Trichomes, essential oil composition and biological activities of Salvia albicaulis Benth. and S. dolomitica Codd, two species from the Cape region of South Africa

Abstract

An investigation of leaf indumentum, the identification of the essential oil components and assessment of various biological activities of Salvia albicaulis and S. dolomitica essential oils were carried out. Non-glandular and both peltate and capitate glandular trichomes were identified using scanning electron microscopy. The essential oil of S. albicaulis was dominated by oxygen-containing sesquiterpenes (47%), with viridiflorol (25%), 1,8-cineole (9%) and limonene (9%) as major components. S. dolomitica oil was mainly composed of oxygen-containing monoterpenes (72%), with geraniol (20%), linalyl acetate (20%) and linalool (17%) being the major components. The in vitro pharmacological properties of the essential oils were also evaluated. Antibacterial activity was assessed against Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 11778), Escherichia coli (ATCC 8739) and Klebsiella pneumoniae (NCTC 9633). The oils showed poor activity against E. coli (MIC value > 32 mg ml − 1 ), while moderate activity was obtained against the other pathogens (MIC values between 2 and 12 mg ml − 1 ). The results of the antiplasmodial activity evaluated against the chloroquine-resistant FCR-3 strain showed that both S. albicaulis and S. dolomitica essential oils exhibited antiplasmodial activity with IC 50 values of 6 ± 2 and 5 ± 1 μg ml − 1 , respectively. The two oils also displayed anti-inflammatory activity (IC 50 value: 39 ± 4 and 65 ± 6 μg ml − 1 , respectively). Poor anti-oxidant activity was obtained against the DPPH ·and the ABTS ·+ radicals (IC 50 values > 100 μg ml − 1 ). The toxicity profile of the two oils evaluated against the human kidney epithelium cells indicated some degree of toxicity in comparison to 5′-fluoro-uracil.