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With an attempt to synthesize high-value isoquercitrin (quercetin-3-O-β-D-glucopyranoside), we carried out the biotransformation of quercetin (1) by Gliocladium deliquescens NRRL 1086. Along with the aimed product quercetin 3-O-β-D-glycoside (2), three additional metabolites, 2-protocatechuoyl-phlorogucinol carboxylic acid (3), 2,4,6-trihydroxybenzoic acid (4), and protocatechuic acid (5), were also isolated. The time-course experiments revealed that there were two metabolic routes, regio-selectivity glycosylation and quercetin 2,3-dioxygenation, co-existing in the culture. Both glycosylation and oxidative cleavage rapidly took place after quercetin feeding; about 98% quercetin were consumed within the initial 8 h and the oxdized product (2-protocatechuoyl-phlorogucinol carboxylic acid) was hydrolyzed into two phenolic compounds (2,4,6-trihydroxybenzoic acid and protocatechuic acid). We also investigated the impact of glucose content and metal ions on the two reactions and found that high concentrations of glucose significantly inhibited the oxidative cleavage and improved the yield of isoquercitrin and that Ca2+, Fe2+, Mn2+, Mg2+, and Zn2+ inhibited glycosylation. To test the promiscuity of this culture, we selected other four flavonols as substrates; the results demonstrated its high regio-selectivity glycosylation ability towards flavonols at C-3 hydroxyl. In conclusion, our findings indicated that the versatile microbe of G. deliquescens NRRL 1086 maitained abundant enzymes, deserving further research.
glycosylation, quercetin, biotransformation, Gliocladium deliquescens NRRL 1086, quercetin-2, 3-dioxygenase
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By the newly developed assay method, the glycolipid Acremomannolipin A (1) was isolated from a filamentous fungus Acremonium strictum as a potential calcium signal modulator. The structure of 1 elucidated on the basis of intensive spectroscopic analyses as well as its degradation studies is quite unique: the d-mannopyranose is connected to d-mannitol through a β-glycoside linkage; all the hydroxyls in the mannose are highly masked as peresters with aliphatic acids, and this moiety is made hydrophobic, whereas the mannitol part exhibits a highly hydrophilic property. The compound (1) showed the characteristic bioactivity property, enabling calcineurin deletion cells to grow in the presence of Cl(-), which would be caused by calcium signal modulating. The activity was so potent as to exert the effect at a concentration of 200 nM.
glycolipid, acremomannolipin A, calcium signal modulator, Acremonium strictum, phenotypic screen
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The culture characteristics, carotenoid production, and associated biosynthetic pathway of strain T-1 were examined. As a result of examining the culture temperature and light irradiation, an increase of neurosporaxanthin and neurosporaxanthin β-D-glucopyranoside was observed at a low temperature and 0 lx. It was suggested that highly polar carotenoids, such as neurosporaxanthin, and carotenoid glycosides were involved in the stabilization of membrane during nutrition storage other than the defense function of fungus bodies. Strain T-1 produced lycopene, β-carotene, γ-carotene, torulene, neurosporaxanthin, and neurosporaxanthin β-D-glucopyranoside, as assessed by HPLC, LC-MS, and NMR analysis. Carotenoid biosynthesis begins with neurosporene, passing to lycopene and γ-carotene through cyclization, and produces β-carotene. In addition, it is saturated, γ-carotene is converted to torulene, and neurosporaxanthin is produced. Thus, the carotenoid biosynthetic pathway in strain T-1 was estimated.
carotenoid, culture characteristics, light irradiation, neurosporaxanthin, neurosporaxanthin β-D-glucopyranoside
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