GC-MS analysis and antibacterial activities of some plants belonging to the genus Euphorbia on selected bacterial isolates

Plant extracts have always been used as an alternative source of antimicrobial compounds. The recent spread of multi-drug-resistant bacteria and their increased treatment costs necessitated the study of alternative, cheap sources. The family Euphorbiaceae has over 300 genera and is widely used in traditional medicine. Euphorbia triaculeata, E. fractiflexa, and E. inarticulata were selected to study the antibacterial activity of the methanolic extract against 13 Gram-positive Staphylococcus aureus strains (including methicillin-resistant S. aureus) and 2 Gram-negative isolates, Escherichia coli and Klebsiella pneumoniae, by the Kirby Bauer Disc diffusion test. Paper discs with different concentrations of the extracts (100, 50, and 25 mu g mL(-1)) were prepared, along with the methanol control and standard antibiotic control. A gas chromatography-mass spectrometry (GC/MS) analysis was done to study the phytochemical components present in the plant methanolic extracts. A total of 50 different phytochemical compounds with antibacterial activity were detected by GC/MS analysis of the plants. Twenty-five compounds were detected in E. inarticulata, 24 in E. triaculeata, and 21 in E. fractiflexa. Out of 37 compounds found in E. inarticulata and E. triaculeata, 12 (32.43%) were common to both. Eleven (22%) compounds were unique to E. inarticulata, while 9 (18%) compounds were unique to E. triaculeata, and 13 (26%) compounds were unique to E. fractiflexa. E. fractiflexa showed the best antibacterial activity against MRSA and Gram-negative bacteria. It also showed higher unique compounds with antibacterial activity (26%), followed by E. inarticulata (11, 22%). This is the first GC/MS analysis and antimicrobial activity report of E. triaculeata and E. fractiflexa.