6-Acetamidoflavone obtained by microbiological and chemical methods and its antioxidant activity.

The aim of this research was to select microbial strains capable of transforming flavonoid compounds containing an amino group. 6-Aminoflavone (1) was used as a model compound. Biotransformation of 1 by the cultures of Rhodococcus sp. DSM 364 and Gordonia sp. DSM 44456 bacteria led to 6-acetamidoflavone (2) with the isolated yields in 86% and 93%, respectively. The structure of the product was determined on the basis of spectroscopic data, including NMR spectra ((1)H, (13)C, (1)H-(1)H, (1)H-(13)C, and DEPT 135°), a UV and IR spectrum and HR ESI-MS analysis. The developed method of microbial replacement of the amino group in 6-aminoflavone (1) by a acetamido one may find application in chemical industry, being an alternative to the reactions involving acetic anhydride. The antioxidant activity of flavone, and its C-6 substituted derivatives: 6-aminoflavone (1), 6-hydroxyflavone and isolated metabolite 6-acetamidoflavone (2) has been examined using the ABTS and DPPH methods.