Evaluation of the phenolic contents and antibacterial activity of different concentrations of Onosma chlorotricum Boiss.

Abstract

Because of side effects and increasing resistance to antibiotics, considerable attention hasbeen given to extract sand biologically active compounds isolated from medicinal plants. In the present study, phytochemical screening and antibacterial activities of different concentrations of various extracts of Onosma chlorotricum were evaluated and compared with those of vancomycin and amikacin. Total phenolic and flavonoid contents and the antibacterial activity of methanol, n-hexane, and aqueous extracts (5 mg/ml to 0.156 mg/ml final concentration) of O. chlorotricum against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli were evaluated using disc diffusion and microdilution methods. Total phenolic and flavonoid contents were determined according to the Folin-Ciocalteu and aluminum chloride colorimetric assays, respectively. The results showed that the total phenolic and flavonoid contents of these extracts ranged from 56.10±0.13 to 74.12±0.05 mg GAE/g dry extract and from 19.3±0.6 to 23.20±0.41 mg QE/g dry extract, respectively. The methanol extract with the highest phenolic and flavonoid content showed the highest antibacterial activity against all the tested bacterial strains, with the highest inhibition zone of 21±0.7 mm and the lowest MIC and MBC values of 78.12 μg/ml for S. aureus. The antibacterial effects and the total phenolic content of O. chlorotricum were remarkable. The results suggest that the effects of methanol extract on wound healing could be tested in an animal model.

Keywords

• phenolic compounds
• flavonoids
• antibacterial activity
• onosma chlorotricum