Phytochemical and antibacterial studies on Ocimum kilimandscharicum

The development of resistance by bacteria to currently available antibiotics is a major problem in the treatment of infectious diseases. To exemplify this, there has been an increase in the number of deaths by MRSA world wide. As part of on-going efforts to characterize new antibacterials with activity against multidrug-resistant (MDR) strains of Staphylococcus aureus, an extract of the aerial parts of Ocimum kilimandscharicum (Lamiaceae), have been investigated. This species is commonly known as camphor Tulsi. Ocimum has been used in the Ayurvedic System of Medicine for bronchitis, bronchial asthma, skin diseases, arthritis, as an astringent, in inflammation and for fever. The plant material was extracted with chloroform, methanol and acetone successively by cold maceration. Further sub-fractionation by SPE and purification by P-TLC led to the isolation of six compounds eugenol, quercitin, cadinol, thymol, β-sitosterol and stigmasterol. The structures of the compounds were characterized by extensive 1 and 2D NMR spectroscopy. The isolated constituents were evaluated for their antibacterial activity by the broth microtitre MIC assay against a panel of multidrug-resistant (MDR) and methicillin-resistant Staphylococcus aureus (MRSA) strains (ATCC-25923, SA-1199B, XU-212, RN-4220, EMRSA-15 and EMRSA-16) and minimum inhibitory concentrations (MICs) of eugenol and cadinol were found to be in the range of 2–128µg/ml. This study corroborates the traditional claims of Ocimum kilimandscharicum as a topical antibacterial.

Acknowledgements: Kamlesh Shinde thanks the Association of Commonwealth Universities for a Split Site Ph.D scholarship.

References: 1. Prakash, P., Gupta, N. (2005)J. Physiol. Pharmacol. 49: 125–131.

2. Smith, ECJ. et al. (2008) Phytochem. Lett. 1:49–53.