Biological activity and a biflavonoid from Hypericum scabrum extracts

Abstract

Flavonoids are present at very high concentrations in the several plant species. These compounds are known to have strong antioxidant activity and thus different beneficial effects on human health. In this study, ethyl acetate extract of aerial parts of Hypericum scabrum, a biflavonoid namely 5, 5″-dihydroxy-7, 4′, 7″, 4″′-tetramethoxybiflavone, has been isolated by column chromatography (CC) and preparative thin layer chromatography (PTLC). Its structure was elucidated by ultra violet (UV), 1H- and 13C- nuclear magnetic resonance (NMR), heteronuclear multiple bond correlation (HMBC), electrospray ionization mass spectrometry (EI-MS) and infrared (IR) spectra. The antimicrobial activity of the aqueous and ethyl acetate extract of aerial part (flowers and leaves) were determined against some Gram-positive and -negative bacteria (Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae), as well as three fungi (Candida albicans, Saccharomyces cerevisiae and Aspergillus niger). The bioassay showed that the ethyl acetate extract exhibited moderate antimicrobial activity. The antioxidant activities of the aqueous and ethyl acetate extracts of H. scabrum aerial part (flowers and leaves), were examined by a 1,1 -diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay. Among the two fractions, the ethyl acetate one showed the highest scavenging activity, with an IC50value of 48.9 μg/ml. The findings exhibited a strong correlation between antioxidant activity and the flavonoids compounds. In addition, this study reveals that the ethyl acetate extract of this plant is an attractive source of flavonoid, especially the essential ones, as well as of effective natural antioxidants. Key words: Hypericum scabrum, hypericaceae, ethyl acetate extract, 5, 5″-dihydroxy-7, 4′, 7″, 4″′-tetramethoxybiflavone, antimicrobial activity, antioxidant activity.