Mortality and morbidity due to bacterial infections continue to threaten humanity in the 21st century. Bacterial resistance to current antibiotics due to overuse has necessitated a search for new alternative novel drugs that are less prone to resistance. This study evaluated antibacterial activity of Chrysanthemum cinerariaefolium (pyrethrum) flower extracts, fractions and isolated compounds which included pyrethrin II, jasmolin I and cinerolone, against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Staphylococcus aureus and Shigella sonnei. The isolated compounds were obtained by carrying out column chromatography on the bioactive dichloromethane extract and purifying the fractions using preparative High Perfomance Liquid Chromatography (HPLC). The structures of the isolated compounds were elucidated using 1D and 2D NMR. The bioactivity of crude extracts, fractions and isolated compounds were determined using disc diffusion assay at a concentration of 100 mg/mL. The MIC and MBC were determined using microdilution method. The bioassay results showed that individually isolated compounds were not active on all the micro-organisms except jasmolin I (compound 1) which showed slight activity on P. aeruginosa with 7.7±0.6 mm. There was significant difference in the activity of the isolated compounds as a mixture and the activity of individual compounds on MRSA, S. aureus, P. aeruginosa, with P= 0.01, P= 0.0002, P= 0.0007 respectively at 95 % confidence. Isolated compounds and isolated compounds as a mixture in a ratio of (1:1:1) were not active on S. sonnie. Those fractions and isolated compounds which caused inhibition zones of above 10 mm were subjected to MIC and MBC. The lowest MIC and MBC observed was for fraction 3 against MRSA which were 6.5 mg/mL and 12.5 mg/mL respectively. The compound mixture had MIC and MBC of 25 mg/ml and 50 mg/ml respectively against P. aeruginosa. Results of this study showed that extracts of C. cinerariaefolium possess antibacterial activity.
Keywords: MIC (Minimum Inhibitory Concentration), MBC (Minimum Bacteriostatic Concentration), Bioassay, Chrysanthemum cinerariaefolium, Jasmolin, pyrethrin II, Cinerolone