The anti-staphylococcal activity of terpenes from Commiphora molmol Engl

Although a large number of antibiotics are available on the market, the development of resistance by bacteria is a major problem in the treatment of infectious diseases. Methicillin-resistant Staphylococcus aureus (MRSA) has been headline news in the UK for the past few years with a sudden increase in death certificates (from 669 in 2000 to 1,168 in 2004) [1]. As a part of an effort to characterize new antibacterials with activity against effluxing multidrug-resistant strains of Staphylococcus aureus, oleo-gum resins from the stems of Commiphora molmol Engl. Have been extracted with chloroform and fractionated by VLC. Further sub-fractionation by SPE and purification by PTLC led to the isolation of a sesquiterpene, β-elemene (1) and two octanordammaranes; mansumbinone (2) and 3,4-seco-mansumbinoic acid (3). The compounds were identified by a series of spectral data, mainly 1D and 2D NMR spectra, and direct comparison to those of published data [2,3]. Compounds 2 and 3 are reported here for the first time from this species. We also unambiguously assigned all ¹H and ¹³C NMR resonances for 3 and revised both ¹H and ¹³C data. The antibacterial activity of these compounds was determined by broth microtitre MIC assay against a number of Staphylococcus aureus strains (SA1199B, ATCC25923, XU212, RN4220 and EMRSA15). MICs of 1 and 3 were found to be in the range of 4–256µg/ml. The highest activity was observed by 3 (MIC=4–8µg/ml) against MDR SA1199B compared to the antibiotic, norfloxacin (MIC=32µg/ml).

Acknowledgements: The Leverhulme Trust.

References: [1] Office for National Statistics. (2006) Report: Deaths involving MRSA:England and Wales 2000–2004. Health Statistics Quarterly 29: 63–68. [2] Adio, AM. et al. (2004) Phytochem. 65: 199–206. [3] Provan GJ., Waterman PG. (1986) Phytochem. 25: 917–922.