Essential oil composition and in vitro antimicrobial and anti-inflammatory activity of South African Vitex species

The essential oil composition of Vitex pooara, V. rehmannii, V. obovata ssp. obovata, V obovata ssp. wilmsii and V. zeyheri was determined using gas chromatography and mass spectrometry. The in vitro antimicrobial activity of the essential oils was assessed on Staphylococcus aureus, Bacillus cereus and Escherichia coli and the minimum inhibitory concentration values recorded. All essential oils were moderately active with V. zeyheri being the most active (8, 4 and 16 mg ml(-1) for S. aureus, B. cereus and E. coli respectively). The in vitro anti-inflammatory activity of the essential oils was evaluated using a 5-lipoxygenase assay and all essential oils effectively inhibited 5-lipoxygenase, a key enzyme in the inflammatory cascade with V. pooara producing the most promising activity (IC50 value of 25 ppm). Using the essential oil data matrix, chemotaxonomic evidence is presented which supports the infrageneric placement of V. pooara in subgenus Vitex while the other four above mentioned taxa are placed in subgenus Holmskiodiopsis.