Glycosylation of 6-methylflavone by the strain Isaria fumosorosea KCH J2

Abstract

Entomopathogenic fungi are known for their ability to carry out glycosylation of flavonoids, which usually results in the improvement of their stability and bioavailability. In this study we used a newly isolated strain of the entomopathogenic filamentous fungus Isaria fumosorosea KCH J2 as a biocatalyst. Our aim was to evaluate its ability to carry out the biotransformation of flavonoids and to obtain new flavonoid derivatives. The fungus was isolated from a spider’s carcass and molecularly identified using analysis of the ITS1-ITS2 rDNA sequence. As a result of biotransformation of 6-methylflavone two new products were obtained: 6-methylflavone 8-O-β-D-(4”-O-methyl)-glucopyranoside and 6-methylflavone 4’-O-β-D-(4”-O-methyl)-glucopyranoside. Chemical structures of the products were determined based on spectroscopic methods (1H NMR, 13C NMR, COSY, HMBC, HSQC). Our research allowed us to discover a new species of filamentous fungus capable of carrying out glycosylation reactions and proved that I. fumosorosea KCH J2 is an effective biocatalyst for glycosylation of flavonoid compounds. For the first time we describe biotransformations of 6-methylflavone and the attachment of the sugar unit to the flavonoid substrate having no hydroxyl group. The possibility of using flavonoid aglycones is often limited by their low bioavailability due to poor solubility in water. The incorporation of a sugar unit improves the physical properties of tested compounds and thus increases the chance of using them as pharmaceuticals.

Biotransformation of Methoxyflavones by Selected Entomopathogenic Filamentous Fungi

“…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.…”

“…The biotransformation of five methoxyflavones with substituents on the B ring is described: 2′-( 1 ), 3′-( 2 ), 4′-( 3 )-methoxyflavones, 2′,5′-dimethoxyflavone( 4 ) and 3′,4′,5′-trimethoxyflavone( 5 ). Listed compounds were biotransformed by the strains of entomopathogenic filamentous fungi belonging to the species Beauveria bassiana KCh J1.5, J2.1, J3.2, J1, BBT, Beauveria caledonica KCh J3.3, J3.4 [ 21 ], Isaria fumosorosea KCh J2 [ 22 ] and Isaria farinosa KCh KW 1.1 [ 21 ]. Fungi of these species are among the most used for biotransformation, along with Aspergillus niger .…”

“…This functionalization takes place mainly at the C-4-OH position of the sugar moiety. Effective 4- O -methylglycosylation of 3-hydroxyflavone, 6-hydroxyflavone, 7-hydroxyflavone, baicalein, quercetin, naringenin, luteolin, diosmetin, and daidzein in entomopathogenic filamentous fungal culture of the genus Isaria has been reported [ 10 , 14 , 22 ]. 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.…”

“…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 ].…”

Cascade biotransformation of dehydroepiandrosterone (DHEA) by Beauveria species

“…Entomopathogenic fungi, such as Isaria and Beauveria , are natural regulatory factors in insect populations. Among them, only Beauveria , Isaria and Metarhizium are used as biocatalysts for the transformation of various compounds 24 – 29 .…”