In vitro antioxidant potential of microbial isolates from diverse habitats

Microbial extracts have served as a treasured source of diverse molecules in many drug discovery efforts and led to the discovery of several important drugs. Identification of microbial strains having promising biological activities and purifying the bio-molecules responsible for the activities, have led to the discovery of many bioactive molecules. Extracellular and intracellular extracts of the metabolites of thirty-six bacterial and twenty-four fungal isolates, grown under unusual conditions such as high temperature, high sodium chloride and low glucose concentrations, were in vitro tested for their antioxidant potential by diphenyl picryl hydrazyl (DPPH) radical scavenging method, ABTS [2, 2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] radical scavenging and superoxide radical scavenging by alkaline DMSO nitro blue tetrazolium (NBT) methods. Among the extracellular and intracellular extracts of bacterial and fungal isolates, F-15E showed the maximum antioxidant potential with IC₅₀ of 188.32±0.42 μg/ml by DPPH method. While maximum superoxide radical scavenging ability was shown by F-21E with an IC₅₀ value of 134.01±1.61 μg/ml. In case of ABTS radical scavenging studies, it is interesting to note that the extracellular ethyl acetate extract of F-12 showed an IC₅₀ value of 10.57±0.14 μg/ml, which was better than standard ascorbic acid. Fungal extracts were more effective as antioxidants than bacterial extracts and extracellular fungal metabolites exhibited maximum antioxidant activity than intracellular metabolites.