Optimization of the solvent system used to prepare cannabis inflorescence samples for cannabidiol and Δ9-Tetrahydrocannabinol quantification using D-optimal design

Abstract

The solvent most commonly used to prepare cannabis inflorescence samples is a mixture of methanol and chloroform (9:1), which poses a health hazard. This study aimed to develop a solvent system that maximizes the extraction of two major cannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC), with superior performance to conventional solvents. The cannabinoid content was determined using high-performance liquid chromatography. The stability of these two cannabinoids in the optimal solvent system was also evaluated. The volume ratios of acetonitrile, methanol, and water were varied for extracting cannabinoids from two cannabis cultivars, Hang Kra Rog Phu Phan and Charlotte’s Angel, based on a D-optimal design. The solvent system developed in this study showed superior extraction efficiency to acetonitrile, as specified in the Thai Herbal Pharmacopoeia, and the methanol:chloroform mixture (9:1), as specified in the United Nations Office on Drugs and Crime manual. The optimal solvent system that provided the highest cannabinoid content consisted of acetonitrile, methanol, and water at a volume ratio of 0.511:0.289:0.200. This solvent system could extract 0.141 % ± 0.023 % of CBD and 3.255 % ± 0.511 % of Δ9-THC from the Hang Kra Rog Phu Phan cultivar, and 2.120 % ± 0.143 % of CBD and 3.813 % ± 0.219 % of Δ9-THC from the Charlotte’s Angel cultivar. The stability of cannabinoids in the optimal solvent system was comparable to that of the methanol:chloroform mixture (9:1) but superior to acetonitrile when stored at 4 °C and − 20 °C for 28 days. In summary, the optimal solvent system developed in this study is less toxic than existing systems and can be valuable for extracting cannabinoids from cannabis during inflorescence sample preparation for analyzing their content.