Antibacterial Activity of Onopordum Espinae: Identification of Hispidulin and Dehydromelitensin-8-(4ꞌ-Hydroxy-Methacrylate)

Hexane, ethyl acetate and methanol extracts of Onopordum espinae leaves were investigated for their antibacterial activities against Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella enteritidis. Hexane and ethyl acetate extracts were toxic to Gram-positive bacteria with inhibition zone diameters ranging between 12 and 30 mm. Two products, hispidulin 1, and dehydromelitensin-8-(4ꞌ- hydroxy-methacrylate) 2 were isolated from the ethyl acetate extract of leaves and identified by 2D-NMR for the first time from this species. Ethyl acetate extractꞌs total flavonoid content was the highest, as 78.73 mg quercetin equivalents (QE)/g. The methanol extract showed the highest total phenolic content as 243.43 mg gallic acid equivalents (GAE)/g and gave the most important 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (EC50 = 86 μg/mL).