Evaluation of antioxidant and antibacterial activities of Crotalaria pallida stem extract

Background Antioxidants play an important role in protecting cellular damage by reactive oxygen species. The aim of the present study is to assess the phytochemical nature, antioxidant and antibacterial activities of petroleum ether, chloroform, methanol, and aqueous extracts of Crotalaria pallida stem. Methods The preliminary screening of the various extracts was carried out using standard methods. Total phenolic content (TPC) was determined by the modified Folin-Ciocalteu method and antioxidant activities were assayed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, reducing power assay, total antioxidant capacity (TAC) and reduction of ferric ions. Antibacterial activity of different extracts were assayed against Gram-positive and Gram-negative bacterial strains by observing the zone of inhibition using disc diffusion method, where Staphylococcus aureus , Bacillus cereus , Escherichia coli and Pseudomonas aeruginosa were used as bacterial strains. Results Petroleum ether, chloroform, methanol and aqueous extracts of stem exhibited remarkable antioxidant activity in terms of all the assays tested. Petroleum ether extract (PEE) showed DPPH radical scavenging activity with IC 50 value of 126.96 µg/ml. In antibacterial assay, the PEE and chloroform extract (CE) showed mild to moderate antibacterial activity against all the bacterial strains except B. cereus while methanol extract (ME) showed no inhibitory effect against any of the tested bacteria. Conclusion PEE, CE and ME of C. pallida stem were found to be the most effective free radical quencher and a potent source of natural antioxidants as well as antibacterial activity. Thus justifying their traditional use in green therapeutics.