Antioxidant and antibacterial activity of aquaethanolic extract of leaves of Cassia fistula

In the present investigation total phenolic contents (TPC), in vitro antioxidant activity and in vitro antibacterial activity of aquaethanolic extracts of leaves of Cassia fistula were evaluated. 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 leaf extract were 16.65 ± 0.37mg of gallic acid equivalent/g of extract. Leaf extract also showed good ABTS scavenging activity (IC₅₀=155.08 jig/ml), DPPH scavenging activity (IC₅₀=215.55jig/ml) and Superoxide radical scavenging activity (IC₅₀=652.38 jig/ml). At 100mg/ml, the highest average inhibition zone was recorded in aquaethanolic leaf extract against E.coli (MTCC 2991) (12.67±0.33mm) and S. aureus (MTCC 7443) (16.0±0.58mm). MIC value of leaf extract against E.coli was 12.5mg/ml and MBC >100mg/ml while MIC against S. aureus was 6.25mg/ml and MBC 50mg/ml.