Abstract

Accumulation of essential oil in herbs depends on development stage. The aim of the present study was to investigate the effect of growth stages (pre-flowering and blooming stages) on the yield and composition of essential oil of thyme (Origanum syriacum L.). Three harvesting times (morning at 8 am, noon at 12 pm and evening at 6 pm) and two harvesting date (growth stage (pre-flowering stage) and blooming stage) were studied. Total yield of oil was higher in the plant at blooming stage in comparison with that at pre-flowering stage. According to the results of multivariate analysis, higher levels of volatile compounds were noticed during the blooming stage, except carvacrol, gamma-terpinene, alpha-terpinene and para-cymene that were found higher in pre-flowering stage. Unexpectedly, carvacrol as structural isomer of thymol depicts higher concentration at pre-flowering stage. Moreover, an accurate valid prediction equation of oil samples was built to predict the growth stage and quality control purposes of the oil.

Key words: Carvacrol, essential oil, harvesting time, blooming stage, Origanum syriacum, thymol.