Effect of andrographis paniculata methanolic leaf extract on alkylhydroperoxide reductase c (AhpC) of staphylococcus aureus (ATCC 25923) in vitro / Nur Habibah Ishak

S.aureus infection nowadays has becomed more difficult to treat because of the emergence of multidrug- resistant strains. To overcome this problem, there is a need to find alternative sources of antimicrobials from non-synthetic sources such as natural plants extracts. Andrographis paniculata which is commonly found in India and Thailand is a plant that has been proven to have antibacterial, antifungal, and antioxidant properties. The aims of this study are to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Andrographis paniculata methanolic extract against Staphylococcus aureus, to determine the killing potential of methanolic extract of A. paniculata against S.aureus in reference to hydrogen peroxide (H2O2) and to study the effect of A. paniculata methanolic extract on expression of alkyl hydroperoxide reductase (AhpC) in S.aureus by using SDS- PAGE analysis. Antimicrobial effect of A.paniculata extract was studied by determination of their minimum inhibitory concentration and minimum bactericidal concentration. The killing potential of extract against S.aureus was determined by killing assay test with hydrogen peroxide as reference. There are significantly difference (p <0.05) in percentage of survival of cells when added three different components which are 7.5mm hydrogen peroxide, 50mg/ml extract and both components. Percentage of survival of S.aureus when treated with 7.5mM hydrogen peroxide is 50.6% while when treated with extract is 3.8 % at 90 minutes incubation. This show that extract can kill S.aureus better than hydrogen peroxide alone. Methanolic extract of A.paniculata also can enhance the killing of S.aureus with 0% of cells survival after 90 minutes with presence of 7.5mM hydrogen peroxide. SDS PAGE is used to analysis the effect of AhpC enzyme in S.aureus after treat with methanolic extract of Andrographis paniculata. Methanolic extract of A.paniculata show antimicrobial effect with MIC and MBC values against S.aureus are 50 mg/ml and 100 mg/ml respectively. SDS PAGE analysis show that there are slightly decrease in intensity of 25.4kDA band of AhpC in S.aureus after treated with methanolic extract of A.paniculata compared with penicillin which is inhibit AhpC better than extract. Thus, there is slightly inhibition of AhpC in S.aureus when treated with Andrographis paniculata methanolic extract.