Quercetin and rutin are well-know flavonoids. In spite of this, the comprehension of their metabolism is still incomplete. In this work, the cytotoxic activity of quercetin and rutin and its metabolites produced by metabolism of filamentous fungi was investigated. Flavonoids metabolism was monitored by HPLC and LC-MS. Both flavonoids were extensively metabolized. Quercetin was converted into metabolite methylquercetin (2) and quercetin glucuronide (3) and rutin into metabolite rutin sulphate (5), methylrutin (6) and rutin glucuronide (7). Cytotoxic effects of rutin, quercetin and its metabolites were measured by MTT tetrazolium reduction test and the trypan blue exclusion assay on HL-60 leukemic cells. The results showed similar concentration-dependent cytotoxic effect for rutin and rutin sulphate (5), while no cytotoxic effect was detected with the metabolites 6 and 7. In relation to the quercetin and its metabolites the results showed that all compounds have a similar concentration-dependent inhibitory effect on HL-60 cells. These findings corroborate the literature, showing that bioconversion is a useful strategy for production of biological active metabolites.

Under the conditions tested herein, this study has shown that mice treated with grandisin presented, in a dose-dependent manner, a protective effect against cyclophosphamide-induced mutagenicity. This effect could be, at least in part, associated to grandisin bioactivation. These data open new perspectives for further investigation into the toxicology and applied pharmacology of grandisin.

Microbial biotransformations constitute an important alternative as models for drug metabolism study in mammalians and have been used for the industrial synthesis of chemicals with pharmaceutical purposes. Several microorganisms with unique biotransformation ability have been found by intensive screening and put in commercial applications. Ten isolates of Beauveria sp genus filamentous fungi, isolated from soil in the central Brazil, and Beauveria bassiana ATCC 7159 were evaluated for their capability of quercetin biotransformation. Biotransformation processes were carried out for 24 up to 96 hours and monitored by mass spectrometry analyses of the culture broth. All strains were able to metabolize quercetin, forming mammalian metabolites. The results were different from those presented by other microorganisms previously utilized, attrackting attention because of the great diversity of reactions. Methylated, sulphated, monoglucuronidated, and glucuronidated conjugated metabolites were simultaneously detected.

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