Antimicrobial and Cytotoxic Activities of Cyanobacteria

Present study screened ten Cyanobacterial extracts for antimicrobial activity, cytotoxicity (against human cervical carcinoma cells Hela and SiHa) & GC-MS for chemical composition. Cyanobacterial extracts were subjected to Agar Well Diffusion Assay at concentration of 100μg. well -1 and incubated at 37 + 2 o C. Inhibition zone was measured in millimetres (mm) after 18-24 hour. Minimum inhibitory concentration (MIC) was determined by using the broth microdilution method in 96-well microtitre plates. Drug dilutions were performed using cation adjusted Mueller Hinton Broth (MHB) in a concentration range of 128-0.25 μg.ml -1 . Cytotoxicities were assessed using MTT assay. GCMS analysis was carried out on a GCMS-QP 2010 Plus Shimadzu system having RTX-5 column (Restek, USA) (60 m, ID 0.25mm, film thickness 0.25 μm). Cyanobacterial extracts exhibited significant antibacterial effect on clinical isolates of S.aureus MRSA & MRSE whereas selectively inhibited Gram-negative. Minimum inhibitory concentrations (MIC) were in the range between 64 to 128 μg/ml. Activity Index of active extracts ranged from 0.33 to 1.50. Activity Index and Zone of Inhibition were significantly correlated with p>0.03.GC-MS detected distinct groups of active compounds with pronounced presence of saturated and unsaturated fatty acids. Pharmaceutically important compounds like sesquiterpenoids (Farnesol), dicarboxylic acids, imidazole, indolinones, α-tocopherol, phenolics, phytosterols, heptadecane, tetradecane and 9-octadecenal were moderately present. Extracts also exhibited cytotoxic effect on human cervical carcinoma cells lines with LD50 values ranging from 34 to 146μg/ml. Cyanobacterial species have distinct active group metabolites which are promising sources of antiproliferative and antimicrobial compounds.