Medicinal plants have long been used and prescribed in Thailand for centuries. Some of them have been used for treating various diseases including infectious diseases. Pouzolzia pentandra Benn., Gelonium multiflorum A. Juss., Erycibe elliptilimba Merr.&Chun., Balanophora abbreviate Bl. are Thai medicinal plants from the Thai pharmacopoeia that have been prescribed for treating unknown fevers including some specific infectious diseases. This investigation demonstrated the effects of these Thai medicinal plants for their antibacterial activities by using the macrodilution assay. Based on the present study, the water methanol fraction ( fraction 2 ) of Balanophora abbreviate Bl. showed the antibacterial activity at the MIC level of 250 g/ml but the activity was bacteriostatic in its effects. Therefore, the use of these medicinal plants in controlling fever and infectious diseases appears to be justified and further investigations may be required to obtain more information.

Keywords: Antibacterial activities, Pouzolzia pentandra Benn, Gelonium multiflorum A Juss, Erycibe
elliptilimba Merr & Chun, Balanophora abbreviate Bl