Antibacterial Activity of Rhinacanthin Rich Rhinacanthus nasutus Extract

Rhinacanthin rich Rhinacanthus nasutus (RRn) extract was prepared using the method described by Panichayupakaranant et al. [1]. In a recent study we have shown that the RRn extract possessed antifungal activity against Trichophyton rubrum, T. mentagrophytes and Microsporum gypseum with the potency was equal to that of rhinacanthin-C, the most antifungal active constituent of R. nasutus leaf extract [1]. In this study, antibacterial activity of the RRn extract as well as rhinacanthin-C against Streptococcus mutans, Propionibacterium acnes, Staphylococcus aureus and S. epidermidis was evaluated by microdilution assay [2]. The RRn extract used in this study was standardized by the HPLC method [1] to contain total rhinacantin content not less than 70% w/w. It was found that the RRn extract exhibited potent antibacterial activity against S. mutans, and moderate antibacterial activity against P. acnes, S. aureus and S. epidermidis with the MIC and MBC values as shown in Table 1. The antibacterial activity of the RRn extract was almost equal to that of rhinacanthin-C.

Table 1 Antibacterial activity of rhinacanthin rich Rhinacanthus nasutus (RRn) extract and rhinacanthin-C

Compounds	S. mutans		P. acnes		S. aureus		S. epidermidis
	MIC (µg/ml)	MBC (µg/ml)	MIC (µg/ml)	MBC (µg/ml)	MIC (µg/ml)	MBC (µg/ml)	MIC (µg/ml)	MBC (µg/ml)
RRn extract	4	4	16	32	16	256	8	512
Rhinacanthin-C	2	2	8	>128	8	>128	2	>128
Tetracycline	1	2	0.5	>32	0.5	>32	0.25	>32

Acknowledgements : Prince of Songkla University

References: [1] Panichayupakaranant, P. et al. (2009)J. Chromatogr. Sci., in press.

[2] Wiegand, I. et al. (2008) Nat. Protoc. 3:163–175.