Antioxidant and antibacterial activities of the methanolic extracts of three Centaurea L. species (Astraceae) from Iran

Centaurea L. with about 700 species in the world and 70 species in Iran is the largest genus in the family Asteraceae. Centaurea species are used for the treatment of various ailments in the popular medicine in some countries. The aim of the present study was to investigate total phenol and flavonoid contents, antioxidant potency and antibacterial activities of the methanolic extracts from capitulum and aerial parts of three Centaurea species, namely C. imperialis, C. iransharii and C. glastifolia. Total phenolic and flavonoid contents were evaluated by Folin-Ciocalteu and aluminum chloride methods, respectively. Antioxidant activity was evaluated by DPPH radical scavenging assay. In addition, antibacterial activities of the extracts were studied by disc diffusion method. Results from the study showed that total phenol content in the extracts were found to a range between 35/92 and 73 mg GAE/g extract and total flavonoid content varied from 4.45 to 5.30 mg QE/g extract. A significant antioxidant capacity was found in all studied extracts and aerial part extract of C. iransharii showed the highest antioxidant activity (IC50 = 0.11 mg/ml). In addition, the studied species represented strong antimicrobial activity against Gram positive bacteria.