eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-05-05 7 1 251 258 9321 article S. Elumalai 1 R. Kesavan 2 S. Ramganesh 2 V. Prakasam 2 R. Murugasen 2 1Department of Plant Biology & Biotechnology, Presidency College, Chennai (India). SAIF (Sophisticated Analytical Instrument Facility), IIT, Chennai (India). The bark and the leaves of Cinnamomum species are commonly used as spices and their distilled essential oils are used as flavouring agent. The extract or essential oil of Cinnamomum zeylanicum stem bark is composed of a number of compounds (Cinnamaldehyde, cinnamic acid, cinnamyl acetate, Benzyl benzoate, a-Terpineol) and not all of them appear to have antimicrobial activities. The two (C. zeylanicum and C. cassia) barks oil extracts were prepared by hydro distillation method. Streptomycin (10μg/disc) and Chloramphenicol (30μg/disc) were used as standard drug, compared with C. zeylanicum and C.cassia crude oil extract. They were used 100μl for each experiment five pathogenic bacteria Bacillus subtilis (ATCC-6633), Klebsiella pneumonia (ATCC-13883), Pseudomonas aeruginosa (ATCC-10145), Staphylococcus aureus (ATCC-126000) and Escherichia coli (ATCC-6633) were used in this study. Among all these experiments the highest percentage of growth inhibition recorded in B. subtilis (53.3%) and S.aureus (53.3%) and the lowest growth inhibition recorded in E. Coli (44.4%), K. Pneumoniae (44.4%) with C. cassia oil extracts. The highest growth inhibition recorded in E. Coli (40%) with C. zeylanicum and lowest growth inhibition recorded in S. aureus (37.8%) with C. zeylanicum. The comparative analysis of bark oil extracts of C. zeylanicum and C. cassia with all these pathogenic bacteria were studied and recorded. C. cassia showed highest growth inhibition range than the C. zeylanicum. https://www.biotech-asia.org/vol7no1/comparative-study-on-anti-microbial-activities-of-bark-oil-extract-from-cinnamomum-cassia-and-cinnamomum-zeylanicum/ Cinnamaldehyde; Cinnamic acid; Benzyl benzoate; C. zeylanicum; C. cassia; Bacillus subtilis.