Antibacterial and Antioxidant Activity of Cirsium englerianum (Asteraceae), an Endemic Plant to Ethiopia

Background and objectives: Cirsium englerianum (Asteraceae) is an endemic medicinal plant to Ethiopia. It is used to treat skin infection, snake bite and cough. The aim of the present study was to evalute the bioactivity of root extracts of C. englerianum. Methods: Phythochemical screening tests were employed by standard protocols to identifiy the phythochemicals. Column chromatographic separation was used to isolate the compounds and the spectroscopic techniques (IR, NMR and ESMS) were used to elucidtae structures of the compounds. Disc diffusion technique was uesd to evalute antibacterial activity. In vitro antioxidant activity was assessed by 1, 1-diphenyl-2-picrylhydrazyl (DPPH), and phosphomolybdenun assays. The total flavonoids content was determined by aluminium chloride method. Results: Phytochemical screening tests revealed presence of alkaloids, steroids, terpenoids, tannins, and flavonoids in the acetone root extract. Column chromatographic separation of chloroform/methanol (1:1) extract offered stigmasterol (1), and stigmasteryl stearate (2). The acetone extract was potentially effective against the tested bacterial strains (Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella typhi) at all concentrations (25, 50 and 100 mg/mL). In vitro antioxidant activity attributed that the acetone extract showed DPPH scavenging (IC50 =154.44±74 μg/mL) and total antioxidant activity (8.24±0.9 mg of ascorbic acid equivalent per gram of dry extract). The total flavonoid content was observed in the range from 5.88 ±0.21 to 8.24±0.9 milligrams of catechin equivalents per gram of dry plant extract. Conclusion: Stigmasterol and stigmasteryl stearate were reported for the first time from this plant. The results proved that acetone extract exhibited potential antibacterial and antioxidant activity which correlated with inhibition zone diameter, and free radical scavenging activity.