• Journal of Microbiology and Biotechnology
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• v.33 no.12
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• pp.1606-1614
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• 2023

Biochemical gut metabolism of dietary bioactive compounds is of great significance in elucidating health-related issues at the molecular level. In this study, a human gut bacterium cleaving C-C glycosidic bond was screened from puerarin conversion to daidzein, and a new, gram-positive C-glycoside-deglycosylating strain, Dorea sp. MRG-IFC3, was isolated from human fecal sample under anaerobic conditions. Though MRG-IFC3 biotransformed isoflavone C-glycoside, it could not metabolize other C-glycosides, such as vitexin, bergenin, and aloin. As evident from the production of the corresponding aglycons from various 7-O-glucosides, MRG-IFC3 strain also showed 7-O-glycoside cleavage activity; however, flavone 3-O-glucoside icariside II was not metabolized. In addition, for mechanism study, C-glycosyl bond cleavage of puerarin by MRG-IFC3 strain was performed in D₂O GAM medium. The complete deuterium enrichment on C-8 position of daidzein was confirmed by ¹H NMR spectroscopy, and the result clearly proved for the first time that daidzein is produced from puerarin. Two possible reaction intermediates, the quinoids and 8-dehydrodaidzein anion, were proposed for the production of daidzein-8d. These results will provide the basis for the mechanism study of stable C-glycosidic bond cleavage at the molecular level.

• Food Science and Preservation
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• v.14 no.6
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• pp.709-715
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• 2007

Korean green tea has been claimed to have health-promoting effects, which may be related to the antioxidant activity in vitro. Korean green teas (Woojeon, WJ ; Sejak, SJ ; Jungjak, JJ ; Daejak, DJ) were subjected to different harvested times and yet little research has examined their bioactive compounds. To assess the effect of this different harvested times on nutritional and health-related properties such as Korean green tea polyphenols, flavonoids, theanine and free amino acids, antioxidant activities and radical scavenging activities were determined. Total polyphenols in JJ (37.16 mg/g) was higher than in other products (WJ, 19.55 ; SJ 24.65 ; DJ, 23.28 mg/g). Contents of flavonol and flavone glycosides were the highest at DJ (350.83 mg%) as compared to WJ (220.81), SJ (256.88) and JJ (270.36 mg%). Contents of theanine and total free amino acids were the highest at WJ (14.11, 23.62 mg/g, respectively), but decreased thereafter. Antioxidant activities were higher in JJ and DJ, using the linoleic acid peroxidation, DPPH and ABTS free radical-scavenging activities. However, WJ and SJ had less active antioxidant activity and free radical-scavenging activity. Reducing powers were increased depend on the concentration of extracts. Antioxidant activity and free radical-scavenging activity of JJ and DJ seemed to relate with total polyphenol and flavonoid contents.