Antimicrobial activity of various extracts of Centaurea cankiriense A. Duran and H. Duman

Abstract

The antimicrobial activity was determined using the single disc diffusion method. The hexane, methanol and ethyl acetate extracts were assessed for antimicrobial activity against 13 bacteria and a yeast-like fungus, Candida albicans. While flower extracts of Centaurea cankiriense showed significant antibacterial activity against tested strains, the susceptibility of the test microorganisms was less pronounced in the cases of the stem extracts. Hexane extracts from both flower and stem did not show any antibacterial activity against gram-negative bacteria at test concentration, whereas ethyl acetate and methanol extract of C. cankiriense demonstrated the growth of both the gram-positive and the gram-negative bacteria. But, methanol extract inhibited the bacteria with the exception of two gramnegative bacteria namely Escherichia coli and Klebsiella pneumoniae. Minimum inhibition concentration (MIC) was determined on ethyl acetate extracts of flower and stem that showed high activity against the test bacteria. The MIC values for bacterial strains were in the range of 7.8 - 250 mg/ml. The results confirmed that E. coli (MIC = 250 mg/ml) and Morganelle morganii (MIC = 125 mg/ml) was the most resistant organisms to plant extracts. The flower extract of C. cankiriense was found to possess the strongest effect on Bacillus cereus with 7.8 mg/ml concentration.