The costus Saussurea lappa is a well-known medicinal plant that has been widely used in the traditional medicines in many Asian countries. Here, we report on the chemistry of the ethanol and water extracts of S. lappa roots using gas chromatography mass spectrometry analysis (GC/MS). We further tested their antimicrobial activities against Staphylococcus aureus (Gram +ve) and Salmonella sp. (Gram ve) isolates. The GC/MS analysis indicate that the ethanol extract has more compounds (37) than does the aqueous extract (18) with sesquiterpene lactones as the most abundant compounds in both extracts. The results also reveal that the ethanol extract has significant antimicrobial activity against S. aureus isolate and no effect was observed against Salmonella sp isolate. In contrast, weak effects were found in the water extract against S. aureus and no effect against Salmonella sp isolate. Together with the GC/MS analyses, we conclude that the ethanol extract contains active secondary metabolites that may have a specific activity likely in a synergy effects with other metabolites against Gram +ve bacteria (18-20 mm inhibition-zone) but not Gram ve isolate, indicating a specific mode of action. Therefore, S. lappa might be used as a potential anti-microbial agent against S. aureus and possibly other Gram +ve strains. Nonetheless, further studies are required to get insights into mechanistic basis of actions of these compounds found in the ethanol extracts.
Key words: Antimicrobial, medicinal plants, drug resistance, Costus, essential oil, GC/MS
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