10.22376/ijpbs.2019.10.1.p1-12 Volume 4 Issue 1 2013 (January - March) In the present study, efforts were made to reveal the total phenolics and flavanoid contents and antioxidant activity in the four cyanobacterial species viz., lessThan i greaterThan Phormidium fragile lessThan /i greaterThan , lessThan i greaterThan Lyngbya limnetica lessThan /i greaterThan , lessThan i greaterThan Scytonema bohnerii lessThan /i greaterThan and lessThan i greaterThan Calothrix fusca lessThan /i greaterThan isolated from a sulfur spring in the Western Ghats of Karnataka. The cultures were maintained in BG lessThan sub greaterThan 11 lessThan /sub greaterThan medium. lessThan i greaterThan In vitro lessThan /i greaterThan screening for antioxidant activity of ethanol and methanol extracts of these cultures was determined by total antioxidant capacity by phosphomolybdenum, DPPH free radical scavenging and ferric ion reducing assays. The study indicates the significant antioxidant potential in lessThan i greaterThan Lyngbya limnetica lessThan /i greaterThan (P lessThan 0.01) followed by lessThan i greaterThan Scytonema bohnerii lessThan /i greaterThan (P lessThan 0.05) and least activity was observed in lessThan i greaterThan Calothrix fusca lessThan /i greaterThan (P greaterThan 0.05). Therefore, mass cultivation of such strains for the production of valuable bioproducts may be a good strategy for future use. The study has revealed the utilization of certain strains of cyanobacteria for the production of biologically active compounds particularly, antioxidants. K. SHARATHCHANDRA AND M. RAJASHEKHAR Cyanobacteria, Sulfur spring, Antioxidants, DPPH, Western Ghats, Karnataka. 275-285