02700nas a2200265   4500008004100000245011100041210006900152260001400221300001400235490000700249520183500256653004102091653001502132653002602147653001602173653002702189653001702216653002802233653003902261100002102300700001902321700002702340700001902367856004802386       2002                        eng d00aGC/MS evaluation of thyme (Thymus vulgaris L.) oil composition and variations during the vegetative cycle.0 aGCMS evaluation of thyme Thymus vulgaris L oil composition and v  c2002/07//  a691 - 7000 v293 aCapillary GC/MS analysis based on polar and non-polar columns has been applied to evaluation of the volatile oils hydrodistilled from thyme (Thymus vulgaris L.) plants. The adopted methodology has been used to monitor seasonal variations in the composition of the oil obtained from thyme herbs harvested at different periods during the plant vegetative and life cycles. Oils from thyme plants of young (2 years) and old (5 years) cultivations have been evaluated from four and two collections, respectively, effected throughout May/December growth period. Generally, the oil was found to be rich in the active monoterpene phenols (thymol and carvacrol) and their corresponding monoterpene hydrocarbon (HC) precursors (p-cymene and gamma-terpinene), which collectively showed synchronized patterns of variation during the different collection periods and in different seasons. The oil from old plant collected in May/June period (0.15% v/w) was characterized by significantly lower levels of monoterpene HCs (mainly gamma-terpinene) and the highest levels of the oxygenated monoterpenes (linalool and borneol), monoterpene phenols (mainly thymol) and their derivatives (mainly carvacrol methyl ether), sesquiterpenes (mainly beta-caryophyllene) and their oxygenated derivatives (e.g. caryophyllene oxide) in comparison with all other samples. A characteristic presence of camphor and thymodihydroquinone was also observed in the old plant oils. On the other hand, the young plant, collected in June/July just before the end of the vegetative cycle, provided the best oil yield (1.2%) with also the highest % content of the monoterpene phenols (thymol: 51.2% and carvacrol: 4%). This latter growth period can represent the best harvest time of young thyme plants in order to obtain an essential oil with better quality and quantity.10aGas Chromatography-Mass Spectrometry10aPlant Oils10aPlant Oils: chemistry10aPlant Stems10aPlant Stems: chemistry10aThymus Plant10aThymus Plant: chemistry10aThymus Plant: growth & development1 aHudaib, Mohammad1 aSperoni, Ester1 aDi Pietra, Anna, Maria1 aCavrini, Vanni  uhttp://www.ncbi.nlm.nih.gov/pubmed/12093498