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Flavonoids are classified as Chalcone, Flavone, Flavanon and etc. Phloretin is a kind of chalcone compounds, and Apigenin and Chrysin are a flavone that are known for their
antitumor, antioxidant, antiarthritic, anti-amyloid and anti-inflammatory properties. However,
very poor oral bioavailability makes them largely ineffective in vivo. In previous studies, Omethylated
or hydroxylated flavonoid compounds are certificated more effective absorption in
vivo than flavonoid compounds. Twelve microorganisms were initially screened for their
abilities to catalyze biotransformation of chrysin and phloretin. Chrysin was orthohydroxylated
by Streptomyces ceolicolor 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 completely 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.In the biotransformation phloretin using Streptomyces avermitilis, two main products were identified in GC/MS analysis. They were interpreted as hydroxylated products of phloretin in A-ring at different position.