Maximizing Cannabinoid and Polyphenol Extraction from Industrial Hemp (Cannabis sativa L. cv. Helena) Areal Parts: A Comparative Study of Ultrasound-Assisted and Conventional Methods at Two Harvest Stages

In this work, two extraction techniques, conventional and ultrasound-assisted extraction (UAE) techniques, were employed for the extraction of natural bioactive compounds (NBCs) from the areal parts of industrial hemp (Cannabis sativa L. cv. Helena) at two harvesting stages: (i) the beginning of flowering and (ii) the full flowering of the hemp plants. In the conventional extraction, the effect of different extraction solvents on the extraction yield and the content of NBCs was examined. The extraction temperature, extraction time, and ultrasonic power were chosen for the process parameters in UAE. The highest value of the investigated responses in UAE-obtained extracts was higher compared to extract obtained with conventional extraction techniques when the same solvent was used (50% ethanol): extraction yield (17.54 compared to 15.28%), content of total phenols and total flavonoids (1.7795 compared to 1.0476 mg GAE/mL and 0.6749 compared to 0.3564 mg CE/mL, respectively) and cannabidiol (0.8752 compared to 0.4310 mg/mL). Comparing the plant material in different developmental stages, it can be concluded that hemp aerial parts at the beginning of the flowering stage represent a good source of the phenolic compound with sinapic acid and apigenin being dominant, while hemp aerial parts in the full flowering stage represent a good source of cannabinoids.