Antibacterial Activity and Total Phenolic Content of the Onopordon acanthium L. Seeds

Onopordon acanthium L. is an important medicinal plant which has been used in Iranian medicine. In the present study, total phenolic content (TPC) was evaluated and antibacterial properties of n-hexane and methanol extracts of O. acanthium L. seeds were screened. TPC was determined by Folin–Ciocalteu reagent method. Antibacterial activities of O. acanthium were investigated using disc diffusion method, minimum inhibitory concentration (MIC) and resazurin microtiter assay against some gram-positive bacteria including Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus loteus as well as gram-negative ones Escherichia coli and Klebsiella pneumonia. The TPC was found to be 168.56 ± 4.89 mg of gallic acid/g of extract. Plant methanol extract showed significant antibacterial activity against gram-positive bacteria; Staphylococcus epidermidis and Micrococcus luteus (with MIC= 0.612 mg/ml), while n-hexane extract demonstrated negligible to no inhibitory activity against gram negative and gram-positive bacteria. The results of the present study suggested the effect of O. acanthium methanol extract against the tested bacteria in vitro, may contribute to the in vivo efficacy of this extract.