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Found 2 structures.
Displayed structures from 1 to 2
| b-D-GlcpA-(1-3)-Quercetin | Show graphically |
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Structure type: monomer
Trivial name: miquelianin
Compound class: saponin glycoside, glycoside, flavonoid glycoside, flavonol glycoside, flavone glycoside
Contained glycoepitopes: IEDB_115136,IEDB_140630,IEDB_423153
Microbial biotransformations constitute an important alternative as models for drug metabolism study in mammalians and have been used for the industrial synthesis of chemicals with pharmaceutical purposes. Several microorganisms with unique biotransformation ability have been found by intensive screening and put in commercial applications. Ten isolates of Beauveria sp genus filamentous fungi, isolated from soil in the central Brazil, and Beauveria bassiana ATCC 7159 were evaluated for their capability of quercetin biotransformation. Biotransformation processes were carried out for 24 up to 96 hours and monitored by mass spectrometry analyses of the culture broth. All strains were able to metabolize quercetin, forming mammalian metabolites. The results were different from those presented by other microorganisms previously utilized, attrackting attention because of the great diversity of reactions. Methylated, sulphated, monoglucuronidated, and glucuronidated conjugated metabolites were simultaneously detected.
quercetin, biotransformation, Beauveria bassiana
Publication DOI: 10.1590/S1517-83822008000200036Flavonols were characterized and measured in experimental (n = 46) and commercial (n = 9) red raspberry juices by HPLC/diode array spectral techniques. Samples were prepared using minicolumns, packed with Polyamide 6. A fraction eluted with methanol contained eight or fewer quercetin glycosides, quercetin, and kaempferol. A second fraction eluted subsequently with 0.5% ammonia in methanol contained three flavonol glucuronides, two flavonol forms, aglycons, ellagic acid, and its derivatives. Quercetin 3-glucuronide was the major flavonol in experimental and commercial juices, respectively (mean of 54 and 51 ppm), and a flavonol presumed to be quercetin 3-sophoroside was the second primary compound (means of 29 and 33 ppm). In addition, 36 flavonol forms were measured in trace amounts. The mean total concentrations of quercetin and kaempferol forms, respectively, in experimental juices (n = 45) were 118 and 3.6 ppm and in commercial juices (n = 7) 121 and 3.4 ppm, respectively. The mean total flavonol concentrations in experimental and commercial juices were 122 and 125 ppm, respectively. Influences of cultivar (n = l0), processing method (standard, high-speed centrifugation, depectinization, diffusion extraction, vacuum and osmotic concentration) and environmental factors (geographic origin, maturity, harvesting method, mold contamination) were evaluated.
Publication DOI: 10.1021/jf00035a025From the roots of Clematis stans three new oleanane-type triterpenoid saponins named clemastanoside A, B and C, and two new lignan glycosides named clemastanin A and B, have been isolated together with three known triterpenoid saponins, huzhangoside B, C and D, and three known lignan glycosides, (+)-lariciresinol 4-O-β-D-glucopyranoside, (+)-lariciresinol 4'-O-β-D-glucopyranoside and (+)-pinoresinol 4,4'-O-bis-β-D-glucopyranoside. In addition, from the leaves, four new oleanane-type triterpenoid saponins, named clemastanoside D, E, F and G, have been isolated together with five known triterpenoid saponins, hederasaponin B, kizutasaponin K_<12>, huzhangoside B, sieboldianoside B and huzhangoside D, and three known flavonoids, isoquercitrin, rutin and quercetin 3-O-β-D-glucuronopyranoside. The structures of the new compounds were elucidated based on chemical and physicochemical evidence as follows : clemastanoside A, 3-O-β-D-ribopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl oleanolic acid 28-O-(4-O-acetyl)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester (terminal rhamnosyl 4-O-acetate of huzhangoside B); clemastanoside B and C, 3-O-β-D-xylopyranosyl- and 3-O-β-D-ribopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl oleanolic acid 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, respectively; clemastanoside D, 3-O-β-D-ribopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl hederagenin 28-O-β-D-glucopyranosyl ester; clemastanoside E, F and G, terminal rhamnosyl 4-O-, 3-O- and 2-O-acetate of 3-O-β-D-ribopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl hederagenin 28-O-α-L-rhamno-pyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, respectively; clemastanin A, (7S, 8R)-3-methoxy-3', 4,9,9'-tetrahydroxy-4', 7-epoxy-5', 8-lignan 3'-O-β-D-glucopyranoside; clemastanin B, (+)-lariciresinol 4,4'-O-bis-β-D-glucopyranoside.
Ranunculaceae, lignan glycoside, Clematis stans, oleanolic acid bisdesmoside, hederagenin bisdesmoside, quercetin glycoside
NCBI PubMed ID: 8582022We have examined the antioxidant activity of one class of polyphenolic compounds in green beans: two novel flavonol glycosides (quercetin 3-O-[xylosyl(1→2)]-rhamnosyl(1→6)-glucoside and the corresponding kaempferol analogue), quercetin 3-O-glucuronide, kaempferol 3-O-glucuronide, quercetin 3-O-rutinoside and kaempferol 3-O-rutinoside. The Trolox equivalent antioxidant capacity (TEAC) and inhibition of iron/ascorbate-induced lipid peroxidation of phosphatidyl choline vesicles were measured. In the aqueous phase TEAC assay, the glucuronide and rutinoside of quercetin were good antioxidants, but not as effective as the quercetin aglycone. TEAC values for the glucuronide and other glycosides of kaempferol were much lower than the corresponding quercetin species but similar to that of the kaempferol aglycone. Quercetin 3-O-glucuronide and quercetin 3-O-rutinoside were both potent inhibitors of lipid peroxidation, in contrast to the those of kaempferol. The compounds described herein demonstrate the antioxidant activity of the flavonols present in green beans and indicate the effect on antioxidant activity of sugar substitutions in the phenolic C ring.
glycoside, flavonoid, Antioxidant activity, Phaseolus vulgaris, polyphenolic compound, green beans
NCBI PubMed ID: 10496415The new flavonol glycosides quercetin 3-O-β-(2-O-α-L-rhamnopyranosyl)-glucopyranoside uronic acid and kaempferol 3-O-β-(2-O-α-L-rhamnopyranosyl)-glucopyranoside uronic acid were isolated from the leaves of Alchemilla speciosa Buser together with 13 known flavonol and flavone glycosides and (+)-catechin. The structures were determined by spectroscopic methods.
flavonol glycosides, Alchemilla speciosa, spectroscopic methods
NCBI PubMed ID: 17260291(3R)-O-β-D-Glucopyranosyloxy-5-phenylvaleric acid (1), (3R)-O-β-D-glucopyranosyloxy-5-phenylvaleric acid n-butyl ester (2), and a new dihydrochalcone diglycoside 4'-O-[β-D-glucopyranosyl-(1→-6)-glucopyranosyl]-oxy-2'-hydroxy-3',6'-dimethoxydihydrochalcone (3), together with six known flavonoid glycosides [kaempferol-3-O-β-D-glucopyranoside (= astragalin) (4), kaempferol-3-O-β-D-galactopyranoside (5), quercetin-3-O-β-D-glucopyranoside (= isoquercitrin) (6), quercetin-3-O-β-D-galactopyranoside (= hyperoside) (7), quercetin-3-O-(2'-O-galloyl)-β-D-glucopyranoside (8), and quercetin-3-O-β-D-glucuronopyranoside (9)] were isolated from the aerial parts of Polygonum salicifolium. The structure elucidation of the isolated compounds was performed by spectroscopic (UV, IR, ESI-MS, 1D- and 2D-NMR), chemical (methylation, enzymatic hydrolysis, partial synthesis), and chromatographic methods (HPLC, Chiralcel OD). The flavonoid glycosides (4-9) demonstrated scavenging properties toward the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in TLC autographic assays.
isoquercitrin, hyperoside, flavonoid glycoside, phenylvaleric acid glycoside, Polygonum salicifolium, astragalin
NCBI PubMed ID: 10479312Quercetin-3-β-glucuronide and kaempferol-3-β-glucuronide were isolated from the fruit of raspberry. In addition, two other glycosides were isolated by TLC.
rosaceae, raspberry, flavonol glucuronide, Rubus ideaeus
Publication DOI: 10.1016/0031-9422(71)85048-3A methanolic extract from dill (Anethum graveolens) herb was subjected to XAD-2 adsorption chromatography. The methanolic eluate was fractionated with the all liquid chromatographic technique of multilayer coil countercurrent chromatography (MLCCC). After acetylation of MLCCC subfractions and flash chromatography, final purification of dill herb constituents was achieved by preparative and/or analytical HPLC. Nine compounds were obtained in pure form, including the beta-D-glucopyranosides of 9-hydroxypiperitone, p-menth-2-ene-1,6-diol, and 8-hydroxygeraniol. Structure elucidation is based on electrospray ionization ion trap multiple mass spectrometry (ESI-MS/MS) as well as one- and two-dimensional nuclear magnetic resonance spectroscopy.
glycosides, multilayer coil countercurrent chromatography, dill herb, 9-hydroxypiperitone β-D-glucopyranoside, p-menth-2-ene-1, 6-diol β-D-glucopyranoside, 8-hydroxygeraniol β-D-glucopyranoside, dill ether
NCBI PubMed ID: 11052739Eight varieties of lettuce (Lactuca sativum) and three varieties of endive (Cichorium endivia) were analyzed for flavonoid composition and content. Total flavonoid contents, expressed as units of aglycon for fresh material, were in the ranges of 0.3-229 μg/g for lettuce and 44-248 μg/g for endive. Five quercetin conjugates [quercetin 3-O-galactoside, quercetin 3-O-glucoside, quercetin 3-O-glucuronide, quercetin 3-O-(6-O-malonyl)glucoside, and quercetin 3-O-rhamnoside] and luteolin 7-O-glucuronide were measured in the green-leafed lettuce and an additional two cyanidin conjugates [cyanidin 3-O-glucoside and cyanidin 3-O-[(6-O-malonyl)glucoside]] in the red-leafed varieties. Three kaempferol conjugates [kaempferol 3-O-glucoside, kaempferol 3-O-glucuronide, and kaempferol 3-O-[6-O-malonyl)glucoside]] were measured in each of the endive varieties. The presence and identity of kaempferol 3-O-(6-O-malonyl)glucoside in endive was shown for the first time. Shredding of lettuce leaf followed by exposure to light produced significant losses of the flavonoid moiety in the green oak leaf (94%), red oak leaf (43%), iceberg (36%), green batavia (25%), lollo biondo (24%), and lollo rosso (6%) samples, whereas cos and green salad bowl samples did not show an overall loss. Shredding of endive also produced loss of the flavonoid moiety in escarole (32%), fine frisee (13%), and coarse frisee (8%). Significant demalonation was observed for both the quercetin and cyanidin glucosides in lettuce, whereas a similar degradation of the kaempferol analogue was found in endive tissue. Storage of whole heads of both lettuce and endive in the dark at 1 degrees C and 98% humidity for 7 days resulted in losses of total flavonol glycosides in the range of 7-46%. The identification of the amounts, position of substitution, and nature of the sugars is important for understanding the potential bioavailability and biological activities of flavonoids in salads.
HPLC, lettuce, flavonoid, endive, flavonoid conjugates
NCBI PubMed ID: 10995297Total flavonol and flavone contents of foods have been determined with validated state-of-the-art methods. Quercetin dominates, and flavonol levels found in vegetables and fruits are below 10 mg kg−1. However, high concentrations are found in onions (300 mg/kg), kale (450 mg/kg), broccoli (100 mg/kg), beans (50 mg/kg), apples (50 mg/kg), blackcurrants (40 mg/kg), and tea (30 mg/l). The dietary intake of flavonols varies 10-fold between countries (6–60 mg/day). Flavones are of minor importance in the diet. Tea, wine and fruits are the most important sources of flavanols, but there are gaps in our knowledge on flavanol levels of many foods. The absorption of dietary quercetin glycosides in humans ranges from 20 to 50%. The sugar moiety is an important determinant of the bioavailability of flavonols. The presence of a glucose moiety significantly enhances absorption. The extent of absorption of flavanols in humans seems similar to that of flavonols but has been little studied. Flavonols and flavanols are extensively metabolised, as only 1–2% of them are excreted with an intact flavonoid backbone. Hepatic biotransformations include glucuronidation and sulphatation of the phenolic hydroxyls and O-methylation of catechol groups. Bacteria of the colon cleave the C-ring of the flavonoid nucleus to phenolic acids which are subsequently absorbed. Apart from conjugates, virtually no metabolites have been characterised in humans. Absorption of flavanols is rather fast, with times to reach peak values between 0.5 and 4 h. Flavanols are rapidly excreted, with elimination half-lives of 1–6 h. Quercetin glycosides show rapid to slow absorption; peak values are reached between < 0.5 and 9 h. The type of glycoside determines the rate of absorption. Excretion of quercetin glycosides is slow: elimination half-lives are 24 h, independent of the type of glycoside. Analytical data for flavanols in foods are needed. Tea, as an important dietary source, has to be studied. Research on the bioavailability of flavonols and flavanols has to be expanded. Attention is needed for the identification and quantification of their metabolites in body fluids.
glycosides, bioavailability, flavones, flavonols, catechins, flavanols, food contents, dietary intake, absorption metabolism, phenolic acids
Publication DOI: 10.1002/(SICI)1097-0010(20000515)80:7<1081::AID-JSFA566>3.0.CO;2-GTwo new gallotannins, pistafolins A (1) and B (2), were isolated from the leaf extract of Pistacia weinmannifolia. Their structures were determined by spectral methods. Four known gallotannins (3 - 6), seven known flavonoid glycosides (7 - 13), along with 1-O-β-D-(6′-O-galloyl)-glucopyranosyl-3-methoxy-5-hydroxybenzene (14), gallic acid (15), methyl gallate (16), (+)-catechin (17), and (+)-gallocatechin (18), were also isolated. Some of these compounds were tested for their cytotoxicity toward K562 cells, and two small molecular phenolic compounds, 15 and 18, showed significant inhibitory effects with IC50 values less than 5 μg/ml.
cytotoxicity, B, polyphenols, Anacardiaceae, Pistacia weinmannifolia, gallotannin, pistafolins A
NCBI PubMed ID: 11105566Red vine leaf extract (RVLE) is a herbal medicine containing several flavonoids, with quercetin-3-O-beta-glucuronide and isoquercitrin (quercetin-3-O-beta-glycoside) as the main components. Objective is to assess the efficacy and safety of once-daily doses of 360 and 720 mg RVLE (pharmaceutical extract code AS 195; Antistax Venenkapseln) compared to placebo in patients with stage I and incipient stage II chronic venous insufficiency (CVI). A 12-week, randomized, double-blind, placebo-controlled, parallel-group, multi-center study was done. Patients is male and female outpatients aged 25 to 75 years with stage I to stage II CVI (i.e. without extensive trophic changes), not having any other significant medical conditions and not treated with compression stockings, diuretics or other drugs affecting fluid balance. Patients were randomly assigned to a double-blind treatment with placebo, 360 mg AS 195 or 720 mg AS 195 once daily for 12 weeks, preceded and followed by a single-blind 2-week placebo treatment for baseline run-in and end-of-trial washout, respectively. Study criteria were evaluated at baseline, after 6 and 12 weeks of treatment and 2 weeks after discontinuation of treatment. Of the 260 patients enrolled and randomized, 219 completed the study in accordance with the protocol. In the intention-to-treat analysis (N = 257), the mean (+/- SD) lower leg volume (measured by water displacement plethysmography) of the patients treated with placebo (N = 87) increased by 15.2 +/- 90.1 g (displaced water mass) and by 33.7 +/- 96.1 g after 6 and 12 weeks compared to baseline. In contrast, for patients treated with AS 195, lower leg volume decreased, and after 12 weeks of treatment, the difference in mean lower leg volume between the active treatment groups and the placebo group was -75.9 g (95% CI: -106.1 to -45.8 g) and -99.9 g (95% CI: -130.3 to -69.6 g) for the group treated with 360-mg AS 195 (N = 86) and 720-mg AS 195 (N = 84), respectively. The changes in calf circumference showed a similar pattern: in patients treated with AS 195, both the higher dose (720 mg) and, albeit to a lesser extent, the lower dose (360 mg) resulted in a clear reduction in circumference over time, whereas, circumference remained largely unchanged in patients treated with the placebo (95% CI of the estimated treatment effects vs. placebo after 12 weeks: -1.40 to -0.56 cm and -1.73 to -0.88 cm for 360 and 720 mg AS 195, respectively). These differences were statistically significant (p < 0.001). The reductions in ankle circumference were qualitatively similar but quantitatively less marked. Subjectively, there was an improvement in key CVI symptoms (VAS) at 6 weeks with all treatments, but a further improvement at week 12 was seen only in the active treatment groups; at 12 weeks, the changes compared to baseline were significantly greater (p < 0.001) in both active treatment groups than in the placebo group. The treatments were well tolerated; Adverse events were rare and usually mild. Two adverse events (AEs) during treatment with the placebo led to hospitalization and were hence labeled as 'serious'. Three further patients were withdrawn because of AEs which occurred during treatment with the placebo. Once-daily doses of 360 and 720 mg AS 195 were confirmed to be safe and effective in the treatment of mild CVI, reducing significantly lower leg edema and circumference whilst improving key CVI-related symptoms to a clinically relevant extent. The edema reduction is at least equivalent to that reported for compression stockings and/or other edema-reducing agents. The higher dose was as well tolerated as the lower dose but resulted in a slightly greater and more sustained improvement.
flavonoids, Vitis vinifera, chronic venous insufficiency
NCBI PubMed ID: 10719612In previous studies, the qualitative and quantitative variation found in defense chemistry among birch populations and even among individual clones has been considerable. However, information about variation among adult, naturally regenerated birch trees from natural populations is still lacking. In this study, the phenolic composition of leaves of 30 naturally regenerated 20-year-old birch (Betula pendula) trees was analyzed for two successive years in order to characterize the chemical composition of individual trees, analyze the annual variation, and determine chemical similarities among individual trees within a population. The main phenolic compounds were flavonoid glycosides, myricetin, and quercetin derivatives. Annual variation in concentration among leaves was large. In most trees, concentrations were markedly higher in 1998 than in 1997; for certain compounds, the detected increase was as much as a 50%. However, for some individual trees, there were no differences between years in chemical quantity. Thus, when selection or grouping of trees is based on secondary chemistry, quantitative variation should be considered carefully. With the qualitative UPGMA method of classification, four chemotypes were found. The grouping was similar for both years, and qualitatively the results of an individual tree seem to be independent of sampling year. The stability in chemical profile of individual trees suggests that quality is tightly controlled by genotype, which provides a recognition tool for chemotaxonomy. The high within-population variation found in leaf defense chemistry may provide protection against different types of insects (generalists or specialists) and, thus, have positive effects on population survival.
variation, population, chemotype, phenolic compounds, birch, Betulaceae, Betula pendula
Publication DOI: 10.1023/A:1005582611863Three new phenol glycosides acylated with (+)-oleuropeic acid, cypellocarpins A (1), B (2), and C (3), along with seven known compounds, were isolated from the dried leaves of Eucalyptus cypellocarpa. Structures of the new compounds were determined on the basis of spectroscopic methods, including 2D NMR experiments and chemical degradation. These new compounds and a known related glucoside (7) showed potent in vitro antitumor-promoting activity in a short-term bioassay evaluating the inhibitory effect on Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA). These compounds also suppressed an in vivo two-stage carcinogenesis induced with nitric oxide and TPA on mouse skin.
antitumor activity, cypellocarpins, Eucalyptus cypellocarpa, carcinogenesis, Epstein-Barr virus
NCBI PubMed ID: 11000030The antimicrobial activity of extracts of Geum rivale (Rosaceae) and that of some isolated constituents, on bacteria and fungi, was evaluated. The activity was concentrated in the triterpenes fraction and, for gram+ and gram- bacteria, also in the flavonoids fraction.
Geum rivale; Rosaceae; triterpenes; flavonoids; tannins; antimicrobial activity
NCBI PubMed ID: 11054853Grape stems contain significant amounts of polyphenolic compounds, especially phenolic acids, flavonols, and flavanonols such as astilbin. The tannin content was characterized after the depolymerization reaction thiolysis. Tannins consisted of polymeric proanthocyanidins (up to 27 units) mainly consisting of (-)-epicatechin units along with smaller amounts of (+)-catechin, (-)-epicatechin gallate, and (-)-epigallocatechin. Flavanonols (astilbin) have been identified for the first time in stem and characterized by LC/MS and NMR. All phenolic compounds in grape stems were quantified by HPLC: quercetin 3-glucuronide was the most important, followed by catechin, caffeoyltartaric acid, and dihydroquercetin 3-rhamnoside (astilbin). Comparison was made of proanthocyanidin characteristics in different white and red grape varieties and also among parts of the cluster (skin, seed, and stem). Stem-condensed tannins were qualitatively intermediate between seed and skin but could not be differentiated between red and white varieties.
grape; stems; proanthocyanidins; flavanols; flavonols; flavanonols; phenolic acids
NCBI PubMed ID: 10775352Four chemical races were detected in Pulicaria dysenterica, when sampled within Europe, on the basis of the surface flavonoids present. One race uniquely contained quercetagetin 3,7-dimethyl ether and another 6-hydroxykaempferol 3,4'-dimethyl ether. A third race was based on plants having 6-hydroxykaempferol 3,7-dimethyl ether together with quercetagetin 3,7,3'-trimethyl ether. The fourth race contained the above two compounds, as well as quercetagetin 3,7,3',4'-tetramethyl ether and 6-hydroxykaempferol 3,7,4'-trimethyl ether. These lipophilic constituents were variously present on the surfaces of leaf, ray floret, disc floret and fruit. By contrast, the vacuolar flavonoid of all tissues and all races was uniformly quercetin 3-glucuronide. The kaempferol 3-glucoside previously reported in flowers was not detected. Of the lipophilic flavonoids newly reported from this plant, one 6-hydroxykaempferol 3,7,4'-trimethyl ether is new to nature.
flavonoids, Pulicaria dysenterica
NCBI PubMed ID: 10854743| b-D-GlcpA-(1-7)-Quercetin3'Me | Show graphically |
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Structure type: monomer
Compound class: glycoside
Contained glycoepitopes: IEDB_115136,IEDB_140630,IEDB_423153
Microbial biotransformations constitute an important alternative as models for drug metabolism study in mammalians and have been used for the industrial synthesis of chemicals with pharmaceutical purposes. Several microorganisms with unique biotransformation ability have been found by intensive screening and put in commercial applications. Ten isolates of Beauveria sp genus filamentous fungi, isolated from soil in the central Brazil, and Beauveria bassiana ATCC 7159 were evaluated for their capability of quercetin biotransformation. Biotransformation processes were carried out for 24 up to 96 hours and monitored by mass spectrometry analyses of the culture broth. All strains were able to metabolize quercetin, forming mammalian metabolites. The results were different from those presented by other microorganisms previously utilized, attrackting attention because of the great diversity of reactions. Methylated, sulphated, monoglucuronidated, and glucuronidated conjugated metabolites were simultaneously detected.
quercetin, biotransformation, Beauveria bassiana
Publication DOI: 10.1590/S1517-83822008000200036The bioactive flavonoids are considered as the most important phytochemicals in food, which exert a wide range of biological benefits for human being. Microbial biotransformation strategies for production of flavonoids have attracted considerable interest because they allow yielding novel flavonoids, which do not exist in nature. In this review, we summarize the existing knowledge on the production and biotransformation of flavonoids by various microbes. The main reactions during microbial biotransformation are hydroxylation, dehydroxylation, O-methylation, O-demethylation, glycosylation, deglycosylation, dehydrogenation, hydrogenation, C ring cleavage of the benzo-γ-pyrone system, cyclization, and carbonyl reduction. Cunninghamella, Penicillium, and Aspergillus strains are very popular to biotransform flavonoids and they can perform almost all the reactions with excellent yields. Aspergillus niger is one of the most applied microorganisms in the flavonoids' biotransformation; for example, A. niger can transfer flavanone to flavan-4-ol, 2'-hydroxydihydrochalcone, flavone, 3-hydroxyflavone, 6-hydroxyflavanone, and 4'-hydroxyflavanone. The hydroxylation of flavones by microbes usually happens on the ortho position of hydroxyl group on the A ring and C-4' position of the B ring and microbes commonly hydroxylate flavonols at the C-8 position. The microorganisms tend to hydroxylate flavanones at the C-5, 6, and 4' positions; however, for prenylated flavanones, dihydroxylation often takes place on the C4α=C5α double bond on the prenyl group (the side chain of A ring). Isoflavones are usually hydroxylated at the C-3' position of the B ring by microorganisms. The microbes convert flavonoids to their 7-O-glycosides and 3-O-glycosides (when flavonoids have a hydroxyl moiety at the C-3 position). The demethylation of multimethoxyl flavonoids by microbes tends to happen at the C-3' and C-4' positions of the B ring. Multimethoxyl flavanones and isoflavone are demethylated at the C-7 and C-4' positions. The O-methylation of flavonols happens at the C-3' and C-4' and microorganisms O-methylate flavones at the C-6 position and the O-methylation of flavanones, usually took place on the hydroxyl groups of the A ring. The prenyl flavanones were cyclized at the prenyl side chain to form a new five-member ring attached to the A ring. Chalcones were regioselectively cyclized to flavanones. Hydrogenation of flavonoids was only reported on transformation of chalcones to dihydrochalcones. The dehydrogenation of flavanoids to flavonoids was not comprehensively studied.
bacteria, fungi, microbial biotransformation, flavonoids
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