Seasonal and geographical variation of Laurus nobilis L. essential oil from Tunisia.

Yield and composition of the essential oil obtained by hydrodistillation from leaves of laurel coming from ten different sites in Tunisia were determined. From each locality, leaves were harvested during four different vegetative stages (October, production of seeds; January, dormancy; April, flowering; July, vegetative activity) to look for some cor- relation between composition and vegetative stage. All 40 essential oil samples produced similar GC profiles containing a total of 71 peaks. 60 Compounds were identified. 1,8-cineole was, in all samples, the main constituent among different compounds such as methyl eugenol, � -terpinyl acetate, sabinene and linalool. All essential oils considered were character- ized by a clear predominance of oxygenated compounds chiefly monoterpenes then phenylporpanoids and sesquiterpenes. The concentration of this class generally decreases during the period October - July; the values are in the range 67.5% - 86.1%. The yields of essential oil ranged between 0.65 and 2.2% by weight. With only one exception, the higher produc- tion of essential oil was obtained during the vegetative period. A seasonal variation in the yield and composition of essen- tial oil was revealed, while geographical variability was not pronounced and no chemotypes were observed among the samples of laurel leaf oil examined.