Microbial metabolism part 9. Structure and antioxidant significance of the metabolites of 5,7-dihydroxyflavone (chrysin), and 5- and 6-hydroxyflavones

Microbial Biotransformation of Cannabidiol (CBD) from Cannabis sativa

Microbial biotransformation of cannabidiol was assessed using 31 different microorganisms. Only Mucor ramannianus (ATCC 9628), Beauveria bassiana (ATCC 7195), and Absidia glauca (ATCC 22 752) were able to metabolize cannabidiol. M. ramannianus (ATCC 9628) yielded five metabolites, namely, 7,4″β-dihydroxycannabidiol (1: ), 6β,4″β-dihydroxycannabidiol (2: ), 6β,2″β-dihydroxycannabidiol (3: ), 6β,3″α-dihydroxycannabidiol (4: ), and 6β,7,4″β-trihydroxycannabidiol (5: ). B. bassiana (ATCC 7195) metabolized cannabidiol to afford six metabolites identified as 7,3″-dihydroxycannabidivarin (6: ), 7-hydroxycannabidivarin-3″-carboxylic acid (7: ), 3″-hydroxycannabidivarin (8: ), 4″β-hydroxycannabidiol (9: ), and cannabidivarin-3″-carboxylic acid (10: ) along with compound 1: . Incubation of cannabidiol with A. glauca (ATCC 22 752) yielded three metabolites, 6α,3″-dihyroxycannabidivarin (11: ), 6β,3″-dihyroxycannabidivarin (12: ), and compound 6: . All compounds were evaluated for their antimicrobial and antiprotozoal activity.

Microbial Conjugation Studies of Licochalcones and Xanthohumol

Microbial conjugation studies of licochalcones (1-4) and xanthohumol (5) were performed by using the fungi Mucor hiemalis and Absidia coerulea. As a result, one new glucosylated metabolite was produced by M. hiemalis whereas four new and three known sulfated metabolites were obtained by transformation with A. coerulea. Chemical structures of all the metabolites were elucidated on the basis of 1D-, 2D-NMR and mass spectroscopic data analyses. These results could contribute to a better understanding of the metabolic fates of licochalcones and xanthohumol in mammalian systems. Although licochalcone A 4'-sulfate (7) showed less cytotoxic activity against human cancer cell lines compared to its substrate licochalcone A, its activity was fairly retained with the IC₅₀ values in the range of 27.35-43.07 μM.

Quality Formation Mechanism of Stiff Silkworm, Bombyx batryticatus Using UPLC-Q-TOF-MS-Based Metabolomics

Bombyx batryticatus is a well-known animal in traditional Chinese medicine. The aim of the research was to reveal the quality formation mechanism of B. batryticatus and to screen out the characteristic component used for the quality control. The anticonvulsant effects of B. batryticatus with a stiff time of one, five, and nine days (D1, D5 and D9, respectively) and healthy silkworm of the same developmental stage (SW) were determined by animal experiment. The dynamic changes in chemical composition were analyzed using UPLC-Q-TOF-MS-based metabolomics. D5 and D9 B. batryticatus exhibited significant anticonvulsant effects (p < 0.05 and p < 0.01, respectively). Accordingly, principal component analysis (PCA) and partial least squares discrimination analysis (PLS-DA) indicated that the chemical composition of D5 and D9 B. batryticatus changed significantly. The different metabolites mainly consisted of primary metabolites such as lipids and amino acids and secondary metabolites such as flavonoids, beauvericin, and glycolipids. Interestingly, the relative abundance of quercetin-7-O-β-d-4-O-methylglucoside, the characteristic component of B. batryticatus, increased with stiff time and was promised to be used as an index component of quality control. The results expand our understanding of the quality formation mechanism of B. batryticatus. In addition, it highlights the potential of UPLC-Q-TOF-MS-based metabolomics for the quality control purpose of TCMs.

Antityrosinase, Antioxidant, and Cytotoxic Activities of Phytochemical Constituents from Manilkara zapota L. Bark

Hyperpigmentation is considered by many to be a beauty problem and is responsible for photoaging. To treat this skin condition, medicinal cosmetics containing tyrosinase inhibitors are used, resulting in skin whitening. In this study, taraxerol methyl ether (1), spinasterol (2), 6-hydroxyflavanone (3), (+)-dihydrokaempferol (4), 3,4-dihydroxybenzoic acid (5), taraxerol (6), taraxerone (7), and lupeol acetate (8) were isolated from Manilkara zapota bark. Their chemical structures were elucidated by analysis of their nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) data, and by comparing them with data found in the literature. The in vitro antityrosinase, antioxidant, and cytotoxic activities of the isolated compounds (1-8) were evaluated. (+)-Dihydrokaempferol (4) exhibited higher monophenolase inhibitory activity than both kojic acid and α-arbutin. However, it showed diphenolase inhibitory activity similar to kojic acid. (+)-Dihydrokaempferol (4) was a competitive inhibitor of both monophenolase and diphenolase activities. It exhibited the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing antioxidant power (FRAP) activities of the isolated compounds. Furthermore, (+)-dihydrokaempferol (4) also demonstrated potent cytotoxicity in breast carcinoma cell line (BT474), lung bronchus carcinoma cell line (Chago-K1), liver carcinoma cell line (HepG2), gastric carcinoma cell line (KATO-III), and colon carcinoma cell line (SW620). These results suggest that M. zapota bark might be a good potential source of antioxidants and tyrosinase inhibitors for applications in cosmeceutical products.

Antiurolithic activity and biotransformation of galloylquinic acids by Aspergillus alliaceus ATCC10060, Aspergillus brasiliensis ATCC 16404, and Cunninghamella elegans ATCC 10028b

Copaifera lucens n-butanolic fraction (BF) was used as a source of galloylquinic acids, and aerobically incubated with Aspergillus alliaceus ATCC10060, Aspergillus brasiliensis ATCC 16404, and Cunninghamella elegans ATCC 10028b cultures for 60 and 120 h. Out of the three studied filamentous fungi, A. alliaceus ATCC10060 was able to degrade galloylquinic acids into one major metabolite, 3-O-methylgallic acid (M1). The product was identified by ¹H-NMR, UPLC-MS/MS and its potential effect on calcium oxalate monohydrate (COM) crystal binding to Madin-Darby canine kidney cells type I surface was studied. Renal cells pretreatment with BF and M1 for 3 h significantly decreased calcium oxalate monohydrate crystal-adherence at 50 μg/mL and 5 μM, respectively. Both M1 and BF significantly reduced surface expression of COM-binding proteins annexin A1 and heat shock protein 90, respectively as evidenced by Western blot analysis of membrane, cytosolic, and whole cell lysate fractions. The compounds also showed antioxidant activities in DPPH assay.

Methylglucosylation of aromatic amino and phenolic moieties of drug-like biosynthons by combinatorial biosynthesis

Glycosylation is a prominent strategy to optimize the pharmacokinetic and pharmacodynamic properties of drug-like small-molecule scaffolds by modulating their solubility, stability, bioavailability, and bioactivity. Glycosyltransferases applicable for "sugarcoating" various small-molecule acceptors have been isolated and characterized from plants and bacteria, but remained cryptic from filamentous fungi until recently, despite the frequent use of some fungi for whole-cell biocatalytic glycosylations. Here, we use bioinformatic and genomic tools combined with heterologous expression to identify a glycosyltransferase-methyltransferase (GT-MT) gene pair that encodes a methylglucosylation functional module in the ascomycetous fungus Beauveria bassiana The GT is the founding member of a family nonorthologous to characterized fungal enzymes. Using combinatorial biosynthetic and biocatalytic platforms, we reveal that this GT is a promiscuous enzyme that efficiently modifies a broad range of drug-like substrates, including polyketides, anthraquinones, flavonoids, and naphthalenes. It yields both O- and N-glucosides with remarkable regio- and stereospecificity, a spectrum not demonstrated for other characterized fungal enzymes. These glucosides are faithfully processed by the dedicated MT to afford 4-O-methylglucosides. The resulting "unnatural products" show increased solubility, while representative polyketide methylglucosides also display increased stability against glycoside hydrolysis. Upon methylglucosidation, specific polyketides were found to attain cancer cell line-specific antiproliferative or matrix attachment inhibitory activities. These findings will guide genome mining for fungal GTs with novel substrate and product specificities, and empower the efficient combinatorial biosynthesis of a broad range of natural and unnatural glycosides in total biosynthetic or biocatalytic formats.

Eleven Microbial Metabolites of 6-Hydroxyflavanone

6-Hydroxyflavanone (1) when fermented with fungal culture Cunninghamella blakesleeana (ATCC 8688a) yielded flavanone 6-O-β-D-glucopyranoside (2), flavanone 6-sulfate (3), and 6-hydroxyflavanone 7-sulfate (4). Aspergillus alliaceus (ATCC 10060) also transformed 1 to metabolite 3 as well as 4'-hydroxyflavanone 6-sulfate (5) and 6,4'-dihydroxyflavanone (6). Beauveria bassiana (ATCC 7159) metabolized 1 to 6 and flavanone 6-O-β-D-4-O-methyglucopyranoside (7). Mucor ramannianus (ATCC 9628) transformed 1 to 2,4-cis-6-hydroxyflavan-4-ol (8), 2,4-trans-6-hydroxyflavan-4-ol (9), 2,4-trans-6,4'-dihydroxyflavan-4-ol 5-sulfate (10), 1,3-cis-1-methoxy-1-(2,5-dihydroxyphenyl)-3-phenylpropane (11) and 2,4-trans-flavan-4-ol 6-sulfate (12). Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antimalarial activities against selected organisms. However, weak antileishmanial activity was observed for metabolite 11 when tested against Leishmania donovani.

Effects of 6-Hydroxyflavone on Osteoblast Differentiation in MC3T3-E1 Cells

Osteoblast differentiation plays an essential role in bone integrity. Isoflavones and some flavonoids are reported to have osteogenic activity and potentially possess the ability to treat osteoporosis. However, limited information concerning the osteogenic characteristics of hydroxyflavones is available. This study investigates the effects of various hydroxyflavones on osteoblast differentiation in MC3T3-E1 cells. The results showed that 6-hydroxyflavone (6-OH-F) and 7-hydroxyflavone (7-OH-F) stimulated ALP activity. However, baicalein and luteolin inhibited ALP activity and flavone showed no effect. Up to 50 μM of each compound was used for cytotoxic effects study; flavone, 6-OH-F, and 7-OH-F had no cytotoxicity on MC3T3-E1 cells. Moreover, 6-OH-F activated AKT and serine/threonine kinases (also known as protein kinase B or PKB), extracellular signal-regulated kinases (ERK 1/2), and the c-Jun N-terminal kinase (JNK) signaling pathways. On the other hand, 7-OH-F promoted osteoblast differentiation mainly by activating ERK 1/ 2 signaling pathways. Finally, after 5 weeks of 6-OH-F induction, MC3T3-E1 cells showed a significant increase in the calcein staining intensity relative to merely visible mineralization observed in cells cultured in the osteogenic medium only. These results suggested that 6-OH-F could activate AKT, ERK 1/2, and JNK signaling pathways to effectively promote osteoblastic differentiation.

Synthesis and characterization of some new complexes of magnesium (II) and zinc (II) with the natural flavonoid primuletin

Two new metal complexes formulated as [Mg(L)₂(H₂O)₂]·H₂O (1) and [Zn(L)₂(H₂O)₂]·0.5H₂O (2), where HL = 5-hydroxyflavone (primuletin), have been synthesized and characterized by elemental and thermal analyses, molar conductance, IR, UV-Vis, ¹H- and ¹³C-NMR, fluorescence and mass spectra. In solid state, complexes had shown higher fluorescence intensities comparing to the free ligand, and this behavior is appreciated as a consequence of the coordination process.

Bioconversion of 7-hydroxyflavanone: isolation, characterization and bioactivity evaluation of twenty-one phase I and phase II microbial metabolites

Microbial metabolism of 7-hydroxyflavanone (1) with fungal culture Cunninghamella blakesleeana (ATCC 8688a), yielded flavanone 7-sulfate (2), 7,4'-dihydroxyflavanone (3), 6,7-dihydroxyflavanone (4), 6-hydroxyflavanone 7-sulfate (5), and 7-hydroxyflavanone 6-sulfate (6). Mortierella zonata (ATCC 13309) also transformed 1 to metabolites 2 and 3 as well as 4'-hydroxyflavanone 7-sulfate (7), flavan-4-cis-ol 7-sulfate (8), 2',4'-dihydroxychalcone (9), 7,8-dihydroxyflavanone (10), 8-hydroxyflavanone 7-sulfate (11), and 8-methoxy-7-hydroxyflavanone (12). Beauveria bassiana (ATCC 7159) metabolized 1 to 2, 3, and 8, flavanone 7-O-β-D-O-4-methoxyglucopyranoside (13), and 8-hydroxyflavanone 7-O-β-D-O-4-methoxyglucopyranoside (14). Chaetomium cochlioides (ATCC 10195) also transformed 1 to 2, 3, 9, together with 7-hydroxy-4-cis-ol (15). Mucor ramannianus (ATCC 9628) metabolized 1 in addition to 7, to also 4,2',4'-trihydroxychalcone (16), 7,3',4'-trihydroxyflavanone (17), 4'-hydroxyflavanone 7-O-α-L-rhamnopyranoside (18), and 7,3',4'-trihydroxy-6-methoxyflavanone (19). The organism Aspergillus alliaceus (ATCC 10060) transformed 1 to metabolites 3, 16, 7,8,4'-trihydroxyflavanone (20), and 7-hydroxyflavanone 4'-sulfate (21). A metabolite of 1, flavanone 7-O-β-D-O-glucopyranoside (22) was produced by Rhizopus oryzae (ATCC 11145). Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antimalarial activities against selected organisms. Metabolites 4 and 16 showed weak antileishmanial activity.

Microbial transformations of 7-methoxyflavanone

Microbial transformations of racemic 7-methoxyflavanone using strains of the genus Aspergillus (A. niger KB, A. ochraceus 456) and the strain Penicillium chermesinum 113 were described. The strain A. niger KB catalysed carbonyl group reduction, leading to (±)-2,4-cis-7-methoxyflavan-4-ol. Biotransformation with the help of A. ochraceus 456 gave two products: (+)-2,4-trans-7-methoxyflavan-4-ol and 4'-hydroxy-7-methoxyflavone. Transformation by means of P. chermesinum 113 resulted in a dihydrochalcone product, 4,2'-dihydroxy-4'-methoxydihydrochalcone. DPPH scavenging activity test proved that all the biotransformations products have higher antioxidant activity that the substrate.

Microbial transformations of 7-hydroxyflavanone

Microbial transformations of racemic 7-hydroxyflavanone using strains of genus Aspergillus (A. niger KB, A. niger 13/5, A. ochraceus 456) and the species Penicillium chermesinum 113 were studied. The products of O-methylation, O-methylation along with hydroxylation at C-3′ and C-4′, reduction of the carbonyl group, reduction of the carbonyl group along with hydroxylation at C-5, and dehydrogenation of C-2 and C-3 were obtained. Most of the products (with the exception of the O-methylation one) have stronger antioxidant properties than the initial substrate.

Bioconversion of silybin to phase I and II microbial metabolites with retained antioxidant activity

Microbial transformation of silybin (1), the major flavonolignan of milk thistle (Silybum marianum, Asteraceae), resulted in the isolation of four metabolites. The structures of the isolated metabolites were determined by spectroscopic methods. One phase I metabolite was produced by Beauveria bassiana and was characterized as 8-hydroxysilybin (2). Three phase II metabolites were produced by two Cunninghamella species and were identified as 2,3-dehydrosilybin-3-O-β-d-glucoside (3), obtained from Cunninghamella species; and silybin-7-sulfate (4) and 2,3-dehydrosilybin-7-sulfate (5), obtained from Cunninghamella blakesleana. Compared to 1 (IC(50) 284 μg/mL), the generated metabolites displayed varying levels of antioxidant activities in the DPPH free-radical scavenging assay.

Microbial metabolism. Part 12. Isolation, characterization and bioactivity evaluation of eighteen microbial metabolites of 4'-hydroxyflavanone

Fermentation of 4'-hydroxyflavanone (1) with fungal cultures, Beauveria bassiana (ATCC 13144 and ATCC 7159) yielded 6,3',4'-trihydroxyflavanone (2), 3',4'-dihydroxyflavanone 6-O-β-D-4-methoxyglucopyranoside (3), 4'-hydroxyflavanone 3'-sulfate (4), 6,4'-dihydroxyflavanone 3'-sulfate (5) and 4'-hydroxyflavanone 6-O-β-D-4-methoxyglucopyranoside (7). B. bassiana (ATCC 13144) and B. bassiana (ATCC 7159) in addition, gave one more metabolite each, namely, flavanone 4'-O-β-D-4-methoxyglucopyranoside (6) and 6,4'-dihydroxyflavanone (8) respectively. Cunninghamella echinulata (ATCC 9244) transformed 1 to 6,4'-dihydroxyflavanone (8), flavanone-4'-O-β-D-glucopyranoside (9), 3'-hydroxyflavanone 4'-sulfate (10), 3',4'-dihydroxyflavanone (11) and 4'-hydroxyflavanone-3'-O-β-D-glucopyranoside (12). Mucor ramannianus (ATCC 9628) metabolized 1 to 2,4-trans-4'-hydroxyflavan-4-ol (13), 2,4-cis-4'-hydroxyflavan-4-ol (14), 2,4-trans-3',4'-dihydroxyflavan-4-ol (15), 2,4-cis-3',4'-dihydroxyflavan-4-ol (16), 2,4-trans-3'-hydroxy-4'-methoxyflavan-4-ol (17), flavanone 4'-O-α-D-6-deoxyallopyranoside (18) and 2,4-cis-4-hydroxyflavanone 4'-O-α-D-6-deoxyallopyranoside (19). Metabolites 13 and 14 were also produced by Ramichloridium anceps (ATCC 15672). The former was also produced by C. echinulata. Structures of the metabolic products were elucidated by means of spectroscopic data. None of the metabolites tested showed antibacterial, antifungal and antiprotozoal activities against selected organisms.

Microbial metabolism of cannflavin A and B isolated from Cannabis sativa

Microbial metabolism of cannflavin A (1) and B (2), two biologically active flavonoids isolated from Cannabis sativa L., produced five metabolites (3-7). Incubation of 1 and 2 with Mucor ramannianus (ATCC 9628) and Beauveria bassiana (ATCC 13144), respectively, yielded 6''S,7''-dihydroxycannflavin A (3), 6''S,7''-dihydroxycannflavin A 7-sulfate (4) and 6''S,7''-dihydroxycannflavin A 4'-O-alpha-L-rhamnopyranoside (5), and cannflavin B 7-O-beta-D-4'''-O-methylglucopyranoside (6) and cannflavin B 7-sulfate (7), respectively. All compounds were evaluated for antimicrobial and antiprotozoal activity.