مشخصات پژوهش

Dracocephalum multicaule is a valuable medicinal and aromatic plant belonging to the Lamiaceae family. Its essential oils exhibit anticholinesterase, antioxidant, antimicrobial, anti-inflammatory, and neuroprotective activities, making them suitable for pharmaceutical and food industry applications. However, the optimal harvest time for maximizing essential oil yield and quality remains unclear. This study aimed to evaluate variations in essential oil content and composition of D. multicaule at different phenological stages to determine the most suitable harvest period. Plant samples were collected in 2023 at eight distinct phenological stages, ranging from vegetative growth to the ripe seed stage. Essential oils were extracted by hydrodistillation using a Clevenger-type apparatus and analyzed by gas chromatography-mass spectrometry (GC-MS). Essential oil content varied significantly across phenological stages, ranging from 0.50 % to 0.72 % (w/w). The highest essential oil content (0.72 % w/w) was observed at the 75 % flowering stage, with no statistically significant differences compared to the 50 % flowering (0.69 %) and full flowering (0.62 %) stages. Seven major compounds were identified, accounting for 96.10 %–99.16 % of the total essential oil composition. The predominant constituents were perilla aldehyde (40.03–65.29 %), limonene (23.06–37.65 %), α-pinene (2.28–5.08 %), and carvone (1.10–20.79 %). Perilla aldehyde reached its maximum concentration (65.29 %) at the 75 % flowering stage, whereas limonene was highest at the ripe seed stage. Considering both essential oil yield and chemical composition, the 75 % flowering stage was identified as the optimal harvest time for D. multicaule, providing superior oil content and a favorable phytochemical profile for pharmaceutical and industrial uses.