SEASONAL VARIATION IN THE ESSENTIAL OIL COMPOSITION OF ORIGANUM SYRIACUM L. SUBSP. SINAICUM GREUTER AND BURDET; EVALUATION OF ITS tocol ACTIVITY

Abstract

The essential oil of Origanum syriacum L. subsp. sinaicum Greuter and Burdet obtained by hydrodistillation during four seasons was analyzed by GC-MS. The composition of the oil showed qualitative and quantitative variation. Carvacrol was the major component (64.71%, 36.50%) in summer and spring oils, respectively. The next major components in these seasons were sabinene hydrate (18.28%) and γ-terpinene (13.50%) in spring, and γ-terpinene (9.30%) and p-cymene (7.60%) in summer. The oil prepared in autumn revealed thymol as the major component (19.55%), followed by sabinene hydrate (18.32%) and sabinene (14.85%),while that prepared in winter showed sabinene hydrate as the major component (32.96%) followed by thymol (30.80%). In vitro study of the tocolytic activity of the essential oil and 70% ethanol extract of O. syriacum L. subsp. sinaicum Greuter and Burdet on rat uterus was carried out. Essential oil (18 g/ml) and 70% ethanol extract (200 g/ml) produced marked inhibitions in the uterine contractility of non-pregnant rats (50% and 65% in the normal frequency and 36% and 48% in the normal amplitude, respectively); the area under the curve was also decreased (60% and 82% respectively). Oxytocin-and KCL-induced uterine contractions were significantly decreased following addition of either the essential oil or the 70% ethanol extract.