مشخصات پژوهش

e essential oil composition of medicinal and aromatic plants may be affected by several factors, such as physiological stages, genetics and agronomic practices. The objective of the current study was to evaluate German chamomile (Matricaria chamomile L.) essential oil content and composition changes during the day by harvesting the flowers at different time (8:00-10:00 am, 10:00-12:00 am, 12:00-14:00 pm, 14:00-16:00 pm, 16:00-18:00 pm and 18:00-20:00 pm, 121 days after seedling transplantation). For each sample essential oil was separately extracted by hydro-distillation and the fixed oil by extraction with hexane, then chemical composition of essential oil was analyzed by GC-MS. The essential oil percentage in chamomile flowers sampled at different time of the day were found as 0.81 2 % for 8:00-10:00 am, 1.11 % for 10:00-12:00 am, 0.952 % for 12:00-14:00 pm, 0.806 % for 14:00-16:00 pm, 0.908 % for 16:00-18:00 pm and 0.652 % for 18:00-20:00 pm. Harvesting between 10:00 and 12:00 pm showed the highest essential oil percentage (1.11 %), whereas flower collection between 18:00 and 20:00 pm indicated the minimum essential oil percentage (0.65 %). The changes in essential oil phytochemical profile suggest the crucial effect of harvesting time on essential oil composition. The most abundant compounds were (E)-anethole, α-bisabolone oxide A and α- bisabolol oxide B in samples harvested in the morning and (E)-β-farnesene, α-bisabolol oxide A, occidol acetate and chamazulene in samples harvested at noon and in the afternoon. According to these results it can be deduced that if higher essential oil content is desired harvesting should be performed at noon and accomplished in one day