Materials and Methods: The fresh aerial parts of the cultivated rosemary were hand-harvested in winter at three different times (i.e., before sunrise, at noon, and after sunset) and then dried at 30°C. Each sample was submitted to the Clevenger-type apparatus for the isolation of the EO. The dried EOs were analyzed by gas chromatography (GC)/flame ionization detector (FID) and gas chromatography-mass spectrometry (GC/MS), and total hydroxycinnamic acid derivatives were determined by the UV/Vis spectrophotometer. Finally, the results were validated by the ANOVA test.

Results: The maximum (3.65%) and minimum (1.61%) of the total EO were obtained before the sunrise and after the sunset with 24 and 26 components, respectively. In addition, the results of GC/MS revealed that 1, 8-cineole, α-pinene, and camphor are the three most dependable components in the EO to the harvesting time. The contents of α-pinene and 1,8-cineole reduced from 32.8% to 23.0% and from 23.6% to 10.5% although the camphor percentage increased from 2.7% to 9.8% in the variation of the harvesting time from before the sunrise to after the sunset. In contrary to the EO, UV/Vis spectrophotometry results showed that hydroxycinnamic acid derivative contents were undependable over different harvesting times.

Conclusions: Based on this investigation, rosemary can change their component in some groups, and thus the harvesting time can be optimized based on our needs.