Evaluation of Antioxidant and Antibacterial Activities of Hydroalcoholic Extract of Cassia fistula Bark

The present study was undertaken to investigate total phenolic contents (TPC), in vitro antioxidant activity and in vitro antibacterial activity of hydroalcoholic extract of bark of Cassia fistula. The TPC of the extracts were determined by Folin-Ciocalteu method. 2, 2’-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging assays were used to evaluate antioxidant activity. Antibacterial activities were assessed using the well diffusion assay, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Bacteria tested were Staphylococcus aureus (MTCC 7443) and Escherichia coli (MTCC 2991). TPC in the bark extract were 39.74 ± 1.08mg of gallic acid equivalent /g of extract. Bark extract also showed good ABTS scavenging activity (IC₅₀=130.97 µg /ml), DPPH scavenging activity (IC₅₀=196.77µg /ml) and Superoxide radical scavenging activity (IC₅₀=333.04 µg /ml). At 100mg/ml, the highest average zone of inhibition was recorded in hydroalcoholic bark extract against E. coli (MTCC 2991) (16.67±0.33mm) and S. aureus (MTCC 7443) (18.33±0.33mm). MIC value of bark extract against E. coli was 6.25mg/ml and MBC >100mg/ml while MIC against S. aureus was 6.25mg/ml and MBC 50mg/ml.