Background: Opportunistic infections in AIDs patients is the leading cause of death in among them. HIV infection was reported as causes of increasing oxidative stress which may lead to progress of many syndrome. Thus medicinal plants as demonstrated antimicrobial and antioxidant activities would be therapeutic values to treat opportunistic infections of AIDs patients.
Objective: To investigate antibacterial, antioxidant activities and total phenolic contents of five Thai medicinal plants using by Thai traditional doctors to treat opportunistic infections of AIDs patients such as Dioscorea bulbifera L. (DB), Momordica charantia L. (MC), Carica papaya L. (female and male trees, CPF and CPM) and Phyllanthus amarus Schum & Thonn. (PA).
Material and Method: The ethanolic and water extracts of those herbs were tested. For antioxidant method was measured using DPPH radical scavenging assay, anti-microbial activity using disc diffusion assay and minimal inhibitory concentration (MIC) was determined by using the modified resazurin assay against four species of micro-organisms: Bacillus subtilis, Escherichia coli, Staphylococcus aureus and Candida albicans. Total phenolic content was determined by Folin Ciocalteau colorimetric method.
Results: For water extract of PA showed the highest antibacterial activity against S. aureus (MIC value = 0.625 mg/ml). The ethanolic extract of MC showed the highest activity against B. subtilis (MIC = 0.625 mg/ml). Only ethanolic extract of DB inhibited growth of E. coli (MIC = 5 mg/ml) it also inhibited growth of gram positive bacteria such as S. aureus and B. subtilis with the same MIC values (2.5 mg/ml). No plant extracts showed activity against C. albicans. The ethanolic extract of CPM, PA and DB and the water extract of PA showed high antioxidant activity (EC50 of 8.48, 9.54, 11.07 and 11.37 μg/ml, respectively). The water extract of PA and the ethanolic extract of DB, CPM showed high total phenolic content of 262.54, 106.26 and 83.78 mg/g, respectively. The total phenolic content of these extracts correlated with DPPH radical scavenging activity, while only ethanolic extract of PA showed high antioxidant activity (9.54 μg/ml) but it contain low phenolic content (45.50 mg/g).
Conclusion: Our findings support the usage of the these plants to treat opportunistic infection of Thai traditional doctors in AIDs patients. Thus, it is recommended that the isolation of pure active antibacterial and antioxidant from these plant extracts should be carried on.

Keywords: Antimicrobial, Antioxidant, DPPH, Dioscorea bulbifera L., Momordica charantia L., Carica papaya L., Phyllanthus amarus Schum & Thonn