Phytochemical investigation and in vitro antibacterial activity of essential oils from Cleome droserifolia (Forssk.) Delile and C. trinervia Fresen. (Cleomaceae)

The evolution of drug resistant strains of microbial pathogens provides an urgent need to develop novel therapeutical regimes with resistance-combating capacity. In this study, the phytochemical composition and antibacterial activities of essential oils from Cleome droserifolia and Cleome trinervia growing in Jordan desert were investigated. Hydro-distilled oils were analyzed using GC?MS and evaluated for antibacterial activity in vitro against a selection of Gram-positive and Gram-negative bacteria by the agar-well diffusion and the micro-dilution methods. Sixty five compounds representing 99.3% of the total composition were detected in oil of C. droserifolia, whereas 30 compounds corresponding to 95.9% of the total were detected in oil of C. trinervia. The principal constituents of C. droserifolia oil were (E)-3,7,11-trimethyl-1,6,10-decatrien (11.8%), carotol (10.1%), ?-cadinene (8.9%), ?-eudesmol (7.0%) and benzyl isothiocyanate (5.9%). The chief constituents of C. trinervia oil were 1,5-hexandien-3-ol (28.3%), santene (20.0%), 3-methyl-2-methylenebutanitrile (14.9%), Z-myroxide (9.3%) and 3,5-dimethyl-1,2,4-trithiolane (7.0%). The chemical profiles revealed the preponderance of sesquiterpenes (86.6%) and monoterpenes (31.1%) in C. droserifolia and C. trinervia oils, respectively. Apprecia-ble proportions of nitrogen and sulfur-containing compounds were found in the examined oils (8.5% in C. droserifolia and 27.1% in C. trinervia). Scanning electron microscopy of C. droserifolia and C. trinervia petioles and leaf surfaces showed that the two species are coated with capitate-type glandular hairs consistent with enrichment of such species with essential oils. The antibacterial activity screen study showed that the oils exerted marked growth inhibitory effects. Most bacterial species tested were suppressed, despite the varying degrees of inhibition observed (MIC values of 150?550 ?g ml?1).