OBJECTIVE:This study investigated the effects of allylpyrocatechol(APC),the major component in ethanolic extract of Piper betle,on key oxidative stress resistance enzymes important for the survival of Staphylococcus aureus,a major pathogen in the human host.METHODS:Effects of APC on expressions of genes encoding catalase(katA),superoxide dismutases(SODs),including sod A and sod M,and alkyl hydroperoxide reductase(ahpC) in S.aureus were quantitated by RT-qPCR in reference to gyrA and 16S rRNA.Corresponding activities of the enzymes were also investigated.The Livak analysis was performed for verification of gene-fold expression data.Effects of APC on intracellular and extracellular reactive oxygen species(ROS) levels were determined using the nitroblue tetrazolium(NBT) reduction assay.RESULTS:APC-treated S.aureus cells had higher sodA and sodM transcripts at 1.5-fold and 0.7-fold expressions respectively with corresponding increase in total SOD activity of 12.24 U/mL compared to untreated cells,10.85 U/mL(P<0.05).Expression of ahpC was highest in APC-treated cells with 5.5-fold increased expression compared to untreated cells(P<0.05).Correspondingly,ahpC activity was higher in APC-treated cells at 0.672(A_(310nm)) compared to untreated cells which was 0.394(A_(310nm)).In contrast,katA expression was 1.48-fold and 0.33-fold lower respectively relative to gyrA and 16 S rRNA.Further,APC-treated cells showed decreased catalase activity of 1.8×10~(-4)(U/L or umol/(minL)) compared to untreated cells,which was 4.8 × 10~(-4)U/L(P<0.05).Absorbance readings(A_(575nm)) for the NBT reduction assay were 0.709 and 0.695 respectively for untreated and treated cells,which indicated the presence of ROS.APC-treated S.aureus cells had lower ROS levels both extracellulariy and intracellularly,but larger amounts remained intracellularly compared to extracellular levels with absorbances of 0.457 and 0.137respectively(P<0.05).CONCLUSION:APC induced expressions of both sodA and sodM,resulting in increased total SOD activity in S.aureus.Higher sodA expression indicated stress induced intracellularly involving O_2~-,presumably leading to higher intracellular pools of H_2O_2.A concommittant decrease in katA expression and catalase activity possibly induced ahpC expression,which was increased the highest in APC-treated cells.Our findings suggest that in the absence of catalase,cells are propelled to seek an alternate pathway involving ahpC to reduce stress invoked by 0_2~- and H_2O_2.Although APC reduced levels of ROS,significant amounts eluded its antioxidative action and remained intracellularly,which adds to oxidative stress in treated cells. OBJECTIVE: This study investigated the effects of allylpyrocatechol (APC), the major component in ethanolic extract of Piper betle, on key oxidative stress resistance enzymes important for the survival of Staphylococcus aureus, a major pathogen in the human host. METHODS: Effects of APC on expressions of genes encoding catalase (katA), superoxide dismutases (SODs), including sod A and sod M, and alkyl hydroperoxide reductase (ahpC) in S. aureus were quantitated by RT-qPCR in reference to gyrA and 16S rRNA. Responsive activities of the enzymes were also investigated. The Livak analysis was performed for verification of gene-fold expression data. Effects of APC on intracellular and extracellular reactive oxygen species (ROS) levels were determined using the nitroblue tetrazolium (NBT) reduction assay .RESULTS: APC -treated S. aureus cells had higher sodA and sodM transcripts at 1.5-fold and 0.7-fold expressions respectively with increased increase in total SOD activity of 12.24 U / mL compared to untreate (P <0.05) .Expression of ahpC was highest in APC-treated cells with 5.5-fold increased expression compared to untreated cells (P <0.05) .Correspondingly, ahpC activity was higher in APC-treated cells at 0.672 (A_ (310 nm)) compared to untreated cells which was 0.394 (A_ (310 nm)). In contrast, katA expression was 1.48-fold and 0.33-fold lower respectively relative to gyrA and 16 S rRNA. cells showed decreased catalase activity of 1.8 × 10 -4 (U / L or umol / (minL)) compared to untreated cells, which was 4.8 × 10 -4 U / L (P <0.05) .Absorbance For the NBT reduction assay were 0.709 and 0.695 respectively for untreated and treated cells, which showed the presence of ROS. APC-treated S. aureus cells had lower ROS levels both extracellulariy and intracellularly, but larger than usual intracellularly compared to extracellular levels with absorbances of 0.457 and 0.137respectively (P <0.05) .CONCLUSION: APC induced expressions of both sodA and sodM, result ing in increased total SOD activity in S. aureus. Higher sodA expression indicated stress induced intracellularly involving O_2 - -, presumably leading to higher intracellular pools of H_2O_2.A concommittant decrease in katA expression and catalase activity potential induced ahpC expression, which was increased the highest in APC-treated cells. Our findings suggest that in the absence of catalase, cells are propelled to seek an alternate pathway involving ahpC to reduce stress invoked by 0_2 ~ - and H_2O_2.Although APC reduced levels of ROS, significant amounts eluded itsfast action and remained intracellularly, which adds to oxidative stress in treated cells.