Antibacterial and Antioxidant Activity of Herbal Extracts of Curcuma longa L., Careya arborea Roxb., Madhuca longifolia (Koenig) Macbr. and Punica granatum L.

Aims: Development of multiple resistances against pathogenic bacteria has become a global concern at the moment. This problem has enforced scientists to search for new antimicrobial substances from various sources including medicinal plants. Hence the study was designed to determine the effect of ethanol extracts of commonly used some herbs rhizomes of Curcuma longa, bark of Careya arborea, seed of Madhuca longifolia and leaves of Punica granatum at different levels of concentrations (125, 100, 75 and 50 mg/ml) in Sri Lanka on (Salmonella typhimrium (ATCC 14028), Bacillus subtilis (ATCC 6633) and Escherichia coli (ATCC 25922)).

Study Design: This is a laboratory-controlled experimental design.

Place and Duration of Study: Laboratory of Livestock Production, Faculty of Agricultural Sciences and Laboratory of Chemistry, Faculty of Applied Sciences, Sabaragamuwa University of Sri Lanka.

Methodology: Ethanol herbal extracts at four different concentrations (125, 100, 75 and 50 mg/ml) were screened for its antimicrobial activity by Kirby-Bauer disc diffusion assay method. In vitro, the antioxidant ability was determined using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay method.

Results: Punica granatum showed the highest inhibition against S. typhimrium; 15.46±0.1, 14.71±0.14, 13.11±0.06 and 11.81±0.09 mm at 125, 100, 75 and 50 mg/ml concentrations respectively. Careya arborea showed the highest inhibition against B. subtilis with inhibitory zones of 10.34±=0.12, 9.22±0.25, 7.55±0.15 and 7.05±0.05 mm and second highest inhibition was against E. coli; 12.89±0.07, 12.43±0.10, 11.34±0.19 and 10.67±0.08 mm for all concentrations respectively. Careya arborea exhibited the highest inhibition against B. subtilis with inhibitory zones of 10.34±=0.12, 9.22±0.25, 7.55±0.15 and 7.05±0.05 mm. When considering the effect of Curcuma longa, B. subtilis and E. coli had shown significant highest inhibition at 125 mg/ml and S. typhimurium had lowest inhibition. Highest antimicrobial effect on B subtilis (7.49±0.31 mm) was shown by the ethanolic extract of M. longifolia (125 mg/ml) compared to other two bacteria (for S. typhimrium, 6.53±0.18 mm and E. coli 6.67±0.18 mm). Careya arborea exhibited the highest ascorbic acid equivalent antioxidant concentrations (718.40±22.78 mg ascorbic/g extract) followed by Punica granatum (213.43±17.82 mg ascorbic/ g extract) and Curcuma longa (144.28±6.40 mg ascorbic/g extract). Madhuca longifolia had lowest (4.11±0.27) and inhibitory concentration at 50% (IC50) of DPPH radical scavenging activity (2.84±0.08, 9.62±0.76, 14.14±0.61 and 498.01±34.63 IC50 µg/ml) in the ethanol extracts of Careya arborea, P. granatum, C. longa and Madhuca longifolia respectively.

Conclusion: This study concluded that there was a significant antimicrobial effect in ethanol extracts of tested herbs against S. typhimurium (ATCC 14028), B. subtilis (ATCC 6633) and E. coli (ATCC 25922) at varying levels.