RESUMO
The present study evaluates the antioxidant and antimicrobial activity of Nostoc linckia which was isolated from Kukkarahalli lake, Mysore and maintained in BG-12 medium. The antioxidant potential of the N. linckia extract was investigated using 2,2- Diphenyl, 1- Picryl Hydrazyl and 2, 2´- Azino- bis-(3- ethylbenzothiazoline- 6- sulfonic acid) radical scavenging assays and ferric reducing power assay. It expressed DPPH radical scavenging activity at 1.58 mMTrolox Equivalent/g extract, ABTS˙ radical scavenging activity at 3.8 mMTE/g extract and total ferric reducing power at 1.05mgButylated Hydroxy Anisole Equivalents/ g extract. The radical scavenging activity was compared with BHA as standard wherein it expressed DPPH and ABTS˙+ radical scavenging activity of 2.8 mMTE/g and 4.3 mMTE/g respectively. In vitro bactericidal screening of ethanol extract of Nostoc linckia was carried out against six species of bacteria namely Bacillus cereus, Bacillus subtilis, Escherichia coli, Klebsiella oxytoca, Proteus vulgaris and Staphylococcus aureus wherein B. cereus, B. subtilis and E.coli expressed minimum bactericidal concentration values more than 1 mg/ml while K. oxytoca, P. vulgaris and S. aureus expressed MBC values of 0.51, 0.77 and 0.79 mg/ml respectiviely. The study also revealed minimum algicidal concentration of the extract at 0.625 mg/ml against Nostoc sp., Spirullina sp. Synecocystis sp., and 1.25 mg/ml against Gleocapsia sp by the 6th day after inoculation. The antimicrobial assay was carried out using micro titre plate method.