Quercetin, one of the most widely distributed flavonoids, has been found to show various biological activities including antioxidant, anticancer, and anti-inflammatory effects. It has been reported that bioactivity enhancement of flavonoids has often been closely associated with nuclear prenylation, as shown in 8-prenylquercetin and 5′-prenylquercetin. It has also been revealed in many studies that the biological activities of flavonoids could be improved after glucosylation. Three prenylated quercetins were prepared in this study, and microbial transformation was carried out in order to identify derivatives of prenylquercetins with increased water solubility and improved bioavailability. The fungus M. hiemalis was proved to be capable of converting prenylquercetins into more polar metabolites and was selected for preparative fermentation. Six novel glucosylated metabolites were obtained and their chemical structures were elucidated by NMR and mass spectrometric analyses. All the microbial metabolites showed improvement in water solubility.
Biotransformation of four bioactive phenolic constituents from licorice, namely licoisoflavanone (1), glycyrrhisoflavone (2), echinatin (3), and isobavachalcone (4), was performed by the selected fungal strain Aspergillus niger KCCM 60332, leading to the isolation of seventeen metabolites (5–21). Structures of the isolated compounds were determined on the basis of extensive spectroscopic methods, twelve of which (5–7, 10–17 and 19) have been previously undescribed. A series of reactions including hydroxylation, hydrogenation, epoxidation, hydrolysis, reduction, cyclization, and alkylation was observed in the biotransformation process. All compounds were tested for their cytotoxic activities against three different human cancer cell lines including A375P, MCF-7, and HT-29. Compounds 1 and 12 exhibited most considerable cytotoxic activities against all the cell lines investigated, while compounds 2 and 4 were moderately cytotoxic. These findings will contribute to expanding the chemical diversity of phenolic compounds, and compounds 1 and 12 may serve as leads for the development of potential cancer chemopreventive agents.
Microbial transformation of licochalcones B (1), C (2), D (3), and H (4) using the filamentous fungi Aspergillus niger and Mucor hiemalis was investigated. Fungal transformation of the licochalcones followed by chromatographic separations led to the isolation of ten new compounds 5-14, including one hydrogenated, three dihydroxylated, three expoxidized, and three glucosylated metabolites. Their structures were elucidated by combined analyses of UV, IR, MS, NMR, and CD spectroscopic data. Absolute configurations of the 2",3"-diols in the three dihydroxylated metabolites were determined by ECD experiments according to the Snatzke's method. The trans-cis isomerization was observed for the metabolites 7, 11, 13, and 14 as evidenced by the analysis of their 1 H-NMR spectra and HPLC chromatograms. This could be useful in better understanding of the trans-cis isomerization mechanism of retrochalcones. The fungal transformation described herein also provides an effective method to expand the structural diversity of retrochalcones for further biological studies.Molecules 2020, 25, 60 2 of 13 reactions [22][23][24]. However, to date few microbial transformation studies have been investigated directly on the series of retrochalcones isolated from licorice. In the present study, we report the microbial transformation of licochalcones B (LB, 1), C (LC, 2), D (LD, 3) and H (LH, 4) by the selected fungi Aspergillus niger and Mucor hiemalis. Results and Discussion2.1. Microbial Transformation of Licochalcones B (1), C (2), D (3) and H (4) by A. niger Microbial transformation of LB (1) by A. niger produced the hydrogenated metabolite 5; microbial transformation of LC (2), LD (3) and LH (4) by A. niger furnished the corresponding dihydroxylated metabolites 6, 8, 10 and expoxidized metabolites 7, 9, 11, respectively (Scheme 1).Molecules 2019, 24, x FOR PEER REVIEW 2 of 13 many novel derivatives by means of cyclization, hydroxylation, reduction, and dehydrogenation reactions [22][23][24]. However, to date few microbial transformation studies have been investigated directly on the series of retrochalcones isolated from licorice. In the present study, we report the microbial transformation of licochalcones B (LB, 1), C (LC, 2), D (LD, 3) and H (LH, 4) by the selected fungi Aspergillus niger and Mucor hiemalis. Results and Discussion Microbial Transformation of Licochalcones B(1), C (2), D (3) and H (4) by A. nigerMicrobial transformation of LB (1) by A. niger produced the hydrogenated metabolite 5; microbial transformation of LC (2), LD (3) and LH (4) by A. niger furnished the corresponding dihydroxylated metabolites 6, 8, 10 and expoxidized metabolites 7, 9, 11, respectively (Scheme 1). Scheme 1. Metabolites 5-11 obtained from microbial transformation of licochalcones B (1), C (2), D (3), and H (4) by A. niger. Selected HMBC correlations ( 1 H→ 13 C) of each metabolite are indicated by arrows. Scheme 1. Metabolites 5-11 obtained from microbial transformation of licochalcones B (1), C (2), D (3), and H (4) by A. niger. Selected HMBC c...
The microbial transformation studies of 7-O-prenylquercetin (1), 4'-O-prenylquercetin (2) and quercetin (3) were investigated with 20 different microbial strains to discover new metabolites. It was revealed that the fungus Mucor hiemalis was the most appropriate micro-organism which was capable of transforming these flavonoids. Structures of the three new (4-6) and one known (7) metabolites were elucidated as 7-O-prenylquercetin 3-O-β-D-glucopyranoside (4), 4'-O-prenylquercetin 3-O-β-D-glucopyranoside (5), 4'-O-prenylquercetin 3'-O-β-D-glucopyranoside (6) and quercetin 5-O-β-D-glucopyranoside (7) by the spectroscopic methods.
Microbial conjugation studies of licochalcones (1–4) and xanthohumol (5) were performed by using the fungi Mucor hiemalis and Absidia coerulea. As a result, one new glucosylated metabolite was produced by M. hiemalis whereas four new and three known sulfated metabolites were obtained by transformation with A. coerulea. Chemical structures of all the metabolites were elucidated on the basis of 1D-, 2D-NMR and mass spectroscopic data analyses. These results could contribute to a better understanding of the metabolic fates of licochalcones and xanthohumol in mammalian systems. Although licochalcone A 4′-sulfate (7) showed less cytotoxic activity against human cancer cell lines compared to its substrate licochalcone A, its activity was fairly retained with the IC50 values in the range of 27.35–43.07 μM.
Galangin (1), 3-O-methylgalangin (2), and galangin flavanone (3), the major bioactive flavonoids isolated from Alpinia officinarum, were biotransformed into one novel and four known metabolites (4–8) by application of the fungal strains Mucor hiemalis and Absidia coerulea as biocatalysts. Their structures were characterized by extensive spectroscopic analyses including one- and two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. Compounds 1–7 were evaluated for their cytotoxic activities against cancer cell lines using the MTT assay. The new compound 3-O-methylgalangin-7-O-β-D-glucopyranoside (6) exhibited the most potent cytotoxic activity against MCF-7, A375P, B16F10, B16F1, and A549 cancer cell lines with the IC50 values at 3.55–6.23 μM.
Microbial transformations of (±)-7-O-prenylnaringenin (7-PN, 1) and (±)-7-O-allylnaringenin (7-AN, 2) have isolated four metabolites (3-6). Structures of these novel compounds were identified as 5,4'-dihydroxy-7-O-[(2E)-4-hydroxy-3-methyl-2-buten-1-yl]flavanone (3), 5,4'-dihydroxy-7-O-(2,3-dihdroxy-3-methylbutyl)flavanone (4), 5,4'-dihydroxy-7-O-(2,3-dihdroxypropyl)flavanone (5), and 5-O-β-D-glucopyranosyl-7-O-allyl-4'-hydroxyflavanone (6) based on spectroscopy. Compounds 1-6 were evaluated for their radical scavenging capacity using DPPH (2,2-diphenyl-1-picrylhydrazyl). The derivatives 3-6 exhibited more potent antioxidant activity than their corresponding substrates 1 and 2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.