Variation in the essential oils of Thymbra spicata L. growing wild in Lebanon according to the date of harvest

Thymbra spicata, an aromatic shrub belonging to Lamiaceae family and growing wild in Lebanon, was collected from Nahr Ibrahim in ten different harvest dates (from 11 October 2011 until 11 May 2012) and the composition of the essential oils (EOs) of air-dried aerial parts extracted by Clevenger-type hydrodistillation was determined by gas chromatography coupled with mass spectrometry (GC-MS). The amount and nature of the chemical compounds varied considerably from one sample to another depending on the harvest date. Oxygenated monoterpenes showed majority over monoterpene hydrocarbons only during the flowering stage (in May). In general, twenty-seven compounds of the EOs, which made up 89.4-98.7%, were identified in the oil of Thymbra spicata and the yield ranged between 3.5% and 6.6%. The main components were: carvacrol (16.1-62.9%), -thujene (1.7-4.8%), myrcene (1.1-5.1%), -terpinene (11.4-24.1%) and p-cymene (8.1-46.8%).