Nodulisporacid A (1) was isolated from a marine-derived fungus Nodulisporium sp. CRIF1, while vermelhotin (5) was obtained from an unidentified fungus CRI247-01 (a member of the Order Pleosporales). Both 1 and 5 occurred as equilibrium E/Z mixtures. Ester derivatives (2 and 3) and vermelhotin (5) showed cytotoxic activity against eleven cancer cell lines. Nodulisporacid A (1) and vermelhotin (5) exhibited moderate antiplasmodial activity.
Two pectinolytic enzymes were purified from the culture broth of Pseudomonas marginalis pv. marginalis MAFF 03-01173 with total 33% recovery of the initial activity. From the substrate specificities against pectin and polygalacturonic acid, the requirement of calcium ion for the enzymatic activity, and the N-terminal sequences, the enzymes were identified as pectin lyase and pectate lyase. The M,s of pectin lyase and pectate lyase were estimated to be 34,000 and 43,000, respectively, by SDS polyacrylamide gel electrophoresis. Both enzymes showed almost the same pH dependent activity curves with the highest activity at pH 8.3
Chemical investigation of the culture broth extracts of the marine-derived fungus Massarina sp. (strain CNT-016) has yielded two secondary metabolites, spiromassaritone (1) and massariphenone (2), as well as the previously reported fungal metabolites 6-epi-5'-hydroxy-mycosporulone (3) and enalin A (4). The structures of these compounds were established by a variety of one- and two-dimensional NMR experiments, while the relative configuration of spiromassaritone (1) was determined by X-ray crystallographic methods. The fungal strain was isolated as a sterile mycelium from an ocean mud sample and identified using ITS sequence analysis.
Cyclopropane-1,1-dicarboxylic acid (CDA) and trans-2-phenylcyclopropane-1-carboxylic acid (PCCA) are the main representatives of a group of compounds that are structural analogues of 1-aminocyclopropane-1-carboxylic acid (ACC) and have been proved to have an inhibitory effect on the wound ethylene produced by Lycopersicum esculentum fruit discs. During the experiments, that were carried out in this work the inhibition pattern of PCCA and CDA were studied when tested on partially purified apple ACO and their Ki values were determined. A mechanistic proposal was given, in order to explain the kinetic behaviour of the inhibitors. The common feature of these molecules is their cyclopropane ring, with different substitutes mainly at the positions C1 and C2. Two other compounds with similar structure where also tested as inhibitors, in order to clarify the relationship between structure and activity. These compounds are: 2-methyl cyclopropanecarboxylic acid (MCA), and cyclopropanecarboxylic acid (CCA).
Phalaenopsis hybrids contain two 1,2-saturated pyrrolizidine monoesters, T-phalaenopsine (necine base trachelanthamidine) and its stereoisomer Is-phalaenopsine (necine base isoretronecanol). T-Phalaenopsine is the major alkaloid accounting for more than 90% of total alkaloid. About equal amounts of alkaloid were genuinely present as free base and its N-oxide. The structures were confirmed by GC-MS. The quantitative distribution of phalaenopsine in various organs and tissues of vegetative rosette plants and flowering plants revealed alkaloid in all tissues. The highest concentrations were found in young and developing tissues (e.g., root tips and young leaves), peripheral tissues (e.g., of flower stalks) and reproductive organs (flower buds and flowers). Within flowers, parts that usually attract insect visitors (e.g., labellum with colorful crests as well as column and pollinia) show the highest alkaloid levels. Tracer feeding experiments with (14)C-labeled putrecine revealed that in rosette plants the aerial roots were the sites of phalaenopsine biosynthesis. However active biosynthesis was only observed in roots still attached to the plant but not in excised roots. There is a slow but substantial translocation of newly synthesized alkaloid from the roots to other plant organs. A long-term tracer experiment revealed that phalaenopsine shows neither turnover nor degradation. The results are discussed in the context of a polyphyletic molecular origin of the biosynthetic pathways of pyrrolizidine alkaloids in various scattered angiosperm taxa. The ecological role of the so called non-toxic 1,2-saturated pyrrolizidine alkaloids is discussed in comparison to the pro-toxic 1,2-unsaturated pyrrolizidine alkaloids. Evidence from the plant-insect interphase is presented indicating a substantial role of the 1,2-saturated alkaloids in plant and insect defense.
Eight new alkaloids, the pyrido[1,2-a]azepines stemokerrin, methoxystemokerrin-N-oxide, oxystemokerrin, oxystemokerrin-N-oxide, and pyridostemin, along with the pyrrolo[1,2-a]azepines dehydroprotostemonine, oxyprotostemonine, and stemocochinin were isolated from four Stemona species together with the known compounds protostemonine, stemofoline, 2'-hydroxystemofoline, and parvistemonine. Their structures were elucidated by 1H and 13C NMR including 2D methods and two key compounds additionally by X-ray diffraction. Besides the formation of a six membered piperidine ring, additional oxygen bridges and N-oxides contributed to structural diversity. The co-occurrence of pyrrolo- and pyridoazepines suggested biosynthetic connections starting from more widespread protostemonine type precursors. Bioassays with lipophilic crude extracts against Spodoptera littoralis displayed very strong insecticidal activity for the roots of S. curtisii and S. cochinchinensis, moderate activity for S. kerrii, but only weak effects for the unidentified species HG 915. The insect toxicity was mainly caused by the accumulation of stemofoline, oxystemokerrin, and dehydroprotostemonine displaying two different modes of action. Based on the various insecticidal activities of 13 derivatives structure-activity relationships became apparent.
A synthase which oxidizes (S)-reticuline to 1,2-dehydroreticuline has been found to occur in seedlings of opium poppy (Papaver somniferum L.). Due to its instability, this enzyme could only be partly purified (ca. 5-fold enrichment). Partial characterization at this stage of purification showed that it does not need a redox cofactor and accepts both (S)-reticuline and (S)-norreticuline as substrates. [1-(2)H, (13)C]-(R,S)-reticuline was enzymatically converted into [1-(13)C]-dehydroreticuline, which has been identified by mass spectrometry. Release of the hydrogen atom in position C-1 of the isoquinoline alkaloid during the oxidative conversion, was exploited as a sensitive assay system for this enzyme. The enzyme has a pH optimum of 8.75, a temperature optimum of 37 degrees C and the apparent K(M) value for the substrate reticuline was shown to be 117 microM. Moreover it could be demonstrated by sucrose density gradient centrifugation that the enzyme is located in vesicles of varying size. In combination with the previously discovered strictly stereoselective and NADPH dependent 1,2-dehydroreticuline reductase the detection of this enzyme, the 1,2-dehydroreticuline synthase, provides the necessary inversion of configuration and completes the pathway from two molecules of L-tyrosine via (S)-norcoclaurine to (R)-reticuline in opium poppy involving a total number of 11 enzymes.
The endemic Mexican genus Pittocaulon (subtribe Tussilagininae, tribe Senecioneae, Asteraceae) belongs to a monophyletic group of genera distributed in Mexico and North America. The five Pittocaulon species represent shrubs with broom-like succulent branches. All species were found to contain pyrrolizidine alkaloids (PAs). With one exception (i.e., stems of Pittocaulon velatum are devoid of PAs) PAs were found in all plant organs with the highest levels (up to 0.3% of dry weight) in the flower heads. Three structural types of PAs were found: (1) macrocyclic otonecine esters, e.g. senkirkine and acetylpetasitenine; (2) macrocyclic retronecine esters, e.g. senecionine, only found in roots, and (3) monoesters of 1,2-saturated necines with angelic acid. For an unambiguous assignment of the different stereoisomeric 1,2-saturated necine bases a GC-MS method was established that allows the separation and identification of the four stereoisomers as their diacetyl or trimethylsilyl derivatives. All otonecine esters that generally do not form N-oxides and the 1,2-saturated PAs were exclusively found as free bases, while the 1,2-unsaturated 7-angeloylheliotridine occurring in P. velatum was found only as its N-oxide. In a comparative study the 1H and 13C NMR spectra of the four stereoisomeric necine bases were completely assigned by the use of DEPT-135, H,H-COSY, H,C-HSQC and H,H-NOESY experiments and by iterative analysis of the 1H NMR spectra. Based on these methods the PA monoesters occurring in Pittocaulon praecox and P. velatum were assigned as 7-O-angeloyl ester respectively 9-O-angeloyl ester of dihydroxyheliotridane which could be identified for the first time as naturally occurring necine base. Unexpectedly, in the monoesters isolated from the three other Pittocaulon species dihydroxyheliotridane is replaced by the necine base turneforcidine with opposite configuration at C-1 and C-7. The species-specific and organ-typical PA profiles of the five Pittocaulon species are discussed in a biogenetic context.
Biotransformation of 3,6-dialkylcyclohexane-1,2-diones by cell suspension cultures of Marchantia polymorpha involves regioselective oxidative cleavage of the C-C bond to give the corresponding oxocarboxylic acids shortened by one carbon unit. In the case of cyclohexane-1,2-dione, adipic acid was obtained.
myo-Inositol-1,2,3,4,5,6-hexakisphosphate (Ins P(6)) was first described as an abundant form of phosphorus in plant seeds and other plant tissues and dubbed "phytic acid". Subsequently it was found to be a common constituent in eukaryotic cells, its metabolism a basic component of cellular housekeeping. In addition to phosphate, myo-inositol (Ins) and mineral storage and retrieval in plant organs and tissues, other roles for Ins P(6) include service as a major metabolic pool in Ins phosphate and pyrophosphate pathways involved in signaling and regulation; possibly as an effector or ligand in these processes; as a form of energy currency and in ATP regeneration; in RNA export and DNA repair; and as an anti-oxidant. The relatively recent demonstration that pyrophosphate-containing derivatives of Ins P(6) can function as phosphate donors in the regeneration of ATP is reminiscent of the proposal, made four decades ago in studies of seed development, that Ins P(6) itself may serve in this function. Studies of Ins P(6) in non-plant systems rarely include the consideration that this compound might represent a significant fraction of cellular P; cellular phosphate nutrition has been viewed as either not interesting or of little importance. However, there may be few fundamental differences among diverse eukaryotes in both the metabolic pathways involving Ins P(6) and the spectrum of possible roles for it and its metabolites.
A novel di-hydroxycinnamoylquinic acid ester, 1,3-di-O-trans-feruloylquinic acid (DFQA), was isolated from roots of nutrient-deprived Brachiaria species--the most widely sown tropical forage grasses in South America. In contrast to other so far characterized quinic-acid esters, DFQA exists in a chair conformation with the carboxylic group in the axial orientation. It accumulates in older parts of the root system, but not in root apices or shoots. Higher levels were found in B. ruziziensis, which is poorly adapted to infertile acid soils, than in well adapted B. decumbens. DFQA was also found in the soil, most likely as a result of root decay, because it was not detected in root exudates of plants cultivated in solution culture. Nitrogen and phosphorus deficiency--but not aluminum toxicity or deprivation of other nutrients--stimulated its synthesis in roots. Its accumulation was correlated with a shift in biomass partitioning toward the root system.
The lutoid-body (bottom) fraction of latex from the rubber tree (Hevea brasiliensis) contains a limited number of major proteins. These are, besides the chitin-binding protein hevein, its precursor and the C-terminal fragment of this precursor, proteins with enzymic activities: three hevamine components, which are basic, vacuolar, chitinases with lysozyme activity, and a beta-1,3-glucanase. Lutoid-body fractions from three rubber-tree clones differed in their contents of these enzyme proteins. The hevamine components and glucanase were isolated and several enzymic and structural properties were investigated. These enzymes are basic proteins and cause coagulation of the negatively charged rubber particles. The coagulation occurs in a rather narrow range of ratios of added protein to rubber particles, which indicates that charg neutralization is the determining factor. Differences in coagulation of rubber particles by lutoid-body fractions from various rubber clones can be explained by their content of hevamine and glucanase. Glucanase from the lutoid-body fraction may dissolve callus tissue and this may explain the observation that rubber-tree clones with a high glucanase content in this fraction produce more latex than clones with little glucanase. Sequence studies of two CNBr peptides of the glucanase indicate that this protein is homologous with glucanases from other plants, and that a C-terminal peptide, possibly involved in vacuolar targeting, may have been cleaved off.
Callose consists mostly of (1,3)-beta-D-glucan and is synthesised in many plant tissues during growth and development, where it is believed to play a fundamental role in cell plate formation during cell division. Callose deposition also represents an important response to pathogen attack, wounding and to various abiotic stresses. Here, the transcription patterns of members of the callose synthase gene family from barley (Hordeum vulgare) were defined. Thus, fragments of six barley (1,3)-beta-D-glucan synthase-like (GSL) cDNAs were obtained by PCR amplification using primers designed to barley expressed sequence tag (EST) sequences. The HvGSL genes, designated HvGSL2 to HvGSL7, were mapped to individual loci that were distributed across the barley genome on chromosomes 3H, 4H, 6H and 7H. The HvGSL1 gene has been isolated and characterised previously. Transcript levels for all the genes were analysed by quantitative real-time PCR in a range of barley tissues and organs, at various developmental stages. High levels of transcript for many of the HvGSL genes were detected in endosperm during the early stages of grain development, when cellularisation of the endosperm was occurring and it is likely that many of the genes participate in this process. Transcripts of HvGSL1 and HvGSL5 mRNAs were significantly more abundant than other GSL mRNAs in the roots of young seedlings, while HvGSL7 mRNA was detected at relatively high levels along the length of two week old shoots.
The Agrobacterium rhizogenes rolC oncogene is capable of stimulating production of secondary metabolites in transformed plant cells that suggest its possible involvement in plant defense reactions. We tested whether the gene could also affect production of pathogenesis-related proteins. Using a well-known group of PR-proteins, such as beta-1,3-glucanases, we observed a 10-fold increase in total beta-1,3-glucanase activity in rolC-transformed Panax ginseng cells compared with normal cells. The increase was due to the production of a salicylic acid-activated beta-1,3-glucanase isoform. We isolated cDNA of the corresponding beta-1,3-glucanase gene (Pg-glu1), which shared 38-60% sequence identity with previously reported sequences of plant beta-1,3-glucanases at the protein level. Levels of Pg-glu1 mRNA transcripts were tightly correlated with expression of the rolC gene. Our data, together with previously reported information, indicate that A. rhizogenes can activate plant defense reactions via expression of T-DNA oncogenes.
Surface extracts from primary leaves of Castor bean were found to contain 1.8 microg cm(-2) of cuticular waxes. The mixture comprised alkanes (C(26)-C(29)), primary alcohols (C(22)-C(38)), aldehydes (C(26) and C(28)), fatty acids (C(20)-C(34)) and triterpenoids (lupeol, beta- and alpha-amyrin). Besides, a series of n-alkane-1,3-diols was detected, with chain lengths ranging from C(22) to C(28), a strong predominance of even-numbered homologs, and a maximum for hexacosane-1,3-diol. Seven other compounds were assigned to a novel class of wax constituents and identified as homologous unbranched 3-hydroxyaldehydes ranging from C(22) to C(28). As the chain length distribution of this series closely paralleled the homolog pattern of 1,3-diols, it seems likely that both compound classes are biosynthetically related.
The only known natural source of the volatile bioactive compounds bullatenone 1 and 4-methyl-1-phenylpentane-1,3-dione 2 is the New Zealand endemic shrub Lophomyrtus bullata (Myrtaceae). GC and NMR analyses of essential oils and solvent extracts of L. bullata, L. obcordata and the hybrid L. "ralphii" showed several chemotypes, which did not correlate with species. Levels of 1 and 2 varied from dominant to low/undetectable and the most common chemotype was rich in allo-aromadendrene and other sesquiterpenes. The rare natural product E-4-methyl-1-phenyl-1-penten-3-one 4 was detected for the first time in this genus. The non-volatile cytotoxic compound bullataketal 5 co-occurred with bullatenone 1. An essential oil from the relatively rare bullatenone 1 chemotype showed antifungal activity against Candida albicans and Cladosporium resinae, and an oil from the 4-methyl-1-phenylpentane-1,3-dione 2 chemotype showed antibacterial activity against Bacillus subtilis.
A 1,3-β-glucanase with potent cryoprotective activity was purified to homogeneity from the mesocarp of CO(2)-treated cherimoya fruit (Annona cherimola Mill.) stored at low temperature using anion exchange and chromatofocusing chromatography. This protein was characterized as a glycosylated endo-1,3-β-glucanase with a M(r) of 22.07kDa and a pI of 5.25. The hydrolase was active and stable in a broad acidic pH range and it exhibited maximum activity at pH 5.0. It had a low optimum temperature of 35°C and it retained 40% maximum activity at 5°C. The purified 1,3-β-glucanase was relatively heat unstable and its activity declined progressively at temperatures above 50°C. Kinetic studies revealed low k(cat) (3.10±0.04s(-1)) and K(m) (0.32±0.03mgml(-1)) values, reflecting the intermediate efficiency of the protein in hydrolyzing laminarin. Moreover, a thermodynamic characterization revealed that the purified enzyme displayed a high k(cat) at both 37 and 5°C, and a low E(a) (6.99kJmol(-1)) within this range of temperatures. In vitro functional studies indicated that the purified 1,3-β-glucanase had no inhibitory effects on Botrytis cinerea hyphal growth and no antifreeze activity, as determined by thermal hysteresis analysis using differential scanning calorimetry. However, a strong cryoprotective activity was observed against freeze-thaw inactivation of lactate dehydrogenase. Indeed, the PD(50) was 8.7μgml(-1) (394nM), 9.2-fold higher (3.1 on a molar basis) than that of the cryoprotective protein BSA. Together with the observed accumulation of glycine-betaine in CO(2)-treated cherimoya tissues, these results suggest that 1,3-β-glucanase could be functionally implicated in low temperature-defense mechanism activated by CO(2).
Our work with almond peptide N-glycosidase A made us interested also in the alpha1,3/4-fucosidase which is used as a specific reagent for glycoconjugate analysis. The enzyme was purified to presumed homogeneity by a series of chromatographic steps including dye affinity and fast-performance anion exchange chromatography. The 63 kDa band was analyzed by tandem mass spectrometry which yielded several partial sequences. A homology search retrieved the hypothetical protein Q8GW72 from Arabidopsis thaliana. This protein has recently been described as being specific for alpha1,2-linkages. However, cDNA cloning and expression in Pichia pastoris of the A. thaliana fucosidase showed that it hydrolyzed fucose in 3- and 4-linkage to GlcNAc in Lewis determinants whereas neither 2-linked fucose nor fucose in 3-linkage to the innermost GlcNAc residue were attacked. This first cloning of a plant alpha1,3/4-fucosidase also confirmed the identity of the purified almond enzyme and thus settles the notorious uncertainty about its molecular mass. The alpha1,3/4-fucosidase from Arabidopsis exhibited striking sequence similarity with an enzyme of similar substrate specificity from Streptomyces sp. (Q9Z4I9) and with putative proteins from rice.
Two benzophenones, hypericophenonoside (1) and annulatophenone (2) were isolated from the methanol extract of the herb of Hypericum annulatum. The structures of the benzophenones were established as 2'-O-beta-D-glucopyranosyl-2,4,5',6-tetrahydroxy benzophenone (1) and 2,3',5',6-tetrahydroxy-4-methoxybenzophenone (2) based on spectral and chemical evidence. Hypericophenonside is the second benzophenone O-glycoside found in nature. Acid and enzymatic hydrolysis of (1) led directly to the formation of 1,3,7-trihydroxyxanthone (gentisein). This fact confirmed the hypothesis that some xanthones could be formed in plants by dehydration of 2,2'-dihydroxybenzophenones, and the intermediate precursors appear to be benzophenone O-glycosides ortho to the carbonyl function.
Theacrine (1,3,7,9-tetramethyluric acid) and caffeine were the major purine alkaloids in the leaves of an unusual Chinese tea known as kucha (Camellia assamica var. kucha). Endogenous levels of theacrine and caffeine in expanding buds and young leaves were ca. 2.8 and 0.6-2.7% of the dry wt, respectively, but the concentrations were lower in the mature leaves. Radioactivity from S-adenosyl-L-[methyl-14C]methionine was incorporated into theacrine as well as theobromine and caffeine by leaf disks of kucha, indicating that S-adenosyl-L-methionine acts as the methyl donor not only for caffeine biosynthesis but also for theacrine production. [8-14C]Caffeine was converted to theacrine by kucha leaves with highest incorporation occurring in expanding buds. When [8-14C]adenosine, the most effective purine precursor for caffeine biosynthesis in tea (Camellia sinensis), was incubated with young kucha leaves for 24 h, up to 1% of total radioactivity was recovered in theacrine. However, pulse-chase experiments with [8-14C]adenosine demonstrated much more extensive incorporation of label into caffeine than theacrine, possibly because of dilution of [14C]caffeine produced by the large endogenous caffeine pool. These results indicate that in kucha leaves theacrine is synthesized from caffeine in what is probably a three-step pathway with 1,3,7-methyluric acid acting an intermediate. This is a first demonstration that theacrine is synthesized from adenosine via caffeine.
In order to clarify the biosynthetic origin of 2-geranyl-1,4-naphthoquinone and its biogenetically related anthraquinone, which are possible intermediates of anthrasesamones, [1-(13)C]glucose was administered to a hairy root culture of Sesamum indicum. The labeling patterns of these quinone derivatives indicated that the naphthoquinone ring and geranyl side-chain of geranylnaphthoquinone were respectively biosynthesized through the shikimate and methylerythritol phosphate pathways, and that these quinone derivatives have the same biosynthetic origin.
From the dichloromethane extract of the leaves and stems of Gunnera perpensa two new, simple 1,4-benzoquinones and a known benzopyran-6-ol were isolated. From the methanol extract phytol was obtained. The two benzoquinones, 2-methyl-6-(-3-methyl-2-butenyl)benzo-1,4-quinone (1) and 3-hydroxy-2-methyl-5-(3-methyl-2-butenyl)benzo-1,4-quinone (2) and the benzopyran, 6-hydroxy-8-methyl-2,2-dimethyl-2H-benzopyran (3) were examined for antimicrobial properties together with the crude stem, leaf and root extracts. Minimum inhibitory concentration (MIC) assays were used to quantify antimicrobial activity and the MIC values for the crude extracts of stems, roots and leaves ranged between 100 microg and >16 mg/ml against the eight microorganisms investigated. Compound 1 showed significant antimicrobial activity with the most sensitive organism being Staphylococcus epidermidis with an MIC of 9.8 microg/ml. For compound 2, no activity was noted. Compound 3 exhibited good activity against the yeasts Cryptococcus neoformans (75 microg/ml) and Candida albicans (37.5 microg/ml).
The ring expansion of 3-hydroxyindolin-2-one to 2-hydroxy-1,4-benzoxazin-3-one (HBOA) was investigated by labelling experiments. Action of the cytochrome P450 enzyme BX4 from maize on 3-hydroxyindolin-2-one under an 18O2 atmosphere induced production of 2-hydroxy-1,4-benzoxazin-3-one in which the ring oxygen--but not the 2-hydroxy group of HBOA--is labelled. A mechanism for this transformation is proposed.
Naturally occurring dimeric 1,4-benzoquinone derivatives, belamcandaquinones F, G, H, and I, as well as one resorcinol derivative and four known compounds, were isolated from rhizomes of Ardisia gigantifolia. Their structures were established by means of spectroscopic analyses. All compounds were tested against cell lines PC-3, EMT6, A549, Hela, RM-1, and SGC7901 for cytotoxicity in vitro. In comparison with cisplatin, compounds 5 and 6 showed a strong cytotoxicity with IC(50) values less than 30 microM for most cell lines tested.
Cellulase expressions in a normal shedding wild-type and a non-abscinding single gene mutant of Lupinus angustifolius have been studied during ethylene treatments of leaf abscission zone explants. Of the range of different glycohydrolases investigated only the abscission cell-specific beta-1,4-glucanhydrolase (cellulase) was not produced in the non-abscinding mutant. An endo-polygalacturonase was induced equally in both wild-type and mutant and other glycohydrolases were equally up-regulated. The abscission cell-specific cellulase induced at shedding of wild-type is antigenically similar to the Phaseolus vulgaris induced leaf abscission pI 9.5 cellulase but with a higher molecular mass (50 kD compared with 48 kD) and like the bean abscission-specific cellulase that of lupin is not glycosylated. Causes of the loss of function of cellulase expression in the non-shedding mutant are discussed.
The kinetic properties and active site amino acids of alpha-1,4-glucan lyase from the marine red macroalga Gracilariopsis sp. were examined. Using 1H NMR spectroscopy the alpha-1,4-glucan lyase was found to degrade alpha- and beta-maltose at different rates. The effect of pH on the kinetic constants suggested the presence of two catalytically important amino acids in the active site with pKa values of 3.5 and 6.2. The former indicated the presence of an ionised aspartate or glutamate residue in the active site. This was tested using the carboxyl specific reagent EDAC, which inhibited enzyme activity in a time dependent manner when an external nucleophile was added. No protection against the inactivation was obtained by addition of amylopectin, maltitol or 1-deoxinojirimycin. Inactivation decreased Vmax over 2.5-fold with little effect on Km which supports the direct involvement of a carboxyl group in catalysis.
Accumulation of 2-(2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one)-beta-D-glucopyranose (HDMBOA-Glc) was induced in maize leaves by treatment with CuCl2, chitopentaose, penta-N-acetylchitopentaose, or jasmonic acid (JA). The accumulation of HDMBOA-Glc was accompanied by a decrease in level of 2-(2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one)-beta-D-glucopyranose (DIMBOA-Glc). When the leaf segments were treated with JA in the presence of [Me-2H3]L-methionine, the label was efficiently incorporated into HDMBOA-Glc, while no incorporation into DIMBOA-Glc or HMBOA-Glc was detected, suggesting the conversion of constitutive DIMBOA-Glc to HDMBOA-Glc by methylation at the 4-position. Levels of endogenous JA and its leucine conjugate transiently increased prior to the accumulation of HDMBOA-Glc in leaf segments treated with CuCl2 and chitopentaose. The lipoxygenase inhibitor ibuprofen suppressed the accumulation of HDMBOA-Glc induced by CuCl2 treatment, and the reduced accumulation of HDMBOA-Glc was recovered by addition of JA. These findings suggested that JA functions as a signal transducer in the induction of HDMBOA-Glc accumulation.
Unknown proteins isolated from mutant tissues of rice (Oryza sativa L.) recovered from inhibitor selections were subsequently peptide microsequenced. Database searches putatively identified one peptide as fructose 1,6-bisphosphate aldolase (EC 184.108.40.206). Tissues of mutant rice, PI564784, and wild type (cv Calrose 76) tissues were evaluated for aldolase activity. Total enzyme activities were slightly lower in the mutant than the control but the differences were not significant. Although the mutant phenotype is for enhanced lysine and protein, we ascribe the small aldolase differences to physiological adjustments, rather than to DNA modifications of the aldolase gene(s). Homologies of rice peptides with aldolases from a range of species, as well as rice cell culture expressed sequence tags (ESTs) are presented. Some amino acids sequences are highly conserved. The mutant phenotype expressing stress proteins is not likely to be defined by a change in rice aldolases.
Biotransformation of sesquiterpene 4beta-hydroxyeudesmane-1,6-dione by the filamentous fungi Gliocladium roseum and Exserohilum halodes was achieved. With Exserohilum halodes, only one metabolite was obtained, as a result of the regio- and stereoselective reduction of the keto group at C-1, which is difficult to achieve by chemical means. Five metabolites were produced with Gliocladium roseum, three of which, the 7alpha-hydroxylated, the 7alpha,11- and the 1alpha,8alpha-dihydroxylated derivatives, have not previously been reported. The hydroxylation at C-11 is the main action of this microorganism. These 11-hydroxylated compounds can be chemically transformed into 6beta,12-eudesmanolides.
Cytosolic fructose-1,6-P(2) (FBP) aldolase (ALD(c)) from germinated mung beans has been purified 1078-fold to electrophoretic homogeneity and a final specific activity of 15.1 micromol FBP cleaved/min per mg of protein. SDS-PAGE of the final preparation revealed a single protein-staining band of 40 kDa that cross-reacted strongly with rabbit anti-(carrot ALD(c))-IgG. The enzyme's native M(r) was determined by gel filtration chromatography to be 160 kDa, indicating a homotetrameric quaternary structure. This ALD is a class I ALD, since EDTA or Mg(2+) had no effect on its activity, and was relatively heat-stable losing 0-25% of its activity when incubated for 5 min at 55-65 degrees C. It demonstrated: (i) a temperature coefficient (Q(10)) of 1.7; (ii) an activation energy of 9.2 kcal/mol active site; and (iii) a broad pH-activity optima of 7.5. Mung bean ALD(c) is bifunctional for FBP and sedoheptulose-1,7-P(2) (K(m) approximately 17 microM for both substrates). ATP, ADP, AMP and ribose-5-P exerted inhibitory effects on the activity of the purified enzyme. Ribose-5-P, ADP and AMP functioned as competitive inhibitors (K(i) values=2.2, 3.1 and 7.5mM, respectively). By contrast, the addition of 2mM ATP: (i) reduced V(max) by about 2-fold, (ii) increased K(m)(FBP) by about 4-fold, and (iii) shifted the FBP saturation kinetic plot from hyperbolic to sigmoidal (h=1.0 and 2.6 in the absence and presence of 2mM ATP, respectively). Potent feedback inhibition of ALD(c) by ATP is suggested to help balance cellular ATP demands with the control of cytosolic glycolysis and respiration in germinating mung beans.
Individual leaves of the three most common chemotypes of Melaleuca alternifolia were examined both quantitatively and qualitatively for volatile constituents from the emergence of the first true leaves, through to 6-week-old tenth leaf set material. The 1,8-cineole and terpinolene chemotypes were investigated and compared with the recently reported commercial terpinen-4-ol chemotype. The 1,8-cineole chemotype was found to accumulate 1,8-cineole and associated p-menthanes limonene, terpinen-4-ol and alpha-terpineol gradually with increasing leaf set number. As with the terpinen-4-ol variety, higher than expected concentrations of the pinenes and terpinolene were found only in the early leaf sets. The terpinolene variety showed two stages of terpinolene accumulation, the first at leaf sets 2-3 similar to the unexpected biosynthesis of terpinolene in the terpinen-4-ol chemotype and the second at leaf sets 8-9 which is characteristic of the terpinolene variety.
From the rootstock of Scabiosa columbria L. loganin and sweroside were isolated. Sweroside showed moderate antibacterial activity. Pure sweroside was converted to the sweroside aglycone 1-acetoxy derivative (DABCO/Ac2O) after hydrolysis of the glucose unit. X-ray crystallography of the monoacetate showed unambiguously that it had been transformed to a new seco-iridoid having the novel trans diaxial configuration for the protons on C-1, C-9 and C-5. The mechanism for the rearrangement is discussed.
The atropisomeric austrocolorins A(1) (7) and B(1) (8), new members of the rare tricolorin class of 10,10'-coupled dihydroanthracenones, are isolated from an indigenous Australian toadstool belonging to the subgenus Dermocybe of Cortinarius, and their structure and absolute central and axial configuration is deduced from the spectroscopic data, and confirmed by chemical degradation and chiral HPLC analysis.
Activity-guided investigation of Cyperus rotundus tubers led to the isolation of patchoulenone, caryophyllene alpha-oxide, 10,12-peroxycalamenene and 4,7-dimethyl-1-tetralone. The antimalarial activities of these compounds are in the range of EC50 10(-4)-10(-6) M, with the novel endoperoxide sesquiterpene, 10,12-peroxycalamenene, exhibiting the strongest effect at EC50 2.33 x 10(-6) M.
The first asymmetric syntheses of the cutin monomers (R)- and (S)-10,16-dihydroxyhexadecanoic acid (10,16-DHPA) and confirmation of (S)(+)-absolute configuration for 10,16-DHPA derived from tomato are reported. The individual DHPA stereoisomers display differences in their ability to activate the fungal pathogen Colletotrichum trifolii.
1H NMR spectroscopy is one of the techniques whose potential is currently being explored in the emerging field of metabolomics. It is a non-targeted method, producing signals for all proton-containing chemical species. For crude plant materials the spectra are always complex, with many signals overlapping. Hence a most suitable approach for analysing them is 'metabolite fingerprinting', which is aimed at highlighting compositional similarities and exploring the overall natural variability in a population of samples. The most commonly used method for this is principal component analysis (PCA), as it allows the whole spectral trace to be analysed and the vast quantity of information to be simplified. In this paper we investigate whether there are factors which may affect the NMR spectra in a way that subsequently decreases the robustness of the metabolite fingerprinting by PCA. Imperfections in the signal registration (i.e. inconsistency of the peak position) are generally detrimental to analysing whole traces by multivariate methods. The sources of such problems are illustrated through specially designed repeatability studies using potato and tomato samples, and the analysis of a tea dataset containing many samples. Careful sample preparation can help to limit peak shifts; for instance here by attempting to control the pH of the extracts. In addition, some compounds are susceptible to interactions affecting their chemical shifts and mathematical alignment of peaks may be necessary. Lastly factors such as resolution can also affect analyses and must be carefully adjusted. Our choice of examples aims to raise awareness of potential problems. We do not question the validity of the NMR approach, but point out those areas where special care may need to be taken.
PR-10c is a unique member of PR-10 proteins in birch, since it is the only one known to be post-translationally modified by glutathione and is not constitutively expressed in pollen. Both reduced and S-glutathiolated forms of PR-10c show low ribonuclease activity. However, the major function of the protein is apparently not yet resolved. Our protein-ligand interaction studies with saturation transfer difference (STD) NMR revealed that PR-10c interacts with several biologically important molecules, including cytokinin, flavonoid glycosides, sterols and emodin. Competition study with deoxycholate and kinetin revealed no statistically significant binding interference, indicating that these ligands have different binding sites in PR-10c. Ligand docking studies with a molecular model of PR-10c support the STD NMR results of ligand binding and binding epitopes, suggesting that there are three potential binding sites in PR-10c: two in the hydrophobic cavity and one in the glycine-rich loop. Our docking calculations suggested that only kinetin interacts with the glycine-rich loop, the binding occurring through its adenine moiety. Clear ligand specificity could be observed in the binding of nucleotide derivatives. S-glutathiolation of PR-10c did not affect kinetin binding. The present results suggest that birch PR-10c is a multifunctional protein, which has diverse roles in plant stress responses.
Profiling of sesquiterpene hydrocarbons in extracts of goldenrod, Solidago canadensis, by GC-MS revealed the presence of both enantiomers of germacrene D and lesser amounts of germacrene A, alpha-humulene, and beta-caryophyllene. A similarity-based cloning strategy using degenerate oligonucleotide primers, based on conserved amino acid sequences in known plant sesquiterpene synthases and RT-PCR, resulted in the isolation of a full length sesquiterpene synthase cDNA. Functional expression of the cDNA in E. coli, as an N-terminal thioredoxin fusion protein using the pET32b vector yielded an enzyme that was readily purified by nickel-chelate affinity chromatography. Chiral GC-MS analysis of products from of (3)H- and (2)H-labelled farnesyl diphosphate identified the enzyme as (+)-(10R)-germacrene A synthase. Sequence analysis and molecular modelling was used to compare this enzyme with the mechanistically related epi-aristolochene synthase from tobacco.
10-Phenyl--cytochalasans (4-6), together with three known derivatives (1-3), were isolated from the MeOH extract of the Indonesian mushroom Microporellus subsessilis by a bioassay-guided fractionation. The compounds 6 and 1-3 induced immotility in Artemia salina.
11-Keto-β-boswellic acid (KBA), as one of the active constituents in the gum resin of Boswellia serrata, possesses significant biological activities including anti-inflammatory activity. However, its extensive metabolism and low polarity has limited the systemic availability of KBA. The present research was aimed to obtain and explore the various possible derivatives of KBA through biotransformation by Cunninghamella blakesleana AS 3.970. A total of ten transformed compounds were isolated and purified, and their chemical structures were characterized as 7β-hydroxy-11-keto-β-boswellic acid; 7β, 15α-dihydroxy-11-keto-β-boswellic acid ; 7β, 16β-dihydroxy-11-keto-β-boswellic acid; 7β, 16α-dihydroxy-11-keto-β-boswellic acid; 7β, 22β-dihydroxy-11-keto-β-boswellic acid; 7β, 21β-dihydroxy-11-keto-β-boswellic acid; 7β, 20β-dihydroxy-11-keto-β-boswellic acid; 7β, 30-dihydroxy-11-keto-β-boswellic acid; 3α, 7β-dihydroxy-11-oxours-12-ene-24, 30-dioic acid and 3α, 7β-dihydroxy-30-(2-hydroxypropanoyloxy)-11-oxours-12-en-24-oic acid by various spectroscopic methods. The biotransformation processes include hydroxylation, oxidation and esterification. Primary structure-activity relationships (SAR) of inhibitory effects on NO production in RAW 264.7 macrophage cells are discussed.
Bioassay directed extraction and purification of mango peels revealed the 5-(11'Z-heptadecenyl)-resorcinol (1) and the known 5-(8'Z,11'Z-heptadecadienyl)-resorcinol (2) previously not described in Mangifera indica L. The structures of both compounds were determined by extensive 1D and 2D NMR studies and MS. Both compounds exhibited potent cyclooxygenase (COX)-1 and COX-2 inhibitory activity with IC(50) values ranging from 1.9 (2) to 3.5 microM (1) and from 3.5 (2) to 4.4 (1) microM, respectively, coming close to the IC(50) values of reference drugs. 5-Lipoxygenase (5-LOX) catalyzed leukotriene formation was only slightly inhibited. Structure-activity studies by referring to synthetic saturated homologues indicated that the degree of unsaturation in the alkyl chain plays a key role for COX inhibitory activity, whereas the influence of chain length was less significant.
11-Hydroxy-4-methyl-2,4,6-dodecatrienoic acid was isolated from fermentations of the Mucor species, strain KL 94-92 aq. The compound exhibits cytotoxic activity and the structural elucidation, as well as the biological properties of the new compound, are described.
From the aerial parts of Clerodendrum inerme, two new sterols (4alpha-methyl-24beta-ethyl-5alpha-cholesta-14, 25-dien-3beta-ol and 24beta-ethylcholesta-5, 9(11), 22E-trien-3beta-ol) and a new aliphatic ketone (11-pentacosanone) were isolated together with another known aliphatic ketone (6-nonacosanone) and a diterpene (clerodermic acid). The structure elucidations were based on analyses of physical and spectroscopic data.
Bioactivity-guided fractionation of a cytotoxic extract of Aspergillus tubingensis, a fungal strain occurring in the rhizosphere of the Sonoran desert plant, Fallugia paradoxa, afforded a dimeric naphtho-gamma-pyrone asperpyrone D, nine known naphtho-gamma-pyrones, funalenone, and the cytotoxic cyclic penta-peptide, malformin A1.
Incubation of 2alpha,13(R)-dihydroxystemodane (3) with Rhizopus oryzae ATCC 11145 gave 2alpha,7beta,13(R)-trihydroxystemodane (11) while biotransformation of 13(R)-hydroxystemodan-2-one (5) yielded 6alpha,13(R)-dihydroxystemodan-2-one (12) and 7beta,13(R)-dihydroxystemodan-2-one (13). Bioconversion of 2beta,13(R)-dihydroxystemodane (7) with Rhizopus afforded 2beta,7,13(R)-trihydroxystemodane (14). The results complement data from our previous work and provide more information about the effect of functional groups of stemodane substrates on the site of hydroxylation.