New Glycosylated Dihydrochalcones Obtained by Biotransformation of 2′-Hydroxy-2-methylchalcone in Cultures of Entomopathogenic Filamentous Fungi

Abstract

Flavonoids, including chalcones, are more stable and bioavailable in the form of glycosylated and methylated derivatives. The combined chemical and biotechnological methods can be applied to obtain such compounds. In the present study, 2′-hydroxy-2-methylchalcone was synthesized and biotransformed in the cultures of entomopathogenic filamentous fungi Beauveria bassiana KCH J1.5, Isaria fumosorosea KCH J2 and Isaria farinosa KCH J2.6, which have been known for their extensive enzymatic system and ability to perform glycosylation of flavonoids. As a result, five new glycosylated dihydrochalcones were obtained. Biotransformation of 2′-hydroxy-2-methylchalcone by B. bassiana KCH J1.5 resulted in four glycosylated dihydrochalcones: 2′-hydroxy-2-methyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside, 2′,3-dihydroxy-2-methyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside, 2′-hydroxy-2-hydroxymethyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside, and 2′,4-dihydroxy-2-methyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside. In the culture of I. fumosorosea KCH J2 only one product was formed—3-hydroxy-2-methyldihydrochalcone 2′-O-β-d-(4″-O-methyl)-glucopyranoside. Biotransformation performed by I. farinosa KCH J2.6 resulted in the formation of two products: 2′-hydroxy-2-methyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside and 2′,3-dihydroxy-2-methyldihydrochalcone 3′-O-β-d-(4″-O-methyl)-glucopyranoside. The structures of all obtained products were established based on the NMR spectroscopy. All products mentioned above may be used in further studies as potentially bioactive compounds with improved stability and bioavailability. These compounds can be considered as flavor enhancers and potential sweeteners.

Glycosylation of Methylflavonoids in the Cultures of Entomopathogenic Filamentous Fungi as a Tool for Obtaining New Biologically Active Compounds

“…The reduction of the double bond of chalcones has been observed in the cultures of many microorganisms, as we highlighted in our previous work [ 29 ], the same as glycosylation of dihydrochalcones [ 41 ]. Our innovation is to perform these reactions simultaneously in one pot using extensive enzymatic systems of the selected strains of entomopathogenic filamentous fungi [ 29 ]. These fungi naturally produce enzymes to penetrate the insect’s cuticle.…”

“…Our previous and other teams’ studies showed that entomopathogenic filamentous fungi can be a valuable tool in the biotransformation of phenolic compounds, especially flavonoids, including 4″- O -methylglucosylation and hydroxylation [ 23 , 25 , 28 , 29 , 30 , 31 , 35 , 36 , 37 ].…”

“…The best known are their cuticular degrading enzymes: proteases, chitinases, chitosanase, and lipases [ 42 , 43 ]. However, our previous studies revealed that both strains accept flavonoid substrates and catalyze reactions of hydroxylation, glycosylation, and reduction [ 25 , 28 , 29 , 30 , 31 , 32 , 33 , 37 ]. Xie and coworkers identified a glycosyltransferase–methyltransferase gene pair that encodes the methyglucosylation functional module in B. bassiana [ 44 ].…”

“…TLC analyses were carried out using TLC Silica gel 60/Kieselguhr F254 (0.2 mm thick) plates (Merck, Darmstadt, Germany) with a mixture of chloroform (Stanlab, Lublin, Poland) and methanol (Chempur, Piekary Śląskie, Poland) (9:1 v / v ) as eluent. The products were observed without additional visualization under the ultraviolet lamp at λ = 254 and λ = 365 nm [ 29 , 30 ].…”

“…The primary goal of the presented study was to investigate the ability of two entomopathogenic filamentous fungi strains, i.e., Isaria fumosorosea KCH J2 and Beauveria bassiana KCH J1.5, to glycosylate 2′-hydroxy-4-methylchalcone and 4′-methyflavone, and to evaluate the potential biological activity of the obtained derivatives using in silico methods. The used strains had been employed in the glycosylation reactions described in our previous studies [ 25 , 28 , 29 , 30 , 31 , 32 , 33 ]. The biotransformation substrates were obtained by our team in a two-step synthesis described in our earlier work [ 34 ].…”