Antimicrobial and antioxidative effects of Piper betle leaves extract on neutrophil survival and katA expression in Staphylococcus Aureus / Nor Anis Nadhirah Md Nasir

P. betle leaves are known to have antimicrobial and antioxidant activities widely used as traditional medicine in Asian countries. This study investigated the antimicrobial activities of ethanolic and aqueous extract of P. betle against S. aureus (ATCC 25923) by determining the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and its effects on the katA expression in S. aureus. The antioxidative activities were tested against H2O2 and oxidative burst in neutrophil. Hydrogen peroxide sensitivity test was performed to determine antioxidant of the ethanolic extract against H2O2. Catalase expression of S. aureuS was analyzed by the SDS-PAGE, NATIVE-PAGE analysis and further confirmed using ferric chloride and potassium ferricyanide. Its effect on oxidative burst was determined using chemiluminescence assay. Ethanolic extract of P.betle leaves showed significant higher antimicrobial activity compared to the aqueous extract where p<0.05. MICs values of ethanolic and aqueous extracts were 5mg/ml and 10mg/ml respectively. The hydrogen peroxide test showed the ethanolic extract able to detoxify hydrogen peroxide resulting in thirteen percent survival of cells. Interestingly, P. betle extract itself showed effective killing of S. aureus within thirty minutes. The RLU in the presence of ethanolic extract showed significant reduction (p<0.05) in oxidative burst by neutrophils. Catalase (58.3kDa) encoded by katA in S. aureus showed significant reduction after one hour treatment with ethanolic extract. The possible mechanism by which ethanolic extract of P.betle is inhibitory to S. aureus by downregulation of an important protein, catalase. Further work is required to quantitate the mRNA of katA expression following treatment with ethanolic of P. betle to confirm mechanism involved.