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Main Phenolic Compounds of the Melanin Biosynthesis Pathway in Bruising-Tolerant and Bruising-Sensitive Button Mushroom (Agaricus bisporus) Strains
Abstract
Browning is one of the most common postharvest changes in button mushrooms, which often results in economic losses. Phenolic compounds, which are associated with browning, were extracted from the non-bruised and bruised skin tissue of various button mushrooms with a sulphite containing solution and analysed with UHPLC-PDA-MS. In total, 34 phenolic compounds were detected. Only small differences in the total phenolic content between bruising-tolerant and sensitive strains were observed. The contents of γ-L-glutaminyl-4-hydroxybenzene (GHB) and γ-L-glutaminyl-3,4-dihydroxybenzene (GDHB) correlated with bruising-sensitivity, for example a R(2) of 0.85 and 0.98 was found for non-bruised brown strains, respectively. In non-bruised skin tissue of the strains with brown caps, the GHB and GDHB contents in sensitive strains were on average 20 times and 15 times higher, respectively, than in tolerant strains. GHB and GDHB likely participate in the formation of brown coloured GHB-melanin, which seemed the predominant pathway in bruising-related discoloration of button mushrooms.
... Similarly, various species within the Amanita genus exhibit a biological diversity of pigments (Fig. 1). Examples include betacyanin muscapurpurin, betaxanthins muscaurins 1-7, muscaflavin, and amavadin, which give rise to purple, orange, yellow, and pale blue colors, as observed in A. muscaria [68]. Another genus, Hygrocybe, synthesizes the yellow muscaflavin pigment. ...
... All mushroom genera belonging to the order Boletales exhibit a diverse range of biopigments in various colors. These pigments are derived from the biosynthesis of terphenylquinones and pulvinic acids [65,68]. The Tapinella genus, found within the Boletales order, produces trace quantities of orange-yellow flavomentins A-D and violet spiromentins A-D [10]. ...
... These pigments are produced by various genera of fungal families within the Boletales order, including Chamonixia and Leccinum (Boletaceae), Gyrodon and Paxillus (Paxillaceae), Gyroporus (Gyroporaceae), and Melanogaster corda (Melanogasteraceae). When the fruiting bodies of these mushrooms are crushed, a distinct deep brown and brilliant blue color can be extracted [18,68]. Mühlbauer et al. [45] investigated the acetylated compound suillin, which is biosynthesized in the fruiting cap of S. granulatus and later oxidizes to give the brown color to the mushroom's fruiting body. ...
Colors are crucial on Earth, but their sourcing and production face sustainability challenges. Humans historically used a wide range of colors from nature, but overexploitation due to growing demands threatens the environment. Synthetic dyes gained popularity in the nineteenth century for their color options and commercial viability. However, they are carcinogenic and persist in the environment. Today, there is a dire need to move toward sustainable alternatives like biodegradable pigments sourced from plants, bacteria, and fungi, particularly mushrooms. Mushroom dyes offer vibrant colors present in the natural palette that decompose easily and can be produced on a large scale. Chemically, mushroom dyes are anthraquinones, xanthophylls, and carotenoids mostly in nature. This chapter explores mushroom-based pigments as a sustainable substitute for synthetic dyes in the textile industry. It discusses isolation methods and the current/future prospects of these eco-friendly pigments.
... The browning of mushroom is usually caused by the enzymatic reaction (Li, Sun, Kitazawa, & Wang, 2017;Weijn et al., 2013). Generally, enzymatic browning starts with initial enzymatic oxidation of phenols into slightly colored quinones, which are then subjected to further reactions, enzymatically catalyzed or not, leading to the formation of browning polymer pigments (Nicolas, Richard-Forget, Goupy, Amiot, & Aubert, 1994). ...
... The poor solubility of melanin makes it hard to be analyzed directly (Eisenman & Casadevall, 2012). Therefore, studies on discoloration used to be focused on the analysis of their precursor phenolic compounds (Garcia, Garcia-Villalba, Gil, & Tomas-Barberan, 2017;Weijn et al., 2013). Phenolic compounds can act as browning substrates or antioxidants, in which oxidation is the key reaction (Robards, Prenzler, Tucker, Swatsitang, & Glover, 1999). ...
... Previously, LC-MS untargeted metabolomics has been employed to explain the signal metabolites inducing browning in fresh-cut lettuce (Garcia et al., 2017), and the metabolites selected were further identified by targeted metabolomics (Garcia, Gil, & Tomas-Barberan, 2019). In addition, main phenolic compounds contributing to the browning of button mushroom were also uncovered by UHPLC-PDA-MS (Weijn et al., 2013). So far, signal metabolites and phenolic compounds associated with the browning of needle mushroom have not been uncovered. ...
Browning seriously causes postharvest deterioration of the yellow cultivars of Flammulina filiformis, yet the browning process and its mechanism have not been described. Changes of L*, a*, b* values, the browning and whiteness index during air contacted storage were evaluated, uncovering the great loss of brightness and meanwhile the accumulation of yellowness and redness. Browning tissue showed an increase of malondialdehyde, total phenolics, and browning-related enzyme activities of polyphenol oxidase and peroxidase, in contrast to the decrease of bioprotective catalase, superoxide, and dismutase. Non-targeted metabolomics revealed an upregulation of melanin synthesis under oxidation stress, and targeted LC-MS/MS verified the upregulation of L-dopa (3,4-dihydroxy-L-phenylalanine) during browning. Pyrrole-2,3,5-tricarboxylic acid was identified in the degradation products of browning pigments after alkaline hydrogen peroxide by LC-MS/MS, suggesting the existence of 5,6-dihydroxyindole-2-carboxylic acid derived units of eumelanin. Therefore, the biosynthesis of eumelanin via L-dopa pathway could participate in the enzymatic browning of postharvest F. filiformis.
... Numerous reports have described the phenolic compounds involved browning of mushrooms. GHB, GDHB and tyrosine have been identified as main phenolic substrates in mushrooms leading to browning (Weijn et al., 2013;Jolivet et al., 1998). In the presence of tyrosinase and oxygen, GHB is oxidized into GDHB and subsequently into quinine which polymerizes into GHB-melanins, and tyrosine is oxidized into DOPA and polymerizes into DOPAmelanins (Weijn et al., 2013;Beaulieu et al., 1999;Espin et al., 1999). ...
... GHB, GDHB and tyrosine have been identified as main phenolic substrates in mushrooms leading to browning (Weijn et al., 2013;Jolivet et al., 1998). In the presence of tyrosinase and oxygen, GHB is oxidized into GDHB and subsequently into quinine which polymerizes into GHB-melanins, and tyrosine is oxidized into DOPA and polymerizes into DOPAmelanins (Weijn et al., 2013;Beaulieu et al., 1999;Espin et al., 1999). More and more studies showed that the oxidation of GHB was crucial for the melanin formation of mushroom browning. ...
... GHB/GDHB pair is more important than L-tyrosine/L-DOPA pair to yield the enzymatic browning (Espin et al., 1999;Pierce andRast, 1995 Pierce andRast, 1995). It was also reported that GDHB and GHB were most abundant in the bruising-sensitive fungi strains, and were 3 and 2.5 times higher than that in the tolerant white strains, respectively, while L-tyrosine did not shown a correlation with bruising sensitivity (Weijn et al., 2013). Formation of brown GHB-melanin in skin tissue seemed to be the predominant pathway in bruising-related discoloration of button mushrooms (Weijn et al., 2013;Sylvie Jolivet et al., 1998). ...
The effect of 1.0 kJ/m2 ultraviolet-C (UV-C) light on antioxidant activity, total phenolics and main phenolic compounds associated with browning of button mushroom (Agaricus bisporus) tissues during 21 days storage at 4 °C was studied. The distribution of antioxidant activity and phenolic compounds varied significantly in different parts of button mushroom. The highest DPPH scavenging activity was investigated in the stipe, and the gill contained the highest concentration of total phenolics, γ-glutaminyl-4-hydroxybenzene (GHB) and γ-glutaminyl-3,4-dihydroxybenzene (GDHB). UV-C irradiation enhanced antioxidant activity, total phenolics and phenolic compounds in inner cap, stipe, gill and whole mushroom during storage compared to control. However, UV-C irradiated mushroom reduced the total phenolics, GHB, GDHB and tyrosine contents of the peel fraction compared to the control sample during the storage. Application of 1.0 kJ/m2 UV-C treatment could effectively induce the increase of antioxidant capacity and compounds in whole mushroom during storage, and likely lead to the oxidation and conversion of phenolic compounds in peel tissue which participate in the formation of melanin associated with browning of mushrooms.
... No essential compounds such as adenine, cyclo(L-phe-L-pro), 2,5-dihydrophenylalanine, 4-hydroxybenzaldehyde and p-aminophenol were also identified in dichloromethane extracts. Adenine, p-aminophenol (Weijn et al., 2013), and 4-hydroxybenzaldehyde had previously been identified in mushrooms (Papaspyridi et al., 2012). p-Aminophenol is, together with other phenols, associated to browning, thus producing the most common postharvest changes in button mushrooms, which often result in economic losses (Weijn et al., 2013). ...
... Adenine, p-aminophenol (Weijn et al., 2013), and 4-hydroxybenzaldehyde had previously been identified in mushrooms (Papaspyridi et al., 2012). p-Aminophenol is, together with other phenols, associated to browning, thus producing the most common postharvest changes in button mushrooms, which often result in economic losses (Weijn et al., 2013). 4-Hydroxybenzaldehyde is a phytotoxic substance with allelopathic activity found in endophytic fungi Aspergillus sp. ...
... The pathway of melanin synthesis in mushrooms involves the conversion of benzoquinone from a γ-glutaminyl-4hydroxybenzene (GHB) precursor by tyrosinase. Weijn et al. [24] discovered the presence of GHB as the most abundant phenolic component in the fruiting body and spores of Agaricus bisporus. One of the highly melanised medicinal mushrooms, Inonotus obliquus, also known as Chaga, contains bioactive phenolic components, such as melanin as well as triterpenoids (e.g., inotodiol) [59]. ...
In 2015, approximately 195 countries agreed with the United Nations that by 2030, they would work to make the world a better place. There would be synergies in accomplishing the 17 Sustainable Development Goals (SDGs). Synergy using a single sustainable resource is critical to assist developing nations in achieving the SDGs as cost-effectively and efficiently possible. To use fungal dye resources, we proposed a combination of the zero hunger and affordable energy goals. Dyes are widely used in high-tech sectors, including food and energy. Natural dyes are more environment-friendly than synthetic dyes and may have medicinal benefits. Fungi are a natural source of dye that can be substituted for plants. For example, medicinal mushrooms offer a wide range of safe organic dyes that may be produced instantly, inexpensively, and in large quantities. Meanwhile, medicinal mushroom dyes may provide a less expensive choice for photovoltaic (PV) technology due to their non-toxic and environmentally friendly qualities. This agenda thoroughly explains the significance of pigments from medicinal mushrooms in culinary and solar PV applications. If executed effectively, such a large, unwieldy and ambitious agenda may lead the world towards inclusive and sustainable development.
... compounds contributing to the browning of lettuces (Garcia et al., 2017;Garcia et al., 2019), Agaricus bisporus (Weijn et al., 2013), and F. filiformis (Fu et al., 2021). However, the complexity of the browning process involves not only various phenolic compounds (Robards et al., 1999) but also phenoloxidase (Nikolaivits et al., 2018) and the diverse participation of enzymes in the browning process. ...
Yellow cultivars of Flammulina filiformis are prone to browning, which causes significant yearly loss. This study investigated the critical factors involved and revealed that oxygen plays an essential role in the browning process. Integrated multi-omic analyses, including genome sequencing, transcriptome profiling, and 4D label-free proteome quantification, were incorporated to dissect essential genes and metabolic pathways in the process of oxidative deterioration of the mushroom. The results revealed genes encoding browning-related enzymes in the F. filiformis genome, which are involved in the metabolism of tyrosine and the biosynthesis of phenylpropanoid. Laccase 4, which is over-regulated in oxygen-treated samples compared to anaerobically treated ones by transcriptomic and proteomic analysis, and further confirmed by qRT-PCR and enzyme assays, could be a crucial polyphenol oxidase catalyzing the browning reaction. DNA damaging, proteolysis, and oxidative phosphorylation accelerate cell senescence, contribute to cell integrity damage, and trigger the biosynthesis of melanin as a defective mechanism. These findings lay the foundations for postharvest preservation and future genetic breeding of F. filiformis.
... The browning of white A. bisporus can be induced by several e including abiotic stimulus and biotic stress. The most well-known abiotic stimulus is mechanical stress such as simple shearing stress [13][14][15]. It has been suggested that mechanical stress/stimulus induces enzymatic reactions, including oxidative reactions. ...
Agaricus bisporus is one of the world’s most popular edible mushrooms, including in South Korea. We performed de novo genome assembly with a South Korean white-colored cultivar of A. bisporus, KMCC00540. After generating a scaffold-level genomic sequence, we inferred chromosome-level assembly by genomic synteny analysis with the representative A. bisporus strains H97 and H39. The KMCC00540 genome had 13 pseudochromosomes comprising 33,030,236 bp mostly covering both strains. A comparative genomic analysis with cultivar H97 indicated that most genomic regions and annotated proteins were shared (over 90%), ensuring that our cultivar could be used as a representative genome. However, A. bisporus suffers from browning even from only a slight mechanical stimulus during transportation, which significantly lowers its commercial value. To identify which genes respond to a mechanical stimulus that induces browning, we performed a time-course transcriptome analysis based on the de novo assembled genome. Mechanical stimulus induces up-regulation in long fatty acid ligase activity-related genes, as well as melanin biosynthesis genes, especially at early time points. In summary, we assembled the chromosome-level genomic information on a Korean strain of A. bisporus and identified which genes respond to a mechanical stimulus, which provided key hints for improving the post-harvest biological control of A. bisporus.
... The melanin precursors γ-glutaminyl-4-hydroxybenzene (GHB) and γ-glutaminyl-3,4-dihydroxybenzene (GDHB), which can be used as biomarkers to predict the browning susceptibility of Agaricus strains (Weijn et al., 2013), were also differentially expressed depending on the A. subrufescens strain and cultivation system. The detection of higher levels of GHB and GDHB in ABL 04/49 and ABL 18/01 suggest that these strains might be the most susceptible to browning, especially under indoor cultivation, while ABL 19/01 and ABL 98/11 strains are likely the least susceptible to browning, especially under indoor cultivation. ...
Agaricus subrufescens has emerged as an important culinary-medicinal mushroom over the last decades. Efforts have been dedicated to upgrade the A. subrufescens productive process via strain selection and cultivation scaling-up. However, little is known on the influence of those variables on the metabolite profiles and nutraceutical properties of this mushroom. In this work, the effects of outdoor versus indoor cultivation on the metabolite profiles of five commercial strains of A. subrufescens were investigated by untargeted metabolomics. UHPLC-MS coupled to multivariate data analysis revealed that the concentration of several metabolites with reported health-related properties as well as related to taste and browning varied significantly between strains and were affected by the cultivation system in a strain-dependent manner. Data suggest that increasing the production scale by means of indoor cultivation may decrease the nutraceutical quality of some A. subrufescens strains while also affecting taste and browning susceptibility to different extents.
... Although not heavily discussed in recent reviews, some mushrooms and basidiomycetes have been shown to produce melanin from the precursor glutaminyl-hydroxybenzene (GHB) [42]. The presence of GHB on mushroom caps of Agaricus biosporus has been correlated with their susceptibility to browning, and the transformed product is commonly dubbed GHB-melanin [43]. Although a synthesis pathway has not been fully outlined, it is thought to occur as GHB is transformed by a polyphenol oxidase (typically tyrosinase) into 2-hydroxy-p-iminobenzoquinone (2-HpIBQ) and polymerized [42,44]. ...
Melanin is a complex multifunctional pigment found in all kingdoms of life, including fungi. The complex chemical structure of fungal melanins, yet to be fully elucidated, lends them multiple unique functions ranging from radioprotection and antioxidant activity to heavy metal chelation and organic compound absorption. Given their many biological functions, fungal melanins present many possibilities as natural compounds that could be exploited for human use. This review summarizes the current discourse and attempts to apply fungal melanin to enhance human health, remove pollutants from ecosystems, and streamline industrial processes. While the potential applications of fungal melanins are often discussed in the scientific community, they are successfully executed less often. Some of the challenges in the applications of fungal melanin to technology include the knowledge gap about their detailed structure, difficulties in isolating melanotic fungi, challenges in extracting melanin from isolated species, and the pathogenicity concerns that accompany working with live melanotic fungi. With proper acknowledgment of these challenges, fungal melanin holds great potential for societal benefit in the coming years.
... In addition to enzyme activity, substrates such as amino acids or phenol compounds, mainly tyrosine and γ-hydroxybutyrate (GHB), may also contribute to changes in color. [5][6][7][8][9][10] Various methods of inactivating PPOs have been developed in order to minimize the enzymatic browning of mushrooms, including spraying, washing, vacuum impregnation or blanching in agents that contain PPO inhibitors. Sodium metabisulfite (SM) is a strong industrial-level PPO inhibitor, which is, however, harmful to human health as it may induce allergies. ...
BACKGROUND
The potential of onion juice, as well as extracts of waste (tunic) (5%) and fleshy scale leaves (25%), to inhibit enzymatic browning of frozen Agaricus bisporus was investigated. The onion materials were used for blanching and their effectiveness in conserving integrity and appearance of mushroom fruiting bodies was compared with the currently accepted method of blanching in a sodium metabisulfite (SM) solution.
RESULTS
It was observed that l‐phenylalanine content may be a useful indicator of the changes in enzymatic activity during frozen storage, and l‐tyrosine may be an indicator of a loss of lightness in color (parameter L*). The enzymes responsible for color changes were mainly monophenolase (MON) and, to a lesser degree, diphenolase (DIP). After being stored frozen for 8 months, these enzymes were detected at a 29:1 (DIP:MON) ratio in untreated mushrooms and a 2:1 (DIP:MON) ratio in mushrooms treated with onion juice.
CONCLUSION
Onion products may be a good alternative to an SM solution. The most effective method to conserve the light color of fruiting bodies was blanching in juice or in an extract of the fleshy scale leaves. The least effective inhibitor of MON was tunic extract, which did, however, cause a favourable increase in the reducing capacity (total polyphenols) and flavonoids. Although the onion waste (tunic) extract changed the color of mushrooms from white to creamy orange, the color of these products was attractive and positively evaluated by panellists. © 2020 Society of Chemical Industry
... Benzoquinone is converted from the precursor γ-glutaminyl-4-hydroxybenzene (GHB) by tyrosinase. GHB is the main phenolic compound in A. bisporus fruiting bodies and spores [36]. ...
Fungi can produce myriad secondary metabolites, including pigments. Some of these pigments play a positive role in human welfare while others are detrimental. This paper reviews the types and biosynthesis of fungal pigments, their relevance to human health, including their interactions with host immunity, and recent progresses in their structure–activity relationships. Fungal pigments are grouped into carotenoids, melanin, polyketides, and azaphilones, etc. These pigments are phylogenetically broadly distributed. While the biosynthetic pathways for some fungal pigments are known, the majority remain to be elucidated. Understanding the genes and metabolic pathways involved in fungal pigment synthesis is essential to genetically manipulate the production of both the types and quantities of specific pigments. A variety of fungal pigments have shown wide-spectrum biological activities, including promising pharmacophores/lead molecules to be developed into health-promoting drugs to treat cancers, cardiovascular disorders, infectious diseases, Alzheimer’s diseases, and so on. In addition, the mechanistic elucidation of the interaction of fungal pigments with the host immune system provides valuable clues for fighting fungal infections. The great potential of fungal pigments have opened the avenues for academia and industries ranging from fundamental biology to pharmaceutical development, shedding light on our endeavors for disease prevention and treatment.
... At the end of storage, the PPO activities were still 27.53% lower in the mushrooms treated with 20 μl L −1 peppermint oil than that in the control mushrooms. In previous study, it is suggested that the browning of the mushrooms results from oxidation of phenolic compounds by PPO activity; it may be inhibited by the antioxidant activities of the essential oil (Karimirad et al. 2019;Weijn et al. 2013). Similar reports suggested that essential oils have an inhibiting effect against PPO activity in fresh-cut lettuce, which could be due to the release of bound PPO and the reduced contact between the enzyme and its substrates (Chen et al. 2017). ...
White button mushrooms (Agaricus bisporus) were treated with 5 μl L⁻¹, 10 μl L⁻¹, 20 μl L⁻¹, and 50 μl L⁻¹ peppermint oil and then stored at 4 °C for 8 days to investigate with respect to browning and postharvest qualities. It was found that 20 μl L⁻¹ peppermint oil treatment could provide the best effect on inhibiting browning of fruit bodies. Our results indicated 20 μl L⁻¹ peppermint oil fumigation restrains browning development and alleviated membrane lipid peroxidation, as reflected by lower electrolyte leakage (17.42%), malondialdehyde (MDA) content (21.95%), and weight loss (1.69%) compared with those of the control mushrooms at 8 days, respectively. In addition, the 20 μl L⁻¹ peppermint oil fumigation had 1.49-fold and 1.24-fold higher phenolics and flavonoids accumulation respectively than those in control and retained high levels of soluble protein and total sugar at the end of the storage time. Furthermore, peppermint oil treatment significantly improved the antioxidant system, which increased the activity of superoxide dismutase (SOD) and phenylalnine ammonia lyase (PAL), and inhibited the activity of polyphenol oxidase (PPO) and peroxidase (POD), as well as regulated the relative expression levels of genes encoding polyphenol oxidase (AbPPO1, AbPPO2, AbPPO5, AbPPO6) and phenylalanine ammonia lyase (AbPAL1, AbPAL2) during the storage period. These findings suggest that peppermint oil fumigation is a promising method to control browning and improve the quality of button mushrooms.
... Polyphenols represent the most abundant compounds among the secondary metabolites produced by plants, with more than 8000 identified compounds, ranging from small molecules such as phenolic acids to highly polymerized substances such as tannins [46]. They are produced via the phenyl propanoid pathway in which phenylalanine represents the starting compound [47]. From a chemical point of view, polyphenols are characterized by the presence of one or more aromatic rings bearing one or more hydroxyl groups. ...
Epidemiologic studies suggest that dietary polyphenol intake is associated with a lower incidence of several non-communicable diseases. Although several foods contain complex mixtures of polyphenols, numerous factors can affect their content. Besides the well-known capability of these molecules to act as antioxidants, they are able to interact with cell-signaling pathways, modulating gene expression, influencing the activity of transcription factors, and modulating microRNAs. Here we deeply describe four polyphenols used as nutritional supplements: quercetin, resveratrol, epigallocatechin gallate (ECGC), and curcumin, summarizing the current knowledge about them, spanning from dietary sources to the epigenetic capabilities of these compounds on microRNA modulation.
... Chorismate is converted into three different compounds including γ-L-glutaminyl-4-hydroxybenzene (GHB), p-aminophenol (PAP) and tyrosine, which are finally oxidized and polymerized into GHB-, PAP-and DOPA-melanin, respectively. Catechol melanin is formed from the starting substrate of catechol (Weijn, van den Berg-Somhorst, et al. 2013a andWeijn, Bastiaan-Net, et al. 2013b). Tyrosinase has greater affinity for dihydroxyphenols than monohydroxyphenols and trihydroxyphenols. ...
... Loss of whiteness upon processing and storage of frozen mushrooms is particularly important in the mushroom industry. According to Weijn et al. [44], there are probably four pathways for melanin synthesis in fresh A. bisporus, and the substrates for PPOs may be the phenols and amino acids, including l-tyrosine, l-phenylalanine and l-DOPA. ...
The mechanism of browning in frozen white and brown A. bisporus stored for 8 months at − 25 °C has been determined based on the level of enzymatic activity, free amino acids, total polyphenols, antioxidant activity and color. The brown variety was less resistant than the white variety to enzymatic browning, due to a higher activity of monophenolase and a minor degree of diphenolase. The mechanism of browning was connected with the regeneration of monophenolase and diphenolase and a reduction in the level of total polyphenols and l-tyrosine. In the white variety, the activity of monophenolase was correlated with the level of l-tyrosine and antioxidant activity, and in the brown variety with the level of l-phenylalanine and parameter a*. Irrespective of the variety, the most effective pre-treatment was vacuum impregnation in sodium metabisulfite and citric acid and then blanching in water. The second pre-treatment in terms of effectiveness was blanching in the sodium erythorbate and citric acid in the brown variety, and blanching in water in the white.
... It has been deeply studied in Agaricus bisporus where it results from production of melanins at a crucial step that is the oxidation of the g-L-glutaminyl-4-hydroxybenzene (GHB) by polyphenol oxidases (PPO). In addition, the variation of bruising sensitivity observed between different strains is correlated with the concentration of GHB (Weijn et al. 2013). Among the different species of Agaricus, the observed discolouration had various nuances (orange, brownish, vinaceous or bloody) suggesting that different melanin biosynthesis pathways may predominate in different species. ...
The genus Agaricus was recently rearranged to accommodate numerous tropical taxa. Accordingly, the genus was split into six subgenera and 22 sections of which 12 are included in A. subg. Pseudochitonia. Preliminary data indicated that three putative new species belong to this subgenus. Our objectives were to describe these species, to determine to which sections they belong, and to experience the interest of some traditional traits in this new context. We morphologically described Agaricus coniferarum from France and Portugal, Agaricus iranicus from Iran, and Agaricus lusitanicus from Portugal. Multi-gene phylogenetic analyses based on ITS, LSU, and tef1 sequence data of representatives of the 12 sections clearly indicated that A. coniferarum and A. lusitanicus are placed in Agaricus sect. Bohusia, while A. iranicus is in A. sect. Sanguinolenti. Incidentally, we replaced the illegitimate name Agaricus magnivelaris by Agaricus fiardianus. In a phylogenetic tree, based on all available ITS sequence data and focussing on six related sections, we examined the phylogenetic distribution of various characters. The intensity of red discolouration when the sporocarp is rubbed or cut appeared as a phylogenetically weak informative trait. We propose a determination key leading to a group of three hardly distinguishable sections (Bohusia, Nigrobrunnescentes, and Sanguinolenti).
... H. erinaceus which is considered as a saprotroph or weak parasite mostly occurs on dead wood, and sometimes on knotholes or cracks of living hardwoods [5][6][7]. The mature fruiting body is fleshy semi-spherical and whitish (Fig. 1a), and the color gradually becomes yellowish to brownish in age [8]. ...
Hericium erinaceus (Bull.) Pers., also known as Yamabushitake, Houtou and Lion’s Mane, is capable of fortifying the spleen and nourishing the stomach, tranquilizing the mind, and fighting cancer. Over the past decade, it has been demonstrated that H. erinaceus polysaccharides possess various promising bioactivities, including antitumor and immunomodulation, anti-gastric ulcer, neuroprotection and neuroregeneration, anti-oxidation and hepatoprotection, anti-hyperlipidemia, anti-hyperglycemia, anti-fatigue and anti-aging. The purpose of the present review is to provide systematically reorganized information on extraction and purification, structure characteristics, biological activities, and industrial applications of H. erinaceus polysaccharides to support their therapeutic potentials and sanitarian functions.
... According to the melanin biosynthesis pathway, a number of enzymes (42 genes identified in the genome, Fig. 4) and phenolic compounds are involved in the mechanism of the bruised-induced discoloration (Weijn et al., 2013a(Weijn et al., , 2013b. The level of gene expression producing these enzymes and phenolic compounds are expected to be associated with the degree of bruising sensitivity. ...
Fresh morels were treated with salicylic acid (SA) and stored at 4 °C, to investigate its effects on the quality and browning status during storage. The results showed that the storage qualities of SA-treated morels were better than that of control, especially 500 μmol L⁻¹ SA-treated morels. It delayed the decline of tyrosine and total phenols, increased quinones contents, and inhibited the activities and gene expressions of tyrosinase and polyphenol oxidase (PPO). In addition, ascorbic acid levels, and the enzyme activities and gene expressions of superoxide dismutase (SOD), catalase (CAT) and ascorbic acid peroxidase (APX) were increased with the treatment of SA, compared to the control group. Furthermore, the increase of electrolyte leakage and malondialdehyde (MDA) levels were decreased with SA treatment. The results revealed that SA was a potential preservative agent applied in the morels storage for inhibiting the browning and maintaining the edible qualities.
To elucidate the browning inhibition mechanism of nanocomposite packaging (nano-PM) Agaricus bisporus during cold storage, we analyzed the biophysical and biochemical indices, including substrates, key enzymes, and relative gene expression associated with browning. The results showed that nano-PM could maintain a higher total phenol content and lower flavonoid content of mushrooms throughout the storage period than the commercial polyethylene packaging treatment (control). The activity of phenylalanine ammonia lyase (PAL) and its relative gene expression were inhibited by nano-PM, whereas cinnamic acid-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) activities were promoted. Nano-PM promoted the synthesis of γ-L-glutaminyl-4-hydroxybenzene (GHB), tyrosine, and catechol, but inhibited the synthesis of soluble quinone, γ-L-glutaminyl-3,4-dihydroxybenzene (GDHB), and 3,4-dihydroxyphenylalanine (DOPA), which were mainly attributed to polyphenol oxidase (PPO), tyrosinase (TYR), and laccase (LAC) activities as well as gene relative expression at low levels. Nano-PM increased the enzyme activities of the phenylpropanoid pathway by activating their relative gene expression, promoting the accumulation of phenolic substances to enhance the resistance of mushrooms to harsh environments. Additionally, nano-PM inhibited TYR activity to delay the conversion of GHB to GDHB and tyrosine to DOPA, which ultimately reduced melanin formation and delayed mushroom browning, leading to a longer shelf life.
Transcriptomics was carried out to analyze the molecular mechanisms of browning that occurred in morels at the storage conditions of 20 °C and 4 °C. During storage, with the browning process, 14 significantly differential expression genes were found to relate to the browning process of morels. In which, 10 genes were upregulated and 4 genes downregulated, and they were mainly enriched in the tyrosine metabolism pathway, shikimate pathway, and MAPK signaling pathway. Notably, the gene expression of the tyrosinase was largely upregulated after browning, compared to the fresh sample, which was also confirmed by qPCR validation. In addition, the activities of polyphenol oxidase (PPO) and peroxidase (POD) were significantly increased, but activities and gene expressions of anti-oxidation enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) were decreased after storage. These results indicated that Tyr/SK/MAPK metabolic pathways were important to the browning of morels. The reduced antioxidant capacity concomitant with the storage might also contribute to the browning process of morels.
We report the finding of an Agaricus specimen in the section Sanguinolenti and describe it as a new species Agaricus hortusdamarum. Based on ITS data, the species is distinct and well separated from all known se-quenced species within this section. The type specimen grew in late autumn, under Cupressus sempervirens, near a Pinus pinea alley in the Villa Borghese Gardens in Rome, in Italy. The new species is phylogenetically close to Agaricus iranicus, a rare species of temperate climate, which is so far described only in the Guilan province in Iran. Its morphological characters and phylogenetic pattern are described and divergence from A. iranicus is discussed.
Browning is a major problem affecting the quality of the morel. This study aims to clarify the browning mechanisms of the morel in terms of metabolite changes during storage. Morels were stored at 20 °C and 4 °C, respectively, and browned gradually with the extension of the storage periods. The soluble quinone content was increased, while the total phenolic content was decreased in the later storage periods. Metabolomics analysis revealed that many metabolic profiles of substances in morel were altered with increased amino acids and fatty acids and decreased soluble sugars, organic acids and some phenolics with the browning process in storage. Especially, dopamine, a precursor of melanin produced from tyrosine oxidation, was up-accumulated after storage. However, quinone, the browning substance was increased after storage. Through the metabolomic results and correlation analysis, it could be suggested that tyrosine metabolism was a vital pathway leading to the browning of morels during storage. The membrane lipid and energy metabolism involved in the upstream of tyrosine metabolism pathway might also concern the browning of morels during storage.
BACKGROUND
Button mushrooms with completely white appearance are popular with consumers. However, button mushrooms are susceptible to infection with Pseudomonas tolaasii (P. tolaasii), which results in browning. This study evaluates the effects of ultraviolet-C (UV-C) treatment on the inactivation of P. tolaasii in vitro and in vivo and on the physiological and chemical changes of button mushrooms during storage for 21 days at 4 °C.
RESULTS
UV-C doses of 0.5-9.0 kJ m⁻² resulted in 3.91-6.26 log CFU mL⁻¹ reduction of P. tolaasii populations in vitro, and UV-C treatment reduced P. tolaasii populations inoculated on mushroom cap surfaces and browning severity. Moreover, P. tolaasii increased polyphenol oxidase (PPO) activity, and decreased phenylalanine ammonia-lyase (PAL) activity, the accumulation of phenolics and contents of brown melanin precursors, including γ-L-glutaminyl-4-hydroxybenzene (GHB), γ-L-glutaminyl-3,4-dihydroxybenzene (GDHB), and tyrosine in button mushrooms. UV-C treatment was found to reduce the negative changes due to P. tolaasii infection.
CONCLUSION
These results indicated that the application of UV-C treatment inhibited browning, inactivated P. tolaasii and reduced P. tolaasii - associated chemical and enzymatic changes of button mushrooms.
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The genus Pleurotus, namely oyster mushroom, is widely cultivated and consumed worldwide. Cap color is an important commercial trait for oyster mushroom. Diverse color is determined by various pigment constituents. However, the pigments of oyster mushrooms are still ambiguous. In this study, we extracted and identified pigments of oyster mushroom species with black, yellow and pink cap color. The extracted pigments appearing the three color types correspondingly to the cap color, which were all identified as melanin using a panel of spectroscopic and physical/imaging techniques. Nevertheless, HPLC and elemental analysis indicated that the melanin in oyster mushrooms was actually a mixture of eumelanin and phaeomelanin. Differences in the quantities and relative proportions of eumelanin and phaeomelanin resulted in the color variation in oyster mushroom caps. Electron microscopy studies showed that the melanin units are likely located in the cell wall, as reported in other fungi. The pigments in oyster mushrooms with three different cap color were extracted and identified for the first time in this study, which provided fundamental knowledge for future studies on the mechanism of color formation in mushrooms.
Enzymatic browning is an important issue affecting the quality and shelf life of fresh-cut potato. Previous research showed post-cut sodium chloride (NaCl) dipping treatment doesn’t have anti-browning effect on fresh-cut potato. In this research, the influence of pre-cut NaCl solution treatment on browning, polyphenol oxidase (PPO) activity and amino acids contents in fresh-cut potato was investigated. The results showed that pre-cut NaCl solution treatment at 5 % for 3 h improved the overall visual quality, reduced browning and surface dehydration and extended shelf-life by 3−4 d at 5 °C. The PPO activity in pre-cut NaCl treated potato tubers and slices was lower than that in control and water treated ones. Compared with control, the contents of glutamic acid and proline in NaCl treated potato were increased, whereas tyrosine and arginine decreased. Exogenous differential compensation of glutamic acid reduced the browning of control potato mash, while the compensation of tyrosine and arginine as well as their mixture aggravated the browning of pre-cut NaCl treated potato mash. The compensation of proline showed no influence on the browning of control potato mash, whereas pre-cut proline solution treatment inhibited the browning of fresh-cut potato. This research showed that pre-cut NaCl solution treatment can effectively inhibit the browning of fresh-cut potato by influencing polyphenol oxidase activity and several free amino acids contents, which provides a new way to prevent the browning of fresh-cut potato and elucidates the anti-browning mechanism of pre-cut NaCl treatment.
The mushrooms have contributed to the development of active ingredients of fundamental importance in the field of pharmaceutical chemistry as well as of important tools in human and animal health, nutrition, and functional food. This review considers studies on the beneficial effects of medicinal mushrooms on the nutrition and health of humans and farm animals. An overview of the chemical structure and composition of mycochemicals is presented in this review with particular reference to phenolic compounds, triterpenoids and sterols, fatty acids and lipids, polysaccharides, proteins, peptides, and lectins. The nutritional value and chemical composition of wild and cultivated mushrooms in Italy is also the subject of this review which also deals with mushrooms as nutraceuticals and the use of mushrooms in functional foods. The nutraceutical benefits of UV irradiation of cultivated species of basidiomycetes to generate high amounts of vitamin D2 is also highlighted and the ability of the muhsrooms to inhibit glycation is analyzed. Finally, attention is paid to studies on bioactivities of some Italian wild and cultivated mushrooms with particular reference to species belonging to the genus Pleurotus . The review highlights the potential of medicinal mushrooms in the production of mycochemicals that represent a source of drugs, nutraceutical, and functional food.
Graphic abstract
The present study was conducted to investigate the effect of Cuminum cyminum essential oil loaded chitosan nanoparticles (CEO-CSNPs) on the shelf life of button mushroom during 20 days of cold storage. CEO-CSNPs were prepared by ionic gelation technique. The size and morphology of nanoparticles were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The size of CEO-CSNPs ranged from 30 to 80 nm. CEO and CEO-CSNPs were spotted onto the whatman filter paper inside containers. CEO-CSNPs treatment was effective in maintaining color, firmness and overall acceptability of mushrooms and inhibiting the investigated bacteria and mold and yeast growth, resulted to significantly higher SOD and APX activity, antioxidant capacity and total phenolic content and lower PPO activity throughout the storage period. In general, treated samples stored for 15 days at 4 °C indicated overall acceptable quality compared to the control samples which lost their quality after 10 days of storage.
The effect of selenium enrichment on the biological efficiency, phenolic compounds, amino acid profile, antioxidant capacity and cellular antioxidant activity (CAA) were evaluated in Pleurotus ostreatus fruiting bodies (FB) harvested during three sequential flushes. Sodium selenate was used to reach selenium content of 17.5 or 5.8 mg/kg in the sorghum straw substrate. Biological efficiency and total selenium content increased. One of the main differences among treatments was in ergothioneine contents, an indicator of oxidative stress that was positively related with valine and isoleucine contents and negatively to leucine and phenylalanine. Besides ergothioneine, nucleosides derived from adenine and uracyl were the major peaks observed in all treatments and no free coumaric and ferulic acids were detected. Selenium enrichment also affected the antioxidant capacity and particularly the methanolic extract obtained from the second flush of FB cultivated in selenium enriched substrate (17.5 mg/kg) had the best CAA.
Soluble sugars and polyols, free amino acids, 5′-nucleotides, and carboxylic acids affect the taste of edible mushrooms. Numerous volatile compounds of various chemical natures produce mushroom flavor. Among them, eight-carbon aliphatic constituents are of the greatest interest. Melanin is formed by the enzymatic oxidation of some phenols after mechanical damage of fruit bodies. Malic, citric, and oxalic acids prevail among aliphatic acids. Numerous phenolics are the main source of antioxidant activity. Available information on sterols, indole and purine compounds, biogenic amines, and polyamines is also provided. Extensive data deal with trace element contents in fresh mushrooms. Some species have accumulating and even hyperaccumulating ability for various elements. Generally, consumption of wild mushrooms growing in polluted areas can be a health risk.
In order to achieve faster drying along with high product quality, microwave freeze drying (MFD) was applied to dry button mushrooms. Although MFD can lead to similar product quality compared with FD, the color deterioration of MFD mushroom is higher than FD ones. Therefore, two drying methods were used to investigate the browning behaviors of button mushrooms during MFD in terms of parameters including polyphenol oxidase (PPO) activity, total phenolic (TP) content, moisture content, reducing sugar (RS) content and vitamin C (VC) content. It was found that both whiteness and browning degree can be used to describe the browning kinetics of button mushrooms during MFD process. Both non-enzymatic browning and enzymatic browning took place during MFD button mushrooms, but effect of enzymatic browning was more significant, which should be controlled during MFD. In order to avoid enzymatic browning during MFD button mushrooms, a relatively low microwave power at initial stage of MFD should be adopted. Meanwhile, a low microwave power also should be used at the end stage of MFD so as to reduce non-enzymatic browning.
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Hericium erinaceus is an important mushroom with edible values and medicinal properties. Both the mycelium and the fruiting bodies contain many bioactive compounds with drug efficacy. Recent evidence demonstrates that it is helpful to various diseases, such as Alzheimer's disease, immunoregulatory, and many types of cancer. Furthermore, emerging pieces of evidence have shown that different active molecules in H. erinaceus have different functions on different organs in different diseases via the different mechanisms. Drawing on current research results, this review mainly focuses on the therapeutic effects of H. erinaceus on various diseases of multiple physiological systems, including the nervous system, digestive system, circulatory system, and immune system. This paper also discusses systematically the efficient protection of H. erinaceus against the diseases from the intricate experimental proofs by using the systematic viewpoints, which provides a framework for future research directions.
NTSYSpc is one of the most popular softwares being used in molecular genetic qualitative data cluster analysis. The present paper is showing how we can integrate this powerful software with Microsoft Office Word and Excel in an innovative method to cluster, screen and more varied individuals selection in a populated group studying. A step by step procedure has been explained here in detail. Using this method may help to select the individuals with the highest possible difference from others in a large population using a logical and mathematical protocol with high accuracy based on the least relativeness with other individuals. The screened individuals can be considered for further assessments such as nucleotide sequencing in the case of biodiversity studying on massive populations.
The inhibition of sulfhydryl enzymes by a red quinonoid compound isolated from sporulating mushrooms was reported elsewhere.
A precursor which is enzymatically converted to the quinone was also described, and identified as γ-glutaminyl-4-hydroxybenzene.
The quinone itself is extremely unstable under a variety of conditions. Acetylated and benzoylated derivatives of the quinone
have been prepared and analyzed by infrared spectroscopy. The data indicate that the red compound is γ-glutaminyl-3,4-benzoquinone.
An enzyme capable of converting the precursor to the quinone has been purified; this enzyme exhibits tyrosinase activity,
in accord with the suggested structure of the quinone.
Melanin is a unique pigment with myriad functions that is found in all biological kingdoms. It is multifunctional, providing defense against environmental stresses such as ultraviolet (UV) light, oxidizing agents and ionizing radiation. Melanin contributes to the ability of fungi to survive in harsh environments. In addition, it plays a role in fungal pathogenesis. Melanin is an amorphous polymer that is produced by one of two synthetic pathways. Fungi may synthesize melanin from endogenous substrate via a 1,8-dihydroxynaphthalene (DHN) intermediate. Alternatively, some fungi produce melanin from L-3,4-dihydroxyphenylalanine (L-dopa). The detailed chemical structure of melanin is not known. However, microscopic studies show that it has an overall granular structure. In fungi, melanin granules are localized to the cell wall where they are likely cross-linked to polysaccharides. Recent studies suggest the fungal melanin may be synthesized in internal vesicles akin to mammalian melanosomes and transported to the cell wall. Potential applications of melanin take advantage of melanin's radioprotective properties and propensity to bind to a variety of substances.
L-Glutamic acid (γ-4′-hydroxyanilide) (GHB) is oxidized by tyrosinase to a quinone which inhibits DNA polymerase, RNA polymerase, and mitochondrial energy production within mushrooms. It was previously shown that GHB can kill B16 melanoma cells in culture, but lacks cytotoxicity for nontyrosinase-containing cells. We have conjugated this drug to a superpotent melanotropic peptide and examined the bioactivity of this conjugate to melanoma cells. 4′-Hydroxyaniline was attached to glutamic acid at position 5 in the superpotent melanotropin fragment analogue, Ac-[Nle4, D-Phe7]α-MSH4–10-NH2. The melanotropin:anilide conjugate, Ac-[Nle4, Glu(γ-4′-hydroxyanilide)5, D-Phe7]α-MSH4–10-NH2, was not cytotoxic to B16 or Cloudman S91 mouse melanoma cells in culture, as determined by cell counts and protein assays. Interestingly, we also found that GHB stimulated melanoma cell tyrosinase above control levels in both melanoma cell lines. In our study, GHB itself also was found not to be cytotoxic to B16 or S91 melanoma cells in culture. In the frog skin bioassay, the melanotropin conjugate was more potent than α-MSH or Ac-[Nle4, D-Phe7]α-MSH4–10 in stimulating melanosome dispersion. These results demonstrate that putative chemotherapeutic ligands can be incorporated into active-site fragment analogues of MSH without loss of biological activity.
Common mushrooms [Agaricus bisporus (Lange) Imbach] were harvested at different stages of maturity and their nonvolatile taste components were studied. The moisture contents were in the range of 89.3–92.3% fresh weight. Based on dry weight, contents of other components were in the order: carbohydrate (38.3–48.9%)>crude protein (21.3–27.0%)>crude fibre (17.7–23.3%)>crude ash (7.77–11.0%)>crude fat (2.53–3.92%). Mannitol was the major soluble sugar and its content increased dramatically with maturation from 157 to 260mg/g. The content of total free amino acids was in the range of 48.8–64.2mg/g and peaked at stage 2 and then decreased significantly with maturation. The content of monosodium glutamate-like components was in the range of 10.6–13.5mg/g and similar to those of sweet components (11.4–14.3mg/g) but lower than those of bitter components (19.7–26.9mg/g). Contents of total 5′-nucleotides fluctuated in the range of 6.59–8.14mg/g. Contents of flavour 5′-nucleotides were higher in mushrooms harvested at stages 1 and 2 and decreased with maturation. Equivalent umami concentration values were 207–284g MSG/100g dry weight and higher at stages 2, 3 and 5. Based on the results obtained, Agaricus mushrooms possessed highly intense umami taste.
Phenolic compounds make up one of the major families of secondary metabolites in plants, and they represent a diverse group of compounds. Phenolics can be broadly divided into non-soluble compounds such as condensed tannins, lignins, and cell-wall bound hydroxycinammic acids, and soluble phenolics such as phenolic acids, phenylpropanoids, flavonoids and quinones. In this article, a method for extracting and analysing the soluble fraction of these phenolics, using HPLC coupled to photodiode array (PDA) detector, is described along with its uses to profile the flavonoid content of Lotus japonicus.literature available on this plant
With the full genome sequence of Agaricus bisporus available, it was possible to investigate the genes involved in the melanin biosynthesis pathway of button mushrooms. Based on different BLAST and alignments, genes were identified in the genome which are postulated to be involved in this pathway. Seven housekeeping genes were tested of which 18S rRNA was the only housekeeping gene that was stably expressed in various tissues of different developmental stages. Gene expression was determined for most gene homologs (26 genes) involved in the melanin pathway. Of the analysed genes, those encoding polyphenol oxidase (PPO), the PPO co-factor L-chain (unique for Agaricus bisporus), and a putative transcription factor (photoregulator B) were among the highest expressed in skin tissue. An in depth look was taken at the clustering of several PPO genes and the PPO co-factor gene on chromosome 5, which showed that almost 25% of the protein encoding genes in this cluster have a conserved NACHT and WD40 domain or a P-loop nucleoside triphosphate hydrolase. This article will be the start for an in depth study of the melanin pathway and the role in quality losses of this economically important product.
The antioxidant activities of ethanolic extract from edible mushroom Agaricus bisporus (A. bisporus) were evaluated by various methods in vitro and in vivo. In antioxidant assays in vitro, ethanolic extract of A. bisporus was found to have strong reducing power, superoxide radical, hydroxyl radical and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, and moderate hydrogen peroxide scavenging activity. In antioxidant assays in vivo, mice were administered with ethanolic extract of A. bisporus via gavage for 30 consecutive days. As a result, administration of ethanolic extract significantly enhanced the activities of antioxidant enzymes in serums, livers and hearts of mice. In addition, the total phenolic content in the extract determined by Folin-Ciocalteu method was 6.18 mg of gallic acid equivalents per g of dry weight. The main phenolic compounds in ethanolic extract analyzed by ultra-high performance liquid chromatography tandem mass spectrometry were determined as gallic acid, protocatechuic acid, catechin, caffeic acid, ferulic acid and myricetin. These results suggested that ethanolic extract of A. bisporus had potent antioxidant activity and could be explored as a novel natural antioxidant.
To explain differences in browning of skin tissue between unwashed and washed mushrooms, changes in soluble phenols, major substrates of polyphenol oxidase (PPO), and PPO isozymes during washing, as well as effects of sodium hpochlorite (NaOCl) on phenolic compounds in mushrooms were investigated. About 15% of the soluble phenols from the skin of mushroms, mostly gamma-L-glutaminyl-4-hydroxybenzene (GHB) and gamma-L-glutaminly-3,4-dihydroxybenzene (GDHB), were leached out during washing. Among four isozymes of partially purified PPO separated by native electrohoresis, the two faster migrating forms were leached out during washing. Phenolic compounds extracted from skin tissue were readily oxidized and degraded by 0.01% sodium hypochlorite. In a model system, NaOCl oxidized L-DOPA to a quinone, which turned black-brown, and degraded GHB and GDHB to unknown compounds. Darkening of washed mushrooms may be due to the reaction of a quinone derived from oxidation of L-DOPA or its derivatives by NaOCl.
Common mushrooms, Agaricus bisporus (Lange) Imbach, were stored at 12 °C for 12 days and composition changes were examined during post-harvest storage. The contents of total sugars, mannitol and fructose decreased steadily during storage, whereas the content of other reducing sugars, excluding fructose, remained constant. The content of total free amino acids increased from 77.92 at day 0 to 140.57 g kg−1 at day 6, and then slightly increased to 151.65 g kg−1 at day 12. The contents of nine amino acids increased over time, of these glutamic acid was the most significant. The content of monosodium glutamate-like components increased from 22.67 at day 0 to 47.12 g kg−1 at day 12. However, the contents of sweet and bitter components increased comparably from 24.08 and 24.17 at day 0 to 47.15 and 50.75 g kg−1 at day 12, respectively. Total 5′-nucleotide content peaked at day 3. The contents of three flavour 5-nucleotides were high at days 3 and 6.© 1999 Society of Chemical Industry
Chemical and enzymological analyses have been carried out to study the mode of action of CO2, in inhibiting germination in Agaricus bisporus and to test the suggestion (Vogel and Weaver, 1972. Exp. Cell Res. 75: 95, Vogel et at, 1974. Am. J. Pathol. 76: 165) that γ-glutaminyl-4-hydroxybenzene (GHB) and/or γ-glutaminyl-3,4-benzoquinone (GBQ) would inhibit the succinate dehydrogenase (SDH) in the mushroom spore and thus represent the causal agent(s) of its dormancy. Evidence is presented that the impairment of SDH is brought about by Ihe CO, fixation product oxaloacelate which is formed in the pyruvate carboxylase reaction, and a mechanism is proposed for the release of the SDH inhibition when activating the spores. These are almost devoid of GHB, whereas fruit bodies of all developmental stages contain considerable amounts of the phenol. GBQ is absent in the spore, and its occurrence in mushroom fruit body extracts appears to be an artifact of extraction. Apart from these analytical results, theoretical reasons are given that vouch against the involvement of the phenolics in the inhibition of SDH in vivo.
Total phenolic and flavonoid contents occurring in eight types of edible mushrooms (Agaricus bisporus, Boletus edulis, Calocybe gambosa, Cantharellus cibarius, Craterellus cornucopioides, Hygrophorus marzuolus, Lactarius deliciosus and Pleurotus ostreatus) have been respectively evaluated by the Folin–Ciocalteau assay and by the colorimetric reaction with NaNO2 and AlCl3 in a basic media. Generally, the assayed mushrooms contained between 1 and 6 mg of phenolics per gram of dried mushroom, depending on the species, while the flavonoid concentrations ranged between 0.9 and 3.0 mg per gram of dried matter. The profile and concentration of individual phenolics was determined by means of high performance liquid chromatography. Homogentisic acid was the free phenolic acid significantly present in all mushrooms although the content varied considerably among the analysed species. Flavonoids, such as myricetin and catechin were also detected in the mushrooms studied. The antioxidant properties of the methanolic extracts from mushrooms were evaluated by monitoring the linoleic acid autoxidation, and all the mushrooms species showed inhibition, with C. cibarius being the most effective against lipid oxidation (74% of inhibition) and A. bisporus the species with lowest antioxidant activity (10% of inhibition).Highlights► The mushrooms contained between 1 and 6 mg of phenolics per gram of dried matter. ► The total flavonoid concentration ranged between 0.9 and 3 mg per gram (DM). ► Homogentisic acid was the free phenolic acid significantly present in all mushrooms. ► Flavonoids, such as myricetin and catechin, are also detected. ► C. cibarius is the most effective inhibiting linoleic acid oxidation.
Biological macromolecules such as proteins and nucleic acids absorb light in the UV-visible region of the spectrum. Absorbance measurements are used for measuring concentrations, for the detection of conformational changes and of ligand binding, and for following enzyme reactions.
Keywords:
absorbance;
proteins;
nucleic acids;
enzymes;
denaturation
The diffuse reflectance Fourier-transform infrared spectra of the spore of the cultivated mushroom, Agaricus bisporus, of the melanin isolated therefrom and of various synthetic melanins related to the native material were recorded. There were prepared from γ-glutaminyl-4-hydroxybenzene (GHB; the presumed precursor of melanin in this fungus) as well as from simple phenol analogues of GHB, through auto- or enzyme-mediated oxidation and with, or without, potential non-phenolic co-reactants. The spectrum of the spore is dominated by distinct IR absorptions due to melanin, chitin and protein, while the isolated pigment is characterized mainly by the melanin absorption band at 1600 cm−1, which can be attributed primarily to aromatic groups whose signal is enhanced by phenol functionalities and, to a lesser extent, by amido groups. In addition, pronounced alkyl and carbonyl absorption bands were observed, and there is evidence of extensive CO and CN bonding in the biopigment. The spectrum of the melanin made from GHB through enzyme catalysis (phenolase, EC 1.14.18.1/1.10.3.1.) most closely matched that of the biopigment. Use of 4-aminocatechol (AC) instead of GHB afforded a product which was similar to the native melanin, whereas the pigment obtained by air oxidation of 4-aminophenol (AP) was largely dissimilar. Cross-linking of the reacting phenol with protein was apparent in the melanin formed enzymatically from AC, but no evidence for such reactivity was present in the AP-derived melanin. Preformed chitin did not become incorporated into either synthetic melanin. The fungus does not synthesize melanin from AP, nor directly from GHB, but from AC in a proteinaceous environment represented in part by the phenol oxidase itself.
Agaricus bisporus browning is a common and economically detrimental phenomenon, in which melanogenic phenols are enzymically processed into quinones, which evolve eventually to melanins. This review deals with the two fundamental sides of this process, enzyme(s) and phenolic substrates. Mushroom tyrosinase, the main polyphenol oxidase encountered in the A. bisporus sporophore, is treated in the first part. Its overall molecular architecture, isoforms, primary sequence and genetic background are considered. The presentation of tyrosinase catalytic features, including enzyme assays, kinetic properties, substrates and inhibitors, is followed by a comprehensive description of the active site and reaction mechanisms. Because of their relevance for studies of mushroom browning during development and post-harvest storage, the occurrence and properties of latent enzyme forms, as well as the location of tyrosinase and variations of its activity during the A. bisporus life cycle, are also reviewed. The second part deals with the substrates, particularly γ-L-glutaminyl-4-hydroxybenzene (GHB) and its derivatives. Main data concerning the nature, obtention (by extraction or synthesis), spectrometric and chromatographic characteristics, chemical stabilities and biological properties of these typical Agaricaceae compounds are presented. Their distribution and levels according to the strains and flushes are described, as well as their variations during storage. Thirdly, the relationship between browning and the natural or pathogenic discolouration intensity is developed.
The effect of sodium hydrogen sulfite (S), used as antibrowning agent, on the phenolic profile of potato extracts was investigated. This extract was compared to one obtained in the presence of ascorbic acid (A). In the presence of A, two major compounds were obtained, 5-O-caffeoylquinic acid (5-CQA) and 4-O-caffeoyl quinic acid. With S, their 2'-sulfo-adducts were found instead, the structures of which were confirmed by nuclear magnetic resonance spectroscopy and mass spectrometry. Also, for minor caffeoyl derivatives and quercetin glycosides, the corresponding sulfo-adducts were observed. Feruloyl and sinapoyl derivatives were not chemically affected by the presence of S. Polyphenol oxidase (PPO) was thought to be responsible for the formation of the sulfo-adducts. This was confirmed by preparing 2'-sulfo-5-O-caffeoyl quinic acid in a model system using 5-CQA, sodium hydrogen sulfite, and PPO. This sulfo-adduct exhibited a small bathochromic shift (λmax 329 nm) as compared to 5-CQA (λmax 325 nm) and a strong hypochromic shift with an extinction coefficient of 9357±395 M(-1) cm(-1) as compared to 18494±196 M(-1) cm(-1), respectively. The results suggest that whenever S is used as an antibrowning agent, the O-quinone formed with PPO reacts with S to produce sulfo-O-diphenol, which does not participate in browning reactions.
L-Glutamic acid (gamma-4'-hydroxyanilide) (GHB) is oxidized by tyrosinase to a quinone which inhibits DNA polymerase, RNA polymerase, and mitochondrial energy production within mushrooms. It was previously shown that GHB can kill B16 melanoma cells in culture, but lacks cytotoxicity for nontyrosinase-containing cells. We have conjugated this drug to a superpotent melanotropic peptide and examined the bioactivity of this conjugate to melanoma cells. 4'-Hydroxyaniline was attached to glutamic acid at position 5 in the superpotent melanotropin fragment analogue, Ac-[Nle4, D-Phe7]alpha-MSH4-10-NH2. The melanotropin:anilide conjugate, Ac-[Nle4, Glu(gamma-4'-hydroxyanilide)5, D-Phe7]alpha-MSH4-10-NH2, was not cytotoxic to B16 or Cloudman S91 mouse melanoma cells in culture, as determined by cell counts and protein assays. Interestingly, we also found that GHB stimulated melanoma cell tyrosinase above control levels in both melanoma cell lines. In our study, GHB itself also was found not to be cytotoxic to B16 or S91 melanoma cells in culture. In the frog skin bioassay, the melanotropin conjugate was more potent than alpha-MSH or Ac-[Nle4, D-Phe7]alpha-MSH4-10 in stimulating melanosome dispersion. These results demonstrate that putative chemotherapeutic ligands can be incorporated into active-site fragment analogues of MSH without loss of biological activity.
The naturally occurring compound agaritine (beta-N-[gamma-L(+)glutamyl]-4-hydroxy-methylphenyl-hydrazine) has been determined in fresh, dried and processed mushrooms. A method was developed involving extraction of the toxin into methanol, clean-up where appropriate (for processed products) by high-performance size exclusion liquid chromatography and determination by reverse-phase HPLC with electrochemical detection. Diode array UV monitoring was used for confirmation. The method had a recovery of 90-98%, a relative standard deviation of 3-5% and a limit of detection of agaritine of 5 mg/kg on a dry-weight basis. Fresh cultivated mushrooms showed agaritine levels of 100-250 mg/kg and 80-190 mg/kg for two different commercial strains. There were slight differences in levels of agaritine between mushrooms of different sizes, and between those of the same size but harvested at different times (different breaks). Retail processed mushrooms products had low agaritine levels in the range 6-33 mg/kg, with the exception of one dried sliced mushroom product found to contain 6520 mg/kg.
Fungal melanins are dark brown or black pigments located in cell walls. They also exist as extracellular polymers. Melanized fungi possess increased virulence and resistance to microbial attack as well as enhanced survival while under environmental stress. Melanins contain various functional groups which provide an array of multiple nonequivalent binding sites for metal ions. Pigmented Cladosporium cladosporoides was shown to biosorb 2.5- to four-fold more Ni, Cu, Zn, Cd, and Pb than albino Penicillium digitatum and at four- to six-fold higher rates. Metal desorption was significantly lower for extracellular melanin than from pigmented or albino biomass which indicated the strength of the melanin-metal bond. At equilibrium, tributyltin chloride (TBTC) concentrations of 2.5 mM, pigmented and albino Aureobasidium pullulans absorbed approximately 0.9 and 0.7 mumol TBTC mg -1 dry wt, respectively, whereas purified extracellular melanin exhibited uptake levels of approximately 22 mumol TBTC mg-1 dry wt at an equilibrium concentration of only 0.4 mM. Addition of melanin to the growth medium reduced the toxic effect of CuSO4 and TBTC due to melanin metal binding and sequestration.
To enhance the shelf life of edible mature mushrooms, Agaricus bisporus, 2 kGy ionizing treatments were applied at two different dose rates: 4.5 kGy/h (I(-)) and 32 kGy/h (I(+)). Both I(+) and I(-) showed a 2 and 4 day shelf-life enhancement compared to the control (C). Before day 9, no significant difference (p>0.05) in L value was detected in irradiated mushrooms. However, after day 9, the highest observed L value (whiteness) was obtained for the mushrooms irradiated in I(-). Analyses of phenolic compounds revealed that mushrooms in I(-) contained more phenols than I(+) and C, the latter containing the lower level of phenols. The fluctuation of the precursors of glutaminyl-4-hydroxyaniline (GHB) was less in I(-) than in I(+). The polyphenol oxidase (PPO) activities of irradiated mushrooms, analyzed via catechol oxidase, dopa oxidase, and tyrosine hydroxylase substrates, were found to be significantly lowered (p = 0.05) compared to C, with a further decrease in I(+). Analyses of the enzymes indicated that PPO activity was lower in I(+), contrasting with its lower phenols concentration. The observation of mushrooms' cellular membranes, by electronic microscopy, revealed a better preserved integrity in I(-) than in I(+). It is thus assumed that the browning effect observed in I(+) was caused by both the decompartmentation of vacuolar phenol and the entry of molecular oxygen into the cell cytoplasm. The synergetic effect of the residual active PPO and the molecular oxygen, in contact with the phenols, allowed an increased oxidation rate and, therefore, a more pronounced browning I(+) than in I(-).
Variation of Agaricus bisporus susceptibility to bacterial blotch in relation to environment was studied at the biochemical level. Significant differences were observed between A. bisporus strains for tyrosinase and gamma-glutamyl transferase (GGT) activities and for gamma-L(+)glutaminyl-4-hydroxybenzene (GHB) content. A lower effect was detected for compost quality. GGT activity and GHB content were related to strain susceptibility to bacterial blotch by a linear model depending on strain type, commercial or wild.
This review compiles and discusses previous reports on the identity of wall-associated enzymes (WAEs) in fungi and addresses critically the widely different terminologies used in the literature to specify the type of bonding of WAEs to other entities of the cell wall compartment, the extracellular matrix (ECM). A facile and rapid fractionation protocol for catalytically active WAEs is presented, which uses crude cell walls as the experimental material, a variety of test enzymes (including representatives of polysaccharide synthases and hydrolases, phosphatases, gamma-glutamyltransferases, pyridine-nucleotide dehydrogenases and phenol-oxidising enzymes) and a combination of simple hydrophilic and hydrophobic extractants. The protocol provides four fully operationally defined classes of WAEs, with constituent members of each class displaying the same basic type of physicochemical interaction with binding partners in situ. The routine application of the protocol to different species and cell types could yield easily accessible data useful for building-up a general objective information retrieval system of WAEs, suitable as an heuristic basis both for the unravelling of the role and for the biotechnological potentialities of WAEs. A detailed account is given of the function played in the ECM by WAEs in the metabolism of chitin (chitin synthase, chitinase and beta-N-acetylhexosaminidase) and of phenols (tyrosinase).
The reaction of ninhydrin with primary amino groups to form the purple dye now called Ruhemann's purple (RP) was discovered by Siegfried Ruhemann in 1910. In addition, imines such as pipecolic acid and proline, the guanidino group of arginine, the amide groups of asparagine, the indole ring of tryptophan, the sulfhydryl group of cysteine, amino groups of cytosine and guanine, and cyanide ions also react with ninhydrin to form various chromophores of analytical interest. Since its discovery, extensive efforts have been made to apply manual and automated ninhydrin reactions as well as ninhydrin spray reagents to the detection, isolation, and analysis of numerous compounds of interest across a broad spectrum of disciplines. These include agricultural, biochemical, clinical, environmental, food, forensic, histochemical, microbiological, medical, nutritional, plant, and protein sciences. This reaction is unique among chromogenic reactions in that at pH 5.5 it results in the formation of the same soluble chromophore by all primary amines which react, be they amines, amino acids, peptides, proteins, and even ammonia. Because the chromophore is not chemically bound to the protein or other insoluble material, it is not lost when the insoluble substrate is removed by centrifugation or filtration after the reaction is completed. The visible color of the chromophore is distinctive and is generally not affected by the yellow colors present in many food, plant, and tissue extracts. Adaptations of the classical ninhydrin reaction to specialized needs in analytical chemistry and biochemistry include the use of acid, alkaline, and fluorogenic ninhydrin reagents. To cross-fertilize information among several disciplines wherein an interest in the ninhydrin reaction has developed, and to enhance its utility, this review attempts to integrate and correlate the widely scattered literature on ninhydrin reactions of a variety of structurally different compounds. Specifically covered are the following aspects: historical perspective, chemistry and mechanisms, applications, and research needs. A better understanding of these multifaceted ninhydrin reactions provide a scientific basis for further improvements of this important analytical technique.
Polyphenol oxidase from plants and fungi is a metalloenzyme containing a type-3 copper center and is homologous to oxygen-carrying hemocyanin of molluscs. Molluscan hemocyanin consists of two domains, an N-terminal domain containing the copper center and a smaller C-terminal domain, connected by an alpha-helical linker. It is presumed that the same is true of polyphenol oxidase from plants and fungi although the structure of a polyphenol oxidase containing the C-terminal domain has not been determined. We show that a number of important structural features are conserved in the N-terminal domains of polyphenol oxidases from various plants and fungi, including a tyrosine motif which can be considered a landmark indicating the beginning of the linker region connecting the N- and C-terminal domains. Our sequence alignments and secondary structure predictions indicate that the C-terminal domains of polyphenol oxidases are likely to be similar in tertiary structure to that of hemocyanin. Detailed bioinformatics analyses of the linker regions predict that this section of the polypeptide chain is intrinsically disordered (lacking fixed tertiary structure) and contains a site of proteolytic processing as well as a potential phosphorylation site.
The more recent reports on polyphenol oxidase in plants and fungi are reviewed. The main aspects considered are the structure, distribution, location and properties of polyphenol oxidase (PPO) as well as newly discovered inhibitors of the enzyme. Particular stress is given to the possible function of the enzyme. The cloning and characterization of a large number of PPOs is surveyed. Although the active site of the enzyme is conserved, the amino acid sequence shows very considerable variability among species. Most plants and fungi PPO have multiple forms of PPO. Expression of the genes coding for the enzyme is tissue specific and also developmentally controlled. Many inhibitors of PPO have been described, which belong to very diverse chemical structures; however, their usefulness for controlling PPO activity remains in doubt. The function of PPO still remains enigmatic. In plants the positive correlation between levels of PPO and the resistance to pathogens and herbivores is frequently observed, but convincing proof of a causal relationship, in most cases, still has not been published. Evidence for the induction of PPO in plants, particularly under conditions of stress and pathogen attack is considered, including the role of jasmonate in the induction process. A clear role of PPO in a least two biosynthetic processes has been clearly demonstrated. In both cases a very high degree of substrate specificity has been found. In fungi, the function of PPO is probably different from that in plants, but there is some evidence indicating that here too PPO has a role in defense against pathogens. PPO also may be a pathogenic factor during the attack of fungi on other organisms. Although many details about structure and probably function of PPO have been revealed in the period reviewed, some of the basic questions raised over the years remain to be answered.
A study was conducted to determine the content of phenolic compounds and the antioxidative activity of five edible and five medicinal mushrooms commonly cultivated in Korea. Phenolic compounds were analyzed using high performance liquid chromatography, and antioxidant activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and superoxide dismutase activity. A total of 28 phenolic compounds were detected in the mushrooms studied. The average total concentration of phenolic compounds was 326 microg/g, the average being of 174 microg/g in edible mushrooms and 477 microg/g in medicinal mushrooms. The average total flavonoids concentration was 49 microg/g, with averages of 22 and 76 microg/g in edible and medicinal mushrooms, respectively. The DPPH radical scavenging activities ranged between 15 (Pleurotus eryngii) and 70% (Ganoderma lucidum) when reaction time was for 1 min. When reaction time was 30 min, the values ranged between 5 (Pleurotus eryngii) and 78% (Agaricus bisporus). The SOD activity averaged 28% among the 10 mushroom species, averages for edible and medicinal mushrooms being comparable. DPPH activities was significantly correlated (p < 0.01) with total content of phenolic compounds in edible mushrooms, while in medicinal mushrooms there was a significant correlation (p < 0.01) between SOD activity and total concentration of phenolic compounds. Numerous significant positive correlations were observed between phenolic compounds detected and antioxidative potential.
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