Biotransformations of Flavones and an Isoflavone (Daidzein) in Cultures of Entomopathogenic Filamentous Fungi

Abstract

Entomopathogenic filamentous fungi of the genus Isaria are effective biocatalysts in the biotransformation of flavonoids as well as steroids. In the present study, the species Isaria fumosorosea and Isaria farinosa isolated from the environment were used. Their catalytic capacity to carry out biotransformations of flavones—unsubstituted, with hydroxy- and amino-substituents as well as a hydroxylated isoflavone—was investigated. Biotransformations of flavone, 5-hydroxyflavone, 6-hydroxyflavone, 7-hydroxyflavone, and daidzein resulted in the formation of O-methylglucosides, in the case of flavone and 5-hydroxyflavone with additional hydroxylations. 7-Aminoflavone was transformed into two acetamido derivatives. The following products were obtained: From flavone–flavone 2′-O-β-d-(4′′-O-methyl)-glucopyranoside, flavone 4′-O-β-d-(4′′-O-methyl)-glucopyranoside and 3′-hydroxyflavone 4′-O-β-d-(4′′-O-methyl)-glucopyranoside; from 5-hydroxyflavone–5-hydroxyflavone 4′-O-β-d-(4′′-O-methyl)-glucopyranoside; from 6-hydroxyflavone–flavone 6-O-β-d-(4′′-O-methyl)-glucopyranoside; from 7-hydroxyflavone–flavone 7-O-β-d-(4′′-O-methyl)-glucopyranoside; from daidzein–daidzein 7-O-β-d-(4′′-O-methyl)-glucopyranoside; and from 7-aminoflavone–7-acetamidoflavone and 7-acetamido-4′-hydroxyflavone. Seven of the products obtained by us have not been previously reported in the literature.

Entomopathogenic fungi: unconventional applications

“…In addition, flavonoids have anti-tumor and immunomodulatory activity and protective effects on the human nervous system. The consumption of foods containing flavonoids can prevent the development of heart disease, diabetes, and depression (Dymarska et al 2018a;Yang et al 2018;Dou et al 2019). They occur naturally in vegetables, fruits, cereals, wine, and tea (Yang et al 2018;Dou et al 2019).…”

Biotransformation of Methoxyflavones by Selected Entomopathogenic Filamentous Fungi

“…Aglycons are characterized by very low solubility in water [ 14 ]; however, addition of a polar moiety such as sugars may increase their activity, bioavailability [ 15 ] and stability [ 10 ]. For example, the water solubility of α-glucosyl-isoquercitrin increases more than 80,000-fold compared to its parent compound, quercetin [ 16 , 17 ].…”

“…Carrying out the biotransformation of flavonoids to their glycosylated derivatives is less complicated and more effective than their de novo chemical synthesis [ 14 ], which makes biotransformation a better and cheaper alternative.…”

“…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 ].…”