Pilot-Scale Preparation of Broad-Spectrum CBD: Extraction Optimization and Purification using Centrifugal Partition Chromatography

Abstract

Introduction: Cannabinoids, a class of compounds found in Cannabis sativa L., possess a wide range of pharmacological properties. While Δ⁹-tetrahydrocannabinol (Δ⁹-THC) is strictly regulated owing to its psychoactive effects, cannabidiol (CBD), a nonpsychoactive compound, is permitted in certain countries. This study aimed to optimize the preparation of ethanolic cannabis extracts using response surface methodology (RSM) and develop an effective system for removing Δ⁹-THC through centrifugal partition chromatography (CPC) to produce broad-spectrum CBD (hemp extract containing CBD and other compounds with minimal or no Δ⁹-THC).

Methods: Three variables and six responses were assessed to optimize extraction conditions. Predictions were made using Design-Expert^® software, and the experimental conditions were identified using the Box-Behnken design (BBD). The extracts were analyzed using high-performance liquid chromatography and a chromameter. Optimal conditions were used for pilot-scale extraction, and the CPC process was optimized by determining the partition coefficient of the target cannabinoids in various solvent systems and maximum sample load.

Results: The optimal extraction conditions were -31°C for 33 min and a sample-to-solvent ratio of 1:8% w/v, with a desirability value of 0.576. Temperature was the most influential factor. Although the total yield decreased, this condition provided the highest concentration of light-colored cannabinoids and was successfully scaled up for the three other cannabis samples. The optimal CPC solvent system, consisting of hexane/0.1% FA in ACN/20 mm ammonium formate at a ratio of 10/6.5/3.5 v/v/v, demonstrated a yield recovery of 89.3 ± 0.21% w/w with a maximum load of 5 g of sample per run. The resulting broad-spectrum CBD extract had a high CBD content (73.3 ± 0.37% w/w) and minimal Δ⁹-THC content (0.2 ± 0.00% w/w).

Conclusion: BBD-RSM optimization of ethanolic cannabis extraction provided the highest cannabinoid concentration with a short extraction time and desirable appearance. The CPC process successfully separated Δ⁹-THC, yielding a high-purity broad-spectrum CBD extract.

Keywords: Broad-spectrum cannabidiol; Cannabinoids; Centrifugal partition chromatography; Extraction optimization.

Fig. 1.

3D surface plots illustrate the interactive effects of temperature and extraction time on the % yield (a), % CBD (b), % CBDA (c), % Δ⁹-THC (d), % THCA (e), and (f) lightness of the cannabis extract. The sample-to-solvent ratio was fixed at 1:7 (w/v) in all experiments.

Fig. 2.

The plots of cannabinoid content in the fractions obtained from CPC separation with 3 g (a), 4 g (b), 5 g (c), 6 g (d), and 7 g of sample loaded (e). The CPC runs for 100 min in ascending mode and 50 min in descending mode, as described in the Methods section.