Evaluation of antibacterial activities of medicinal plants widely used among AIDS patients in Thailand

Antibacterial activity of 12 selected Thai medicinal plants used as self-medication by HIV/AIDS patients in Thailand was studied. Thirty-nine chloroform, methanol, and aqueous extracts from these plants were investigated for their antibacterial activity against important pathogenic bacteria commonly associated with AIDS infection. These included Staphylococcus aureus , methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus mutans , and Salmonella typhi . Inhibition of growth was tested using paper disk agar diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by agar microdilution method and agar dilution method in Petri dishes with millipore filters. The Gram-positive bacteria were proved to be susceptible to the chloroform extracts of Alpinia galanga (L.) Willd., Boesenbergia rotunda Mansf. (L.), Piper betle (L.), Spilanthes acmella (L.) Murray, and Zingiber zerumbet (L.) Roscoe ex Sm. and the methanol extract of Boesenbergia rotunda . Chloroform extract of Alpinia galanga demonstrated the greatest inhibition zones of 29.1 and 23.7 mm against Staphylococcus aureus and MRSA, respectively. The MIC values of this extract against Staphylococcus aureus and MRSA were 128 and 256 mu g/ml and the MBC values were 256 and 256 mu g/ml, respectively. An active compound, 1 '-acetoxy-chavicol acetate, was identified with MIC values against MRSA and Staphylococcus aureus of 64 and 128 mu g/ml, respectively.