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Antimicrobial and Cytotoxic Activities of Cyanobacteria

Naveen Bharat, Md. Irshad, Md. Moshahid Alam Rizvi, and Tasneem Fatma

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 + 2oC. 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