4'-Methylflavanone Glycosides Obtained Using Biotransformation in the Entomopathogenic Filamentous Fungi Cultures as Potential Anticarcinogenic, Antimicrobial, and Hepatoprotective Agents

Enhancing the physicochemical properties and bioactivities of 2'-hydroxyflavanone through fungal biotransformation

Flavonoids comprise a group of natural compounds with diverse bioactivities; however, their low water solubility and limited bioavailability often impede their potential health benefits for humans. In this study, five derivatives, namely 2',5'-dihydroxyflavanone (1), 2'-dihydroxyflavanone-5'-O-4″-O-methyl-β-d-glucoside (2), 2'-dihydroxyflavanone-6-O-4″-O-methyl-β-d-glucoside (3), 2'-dihydroxyflavanone-3'-O-4″-O-methyl-β-d-glucoside (4) and hydroxyflavanone-2'-O-4″-O-methyl-β-d-glucoside (5), were biosynthesized from 2'-hydroxyflavanone through microbial transformation using Beauveria bassiana ATCC 7159. Product 1 was identified as a known compound while 2-5 were structurally characterized as new structures through extensive 1D and 2D NMR analysis. The water solubility of biotransformed products 1-5 was enhanced by 30-280 times compared to the substrate 2'-hydroxyflavanone. Moreover, the antioxidant assay revealed that 1 and 2 exhibited improved 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity relative to the substrate, decreasing the logIC50 from 8.08 ± 0.11 μM to 6.19 ± 0.08 μM and 7.15 ± 0.08 μM, respectively. Compound 5 displayed significantly improved anticancer activity compared to the substrate 2'-hydroxyflavanone against Glioblastoma 33 cancer stem cells, decreasing the IC50 from 25.05 μM to 10.59 μM. Overall, fungal biotransformation represents an effective tool to modify flavonoids for enhanced water solubility and bioactivities.

Antimicrobial Properties of Flavonoid Derivatives with Bromine, Chlorine, and Nitro Group Obtained by Chemical Synthesis and Biotransformation Studies

The search for new substances of natural origin, such as flavonoids, is necessary in the fight against the growing number of diseases and bacterial resistance to antibiotics. In our research, we wanted to check the influence of flavonoids with chlorine or bromine atoms and a nitro group on pathogenic and probiotic bacteria. We synthesized flavonoids using Claisen-Schmidt condensation and its modifications, and through biotransformation via entomopathogenic filamentous fungi, we obtained their glycoside derivatives. Biotransformation yielded two new flavonoid glycosides: 8-amino-6-chloroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside and 6-bromo-8-nitroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside. Subsequently, we checked the antimicrobial properties of the aforementioned aglycon flavonoid compounds against pathogenic and probiotic bacteria and yeast. Our studies revealed that flavones have superior inhibitory effects compared to chalcones and flavanones. Notably, 6-chloro-8-nitroflavone showed potent inhibitory activity against pathogenic bacteria. Conversely, flavanones 6-chloro-8-nitroflavanone and 6-bromo-8-nitroflavanone stimulated the growth of probiotic bacteria (Lactobacillus acidophilus and Pediococcus pentosaceus). Our research has shown that the presence of chlorine, bromine, and nitro groups has a significant effect on their antimicrobial properties.

Biotransformation of Patchouli Alcohol by Cladosporium cladosporioides and the Anti-Influenza Virus Activities of Biotransformation Products

The biotransformation of patchouli alcohol by Cladosporium cladosporioides afforded 31 products, including 21 new ones (1-3, 5, 6, 8-14, and 17-25). Their structures were determined by extensive spectroscopic data analysis (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, ROESY, and HRESIMS), and the absolute configuration of compounds 1, 2, 8, 9, and 17 was determined by single-crystal X-ray diffraction using Cu Kα radiation. Structurally, compounds 21-24 were patchoulol-type norsesquiterpenoids without Me-12. Among them, a Δ3(4) double bond existed in compounds 21 and 22; a three-membered ring was formed between C-4, C-5, and C-6 in compound 23; an epoxy moiety appeared between C-3 and C-4 in compound 24. Furthermore, the biotransformation products 9, 10, 12, and 25 showed potent anti-influenza virus activity with EC50 values of 2.11, 7.94, 20.87, and 3.45 μM, respectively.

Multienzymatic biotransformation of flavokawain B by entomopathogenic filamentous fungi: structural modifications and pharmacological predictions

BACKGROUND

Flavokawain B is one of the naturally occurring chalcones in the kava plant (Piper methysticum). It exhibits anticancer, anti-inflammatory and antimalarial properties. Due to its therapeutic potential, flavokawain B holds promise for the treatment of many diseases. However, due to its poor bioavailability and low aqueous solubility, its application remains limited. The attachment of a sugar unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Biotransformation is an environmentally friendly way to improve the properties of compounds, for example, to increase their hydrophilicity and thus affect their bioavailability. Recent studies proved that entomopathogenic filamentous fungi from the genera Isaria and Beauveria can perform O-methylglycosylation of hydroxyflavonoids or O-demethylation and hydroxylation of selected chalcones and flavones.

RESULTS

In the present study, we examined the ability of entomopathogenic filamentous fungal strains of Beauveria bassiana, Beauveria caledonica, Isaria farinosa, Isaria fumosorosea, and Isaria tenuipes to transform flavokawain B into its glycosylated derivatives. The main process occurring during the reaction is O-demethylation and/or hydroxylation followed by 4-O-methylglycosylation. The substrate used was characterized by low susceptibility to transformations compared to our previously described transformations of flavones and chalcones in the cultures of the tested strains. However, in the culture of the B. bassiana KCh J1.5 and BBT, Metarhizium robertsii MU4, and I. tenuipes MU35, the expected methylglycosides were obtained with high yields. Cheminformatic analyses indicated altered physicochemical and pharmacokinetic properties in the derivatives compared to flavokawain B. Pharmacological predictions suggested potential anticarcinogenic activity, caspase 3 stimulation, and antileishmanial effects.

CONCLUSIONS

In summary, the study provided valuable insights into the enzymatic transformations of flavokawain B by entomopathogenic filamentous fungi, elucidating the structural modifications and predicting potential pharmacological activities of the obtained derivatives. The findings contribute to the understanding of the biocatalytic capabilities of these microbial cultures and the potential therapeutic applications of the modified flavokawain B derivatives.

Glycosylation of Quercetin by Selected Entomopathogenic Filamentous Fungi and Prediction of Its Products' Bioactivity

Quercetin is the most abundant flavonoid in food products, including berries, apples, cauliflower, tea, cabbage, nuts, onions, red wine and fruit juices. It exhibits various biological activities and is used for medical applications, such as treating allergic, inflammatory and metabolic disorders, ophthalmic and cardiovascular diseases, and arthritis. However, its low water solubility may limit quercetin's therapeutic potential. One method of increasing the solubility of active compounds is their coupling to polar molecules, such as sugars. The attachment of a glucose unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Entomopathogenic fungi are biocatalysts well known for their ability to attach glucose and its 4-O-methyl derivative to bioactive compounds, including flavonoids. We investigated the ability of cultures of entomopathogenic fungi belonging to Beauveria, Isaria, Metapochonia, Lecanicillium and Metarhizium genera to biotransform quercetin. Three major glycosylation products were detected: (1), 7-O-β-D-(4″-O-methylglucopyranosyl)-quercetin, (2) 3-O-β-D-(4″-O-methylglucopyranosyl)-quercetin and (3) 3-O-β-D-(glucopyranosyl)-quercetin. The results show evident variability of the biotransformation process, both between strains of the tested biocatalysts from different species and between strains of the same species. Pharmacokinetic and pharmacodynamic properties of the obtained compounds were predicted with the use of cheminformatics tools. The study showed that the obtained compounds may have applications as effective modulators of intestinal flora and may be stronger hepato-, cardio- and vasoprotectants and free radical scavengers than quercetin.

Biotransformation of Flavonoids with -NO2, -CH3 Groups and -Br, -Cl Atoms by Entomopathogenic Filamentous Fungi

Combining chemical and microbiological methods using entomopathogenic filamentous fungi makes obtaining flavonoid glycosides possible. In the presented study, biotransformations were carried out in cultures of Beauveria bassiana KCH J1.5, Isaria fumosorosea KCH J2, and Isaria farinosa KCH J2.6 strains on six flavonoid compounds obtained in chemical synthesis. As a result of the biotransformation of 6-methyl-8-nitroflavanone using the strain I. fumosorosea KCH J2, two products were obtained: 6-methyl-8-nitro-2-phenylchromane 4-O-β-D-(4″-O-methyl)-glucopyranoside and 8-nitroflavan-4-ol 6-methylene-O-β-D-(4″-O-methyl)-glucopyranoside. 8-Bromo-6-chloroflavanone was transformed by this strain to 8-bromo-6-chloroflavan-4-ol 4'-O-β-D-(4″-O-methyl)-glucopyranoside. As a result of microbial transformation by I. farinosa KCH J2.6 effectively biotransformed only 8-bromo-6-chloroflavone into 8-bromo-6-chloroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside. B. bassiana KCH J1.5 was able to transform 6-methyl-8-nitroflavone to 6-methyl-8-nitroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside, and 3'-bromo-5'-chloro-2'-hydroxychalcone to 8-bromo-6-chloroflavanone 3'-O-β-D-(4″-O-methyl)-glucopyranoside. None of the filamentous fungi used transformed 2'-hydroxy-5'-methyl-3'-nitrochalcone effectively. Obtained flavonoid derivatives could be used to fight against antibiotic-resistant bacteria. To the best of our knowledge, all the substrates and products presented in this work are new compounds and are described for the first time.

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

Flavonoid compounds are secondary plant metabolites with numerous biological activities; they naturally occur mainly in the form of glycosides. The glucosyl moiety attached to the flavonoid core makes them more stable and water-soluble. The methyl derivatives of flavonoids also show increased stability and intestinal absorption. Our study showed that such flavonoids can be obtained by combined chemical and biotechnological methods with entomopathogenic filamentous fungi as glycosylation biocatalysts. In the current paper, two flavonoids, i.e., 2′-hydroxy-4-methylchalcone and 4′-methylflavone, have been synthesized and biotransformed in the cultures of two strains of entomopathogenic filamentous fungi Isaria fumosorosea KCH J2 and Beauveria bassiana KCH J1.5. Biotransformation of 2′-hydroxy-4-methylchalcone resulted in the formation of two dihydrochalcone glucopyranoside derivatives in the culture of I. fumosorosea KCH J2 and chalcone glucopyranoside derivative in the case of B. bassiana KCH J1.5. 4′-Methylflavone was transformed in the culture of I. fumosorosea KCH J2 into four products, i.e., 4′-hydroxymethylflavone, flavone 4′-methylene-O-β-d-(4″-O-methyl)-glucopyranoside, flavone 4′-carboxylic acid, and 4′-methylflavone 3-O-β-d-(4″-O-methyl)-glucopyranoside. 4′-Methylflavone was not efficiently biotransformed in the culture of B. bassiana KCH J1.5. The computer-aided simulations based on the chemical structures of the obtained compounds showed their improved physicochemical properties and antimicrobial, anticarcinogenic, hepatoprotective, and cardioprotective potential.