ABSTRACT
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 Ca, Fe, Mn, Mg, and Zn 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.
Subject(s)
Biotransformation , Gliocladium , Chemistry , Metabolism , Molecular Structure , Quercetin , Chemistry , MetabolismABSTRACT
The present study was designed to explore the substrate scope and biocatalytic capability of Gliocladium deliquescens NRRL 1086 on phenolic natural products. Emodin was subjected to the fermentation culture of Gliocladium deliquescens NRRL 1086 according to the standard two-stage protocol. The biotransformation process was monitored by HPLC-DAD-MS, the main product was isolated by column chromatography, and the structure was elucidated on the basis of NMR spectroscopy. Emodin could be fully metabolized by Gliocladium deliquescens NRRL 1086, resulting in high yield of emodin 6-O-β-D-glucopyranoside and small amount of sulfated product. In conclusion, our results may provide a convenient method to prepare emodin 6-O-β-D-glucopyranoside and the microbe catalyzed glucosylation/sulfation will give an inspiration to pharmacokinetic model studies in vitro.