Green method for recovery of cannabinoids from Cannabis sativa flowers: pH-controlled aqueous leaching

Abstract

Cannabis sativa is a remarkable plant containing a wide variety of valuable secondary metabolites, especially cannabinoids, which are valued for their clinical relevance. In this investigation, an efficient and environmentally friendly method to recover cannabinoids from cannabis plant tissues using organic solvent-free pH-controlled solution has been developed. The impact of leaching pH and solid/liquid ratios on the recovery of thirteen acidic and neutral cannabinoids from a wide range of cannabis plant tissues, which are either high tetrahydrocannabinol (THC) or high cannabidiol (CBD) cultivars in fresh, dried and decarboxylated forms, was investigated. The results revealed acidic cannabinoids, the predominant cannabinoids in fresh and cannabis dried at low temperature, were recovered efficiently at pH ≥ 12, demonstrating the potential of alkaline leaching to replace the conventional alcohol leaching widely utilized in the cannabis industry. Alkaline leaching also enables a highly efficient means of obtaining a cannabinoid concentrate directly from fresh material and avoids the long (4–6 d) and energy-intensive drying process. Alkaline leaching was also viable for neutral cannabinoid recovery from decarboxylated cannabis at low solid/liquid ratio. Finally, the stability of cannabinoids in leached solutions at room temperature and in the dark was tracked and analyzed for up to 15 d. These data offer the cannabis industry a range of options for cannabinoid storage and extraction during the enrichment processes.