The anti-staphylococcal activity of Hypericum species

The genus Hypericum has attracted much attention in the past decade due to the popular use of St John's Wort (Hypericum perforatum L.) as an herbal remedy to treat depression. Its antibacterial action has been studied and the major anti-staphylococcal principal was found to be hyperforin, an acylphloroglucinol derivative, with minimum inhibitory concentration (MIC) ranging from 0.1 to 1µg/ml against Staphylococcus aureus strains [1]. As with the ongoing project to investigate the anti-staphylococcal activity of the Hypericum genus [2], the aim of this study was to investigate the anti-staphylococcal activity of four different species, namely H. beanii Robson, H. revolutum Vahl, H. kouyhtchense Robson and H. choisianum H. Léveillé. Air-dried, powered aerial parts of the plants were extracted sequentially in n-hexane, dichloromethane and methanol. The multidrug-resistant (MDR) strain SA1199B which over expresses the NorA efflux protein was used in the MIC assay. The MICs of these extracts ranged from 16–512µg/ml, with the hexane and dichloromethane extracts being more active than the methanol extracts (Table 1). In conclusion, the genus Hypericum is a promising candidate which produces metabolites that show anti-staphylococcal activity. Further bioassay-guided fractionation of the above plants will allow the identification of the individual antibacterial components.

Species	n-Hexane	Dichloromethane	Methanol
H. beanii	16	64	256
H. revolutum	128	256	512
H. kouytchense	256	256	512
H. choisianum	64	64	512

Table 1. MICs (µg/ml) of n-hexane, dichloromethane and methanol extracts against MDR strain SA1199B

Acknowledgements: Mr Chris Clennett (Royal Botanic Gardens Kew at Wakehurst Place)

References: [1] Schempp, C.M. et al. (1999) Lancet 353: 2129. [2] Gibbons, S. et al. (2002) Fitoterapia 73: 300.