Antimicrobial and Antioxidant Activities of Careya arborea     Roxb. Stem Bark

The present study was carried out to evaluate the antimicrobial and antioxidant activities of methanol extract of Careya arborea (MECA) stem barks (Myrtaceae) in various in-vitro systems. Antimicrobial activities of MECA were carried out using disc diffusion methods with Gram positive and Gram negative bacteria and some fungal species. MECA showed broad-spectrum antimicrobial activity against all tested microorganisms. Antioxidant and free radical scavenging activities of MECA was assessed by using 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH), superoxide anion radical, nitric oxide radical and hydroxyl radical scavenging assays. The antioxidant activity of MECA increased in a concentration dependent manner. In DPPH radical scavenging assay the IC₅₀ value of the extract was found to be 132.25 mg/mL. MECA was found to inhibit the nitric oxide radicals generated from sodium nitroprusside. The IC₅₀ value was found to be 72.54 mg/mL, whereas the IC₅₀ value of curcumin was 20.4 mg/mL. Moreover, the MECAwas found to scavenge the superoxide generated by phenazine methosulphate (PMS) / nicotinamide adenine dinucleotide (NADH)-nitroblue tetrazolium (NBT) system. MECA was also found to inhibit the hydroxyl radical generated by Fenton’s reaction, where the IC₅₀ value of MECA was found to be more than 1000 mg/mL and for catechin the IC₅₀ value was found to be 5 mg/mL. The results obtained in the present study indicate that the MECA can be a potential source of natural antimicrobial and antioxidant agents.

Keywords
Careya arborea, Antimicrobial activity, Antioxidant activity, Free radical scavenging, DPPH assay