بررسي تأثير زمان برداشت و روش اسانس گيري بر كميت و كيفيت اسانس Thymus vulgaris L

The effect of distillation methods and plant growth stages on the essential oil content and composition of Thymus vulgaris L.

The aerial parts of Thymus vulgaris were collected in three stages of plant growth (before flowering, at the beginning and full flowering stage) from Research Field of Shahid Beheshti University (Tehran) at spring. The plant materials were dried in shade and their essential oils were isolated by hydro-distillation in three replications. In addition, the essential oils of plant materials at full flowering stage were obtained by water-steam distillation and direct steam distillation. The oil yields were calculated based on dried weigh and compared by statistic analysis. The oils were analyzed by capillary GC and GC/MS. Statistic analysis showed different stages of plant growth and different distillation methods had significant effect on oil yield. The highest oil yield was obtained at the beginning of flowering (1.18% w/w). Among distillation methods, the highest oil yield was obtained by direct steam distillation (1.20%). Analysis and identification of components showed thymol, P-cymene and y-terpinene as main compounds in all samples. The percentage of thymol at the beginning and full flowering stage was the same, but at the beginning of flowering was lower. There was no remarkable difference between different distillation methods for producing thymol, but by hydro-distillation the thymol amount was little higher. Based on the results of this investigation it can be concluded that the beginning of flowering and hydro-distillation are the best for obtaining the higher oil content and thymol percentage.