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Objective: To investigate the effects of Andrographis paniculata(Burm.f.) Wall. Ex Nees(A. paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus(S. aureus) with respect to its survival in vitro. Methods: Antioxidative property of methanolic leaves extract of A. paniculata(0.06 mg/m L). Minimum inhibitory concentration(MIC) was determined by its ability to reduce hydrogen peroxide(H_2O_2) toxicity against S. aureus ATCC 25923(3.8×10~8 cfu/m L). Effects of the extract on expressions of kat A(encoding catalase), sod A and sod M [encoding superoxide dismutases(SODs)], and ahp C [encoding alkylhydroperoxide reductase C(AhpC)] in S. aureuswere determined by RT-q PCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction(NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O_2-in S. aureus. Results: Cells challenged with 7.5 mmol/L H_2O_2 showed 0% survival in 30 min whereas 25% survived after treatment with the extract and H_2O_2. Cells that were treated with the extract alone had 43% survival in the same exposure period. Expressions of sod A and sod M genes in extract-treated cells were lowered 0.8-fold and 0.7-fold, respectively with decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U(P<0.05). In contrast, extract-treated S. aureus cells showed 3.3-fold increase in kat A expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U,(P<0.05). More profoundly, ahp C expression was increased 61-fold in extract-treated cells,(P<0.05) with corresponding increase in Ahp C activity of 0.018 U compared to untreated cells, 0.012U,(P<0.05). Extract-treated cells had significantly lower intra-and extracellular O_2-levels with absorbance readings(A_(575nm)) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928(P<0.05), respectively. Conclusions: Taken together these results suggest that the low MIC of A. paniculatamethanolic leaves extract(0.06 mg/m L) reduce H_2O_2 toxicity and more importantly, was in itself effectively inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sod A and sod M expressions.
Objective: To investigate the effects of Andrographis paniculata (Burm. F.) Wall. Ex Nees (A. Paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus (S. aureus) with respect to its survival In vitro. Methods: Antioxidative property of methanolic leaves extract of A. paniculata (0.06 mg / mL). Minimum inhibitory concentration (MIC) was determined by its ability to reduce hydrogen peroxide (H 2 O 2) toxicity against S. aureus ATCC 25923 × 10-8 cfu / m L). Effects of the extract on expressions of kat A (encoding catalase), sod A and sod M [encoding superoxide dismutases (SODs)], and ahp C [encoding alkylhydroperoxide reductase C (AhpC) in S. aureuswere determined by RT-q PCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction (NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O_2-in S. aureus. Results: Cells challenged with 7.5 mmol / L H_2O_2 showed 0% survival in 30 min. 25% survived after treatment with the extract and H_2O_2. Cells that were treated with the extract alone had had 43% survival in the same exposure period. Expressions of sod A and sod M genes in extract-treated cells were reduced by 0.8-fold and 0.7-fold, respectively with a decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U (P <0.05) fold increase in kat A expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U, (P <0.05). More profoundly, ahp C expression was increased 61-fold in extract-treated cells, (P < 0.05) with corresponding increase in Ahp C activity of 0.018 U compared to untreated cells, 0.012 U, (P <0.05). Of Extract-treated cells had significantly lower lower intra-and extracellular O 2-levels with absorbance readings (A_ (575 nm)) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928 (P <0.05 ), respectively. Conclusions: Taken together these results suggest that the low MIC of A. paniculatamethanolic leaf extract (0.06 mg / m L) reduce H 2 O 2 toxicity and more importantly, was in itself effective inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sod A and sod M expressions.