Flavonoids are plant secondary metabolites with a broad spectrum of biological activities. In nature, they occur mainly in the form of glycosides, but their extraction is often difficult and expensive, as is chemical synthesis. We have shown that biotransformations are an excellent method for obtaining flavonoid glycosides. We are the first team to describe the use of Isaria microorganisms in biotransformations of flavonoid compounds. In the present study as biocatalysts, we used one strain of Isaria fumosorosea KCH J2 isolated from a spider carcass in green areas of Wroclaw and two strains of I. farinosa (J1.4 and J1.6) isolated from insects found in already unused mines in Lower Silesia. The substrates were 3-hydroxyflavone, 3-methoxyflavone, quercetin (3,3′,4′,5,7-pentahydroxyflavone), and baicalein (5,6,7-trihydroxyflavone). For all the substrates that were used in this study, we obtained 4-O-methylglucopyranosides. In the case of substrates with a hydroxyl group in the third position, O-β-D-glucopyranosides were also formed. Isoquercetin that was obtained by biotransformation was used as a substrate to check the kinetics of the formation of flavonoid 4-O-methylglucopyranosides in I. fumosorosea KCH J2 culture. We did not observe the attachment of the methyl group to glucose unit in isoquercetin. Our finding suggest that the attachment of 4-O-methylglucopyranose occurs in one step.

glycosylation, quercetin, biotransformations, flavonoids, 3-hydroxyflavone, 3-methoxyflavone, isoquercetin, baicalein, O-methylglucosides, Isaria

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16
3	bDGlcp	105.0	75.5	78.1	70.9	77.8	62.7
	xXQuercetin	-	158.8	135.6	179.2	158.0	94.7	165.4	99.7	162.9	105.4	122.7	117.9	145.3	149.3	115.8	122.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16
3	bDGlcp	5.30	3.52	3.52	3.44	3.37	3.64-3.78
	xXQuercetin	-	-	-	-	-	6.32	-	6.55	-	-	-	8.04	-	-	6.99	7.62


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7	C8/H8	C9/H9	C10/H10	C11/H11	C12/H12	C13/H13	C14/H14	C15/H15	C16/H16
3	bDGlcp	105.0/5.30	75.5/3.52	78.1/3.52	70.9/3.44	77.8/3.37	62.7/3.64-3.78
	xXQuercetin						94.7/6.32		99.7/6.55				117.9/8.04			115.8/6.99	122.6/7.62

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

O=c1c(O[C@@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@H]2O)c(-c2ccc(O)c(O)c2)oc2cc(O)cc(O)c12

464.379 g/mol (C₂₁H₂₀O₁₂)