The antibacterial activity of the RRn extract was almost equal to that of rhinacanthin-C. This may be due to the synergistic effect of the rhinacanthins. This effect seems to be the same as its antifungal activity against dermatophytes ( Panichayupakaranant et al. 2009). In case of H. pylori, a Gram-negative microaerophilic bacterium, only the RRn extract exhibited bacteriostatic activity with MIC value of 512 μg/ml. Although, it has been reported that an aqueous ethanolic extract of R. nasutus was inactive against Gram-negative bacteria ( Sattar et al. 2004), the RRn extract was active against H. pylori. This may be due to the high content of rhinacanthins in the extract as well as their synergistic effect. The result of this study confirms the potential of the RRn extract as an active antibacterial agent, especially against Gram-positive bacteria.