Green extraction of hemp (Cannabis sativa L.) using microwave method for recovery of three valuable fractions (essential oil, phenolic compounds and cannabinoids): a central composite design optimization study

Background: Solvent-free microwave-assisted extraction (MAE) is a green extraction capable of boosting the yield and quality profile of hemp essential oil when compared with other conventional extraction techniques. During this process, two by-products are produced, namely the aqueous residue containing bioactive phenolics, and the residual deterpenated biomass which can be used for further extraction and purification of phytocannabinoids. To date, the hemp industry has not utilized these products, although they can be valuable for the food, cosmetic, nutraceutical and pharmaceutical market.

Results: This study assessed and optimized the variables affecting microwave-assisted extraction efficiency, namely microwave irradiation power, extraction time, and added water, that were studied using a Central Composite Design approach and results were used to optimize the extraction process for recovering three valuable fractions such as essential oil, polyphenols and phytocannabinoids. The products obtained using the optimized conditions were characterized in terms of yield, chemical profile and biological activity. Moreover, the by-products obtained during the optimized run was further analyzed in term of their biological activity using both enzymatic and non-enzymatic assays. The aqueous residue demonstrated a powerful α-glucosidase inhibition, a good activity in term of superoxide radical scavenging activity, a modest efficacy in term of AGE formation inhibition and no activity in term of lipase inhibition. The residual deterpenated biomass did not give noteworthy results in term of biological activity.

Conclusion: This work support the valorization of industrial hemp EO and its by-products, obtained by a sustainable and eco-friendly extraction method, through an almost waste-free approach. Cannabinoids as well as other valuable bioactive compounds such as glycosidic flavones may be recovered from the residues of the EO extraction, representing interesting substances in the pharmaceutical, cosmetic and nutraceutical fields. This article is protected by copyright. All rights reserved.