Regioselective O-glycosylation of flavonoids by fungi Beauveria bassiana, Absidia coerulea and Absidia glauca

Synthesis, fungal biotransformation, and evaluation of the antimicrobial potential of chalcones with a chlorine atom

Chalcones are intermediate products in the biosynthesis of flavonoids, which possess a wide range of biological properties, including antimicrobial and anticancer activities. The introduction of a chlorine atom and the glucosyl moiety into their structure may increase their bioavailability, bioactivity, and pharmacological use. The combined chemical and biotechnological methods can be applied to obtain such compounds. Therefore, 2-chloro-2'-hydroxychalcone and 3-chloro-2'-hydroxychalcone were synthesized and biotransformed in cultures of two strains of filamentous fungi, i.e. Isaria fumosorosea KCH J2 and Beauveria bassiana KCH J1.5 to obtain their novel glycosylated derivatives. Pharmacokinetics, drug-likeness, and biological activity of them were predicted using cheminformatics tools. 2-Chloro-2'-hydroxychalcone, 3-chloro-2'-hydroxychalcone, their main glycosylation products, and 2'-hydrochychalcone were screened for antimicrobial activity against several microbial strains. The growth of Escherichia coli 10,536 was completely inhibited by chalcones with a chlorine atom and 3-chlorodihydrochalcone 2'-O-β-D-(4″-O-methyl)-glucopyranoside. The strain Pseudomonas aeruginosa DSM 939 was the most resistant to the action of the tested compounds. However, chalcone aglycones and glycosides with a chlorine atom almost completely inhibited the growth of bacteria Staphylococcus aureus DSM 799 and yeast Candida albicans DSM 1386. The tested compounds had different effects on lactic acid bacteria depending on the tested species. In general, chlorinated chalcones were more effective in the inhibition of the tested microbial strains than their unchlorinated counterparts and aglycones were a little more effective than their glycosides.

Investigation on production and reaction conditions of sucrose synthase based glucosylation cascade towards flavonoid modification

Enzyme-based glycosylation is of great interest in the context of natural products decoration. Yet, its industrial application is hindered by optimisation difficulties and hard-to-standardise productivities. In this study, five sugar nucleotide-dependent glucosyltransferases from different origins (bacterial, plant and fungal) were coupled with soy sucrose synthase (GmSuSy) to create a set of diverse cascade biocatalysts for flavonoid glucosylation, which evaluation brought new insights into the field. Investigations into co-expression conditions and reaction settings enabled to define optimal induction temperature (25 °C) and uridine diphosphate (UDP) concentration (0.5 mM) for all tested pairs of enzymes. Moreover, the influence of pH and substrate concentration on the monoglucosylated product distribution was detected and analysed. The utilisation of crude protein extracts as a cost-effective source of catalysts unveiled their glycosidase activity against flavonoid glucosides, resulting in decreased productivity, which, to our knowledge, has not previously been discussed in such a context. Additionally, examination of the commercially available EziG immobilisation resins showed that selection of suitable carrier for solid catalyst production can be problematic and not only enzyme's but also reagent's properties have to be considered. Flavonoids, due to their complexation and hydrophobic properties, can adsorb on different types of surfaces, including divalent metal ions required for IMAC based immobilisation, necessitating detailed examination of the resins while the catalysis design.

Endophytic Beauveria bassiana induces biosynthesis of flavonoids in oilseed rape following both seed inoculation and natural colonization

BACKGROUND

Cultivation of oilseed rape Brassica napus is pesticide-intensive, and alternative plant protection strategies are needed because both pesticide resistance and legislation narrow the range of effective chemical pesticides. The entomopathogenic fungus Beauveria bassiana is used as a biocontrol agent against various insect pests, but little is known about its endophytic potential and role in plant protection for oilseed rape. First, we studied whether B. bassiana can establish as an endophyte in oilseed rape, following seed inoculation. To evaluate the plant protection potential of endophytic B. bassiana on oilseed rape, we next examined its ability to induce plant metabolite biosynthesis. In another experiment, we tested the effect of seed inoculation on seedling survival in a semi-field experiment.

RESULTS

Beauveria bassiana endophytically colonized oilseed rape following seed inoculation, and, in addition, natural colonization was also recorded. Maximum colonization rate was 40%, and generally increased with inoculation time. Seed inoculation did not affect the germination probability or growth of oilseed rape, but B. bassiana inoculated seeds germinated more slowly compared to controls. Endophytic colonization of B. bassiana induced biosynthesis of several flavonoids in oilseed rape leaves under controlled conditions. In the experiment conducted in semi-field conditions, inoculated seedlings had slightly higher mortality compared to control seedlings.

CONCLUSION

Beauveria bassiana showed endophytic potential on oilseed rape via both natural colonization and seed inoculation, and it induced the biosynthesis of flavonoids. However, its use as an endophyte for plant protection against pests or pathogens for oilseed rape remains unclear. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Biosynthesis and Anticancer Activity of Genistein Glycoside Derivatives

As a beneficial natural flavonoid, genistein has demonstrated a wide range of biological functions via regulating a number of targets and signaling pathways, such as anti-cancer, antioxidant, antibacterial, antiinflammatory, antifungal, antiviral, iron chelation, anti-obesity, anti-diabetes, and anti-hypertension. Pub- Med/Medline and Web of Science were searched using appropriate keywords until the end of December 2023. Despite its many potential benefits, genistein's clinical application is limited by low hydrophilicity, poor solubility, and suboptimal bioavailability due to its structure. These challenges can be addressed through the conversion of genistein into glycosides. Glycosylation of active small molecules may enhance their solubility, stability, and biological activity. In recent years, extensive research has been conducted on the synthesis, properties, and anticancer activity of glycoconjugates. Previous reviews were devoted to discussing the biological activities of genistin, with a little summary of the biosynthesis and the structure-activity relationship for their anticancer activity of genistein glycoside derivatives. Therefore, we summarized recent advances in the biosynthesis of genistein glycosylation and discussed the antitumor activities of genistein glycoside derivatives in a structure-activity relationship, which may provide important information for further development of genistein derivatives.

A new terrein dimer and a new meroterpene from the mangrove endophytic fungus Lichtheimia sp

A new terrein dimer named lichtheicol A (1) and a new meroterpene named lichtheiterpene A (2), were isolated from the mangrove endophytic fungus Lichtheimia sp. J2B1, together with 10 known compounds (3-12). The planar structures and absolute configurations of 1 and 2 were established by a combination of extensive spectroscopic data analyses and electronic circular dichroism (ECD) calculations. Compounds 4 and 5 exhibited marked inhibitory effects against butyrylcholinesterase (BuChE) with IC50 values of 0.71 and 0.53 μM, respectively.

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.

Microbial biotransformation to obtain stilbene methylglucoside with GPR119 agonistic activity

Introduction

Limitation of pharmaceutical application of resveratrol (RSV) and piceatannol (PIC) continue to exist, there is a need to obtain the superior analogs of two stilbenes with promoted activity, stability, and bioavailability. Microbial transformation has been suggested as a common and efficient strategy to solve the above problems.

Methods

In this study, Beauveria bassiana was selected to transform RSV and PIC. LC-MS and NMR spectroscopies were used to analyze the transformed products and identify their structures. The biological activities of these metabolites were evaluated in vitro with GPR119 agonist and insulin secretion assays. Single factor tests were employed to optimize the biotransformation condition.

Results

Three new methylglucosylated derivatives of PIC (1-3) and two known RSV methylglucosides (4 and 5) were isolated and characterized from the fermentation broth. Among them, 1 not only showed moderate GPR119 agonistic activity with 65.9%, but also promoted insulin secretion level significantly (12.94 ng/mg protein/hour) at 1 μM. After optimization of fermentation conditions, the yield of 1 reached 45.53%, which was increased by 4.2-fold compared with the control.

Discussion

Our work presents that 3-O-MG PIC (1), obtained by microbial transformation, is an effective and safer ligand targeting GPR119, which lays a foundation for the anti-diabetic drug design in the future.

Microbial Bioconversion of Phenolic Compounds in Agro-industrial Wastes: A Review of Mechanisms and Effective Factors

Agro-industrial wastes have gained great attention as a possible source of bioactive compounds, which may be utilized in various industries including pharmaceutics, cosmetics, and food. The food processing industry creates a vast amount of waste which contains valuable compounds such as phenolics. Polyphenols can be found in soluble (extractable or free), conjugated, and insoluble-bound forms in various plant-based foods including fruits, vegetables, grains, nuts, and legumes. A substantial portion of phenolic compounds in agro-industrial wastes is present in the insoluble-bound form attached to the cell wall structural components and conjugated form which is covalently bound to sugar moieties. These bound phenolic compounds can be released from wastes by hydrolysis of the cell wall and glycosides by microbial enzymes. In addition, they can be converted into unique metabolites by methylation, carboxylation, sulfate conjugation, hydroxylation, and oxidation ability of microorganisms during fermentation. Enhancement of concentration and antioxidant activity of phenolic compounds and production of new metabolites from food wastes by microbial fermentation might be a promising way for better utilization of natural resources. This review provides an overview of mechanisms and factors affecting release and bioconversion of phenolic compounds in agro-industrial wastes by microbial fermentation.

Modification of flavonoids: methods and influences on biological activities

Flavonoids are important active ingredients in plant-based food, which have many beneficial effects on health. But the low solubility, poor oral bioavailability, and inferior stability of many flavonoids may limit their applications in the food, cosmetics, and pharmaceutical industries. Structural modification can overcome these shortcomings to improve and extend the application of flavonoids. The study of how to modify flavonoids and the influence of various modifications on biological activity have drawn great interest in the current literature. In this review, the working principles and operating conditions of modification methods were summarized along with their potential and limitations in terms of operational safety, cost, and productivity. The influence of various modifications on biological activities and the structure-activity relationships of flavonoids derivatives were discussed and highlighted, which may give guidance for the synthesis of highly effective active agents. In addition, the safety of flavonoids derivatives is reviewed, and future research directions of flavonoid modification research are discussed.

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

Flavonoid compounds exhibit numerous biological activities and significantly impact human health. The presence of methyl or glucosyl moieties attached to the flavonoid core remarkably modifies their physicochemical properties and improves intestinal absorption. Combined chemical and biotechnological methods can be applied to obtain such derivatives. In the presented study, 4'-methylflavanone was synthesized and biotransformed in the cultures of three strains of entomopathogenic filamentous fungi, i.e., Isaria fumosorosea KCH J2, Beauveria bassiana KCH J1.5, and Isaria farinosa KCH J2.1. The microbial transformation products in the culture of I. fumosorosea KCH J2, flavanone 4'-methylene-O-β-D-(4″-O-methyl)-glucopyranoside, 2-phenyl-(4'-hydroxymethyl)-4-hydroxychromane, and flavanone 4'-carboxylic acid were obtained. Biotransformation of 4'-methylflavanone in the culture of B. bassiana KCH J1.5 resulted in the formation of one main product, i.e., flavanone 4'-methylene-O-β-D-(4″-O-methyl)-glucopyranoside. In the case of I. farinosa KCH J2.6 as a biocatalyst, three products, i.e., flavanone 4'-methylene-O-β-D-(4″-O-methyl)-glucopyranoside, flavanone 4'-carboxylic acid, and 4'-hydroxymethylflavanone 4-O-β-D-(4″-O-methyl)-glucopyranoside were obtained. The Swiss-ADME online simulations confirmed the increase in water solubility of 4'-methylflavanone glycosides and analyses performed using the Way2Drug Pass Online prediction tool indicated that flavanone 4'-methylene-O-β-D-(4″-O-methyl)-glucopyranoside and 4'-hydroxymethylflavanone 4-O-β-D-(4″-O-methyl)-glucopyranoside, which had not been previously reported in the literature, are promising anticarcinogenic, antimicrobial, and hepatoprotective agents.

Combination Strategy of Genetic Dereplication and Manipulation of Epigenetic Regulators Reveals a Novel Compound from Plant Endophytic Fungus

The strategies of genetic dereplication and manipulation of epigenetic regulators to activate the cryptic gene clusters are effective to discover natural products with novel structure in filamentous fungi. In this study, a combination of genetic dereplication (deletion of pesthetic acid biosynthetic gene, PfptaA) and manipulation of epigenetic regulators (deletion of histone methyltransferase gene PfcclA and histone deacetylase gene PfhdaA) was developed in plant endophytic fungus Pestalotiopsis fici. The deletion of PfptaA with PfcclA and/or PfhdaA led to isolation of 1 novel compound, pestaloficiol X (1), as well as another 11 known compounds with obvious yield changes. The proposed biosynthesis pathway of pestaloficiol X was speculated using comparative analysis of homologous biosynthetic gene clusters. Moreover, phenotypic effects on the conidial development and response to oxidative stressors in the mutants were explored. Our results revealed that the new strain with deletion of PfcclA or PfhdaA in ΔPfptaA background host can neutralise the hyperformation of conidia in the PfptaA mutant, and that the ΔPfptaA ΔPfhdaA mutant was generally not sensitive to oxidative stressors as much as the ΔPfptaA ΔcclA mutant in comparison with the single mutant ΔPfptaA or the parental strains. This combinatorial approach can be applied to discover new natural products in filamentous fungi.

Ventilation induced evolution pattern of archaea, fungi, bacteria and their potential roles during co-bioevaporation treatment of concentrated landfill leachate and food waste

To obtain a favorable aeration type in co-bioevaporation treatment of concentrated landfill leachate and food waste, and to deeply understand the co-bioevaporation mechanisms, the temporal evolution differences of archaea, fungi and bacteria as well as the related microbial metabolism genes and functional enzymes under intermittent ventilation (IV) and continuous ventilation (CV) were investigated. Results through metagenomics analysis showed that the less sufficient oxygen and longer thermophilic phase in IV stimulated the vigorous growth of archaea, while CV was beneficial for fungal growth. Even genes of carbohydrates and lipids metabolism and ATP-associated enzymes (enzyme 2.7.13.3 and 3.6.4.12), as well as peptidoglycan biosynthesis enzyme (enzyme 3.4.16.4), were more abundant in CV, IV hold better DNA repair ability, higher microbial viability, and less dehydrogenase sensitivity to temperatures due to the critical contribution of Pseudomonas (3.1-45.9%). Furthermore, IV consumed a similar amount of heat for water evaporation with nearly half of the ventilation of CV and was a favorable aeration type in the practical application of co-bioevaporation.

A highly versatile fungal glucosyltransferase for specific production of quercetin-7-O-β-D-glucoside and quercetin-3-O-β-D-glucoside in different hosts

Glycosylation is an effective way to improve the water solubility of natural products. In this work, a novel glycosyltransferase gene (BbGT) was discovered from Beauveria bassiana ATCC 7159 and heterologously expressed in Escherichia coli. The purified enzyme was functionally characterized through in vitro enzymatic reactions as a UDP-glucosyltransferase, converting quercetin to five monoglucosylated and one diglucosylated products. The optimal pH and temperature for BbGT are 35 ℃ and 8.0, respectively. The activity of BbGT was stimulated by Ca²⁺, Mg²⁺, and Mn²⁺, but inhibited by Zn²⁺. BbGT enzyme is flexible and can glycosylate a variety of substrates such as curcumin, resveratrol, and zearalenone. The enzyme was also expressed in other microbial hosts including Saccharomyces cerevisiae, Pseudomonas putida, and Pichia pastoris. Interestingly, the major glycosylation product of quercetin in E. coli, P. putida, and P. pastoris was quercetin-7-O-β-D-glucoside, while the enzyme dominantly produced quercetin-3-O-β-D-glucoside in S. cerevisiae. The BbGT-harboring E. coli and S. cerevisiae strains were used as whole-cell biocatalysts to specifically produce the two valuable quercetin glucosides, respectively. The titer of quercetin-7-O-β-D-glucosides was 0.34 ± 0.02 mM from 0.83 mM quercetin in 24 h by BbGT-harboring E. coli. The yield of quercetin-3-O-β-D-glucoside was 0.22 ± 0.02 mM from 0.41 mM quercetin in 12 h by BbGT-harboring S. cerevisiae. This work thus provides an efficient way to produce two valuable quercetin glucosides through the expression of a versatile glucosyltransferase in different hosts. KEY POINTS: • A highly versatile glucosyltransferase was identified from B. bassiana ATCC 7159. • BbGT converts quercetin to five mono- and one di-glucosylated derivatives in vitro. • Different quercetin glucosides were produced by BbGT in E. coli and S. cerevisiae.

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

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.

Fungal Biotransformation of 2'-Methylflavanone and 2'-Methylflavone as a Method to Obtain Glycosylated Derivatives

Methylated flavonoids are promising pharmaceutical agents due to their improved metabolic stability and increased activity compared to unmethylated forms. The biotransformation in cultures of entomopathogenic filamentous fungi is a valuable method to obtain glycosylated flavones and flavanones with increased aqueous solubility and bioavailability. In the present study, we combined chemical synthesis and biotransformation to obtain methylated and glycosylated flavonoid derivatives. In the first step, we synthesized 2'-methylflavanone and 2'-methylflavone. Afterwards, both compounds were biotransformed in the cultures of two strains of entomopathogenic filamentous fungi Beauveria bassiana KCH J1.5 and Isaria fumosorosea KCH J2. We determined the structures of biotransformation products based on NMR spectroscopy. Biotransformations of 2'-methyflavanone in the culture of B. bassiana KCH J1.5 resulted in three glycosylated flavanones: 2'-methylflavanone 6-O-β-d-(4″-O-methyl)-glucopyranoside, 3'-hydroxy-2'-methylflavanone 6-O-β-d-(4″-O-methyl)-glucopyranoside, and 2-(2'-methylphenyl)-chromane 4-O-β-d-(4″-O-methyl)-glucopyranoside, whereas in the culture of I. fumosorosea KCH J2, two other products were obtained: 2'-methylflavanone 3'-O-β-d-(4″-O-methyl)-glucopyranoside and 2-methylbenzoic acid 4-O-β-d-(4'-O-methyl)-glucopyranoside. 2'-Methylflavone was effectively biotransformed only by I. fumosorosea KCH J2 into three derivatives: 2'-methylflavone 3'-O-β-d-(4″-O-methyl)-glucopyranoside, 2'-methylflavone 4'-O-β-d-(4″-O-methyl)-glucopyranoside, and 2'-methylflavone 5'-O-β-d-(4″-O-methyl)-glucopyranoside. All obtained glycosylated flavonoids have not been described in the literature until now and need further research on their biological activity and pharmacological efficacy as potential drugs.

Simple and Rapid Method for Wogonin Preparation and Its Biotransformation

Wogonin is one of the most active flavonoids from Scutellaria baicalensis Georgi (baikal skullcap), widely used in traditional Chinese medicine. It exhibits a broad spectrum of health-promoting and therapeutic activities. Together with baicalein, it is considered to be the one of main active ingredients of Chinese medicines for the management of COVID-19. However, therapeutic use of wogonin may be limited due to low market availability connected with its low content in baikal skullcap and lack of efficient preparative methods for obtaining this compound. Although the amount of wogonin in skullcap root often does not exceed 0.5%, this material is rich in wogonin glucuronide, which may be used as a substrate for wogonin production. In the present study, a rapid, simple, cheap and effective method of wogonin and baicalein preparation, which provides gram quantities of both flavonoids, is proposed. The obtained wogonin was used as a substrate for biotransformation. Thirty-six microorganisms were tested in screening studies. The most efficient were used in enlarged scale transformations to determine metabolism of this xenobiotic. The major phase I metabolism product was 4′-hydroxywogonin—a rare flavonoid which exhibits anticancer activity—whereas phase II metabolism products were glucosides of wogonin. The present studies complement and extend the knowledge on the effect of substitution of A- and B-ring on the regioselective glycosylation of flavonoids catalyzed by microorganisms.

Chrysin: Perspectives on Contemporary Status and Future Possibilities as Pro-Health Agent

Chrysin belongs to the group of natural polyphenols. It can be found, among others, in honey, propolis and fruits and has a wide range of biological activities, including the prevention of oxidative stress, inflammation, neurodegeneration and carcinogenesis. Being a part of the human diet, chrysin is considered to be a promising compound to be used in the prevention of many diseases, including cancers, diabetes and neurodegenerative diseases such as Alzheimer's or Parkinson's. Nevertheless, due to the low solubility of chrysin in water and under physiological conditions, its bioavailability is low. For this reason, attempts at its functionalization have been undertaken, aiming to increase its absorption and thus augment its in vivo therapeutic efficacy. The aim of this review is to summarize the most recent research on chrysin, including its sources, metabolism, pro-health effects and the effects of its functionalization on biological activity and pharmacological efficacy, evaluated both in vitro and in vivo.

Optimization of (-)-cubebin biotransformation to (-)-hinokinin by the marine fungus Absidia coerulea 3A9

The genus Absidia is widely used in the biotransformation of different classes of natural products. This study evaluates the ability of the Absidia coerulea 3A9 marine derived strain isolated from the ascidian Distaplia stilyfera to perform biotransformations by conducting assays with (-)-cubebin, as substrate. The experiment was optimized using the experimental design proposed by Plackett-Burman for seven factors and eight experiments, to establish the biotransformation conditions that would allow maximum production of biotransformed dibenzylbutyrolactone (-)-hinokinin. An analytical method based on Reverse-Phase-High Performance Liquid Chromatography (RP-HPLC) was developed to quantify the fungal biotransformation product. The factor that influenced the (-)-hinokinin peak area the most positively was the percentage of seawater (%seawater) given that its %relative standard deviation (%RSD) showed a 32.92% deviation from the real value.

Biotransformation of 5,7-Methoxyflavones by Selected Entomopathogenic Filamentous Fungi

5,7-Dimethoxyflavone, a chrysin derivative, occurs in many plants and shows very low toxicity, even at high doses. On the basis of this phenomenon, we biotransformed a series of methoxy-derivatives of chrysin, apigenin, and tricetin obtained by chemical synthesis. We used entomopathogenic fungal strains with the confirmed ability of simultaneous hydroxylation/demethylation and glycosylation of flavonoid compounds. Both the amount and the place of attachment of the methoxy group influenced the biotransformation rate and the product's amount nascent. Based on product and semi-product structures, it can be concluded that they are the result of cascading transformations. Only in the case of 5,7,3',4',5'-pentamethoxyflavone, the strains were able to attach a sugar molecule in place of the methoxy substituent to give 3'-O-β-d-(4″-O-methylglucopyranosyl)-5,7,4',5'-tetramethoxyflavone. However, we observed the tested strains' ability to selectively demethylate/hydroxylate the carbon C-3' and C-4' of ring B of the substrates used. The structures of four hydroxyl-derivatives were determined: 4'-hydroxy-5,7-dimethoxyflavone, 3'-hydroxy-5,7-dimethoxyflavone, 3'-hydroxy-5,7,4',5'-tetramethoxyflavone, and 5,7-dimethoxy-3',4'-dihydroxyflavone (5,7-dimethoxy-luteolin).

Entomopathogenic Filamentous Fungi as Biocatalysts in Glycosylation of Methylflavonoids

Flavonoids are known for their numerous biological activities; however, their pharmacological application is limited by poor bioavailability. Glycosides are usually more stable and more soluble in water and in this form, flavonoids are present in nature. Likewise, the presence of the methyl group in the flavonoid skeleton results in facilitated absorption and greater bioavailability. Entomopathogenic filamentous fungi are effective in the biotransformation of flavonoids; they are known especially for efficient glycosylation. In the current study we used strains of Beauveria bassiana KCH J1.5 and Isaria fumosorosea KCH J2 to biotransform flavonoids with a single methyl group. 2′-Hydroxy-5′-methylchalcone was biotransformed by both strains into 2′-hydroxy-5′-methylchalcone 3-O-β-D-(4″-O-methyl)-glucopyranoside. In the culture of B. bassiana KCH J1.5 four products were obtained from 6-methylflavanone: 4′-hydroxy-6-methylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside; 4′-hydroxyflavanone 6-methylene-O-β-D-(4″-O-methyl)-glucopyranoside; 6-hydroxymethylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside and 4′-hydroxy-6-hydroxymethylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside. Biotransformation with I. fumosorosea KCH J2 as a biocatalyst resulted in the formation of 6-methylflavanone 4′-O-β-D-(4″-O-methyl)-glucopyranoside and 2-phenyl-6-methylchromane 4-O-β-D-(4″-O-methyl)-glucopyranoside. All of these flavonoids can be used in biological activity tests and can be useful in studies concerning structure—bioactivity relationships.

Biotransformation of Methoxyflavones by Selected Entomopathogenic Filamentous Fungi

The synthesis and biotransformation of five flavones containing methoxy substituents in the B ring: 2'-, 3'-, 4'-methoxyflavones, 2',5'-dimethoxyflavone and 3',4',5'-trimethoxyflavone are described. Strains of entomopathogenic filamentous fungi were used as biocatalysts. Five strains of the species Beauveria bassiana (KCh J1.5, J2.1, J3.2, J1, BBT), two of the species Beauveria caledonica (KCh J3.3, J3.4), one of Isaria fumosorosea (KCh J2) and one of Isaria farinosa (KCh KW 1.1) were investigated. Both the number and the place of attachment of the methoxy groups in the flavonoid structure influenced the biotransformation rate and the amount of nascent products. Based on the structures of products and semi-products, it can be concluded that their formation is the result of a cascading process. As a result of enzymes produced in the cells of the tested strains, the test compounds undergo progressive demethylation and/or hydroxylation and 4-O-methylglucosylation. Thirteen novel flavonoid 4-O-methylglucosides and five hydroxy flavones were isolated and identified.

Advances on the in vivo and in vitro glycosylations of flavonoids

Flavonoids possess diverse bioactivity and potential medicinal values. Glycosylation of flavonoids, coupling flavonoid aglycones and glycosyl groups in conjugated form, can change the biological activity of flavonoids, increase water solubility, reduce toxic and side effects, and improve specific targeting. Therefore, it is desirable to synthesize various flavonoid glycosides for further investigation on their medicinal values. Compared with chemical glycosylations, biotransformations catalyzed by uridine diphospho-glycosyltransferases provide an environmentally friendly way to construct glycosidic bonds without repetitive chemical synthetic steps of protection, activation, coupling, and deprotection. In this review, we will summarize the existing knowledge on the biotechnological glycosylation reactions either in vitro or in vivo for the synthesis of flavonoid O- and C-glycosides and other rare analogs.Key points• Flavonoid glycosides usually show improved properties compared with their flavonoid aglycones.• Chemical glycosylation requires repetitive synthetic steps and purifications.• Biotechnological glycosylation reactions either in vitro or in vivo were discussed.• Provides representative synthetic examples in detail.

Flavonoids, terpenoids, and polyketide antibiotics: Role of glycosylation and biocatalytic tactics in engineering glycosylation

Flavonoids, terpenoids, and polyketides are structurally diverse secondary metabolites used widely as pharmaceuticals and nutraceuticals. Most of these molecules exist in nature as glycosides, in which sugar residues act as a decisive factor in their architectural complexity and bioactivity. Engineering glycosylation through selective trimming or extension of the sugar residues in these molecules is a prerequisite to their commercial production as well to creating novel derivatives with specialized functions. Traditional chemical glycosylation methods are tedious and can offer only limited end-product diversity. New in vitro and in vivo biocatalytic tools have emerged as outstanding platforms for engineering glycosylation in these three classes of secondary metabolites to create a large repertoire of versatile glycoprofiles. As knowledge has increased about secondary metabolite-associated promiscuous glycosyltransferases and sugar biosynthetic machinery, along with phenomenal progress in combinatorial biosynthesis, reliable industrial production of unnatural secondary metabolites has gained momentum in recent years. This review highlights the significant role of sugar residues in naturally occurring flavonoids, terpenoids, and polyketide antibiotics. General biocatalytic tools used to alter the identity and pattern of sugar molecules are described, followed by a detailed illustration of diverse strategies used in the past decade to engineer glycosylation of these valuable metabolites, exemplified with commercialized products and patents. By addressing the challenges involved in current bio catalytic methods and considering the perspectives portrayed in this review, exceptional drugs, flavors, and aromas from these small molecules could come to dominate the natural-product industry.

Conventional and Emerging Extraction Processes of Flavonoids

Flavonoids are a group of plant constituents called phenolic compounds and correspond to the nonenergy part of the human diet. Flavonoids are found in vegetables, seeds, fruits, and beverages such as wine and beer. Over 7000 flavonoids have been identified and they have been considered substances with a beneficial action on human health, particularly of multiple positive effects because of their antioxidant and free radical scavenging action. Although several studies indicate that some flavonoids have provident actions, they occur only at high doses, confirming in most investigations the existence of anti-inflammatory effects, antiviral or anti-allergic, and their protective role against cardiovascular disease, cancer, and various pathologies. Flavonoids are generally removed by chemical methods using solvents and traditional processes, which besides being expensive, involve long periods of time and affect the bioactivity of such compounds. Recently, efforts to develop biotechnological strategies to reduce or eliminate the use of toxic solvents have been reported, reducing processing time and maintaining the bioactivity of the compounds. In this paper, we review, analyze, and discuss methodologies for biotechnological recovery/extraction of flavonoids from agro-industrial residues, describing the advances and challenges in the topic.

Microbial Transformation of Prenylquercetins by Mucor hiemalis

Quercetin, one of the most widely distributed flavonoids, has been found to show various biological activities including antioxidant, anticancer, and anti-inflammatory effects. It has been reported that bioactivity enhancement of flavonoids has often been closely associated with nuclear prenylation, as shown in 8-prenylquercetin and 5'-prenylquercetin. It has also been revealed in many studies that the biological activities of flavonoids could be improved after glucosylation. Three prenylated quercetins were prepared in this study, and microbial transformation was carried out in order to identify derivatives of prenylquercetins with increased water solubility and improved bioavailability. The fungus M. hiemalis was proved to be capable of converting prenylquercetins into more polar metabolites and was selected for preparative fermentation. Six novel glucosylated metabolites were obtained and their chemical structures were elucidated by NMR and mass spectrometric analyses. All the microbial metabolites showed improvement in water solubility.

Cascade biotransformation of estrogens by Isaria fumosorosea KCh J2

Estrone, estradiol, ethynylestradiol and estrone 3-methyl ether underwent a biotransformation process in the submerged culture of Isaria fumosorosea KCh J2. Estrone was transformed into seven metabolites, four of which were glycosylated. Estradiol was selectively glycosylated at C-3 and then transformed to D-ring lactone. Ethynylestradiol was coupled with methylglucoside and 6β-hydroxyderivative was obtained. Estrone 3-methyl ether was not transformed indicating that a free hydroxyl group at C-3 is necessary for glycosylation. Baeyer-Villiger oxidation combined with hydroxylation and glycosylation was observed. All glycosides obtained in this study are 3-O-β-methylglucosides.

Structure-Antioxidant-Antiproliferative Activity Relationships of Natural C7 and C7-C8 Hydroxylated Flavones and Flavanones

Common food flavonoids: chrysin, apigenin, luteolin, diosmetin, pinocembrin, naringenin, eriodictyol, hesperetin, and their analogues with an additional hydroxyl group at the C-8 position obtained via biotransformation were tested for antioxidant activity using the ABTS, DPPH, and ferric ion reducing antioxidant power (FRAP) methods. They were also tested for antiproliferative activity against selected human cancer cell lines-MV-4-11 (biphenotypic B myelomonocytic leukemia), MCF7 (breast carcinoma), LoVo (colon cancer), LoVo/DX (colon cancer doxorubicin resistant), and DU 145 (prostate cancer)-and two normal human cell lines-MCF 10A (breast cells) and HLMEC (lung microvascular endothelial cells). Flavonoids with a C7-C8 catechol moiety indicated much higher antioxidant activity compared with the C7 hydroxy analogues. However, because they were unstable under the assay conditions, they did not show antiproliferative activity or it was very low.