The composition of the essential oil and aqueous distillate of Origanum vulgare L. growing in Saudi Arabia and evaluation of their antibacterial activity

The essential oil and aqueous distillate composition of Origanum vulgare L. were analyzed by GC/MS. Sixty-seven different components were detected in both oils. Sixty-four components were characterized for the oil derived from the aerial parts, whereas thirty-three components in the volatile oil from the aqueous distillates of O. vulgare L., representing 99.8% and 98.5% of the oils, respectively. The main components of the volatile oil from the aerial parts of O. vulgare L. were carvacrol (70.2 +/- 1.37%), c-terpinene (5.6 +/- 0.11%), p-cymene (4.5 +/- 0.42 %), trans-sabinene hydrate (3.8 +/- 0.07%), and thymol (2.2 +/- 0.12%). In comparison, the main compounds of the volatile oil of the O. vulgare L. aqueous distillates were carvacrol (92.5 +/- 0.97 %), thymol (2.5 +/- 0.09%), and terpinen-4-ol (1.0 +/- 0.03%). The antibacterial activity of both oils, along with that of the purified major component, carvacrol, against Gram-positive and Gramnegative strains was assessed. The results revealed that all three samples showed significant antibacterial activity against all tested strains. The IC50 values of the oils derived from the aerial parts and aqueous distillates of O. vulgare L. against the tested strains was in the range of 107-383 mu g.mL(-1), whereas, the IC50 value of carvacrol was in the range of 53-151 mu g.mL(-1). The data suggest that carvacrol, a major component of both oils, possesses the highest antibacterial activity of all the constituents and is the main component responsible for the antibacterial activity of Saudi O. vulgare L. oils. (C) 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.