The effect of drying time on the yield and the chemical composition of essential oil and dissolved oil in hydrolat from aerial parts of Moroccan Thymbra capitata (L.) Cav

The present research aimed to study the effect of drying time on the yield and chemical composition of essential oil (EO) and dissolved oil in hydrolat (HY) from aerial parts of Moroccan Thymbra capitata (L.) Cav. Drying of plant material was carried out naturally in the shade of a draughty place at room temperature  (25–27°C). A series of 10 plant samples were subjected to hydrodistillation using a Clevenger-type apparatus. The results indicated that the yield of EO increased with drying time to reach the highest value on the 8 th drying day (2.7%), while the yield of HY has not undergone an apparent variation   (0.2% – 0.6%). Based on the GC-MS analyses, EO was composed mainly of the phenolic monoterpene carvacrol (80.10%–92.27%) along with its biogenetic precursors' monoterpene hydrocarbons in a 1.02%–4.81% range p -cymene and 0.24% -1.86 %  γ -terpinene. Other essential components occurring in minor quantity were sesquiterpene hydrocarbon  a -humulene (2.58% – 4.67%) and oxygenated monoterpene linalool (0.80% –2.06%). At the same time, HY was constituted mainly of carvacrol (94.67–98.42%) along with a -humulene at much lower concentrations     (0.31%–0.86%) and the oxygenated derivative acetovanillone acetate (0.2%–1.80%). On the other hand, the highest concentration of carvacrol in EO was reached on the 5 th day of the drying plant process (92.27%), while the HY recovered on the 7 th day has shown carvacrol in its highest concentration (98.42%).