Effect of harvesting time on essential oils content and composition of Salvia officinalis L. and Mentha piperita L. in Khuzestan province

In this research, the effect of different harvesting stages on essential oils content and composition of Mentha piperita L. and Salvia officinalis L. was studied. The rhizome of Mentha piperita was planted at 5 cm soil depth in the field of "Jangalkar Ferdos Company", 2008. The salvia seeds were received from Isfahan research center. Their seedlings were transplanted on the furrows of the main field. The experimental design was randomized complete blocks and the treatments included early, full and after flowering stages. The experiment included six treatments and three replications in a total of 18 experimental units. After drying the samples in room air condition and removing all woody parts, essential oils of both species were obtained by water-distillation method in three replications and then analyzed by GC & GC/MS. According to the results obtained from analysis of variance, the effect of different harvesting stages on oil yield of Mentha piperita (P<0.05) and Salvia officinalis (P<0.01) was significant. Comparison of treatment means showed that the highest percentage of essential oil (2/8%) was recorded in full flowering stage of M. piperita while S. officinalis had the highest percentage of essential oil in early flowering stage (3%), with a significant difference in comparison to the other stages. Analysis and Identification of essential oils components showed that the major constituents of essential oil in S officinalis were α-thujene (20/8%, 27/1%, 35/9%) camphor (29/2%, 14/6%, 17/2%) and β-thujene (15/1%, 14/6%, 4/1%) in early, full and after flowering stages respectively. The major constituents of essential oils in M.piperita at early, full and after flowering stages were menthol (27/7%, 26/9%, 27/0%), menthon (37/0%, 21/9%, 17/2%), and menthofuran (16/0%, 22/0%, 25/3%).