Glycosylation of Methoxylated Flavonoids in the Cultures of Isaria fumosorosea KCH J2

Abstract

Flavonoids are widely described plant secondary metabolites with high and diverse pro-health properties. In nature, they occur mostly in the form of glycosides. Our research showed that an excellent way to obtain the sugar derivatives of flavonoids is through biotransformations with the use of entomopathogenic filamentous fungi as biocatalysts. In the current paper, we described the biotransformations of five methoxylated flavonoid compounds (2′-methoxyflavanone, 3′-methoxyflavanone, 4′-methoxyflavanone, 6-methoxyflavanone, and 6-methoxyflavone) in cultures of Isaria fumosorosea KCH J2. As a result, we obtained twelve new flavonoid 4-O-methylglucopyranosides. The products were purified with methods that enabled the reduction of the consumption of organic solvents (preparative TLC and flash chromatography). The structures of the products were confirmed with spectroscopic methods (NMR: 1H, 13C, HSQC, HMBC, COSY). The compounds obtained by us expand the library of available flavonoid derivatives and can be used in biological research.

Biotransformation of Methoxyflavones by Selected Entomopathogenic Filamentous Fungi

“…Firstly five different methoxychalcones were synthesized in the Claisen-Schmidt reaction of 2-hydroxyacetophenone with suitable methoxybenzaldehyde in reaction, described earlier and shown in Scheme 2 [ 34 , 35 , 36 , 37 , 38 ]. The resulting flavones ( 1 – 5 ) were used as substrates for the biotransformation and their NMR spectral data are identical to those previously published [ 32 , 39 ].…”

“…For the first time in flavonoid biotransformations, we also tested two strains of Beauveria caledonica species. The Isaria fumosorosea KCh J2 strain has already been described in our previous study as an effective biocatalyst of flavanones and flavones as substrates [ 14 , 22 , 32 , 33 ]. Comparing those previously described results for I. fumosorosea KCh J2 to the results obtained from the transformations by the B. bassiana strains, we noted the similarity in the biotransformations of flavonoid compounds.…”

“…Comparing the biotransformation rate of substrates having a single-methoxy group, it is seen that 3′-methoxyflavone undergoes the fastest demethylation. In the literature to date, in the processes of hydroxylation and 4″- O -methylglucosylation observed in cultures of entomopathogenic strains, in most cases, functionalization took place at the C-4′ carbon of the flavonoid skeleton [ 14 , 22 , 32 , 33 ]. Based on the experiments carried out here, the demethylation and 4″-O-methylglucosylation processes are the fastest when the methoxy group is located on the C-3′ carbon ( Scheme 1 )…”

“…Moreover, the formation of appropriate glycosides in the cultures of Isaria fumosorosea KCh J2, I. farinosa KCh J1.4, I. farinosa KCh J1.6 and I. farinosa KCh KW1.2 cultures was preceded by hydroxylation of the C-4′ carbon. Subsequent C-4′ hydroxylation and 4- O -methylglycosylation was observed during the incubation of flavone, 3-methoxyflavone, 5-hydroxyflavone, 6-methoxyflavone, 6-methoxyflavanone and 6-methylflavone in the cultures of the genus Isaria [ 14 , 22 , 32 ]. The capacity of the I. fumosorosea KCh J2 strain for simultaneous O -demethylation and glycosylation of 2′-, 3′- and 4′-methoxyflavanone was also described [ 32 ].…”

“…Subsequent C-4′ hydroxylation and 4- O -methylglycosylation was observed during the incubation of flavone, 3-methoxyflavone, 5-hydroxyflavone, 6-methoxyflavone, 6-methoxyflavanone and 6-methylflavone in the cultures of the genus Isaria [ 14 , 22 , 32 ]. The capacity of the I. fumosorosea KCh J2 strain for simultaneous O -demethylation and glycosylation of 2′-, 3′- and 4′-methoxyflavanone was also described [ 32 ]. Based on this phenomenon, in this study, we biotransformed flavones with methoxyl groups (in different positions) located in the B ring obtained by chemical synthesis.…”