# Naturally Occurring Flavonoids and Isoflavonoids and Their Microbial Transformation: A Review
## 3 Microbiological Transformation of Isoflavonoids and Flavonoids
### Biotransformation of Isoflavones and Flavonoids by Fungi
Compound **185** was also obtained when strain J1.4 and J1.6 were used as biocatalysts. When the strain KCH J2 was cultivated for 10 days, 3\({}^{\prime}\),4\({}^{\prime}\),5,7-tetrahydroxyflavone 3-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methyl)- glucopyranoside (**187**) and 3\({}^{\prime}\),4\({}^{\prime}\),5,7-tetrahydroxyflavone 3-O-\(\beta\)-D-glucopyranoside (isoquercetin) (**69**) were obtained by biotransformation of 3,3\({}^{\prime}\),4\({}^{\prime}\),5,7-pentahydroyl flavone (quercetin) (**186**) with yields of 18.5% and 12%, respectively. 5,6,7-Trihydroxyflavone (baialein) (**188**) was transformed in the broth of the strain KCH J2 to 5,7-dihydroxyflavone 6-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methyl)-glucopyranoside (**189**) with yield of 9.7% after 14 days [84]. Glycosylation is an effective means to regulate the solubility, stability, bioavailability, and bioactivity of natural product drugs. Several important flavonoid aglycones were studied for their glycosylated transformation by microorganisms. Naringenin (**116**) was glycosylated to form 4\({}^{\prime}\),5-dihydroxyflavanone 7-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**190**), 5,7-dihydroxyflavanone 4\({}^{\prime}\)-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**191**), 5,7-dihydroxyflavanone 4\({}^{\prime}\)-O-\(\beta\)-D-glucopyranoside (**192**) and 5-hydroxyflavanone 4\({}^{\prime}\),7-di-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**193**) by _I. fumosorosea_ ATCC 37814. Luteolin (**194**) was transformed to 4\({}^{\prime}\),5,7-trihydroxyflavone 3\({}^{\prime}\)-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**195**) and 3\({}^{\prime}\),5,7- trihydroxyflavone 4\({}^{\prime}\)-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**196**) by the strain ACCC 37814 via (4-O-methyl)-glucosyl substituted. Diosmetin (**197**) was transformed to 5,7-dihydroxy-4\({}^{\prime}\)-methoxyflavone 3\({}^{\prime}\)-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**198**) by the strain ACCC 37814 via 4-O-methyl-glucosyl substituted. Formononentin (**6**) was glycosylated to generate 4\({}^{\prime}\)-methoxyisoflavone 7-O-\(\beta\)-D-(4-O-methyl) glucopyranoside (**199**) by the strain ACCC 37814 [85]. The host plant-derived flavonoid, kaempfer-O-glycoside (**203**), was glycosylated and acetylated to produce kaempferol 3-O-[\(\alpha\)-thamnopyranosyl-(1\(\to\)6)-\(\beta\)-galactopyranoside) (**201**), flavonoid kaempferol (**202**), and acetylated flavonoid glycoside (**200**) by the fungal endophyte _Epicoccum nigrum_. Among them, compound **200** was a new kaempferol-O-diglycoside [86]. 2\({}^{\prime}\)-Methoxyflavone (**204**) was transformed by _I. fumosorosea_ KCh J2 via demethylation and 4-O-methylglycosylation. The substrate 2\({}^{\prime}\)-methoxyflavone was metabolized in 10 days to produce 2\({}^{\prime}\)-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglucopyranoside)-flavone (**209**), 8-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglucopyranoside)-2\({}^{\prime}\)-methoxyflavone (**210**), 5\({}^{\prime}\)-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglucopyranoside)-2\({}^{\prime}\)-methoxyflavone (**211**) and 3-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglucopyranoside)-2\({}^{\prime}\)-methoxyflavone (**212**). Compound **204** was transformed to 2\({}^{\prime}\)-hydroxyflavone (**213**) by _Beauveria bussiana_ KCh J1. Similar to the biotransformation of compound **204**, 3\({}^{\prime}\)-methoxyflavone (**205**) was converted to 3\({}^{\prime}\)-hydroxyflavone (**214**) by the strain KCh J1. Apart from this, the strain _I. farinosa_ KCh KW 1.1 biotransformed 3\({}^{\prime}\)-methoxyflavone (**205**) to 3\({}^{\prime}\)-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglylucopyranoside)-flavone (**215**) efficiently. The strain _B. bassiana_ KCh J1.5 enabled to biotransformation 4\({}^{\prime}\)-methoxyflavone (**206**) to 4\({}^{\prime}\)-hydroxyflavone (**216**). Besides, compound **206** was transformed to 4\({}^{\prime}\)-O-\(\beta\)-D-(4\({}^{\prime\prime}\)-O-methylglucopyranoside)-flavone (**217**) by _B. bassiana_ KCh J1.5.