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Chrysin (5,7-dihydroxyflavone) is a naturally occurring flavone chemically extracted from the blue passion flower. Dietary flavonoids have many biological properties that could make them useful as chemopreventive agents. However, very poor oral bioavailability makes them largely ineffective in vivo. In previous studies, hydroxylated flavonoid compounds are certificated more effctive absorption in vivo than flavonoid compounds. We selected chrysin as substrate and more than 10 species of microorganism including Streptomyces Ceolicolor, Streptomyces Avermitilis, Streptomyces Griceus, Nocardia farcinica . Streptomyces Ceolicolor was cultivated for 6 days at 28℃ and under 220rpm with shaking incubator using R2YE media. 50ml of culture was harvested
every 24 hours, and used for biotransformation of chrysin. Reaction was performed using 50ml of PBS (Phosphate buffered saline) buffer with 0.2mM of chrysin as substrate at 28℃ and under 220rpm with shaking incubator for 6 hours. Reaction product was sampled every 30 minute or 1 hour, extracted with ethyl acetate and derivatized with BSTFA (N,O-Bis(trimethylsilyl)trifluoro-acetamide). Derivatized reaction product was analyzed with LC, GC-Mass. Chrysin was ortho-hydroxylated to produce baicalein (5,6,7-tetrahydroxyflavone), which was confirmed using authentic baicalein with mass analysis. Maximum conversion was 12 %, which was achieved for 4 hours of reaction, and the substrate (chrysin) and reaction product (baicalein) was ompletely metabolized after 6 hours of reaction. Three kinds of Cytochrome P450 inhibitor, Coumarin, Erythromycin and Quinidine was added with 0.5mM final concentration. Coumarin had no effect on the bioconversion of chrysin and Quinidine inhibited conversion of chrysin into baicalein about 45 ~ 70 %, and Erythromycin completely blocked the bioconversion, which suggest bioconversion of chrysin was mediated through P450 system of Streptomyces Ceolicolor. Addition of different kinds of detergent (Triton X-100, Tween 80, Brij 35) into reaction
mixture, was not effective for the enhancement of bioconversion using Streptomyces Ceolicolor.