How do essential oil composition and phenolic acid profile of fluctuate at different phenological stages?

, commonly named Persian hogweed, is a principal native medicinal plant in Iran. Collecting at the most appropriate growing stage is the key factor to achieve the high phytochemical quality to meet consumer's needs. In the present experiment, the aerial parts of this plant were harvested at up to six different developmental stages during the growing season to determine the phytochemical profiles. Our results indicated that the highest essential oil content was obtained in the mid-mature seed stage (3.5%). The most elevated extract content was recorded in the floral budding stage (10.4%). In the vegetative stage, limonene (18.1%), in floral budding stage, caryophyllene (14.1%), anethole (14.6%), and β-bisabolene (12.7%), in the full flowering stage, myristicin (15.0%), and hexyl butyrate (9.1%), in the early development of seeds stage, hexyl butyrate (32.1%), and octyl acetate (11.7%), in the mid-mature seeds stage hexyl butyrate (38.8%), octyl acetate (14.5%), in the late-mature/ripe seeds stage, hexyl butyrate (23.6%), and octyl acetate (10.5%) are recorded as the main components. The highest phenolic acids content was obtained in the floral budding stage (287.40 mg/g dried extract). The analysis of phenolic acids demonstrated cinnamic acid (8.0-225.3 mg/g extract), p-coumaric acid (1.7-39.2 mg/g extract), p-hydroxybenzoic acid (0.8-16.8 mg/g extract), and ferulic acid (2.4-15.8 mg/g extract) as the main phenolic acids. Cinnamic acid was found as the major phenolic compound in the vegetative stage following by floral budding, the full flowering stage, the early development of seeds, and late-mature/ripe seeds stages. P-coumaric acid was the most abundant phenolic compounds in the mid-mature seeds stage. In this regard, the harvest time of aerial parts can be selected to achieve the highest secondary metabolites of interest. The results of this study can be used as a guideline for grower to obtain the highest possible amount of desirable metabolites, beneficial in both food and pharmaceutical industries as well as their undeniable economical benefits.