Assessment of in vitro antibacterial activity and MIC of cinnamon bark powder ethanolic and aqueous extracts against bacteria

Abstract

The study was planned to evaluate the in vitro antibacterial activity and minimum inhibitory concentration (MIC) of cinnamon (Cinnamomum zeylanicum) bark powder ethanolic and aqueous extracts. Screening of cinnamon powder ethanolic and aqueous extracts for antibacterial sensitivity and MIC against Staphylococcus aureus, Streptococcus agalactiae, Bacillus cereus, Listeria monocytogenes, Escherichia coli and Pseudomonas aeruginosa was carried out. ABST was performed by the disc diffusion method. The cinnamon powder ethanolic and aqueous extracts were suspended in a solution containing 10% dimethyl sulfoxide and 0.5% tween 80. Under aseptic condition, empty sterilized discs were impregnated with 50 μl of different concentrations (50%, 25%, 12.5%, 6.25% and 3.12%) of the cinnamon powder ethanolic and aqueous extracts and placed on the agar plate surface. Paper disc moistened with vehicle (DMSO plus tween 80) was placed on the seeded petri plate as a vehicle control. Standard disc containing antibacterial drugs (gentamicin, tetracycline, cefpirome and ampicillin) were used as reference control. The petri plates were incubated at 37°C for 18 h. After the incubation period, the zone of inhibition was measured. Among the tested bacteria, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes and Escherichia coli showed the sensitivity at different concentration of cinnamon powder ethanolic extract whereas Streptococcus agalactiae and Pseudomonas aeruginosa showed no zone of inhibition. Aqueous extract of cinnamon powder showed no antibacterial activities against all tested bacteria. The minimum inhibitory concentration of cinnamon powder ethanolic and aqueous extracts were determined by micro-broth dilution technique. The results of MIC revealed that both ethanolic and aqueous extracts showed various MIC against all tested bacteria. Ethanolic extract of cinnamon powder has lower MIC value against Staphylococcus aureus among tested bacteria.