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Title: Eleven microbial metabolites of 6-hydroxyflavanone

Author
item MIKELL, JULIE - University Of Mississippi
item HERATH, WIMAL - University Of Mississippi
item KHAN, IKHLAS - University Of Mississippi

Submitted to: Chemical and Pharmaceutical Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2015
Publication Date: 7/31/2015
Publication URL: http://handle.nal.usda.gov/10113/62342
Citation: Mikell, J.R., Herath, W., Khan, I.A. 2015. Eleven microbial metabolites of 6-hydroxyflavanone. Chemical and Pharmaceutical Bulletin. 63(8):579-583.

Interpretive Summary: Flavonoids bind to target proteins to bring about biological effects. Evaluation of such processes are somewhat complicated specially with the formation of metabolites which bind to different sets of enzymes leading to conflicting results of in vitro and in vivo experiments. Small structural differences caused by functionalization could alter biological properties significantly. Thus, there is a need to analyze molecular targets to determine the risks and benefits of flavonoids for pharmaceutical applications. Lower metabolite levels in biological fluids are added limitations for such investigations. As such, only a few studies are reported on the interaction of flavonoids with defined cellular proteins. The ability of microorganism to mimic mammalian metabolism is suggested to be helpful in obtaining desired quantities of completely characterized metabolites (where appropriate) for complete biological evaluations and to use them as reference material. It is noteworthy that the number of microbial metabolites formed with flavanones far exceeds those reported for other classes of flavonoids making them difficult subjects for biological evaluations. Identification of potential metabolites by microbial transformation studies could be a source of valuable information for such investigations. The possible antioxidant capabilities together with the observation that hydroxyl or propionoxyl group located at the C-6 position of flavanone can have strong cytotoxic and apoptotic activities against cancer cells prompted us to carry out microbial transformation studies on 6-hydroxyflavanone prospectively to obtain metabolites for further investigations. The study yielded twelve metabolites whose structures were elucidated using spectral data. None of the metabolites tested showed antibacterial, antifungal and antimalarial activities against selected organisms. However, weak antileishmanial activity was observed for metabolites (11 & 12) when tested against Leishmania donovani.

Technical Abstract: 6-Hydroxyflavanone (1) when fermented with fungal culture Cunninghamella blakesleeana (ATCC 8688a) yielded flavanone 6-O-ß-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-ß-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), 1,3-trans-1-methoxy-1-(2,5-dihydroxyphenyl)-3-phenylpropane (12), 2,4-trans-flavan-4-ol 6-sulfate (13). 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 metabolites (11 & 12) when tested against Leishmania donovani.