Antibacterial activity test of red chili fruit (Capsicum annuum L.) extract against Xanthomonas oryzae pv. oryzae, the causal agent of bacterial leaf blight

Abstract

Red chili fruit (Capsicum annuum L.) contain bioactive compounds with antimicrobial activity. The bacterium Xanthomonas oryzae pv oryzae (Xoo) is the causal pathogen of bacterial leaf blight (BLB). This study aims to evaluate the antibacterial activity of C. annuum fruit extract against Xoo. The red chili fruits were macerated using acetone, ethanol, and chloroform as solvents. The antibacterial activity was tested using diffusion and dilution methods. The diffusion test was conducted with concentrations of 50%; 25%; 12.5%; 6.25%; 3.12%; 1.56%; 0.78%; and 0.39%. Antibacterial activity was observed in the red chili fruit extract against Xoo, with the largest inhibition zone at 25% concentration. There was no significant difference between the inhibition zone and the type of solvent (p>0.05), while concentration showed a significant difference (p<0.05). The MIC from the diffusion test of acetone, ethanol, and chloroform extracts were 3.12%; 12.5%; and 12.5%, respectively. The dilution test compared the absorbance value of the test cultures before and after incubation. The MICs from the dilution test were 0.78% for acetone extract, undetected for ethanol extract, and 12.5% for chloroform extract. The best antibacterial activity observed was with 25% acetone extract.