.
A revised and updated classification for the families of the flowering plants is provided. Newly adopted orders include Austrobaileyales, Canellales, Gunnerales, Crossosomatales and Celastrales. Pertinent literature published since the first APG classification is included, such that many additional families are now placed in the phylogenetic scheme. Among these are Hydnoraceae (Piperales), Nartheciaceae (Dioscoreales), Corsiaceae (Liliales), Triuridaceae (Pandanales), Hanguanaceae (Commelinales), Bromeliacae, Mayacaceae and Rapateaceae (all Poales), Barbeuiaceae and Gisekiaceae (both Caryophyllales), Geissolomataceae, Strasburgeriaceae and Vitaceae (unplaced to order, but included in the rosids), Zygophyllaceae (unplaced to order, but included in eurosids I), Bonnetiaceae, Ctenolophonaceae, Elatinaceae, Ixonanthaceae, Lophopyxidaceae, Podostemaceae (Malpighiales), Paracryphiaceae (unplaced in euasterid II), Sladeniaceae, Pentaphylacaceae (Ericales) and Cardiopteridaceae (Aquifoliales). Several major families are recircumscribed. Salicaceae are expanded to include a large part of Flacourtiaceae, including the type genus of that family; another portion of former Flacourtiaceae is assigned to an expanded circumscription of Achariaceae. Euphorbiaceae are restricted to the uniovulate subfamilies; Phyllanthoideae are recognized as Phyllanthaceae and Oldfieldioideae as Picrodendraceae. Scrophulariaceae are recircumscribed to include Buddlejaceae and Myoporaceae and exclude several former members; these are assigned to Calceolariaceae, Orobanchaceae and Plantaginaceae. We expand the use of bracketing families that could be included optionally in broader circumscriptions with other related families; these include Agapanthaceae and Amaryllidaceae in Alliaceae s.l., Agavaceae, Hyacinthaceae and Ruscaceae (among many other Asparagales) in Asparagaceae s.l., Dichapetalaceae in Chrysobalanaceae, Turneraceae in Passifloraceae, Erythroxylaceae in Rhizophoraceae, and Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae and Valerianaceae in Caprifoliaceae s.l. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 141, 399–436.
A cDNA encoding the multifunctional cytochrome P450, CYP71E1, involved in the biosynthesis of the cyanogenic glucoside dhurrin from Sorghum bicolor (L.) Moench was isolated. A PCR approach based on three consensus sequences of A-type cytochromes P450 – (V/I)KEX(L/F)R, FXPERF, and PFGXGRRXCXG – was applied. Three novel cytochromes P450 (CYP71E1, CYP98, and CYP99) in addition to a PCR fragment encoding sorghum cinnamic acid 4-hydroxylase were obtained.
Reconstitution experiments with recombinant CYP71E1 heterologously expressed in Escherichia coli and sorghum NADPH–cytochrome P450–reductase in L-α-dilaurylphosphatidyl choline micelles identified CYP71E1 as the cytochrome P450 that catalyses the conversion of p-hydroxyphenylacetaldoxime to p-hydroxymandelonitrile in dhurrin biosynthesis. In accordance to the proposed pathway for dhurrin biosynthesis CYP71E1 catalyses the dehydration of the oxime to the corresponding nitrile, followed by a C-hydroxylation of the nitrile to produce p-hydroxymandelonitrile. In vivo administration of oxime to E. coli cells results in the accumulation of the nitrile, which indicates that the flavodoxin/flavodoxin reductase system in E. coli is only able to support CYP71E1 in the dehydration reaction, and not in the subsequent C-hydroxylation reaction.
CYP79 catalyses the conversion of tyrosine to p-hydroxyphenylacetaldoxime, the first committed step in the biosynthesis of the cyanogenic glucoside dhurrin. Reconstitution of both CYP79 and CYP71E1 in combination with sorghum NADPH-cytochrome P450–reductase resulted in the conversion of tyrosine to p-hydroxymandelonitrile, i.e. the membranous part of the biosynthetic pathway of the cyanogenic glucoside dhurrin. Isolation of the cDNA for CYP71E1 together with the previously isolated cDNA for CYP79 provide important tools necessary for tissue-specific regulation of cyanogenic glucoside levels in plants to optimize food safety and pest resistance.
A bitter tasting cyanoglucoside, sarmentosin, was isolated from an aposematic Apollo butterfly,Parnassius phoebus, and from its plant-host,Sedum stenopetalum. The content of sarmentosin in the body tissues was as high as 500 g/insect, suggesting a defensive role for this substance; a high concentration was detected in the wings. Sarmentosin was also present in the eggs.
Cyanogenic glycosides are ancient biomolecules found in more than 2,650 higher plant species as well as in a few arthropod species. Cyanogenic glycosides are amino acid-derived β-glycosides of α-hydroxynitriles. In analogy to cyanogenic plants, cyanogenic arthropods may use cyanogenic glycosides as defence compounds. Many of these arthropod species have been shown to de novo synthesize cyanogenic glycosides by biochemical pathways that involve identical intermediates to those known from plants, while the ability to sequester cyanogenic glycosides appears to be restricted to Lepidopteran species. In plants, two atypical multifunctional cytochromes P450 and a soluble family 1 glycosyltransferase form a metabolon to facilitate channelling of the otherwise toxic and reactive intermediates to the end product in the pathway, the cyanogenic glycoside. The glucosinolate pathway present in Brassicales and the pathway for cyanoalk(en)yl glucoside synthesis such as rhodiocyanosides A and D in Lotus japonicus exemplify how cytochromes P450 in the course of evolution may be recruited for novel pathways. The use of metabolic engineering using cytochromes P450 involved in biosynthesis of cyanogenic glycosides allows for the generation of acyanogenic cassava plants or cyanogenic Arabidopsis thaliana plants as well as L. japonicus and A. thaliana plants with altered cyanogenic, cyanoalkenyl or glucosinolate profiles.