Microbial metabolism. Part 6. Metabolites of 3- and 7-hydroxyflavones

Fermentation of 3-hydroxyflavone (1) with Beauveria bassiana (ATCC 13144) yielded 3,4'-dihdroxyflavone (3), flavone 3-O-beta-D-4-O-methylglucopyranoside (4) and two minor metabolites. 7-Hydroxyflavone (2) was transformed by Nocardia species (NRRL 5646) to 7-methoxyflavone (5) whilst Aspergillus alliaceus (ATCC 10060) converted it to 4',7-dihydroxyflavone (6). Flavone 7-O-beta-D-4-O-metylglucopyranoside (7) and 4'-hydroxyflavone 7-O-beta-D-4-O-methylglucopyranoside (8) were the metabolic products of 7-hydroxyflavone (2) when fermented with Beauveria bassiana (ATCC 7159). One of the minor metabolites of 3-hydroxyflavone (1) was tentatively assigned a beta'-chalcanol structure (9). Compounds 4, 7 and 8 are reported as new compounds. Structure elucidation of the metabolites was based on spectroscopic data.     

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 biologically active secondary metabolites from Nerium oleander L

Ursolic acid (1) and kaempferol (3) are two major constituents of the Mediterranean plant Nerium oleander L. Microbial metabolism of (1) with Aspergillus flavus (ATCC 9170) resulted in the formation of 3-oxo-ursolic acid derivative, ursonic acid (2). On the other hand, Cunninghamella blakesleeana (ATCC 8688A) was able to convert (3) into kaempferol 3-O-beta-D-glucopyranoside (4) as well as the new natural product kaempferol 4'-sulfate (5). Incubation of kaempferol with Mucor ramannianus (ATCC 9628) led to the isolation of one metabolite identified as kaempferol 4'-O-alpha-L-rhamnopyranoside (6). Transformation of kaempferol to the new compound kaempferol 7-O-beta-D-4-O-methylglucopyranoside (7) and herbacetin 8-O-beta-D-glucopyranoside (8) was observed after fermentation with Beauveria bassiana (ATCC 13144). Cytotoxic as well as antioxidant activities of the isolated metabolites were determined.     

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.     

Flavonoids from Halostachys caspica and their antimicrobial and antioxidant activities

Seven flavonoids have been isolated from the aerial parts of Halostachys caspica C. A. Mey. (Chenopodiaceae) for the first time. By means of physicochemical and spectrometric analysis, they were identified as luteolin (1), chrysin (2), chrysin 7-O-β-D-glucopyranoside (3), quercetin (4), quercetin 3-O-β-D-glucopyranoside (5), isorhamentin-3-O-β-D-glucopyranoside (6), and isorhamentin-3-O-β-D-rutinoside (7). All flavonoids were evaluated to show a broad antimicrobial spectrum of activity on microorganisms including seven bacterial and one fungal species as well as pronounced antioxidant activity. Among them, the aglycones with relatively low polarity had stronger bioactivity than their glycosides. The results suggested that the isolated flavonoids could be used for future development of antimicrobial and antioxidant agents, and also provided additional data for supporting the use of H. caspica as forage.     

Chiral HPLC analysis of donepezil, 5-O-desmethyl donepezil and 6-O-desmethyl donepezil in culture medium: application to fungal biotransformation studies

An high performance liquid chromatography (HPLC) method for the enantioselective determination of donepezil (DPZ), 5-O-desmethyl donepezil (5-ODD), and 6-O-desmethyl donepezil (6-ODD) in Czapek culture medium to be applied to biotransformation studies with fungi is described for the first time. The HPLC analysis was carried out using a Chiralpak AD-H column with hexane/ethanol/methanol (75:20:5, v/v/v) plus 0.3 % triethylamine as mobile phase and UV detection at 270 nm. Sample preparation was carried out by liquid-liquid extraction using ethyl acetate as extractor solvent. The method was linear over the concentration range of 100-10,000 ng mL(-1) for each enantiomer of DPZ (r ≥ 0.9985) and of 100-5,000 ng mL(-1) for each enantiomer of 5-ODD (r ≥ 0.9977) and 6-ODD (r ≥ 0.9951). Within-day and between-day precision and accuracy evaluated by relative standard deviations and relative errors, respectively, were lower than 15 % for all analytes. The validated method was used to assess DPZ biotransformation by the fungi Beauveria bassiana American Type Culture Collection (ATCC) 7159 and Cunninghamella elegans ATCC 10028B. Using the fungus B. bassiana ATCC 7159, a predominant formation of (R)-5-ODD was observed while for the fungus C. elegans ATCC 10028B, DPZ was biotransformed to (R)-6-ODD with an enantiomeric excess of 100 %.     

Studies on Nepalese crude drugs. XXIX. Chemical constituents of Dronapuspi, the whole herb of Leucas cephalotes SPRENG

From the whole herb of Leucas cephalotes SPRENG., new labdane-, norlabdane- and abietane-type diterpenes named leucasdins A (1), B (2) and C (3), respectively, and two protostane-type triterpenes named leucastrins A (4) and B (5) were isolated, together with a known triterpene, oleanolic acid, five sterols, 7-oxositosterol, 7-oxostigmasterol, 7alpha-hydroxysitosterol, 7alpha-hydroxystigmasterol and stigmasterol, and eight flavones, 5-hydroxy-7,4'-dimethoxyflavone, pillion, gonzalitosin I, tricin, cosmosin, apigenin 7-O-beta-D-(6-O-p-coumaroyl)glucopyranoside, anisofolin A and luteolin 4'-O-beta-D-glucuronopyranoside. The structures of 1--5 were determined as (3S,6R,8R,9R,13S,16S)-9,13,15,16-bisepoxy-3,16-diacetoxy-6-formyloxylabdane, (3S,6R)-3-acetoxy-6-formyloxy-iso-ambreinolide, (4R,9S,12R,13R)-12,13-dihydroxyabiet-7-en-18-oic acid, (3S,17S,20S,24S)-3,20-dihydroxy-24-methylprotost-25-en, and (3S,17S,20S,24S)-3,20,24-trihydroxyprotost-25-en respectively, based on spectral and chemical data.     

Novel microbial transformations of sclareolide

Fungal catalysis of sclareolide (1) using Mucor plumbeus (ATCC 4740), Cunninghamella blakesleeana (ATCC 9245), Cunninghamella echinulata (ATCC 9244), Curvularia lunata (ATCC 12017) and Aspergillus niger (ATCC 1004), was performed. Cunninghamella blakesleeana (ATCC 9245) metabolized compound 1 to afford O(6)-sclareolide (2), 3beta,6alpha-dihydroxysclareolide (3), 9-hydroxysclareolide (4), along with three known metabolites, 1beta,3beta-dihydroxysclareolide (5), 3-oxosclareolide (6) and 3beta-hydroxysclareolide (7). Biotransformation experiments of compound 1 with Cunninghamella echinulata (ATCC 9244) also yielded two new compounds, 5-hydroxysclareolide (8), and 7beta-hydroxysclareolide (9) along with two known compounds 5 and 7. Spectroscopic methods were used to establish the structures of compounds 2-9. Compounds 2-9 exhibited modest acetylcholinesterase inhibitory activity.     

Generation of two new macrolactones through sequential biotransformation of dihydroresorcylide

Biotransformation is an effective method to generate new derivatives from natural products. Combination of various enzymes or whole-cell biocatalysts creates new opportunities for natural product biosynthesis. Dihydroresorcylide (1) is a phytotoxic macrolactone from Acremonium aeae. It was first chlorinated at C-11 by an engineered Escherichia coli BL21-CodonPlus (DE3)-RIL/pJZ54 strain that overexpresses a fungal flavin-dependent halogenase, and subsequently glycosylated at 12-OH by Beauveria bassiana ATCC 7159, giving rise to a novel derivative, 11-chloro-4'-O-methyl-12-O-beta-D-glucosyl-dihydroresorcylide (3). Although 1 can be converted into a new 4'-O-methyl-glucosylated derivative 4 by B. bassiana, this product cannot be further chlorinated by E. coli BL21-CodonPlus (DE3)-RIL/pJZ54 to afford 3. The sequence of these two biotransformation steps was thus restricted and not interchangeable. This sequential biotransformation approach can be applied to other structurally similar natural products to create novel derivatives.     

Studies on nepalese crude drugs. XXVIII. Chemical constituents of Bhote Khair, the underground parts of Eskemukerjea megacarpum HARA

From the underground parts of Eskemukerjea megacarpum HARA, two new stilbenes (14, 15) were isolated, together with a known coumarin, 5,7-dihydroxycoumarin (1), a tyramine derivative, trans-feruloyltyramine (2), two pyrogallol derivatives, gallic acid (3) and beta-glucogallin (4), four flavonoids, trifolin (5), hyperin (6), myricetin 3-O-beta-D-galactopyranoside (7), and myricitrin (8), five stilbenes, resveratorol (9), astringenin (10), piceid (11) astringin (12), and resveratorol 3-O-beta-D-(6-O-galloyl)glucopyranoside (13), a flavan-3-ol, (-)-epigallocatechin 3-O-gallate (16), two proanthocyanidins, catechin-(4alpha-->8)-epigallocatechin 3-O-gallate (17) and epicatechin 3-O-gallate-(4beta-->8)-epigallocatechin 3-O-gallate (18), and an anthocyanin, idaein (19). Compounds 14 and 15 were identified as (E)-3,5,3',4'-tetrahydroxystilbene 3-O-beta-D-(6-O-galloyl)glucopyranoside and (E)-3,5,4'-trihydroxystilbene 3-O-beta-D-(6-O-galloyl)glucopyranoside, respectively, based on spectral and chemical data.     

Flavone glycosides from Calycotome villosa Subsp. Intermedia

The known flavonoid chrysin-7-O-(beta-D-glycopyranoside) (chrysin glucoside,1) as a major fraction and a new glycoside flavone, chrysin-7-O-beta-D-[(6"-acetyl)glycopyranoside] (2) were isolated from the flowers and leaves of Calycotome Villosa Subsp. Intermedia, They were identified by UV-Vis, 1R, (1)H-, (13)C-NMR and ESI-MS.     

Human intestinal bacteria capable of transforming secoisolariciresinol diglucoside to mammalian lignans, enterodiol and enterolactone

Seven metabolites were isolated after anaerobic incubation of secoisolariciresinol diglucoside (1) with a human fecal suspension. They were identified as (-)-secoisolariciresinol (2), 3-demethyl-(-)-secoisolariciresinol (3), 2-(3-hydroxybenzyl)-3-(4-hydroxy-3-methoxybenzyl)butane-1,4-diol (4), didemethylsecoisolariciresinol (5), 2(3-hydroxybenzyl)-3-(3,4-dihydroxybenzyl)butane-1,4-diol (6), enterodiol (7) and enterolactone (8). Furthermore, two bacterial strains, Peptostreptococcus sp. SDG-1 and Eubacterium sp. SDG-2, responsible for the transformation of 1 to a mammalian lignan 7, were isolated from a human fecal suspension. The former transformed 2 to 3 and 5, as well as 4 to 6, and the latter transformed 5 to 6 and 7.     

Microbial transformation of dehydroepiandrosterone

Transformation of dehydroepiandrosterone (DHEA) (1) was carried out by a plant pathogen Rhizopus stolonifer, which resulted in the production of seven metabolites. These metabolites were identified as 3beta,17beta-dihydroxyanandrost-5-ene (2), 3beta,17beta-dihydroxyandrost-4ene (3), 17beta-hydroxyandrost-4-ene-3-one (4), 3beta,11-dihydroxyandrost-4-ene-17-one (5), 3beta,7alpha-dihydroandrost-5-ene-17-one (6), 3A,7alpha,17beta-trihydroxyandrost-5-ene (7) and 11beta-hydroxyandrost-4,6-diene-3,17-dione (8). The structures of the transformed products were determined by the spectroscopic techniques.     

Microbial Transformation of (−)-Δ1-3,4-trans-Tetrahydrocannabinol by Cunninghamella blakesleeana LENDER

Incubation of (?)-Δ¹-3, 4-trans-tetrahydrocannabinol (= Δ¹-THC; 3 ) with stationary cultures of Cunninghamella blakesleeana LENDER (Zygomycetales) (ATCC 8688a) yielded a number of metabolic conversion products. Isolation and structure elucidation of 6α-hydroxy-Δ¹-THC ( 4 ), the potential psychoactive 3″-hydroxy-Δ¹-THC ( 2 ) and 4″-hydroxy-Δ¹-THC ( 1 ), and the hitherto unknown metabolites 4″-hydroxy-6-oxo-Δ¹-THC ( 5 ), 4″, 6α-dihydroxy-Δ¹-THC ( 7 ) and 4″, 7 -dihydroxy-Δ¹-THC ( 6 ) is described.     

Microbial metabolism. Part 7 : Curcumin

Microbial metabolism of the cancer chemopreventive agent, curcumin [(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione] (1) with Pichia anomala (ATCC 20170) yielded four major metabolites, 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)heptan-3-one (2), 5-hydroxy-7-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)heptan-3-one (3), 1,7-bis(4-hydroxy-3-methoxyphenyl)heptan-3,5-diol (4), 5-hydroxy-1,7-bis(4-hydroxyphenyl)heptane-3-one (5) and two minor products, 1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)heptane-3,5-diol (6) and 1,7-bis(4-hydroxyphenyl)heptane-3,5-diol (7). The structures of compounds 2-5 were established on the basis of spectroscopic data. Compounds 6 and 7 were assigned tentative structures.     

Bassianolone: an antimicrobial precursor of cephalosporolides E and F from the entomoparasitic fungus Beauveria bassiana

We have established the chemical structure of (+)-bassianolone (3), the antimicrobial compound precursor of cephalosporolides E and F, and that of the furan metabolite 4 from the entomopathogenic fungus Beauveria bassiana.     

Flavonoids from Millettia nitida var. hirsutissima

From the stems of Millettia nitida var. hirsutissima, three new isoflavone glycosides, formononetin 7-O-beta-D-(6'-ethylmalonyl)-glucopyranoside (1, hirsutissimiside A), 5-O-methyl genistein 7-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside (3, hirsutissimiside B), retusin 7,8-di-O-beta-D-glucopyranoside (4, hirsutissimiside C) and two known isoflavone glycosides (2) and (5) have been isolated. The structures of the compounds were determined by spectroscopic and chemical means.     

Benzolignanoid and Polyphenols from Origanum Vulgare

A new dihydrobenzodioxane derivative, origalignanol ( 10 ), together with nine polyphenolic compounds, salvianolic acid A ( 1 ), salvianolic acid C ( 2 ), lithospermic acid ( 3 ), apigenin 7‐O‐β‐D‐glucuronide ( 4 ), apigenin 7‐O‐β‐D‐(6″‐methyl)glucuronide ( 5 ), luteolin, ( 6 ), luteolin 7‐O‐β‐D‐glucopyranoside ( 7 ), luteolin 7‐O‐β‐D‐glucuronide ( 8 ), and luteolin 7‐O‐β‐D‐xylopyranoside ( 9 ), were isolated from the aqueous ethanolic extract of the aerial parts of Origanum vulgare for the first time. The structure of new compound 10 was determined on the basis of spectroscopic methods. Compound 5 is probably an artifact formed during the isolation. Compounds 1, 2 and 3 showed strong DPPH radical scavenging activity with an EC₅₀ of 7.2 ± 0.4, 9.6 ± 0.9, and 9.5 ± 0.7 μM, respectively, and protected rat hepatocytes from CCl₄‐damage at 100 μM.     

Microbial metabolites of harman alkaloids

Several microorganisms showed the ability to transform the harman alkaloids, harmaline (1), harmalol (2) and harman (5). Harmaline (1) and harmalol (2) were converted by Rhodotorula rubra ATCC 20129 into the tryptamines, 2-acetyl-3-(2-acetamidoethyl)-7-methoxyindole (3) and 2-acetyl-3-(2-acetamidoethyl)-7-hydroxyindole (4), respectively. Harman (5) was biotransformed by Cunninghamella echinulata NRRL 3655 into 6-hydroxyharman (6) and harman-2-oxide (7).