1 DRUG FORMULATIONS AND CLINICAL METHODS Gul et al.: Journal of AOAC International Vol. 98, No. 6, Determination of 11 Cannabinoids in Biomass and Extracts of Different Varieties of Cannabis Using High-Performance Liquid Chromatography Waseem Gul and Shahbaz W. Gul ElSohly Laboratories, Inc., 5 Industrial Park Dr, Oxford, MS Mohamed M. Radwan National Center for Natural Products Research, School of Pharmacy, the University of Mississippi, University, MS 38677, and Department of Pharmacognosy, Faculty of Pharmacy, University of Alexandria, Alexandria, Egypt Amira S. Wanas National Center for Natural Products Research, School of Pharmacy, the University of Mississippi, University, MS 38677, and Department of Pharmacognosy, Faculty of Pharmacy, Minia University, Minia, Egypt Zlatko Mehmedic National Center for Natural Products Research, School of Pharmacy, the University of Mississippi, University, MS Ikhlas I. Khan National Center for Natural Products Research, School of Pharmacy, the University of Mississippi, University, MS 38677, and Department of Bimolecular Sciences, School of Pharmacy, the University of Mississippi, University, MS Maged H.M. Sharaf American Herbal Products Association, 8630 Fenton St, Suite 918, Silver Spring, MD Mahmoud A. ElSohly 1 ElSohly Laboratories, Inc., 5 Industrial Park Dr, Oxford, MS 38655, and National Center for Natural Products Research and Department of Pharmaceutics and Drug Delivery, School of Pharmacy, the University of Mississippi, University, MS An HPLC single-laboratory validation was performed for the detection and quantification of the 11 major cannabinoids in most cannabis varieties, namely, cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), cannabigerol (CBG), cannabidiol (CBD), tetrahydrocannabivarin (THCV), cannabinol (CBN), Δ 9 -trans-tetrahydrocannabinol (Δ 9 -THC), Δ 8 -transtetrahydrocannabinol (Δ 8 -THC), cannabicyclol (CBL), cannabichromene (CBC), and Δ 9 - tetrahydrocannabinolic acid-a (THCAA). The analysis was carried out on the biomass and extracts of these varieties. Methanol chloroform (9:1, v/v) was used for extraction, 4-androstene-3,17-dione was used as the internal standard, and separation was achieved in 22.2 min on a C 18 column using a twostep gradient elution. The method was validated for the 11 cannabinoids. The concentration-response relationship of the method indicated a linear relationship between the concentration and peak area with r 2 values of >0.99 for all 11 cannabinoids. Method accuracy was determined through a spike study, and recovery ranged from 89.7 to 105.5% with an RSD of 0.19 to 6.32% for CBDA, CBD, THCV, CBN, Δ 9 -THC, CBL, CBC, and THCAA; recovery was 84.7, 84.2, and 67.7% for the minor constituents, CBGA, CBG, and Δ 8 -THC, respectively, with an RSD of 2.58 to 4.96%. The validated method is simple, sensitive, and reproducible and is therefore suitable for the Received April 21, Accepted by AP July 24, Corresponding author s DOI: /jaoacint detection and quantification of these cannabinoids in different types of cannabis plant materials. The cannabis plant (Cannabis sativa) is an annual herbaceous plant belonging to the family Cannabaceae. It is one of the oldest plant sources for food and textile fiber (1). The plant is found in a variety of habitats and altitudes (2). The cultivation of hemp started in North America in 1606 (3). It was legal in the United States for many years, ending in Current federal laws prohibit cultivation of cannabis in the United States. Most recently, however, with the passage of the Farm Bill, it is legal to grow hemp plants in states that enacted laws allowing hemp production. There are limits on acceptable levels of Δ 9 -trans-tetrahydrocannabinol (Δ 9 -THC) in the produced plants (<0.3%). The medicinal use of cannabis is legal in a number of countries, including Canada, the Czech Republic, and Israel. While federal law in the United States bans all sale and possession of cannabis, the legal status of cannabis products is in a transitional phase in many states and the District of Columbia in the United States, where use of cannabis for medicinal purposes is allowed. Furthermore, the states of Colorado, Washington State, and Alaska allow recreational use of cannabis. More than 540 different secondary metabolites have been identified in cannabis. These constituents belong to diverse phytochemical classes, mainly, cannabinoids, terpenoids, and noncannabinoid phenols (4). Cannabinoids are the most studied and well known cannabis compounds, exhibiting the typical
2 1524 Gul et al.: Journal of AOAC International Vol. 98, No. 6, 2015 Figure 1. Chemical structures of the major cannabinoids of cannabis. C-21 terpenophenolic skeleton, and their derivatives and transformation products. To date, a total of 104 cannabinoids have been isolated from cannabis (4, 5) and have been the focus of extensive chemical and biological research for almost half a century since the discovery of the chemical structure of its major active constituent, Δ 9 -THC. The plant has been reported for the treatment of a variety of ailments including, pain, glaucoma, nausea, depression, and neuralgia (5 9). In this paper, we report the development and validation of a simple HPLC method for the simultaneous identification and quantification of the main 11 cannabinoids in biomass and extracts of different varieties of cannabis. The method is currently used for routine analysis of cannabis samples in our laboratories. Experimental Standards All cannabinoid standards, namely cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), cannabigerol (CBG), cannabidiol (CBD), tetrahydrocannabivarin (THCV), cannabinol (CBN), Δ 9 -THC, Δ 8 -trans-tetrahydrocannabinol (Δ 8 -THC), cannabicyclol (CBL), cannabichromene (CBC), and Δ 9 -tetrahydrocannabinolic acid-a (THCAA) were isolated and identified by our group with a purity of more than 95% (Figures 1 and 2). Cannabis Plant Material Three different varieties of cannabis were grown at the medicinal plant garden of the University of Mississippi. Additional plant samples with different cannabinoid profiles were obtained from seizures made by the Drug Enforcement Administration (DEA), submitted to our laboratory at the University of Mississippi for potency monitoring. Instruments and Reagents All solvents were of HPLC analytical grade and were purchased from Sigma-Aldrich (St. Louis, MO). A Shimadzu (Columbia, MD) Ultra Fast LC Prominence system equipped with an autosampler, degasser, communications bus module, photodiode array detector, and column heater was used. Chromatographic Conditions HPLC analysis was performed on a Luna C 18 (2) column ( mm id, 3 µm particle size; Phenomenex, Torrance, CA). The column was equipped with a C 18 guard column cartridge (Phenomenex). The temperature of the column was maintained at 28 C. The mobile phase consisted of (A) 0.1% (v/v) formic acid in water and (B) 0.1% (v/v) formic acid in acetonitrile with the following gradient elution program: started and kept at 30% A and 70% B from 0 to 6 min; then to 23% A and 77% B in 6 min; kept at 23% A and 77% B for 10 min; after that, the system was restored to the initial conditions in 0.2 min. The flow rate was maintained at 1.2 ml/min. Injection volume was 10.0 µl. UV spectra were recorded from 210 to 400 nm,
3 Gul et al.: Journal of AOAC International Vol. 98, No. 6, Figure 2. Representative chromatogram of the standard cannabinoids mixture. Figure 3. Average calibration curves for standard cannabinoids.
4 1526 Gul et al.: Journal of AOAC International Vol. 98, No. 6, 2015 Figure 4. Representative chromatogram of an extract of a high Δ 9 -THC/low CBD cannabis variety. Figure 5. Representative chromatogram of an extract of a variety of cannabis rich in both CBD and Δ 9 -THC. Figure 6. Representative chromatogram of an extract of a fiber-type variety of cannabis (high CBD/low THC).
5 Gul et al.: Journal of AOAC International Vol. 98, No. 6, Table 1. LOD and LOQ of various cannabinoids CBDA CBGA CBG CBD THCV CBN Δ 9 -THC Δ 8 -THC CBL CBC THCAA LOD, µg/ml LOQ, µg/ml and the quantification wavelength was set at 220 nm. Run time was 22.2 min. Internal Standard Preparation A solution of 1 mg/ml 4-androstene-3,17-dione was prepared in methanol chloroform (9:1, v/v). Stock Standard Solutions For cannabinoids known to be present at high concentrations in cannabis, nine concentrations ranging from to 5 mg/ml were prepared in methanol. These were Δ 9 -THC, THCAA, CBD, and CBDA. Each solution was further diluted with internal standard solution (1:1) to make a final concentration range of mg/ml. For cannabinoids known to exist at low levels in cannabis, seven concentrations ranging from to 1.0 mg/ml were prepared in methanol. These were CBG, CBGA, Δ 8 -THC, THCV, CBC, CBN, and CBL. Each solution was further diluted with internal standard solution (1:1) to make a final concentration range of to 0.5 mg/ml. These solutions were used to construct individual cannabinoid calibration curves. Calibration Curves Five concentrations, 5.0, 12.5, 25, 50, and 100 µg/ml, were prepared by mixing the 11 cannabinoids stock standard solutions and internal standard solution. These solutions were used to construct the calibration curves (Figure 3). Sample Solution Preparation Cannabis samples were dried for 24 h in a 40 C ventilated oven and then powdered. A 100 mg amount of the powder was extracted with 3 ml of internal standard solution by sonication for 15 min. The extract was filtered through a cellulose membrane filter of 0.2 µm pore size and then diluted 1:1 with methanol. Validation The method was validated according to the International Conference on Harmonization (ICH) Tripartite Guideline for Validation of Analytical Procedures (10). Accuracy was measured by the method of standard addition. The developed method was used to determine the cannabinoid content before and after spiking. The ratio of measured to added amount was used to calculate recovery. The intraday, interday, and intermediate precisions were assessed using a series of measurements. LOD and LOQ were determined as: LOD = 3.3 σ/s LOQ= 10 σ/s where σ = SD of response of each cannabinoid and S = slope of the calibration curve of each cannabinoid. Results and Discussion Several methods have been published for the analysis of cannabinoids in cannabis, including TLC (11), HPTLC (12), GC with and without derivatization (5), and HPLC (13). GC is the Table 2. Average concentration of the 11 cannabinoids in 13 different samples Avg. concn, % (w/w) Sample CBG CBGA CBD CBDA Δ 9 -THC THCAA Δ 8 -THC THCV CBC CBN CBL Equal THC-CBD High THC Low CBD a bloq b bloq bloq bloq bloq Fiber type bloq 1 bloq bloq bloq bloq bloq 2.47 bloq 11.2 bloq bloq bloq bloq bloq bloq bloq 0.80 bloq 1.28 bloq bloq bloq bloq 6 bloq bloq bloq bloq bloq bloq bloq bloq bloq bloq 0.51 bloq bloq bloq bloq bloq bloq 0.26 a b = Not detected. bloq = Below limit of quantitation.
6 1528 Gul et al.: Journal of AOAC International Vol. 98, No. 6, 2015 most commonly used technique (5); however, GC will not detect cannabinoid acids, which will undergo decarboxylation at the temperature of the injection port. HPLC is a suitable alternative that allows the analysis of both free cannabinoids and their acids in the same run without the need of derivatization. The developed method is used for the analysis of cannabinoids of the high Δ 9 - THC/low CBD variety, variety rich in both Δ 9 -THC and CBD, and the fiber-type variety (high CBD/low Δ 9 -THC; Figures 4 6). Optimization Studies Extraction and chromatography parameters were optimized. For extraction, different solvents, extraction methods, and temperature were tried. For chromatographic conditions, various parameters such as analytical column type and dimensions and mobile phase composition were examined. Good separation of the 11 cannabinoids was observed, and the following approximate retention times (min) were obtained: CBDA (7.77), CBGA (8.68), CBG (9.07), CBD (9.41), THCV (10.16), CBN (13.38), Δ 9 -THC (15.84), Δ 8 -THC (16.34), CBL (18.63), CBC (19.18), and THCAA (19.69; Figure 2). Representative chromatograms of extracts of the high Δ 9 -THC/low CBD, approximately equal Δ 9 -THC/CBD, and fiber type (High CBD/Low THC) varieties are shown in Figures 4 6, respectively. Method Validation Results Specificity. Sufficient resolution between the different cannabinoids in the chromatogram and peak purity check were used to establish specificity of the method. Resolution (Rs) 0.9 of each cannabinoid from the preceding peak was observed. Linearity. Five-point standard calibration curves were used to evaluate linearity. The concentration-response relationship of the present method was linear between the concentration and peak area with r 2 values of >0.99 for all 11 cannabinoids as follows: CBDA (0.9988), CBGA (0.9997), CBG (0.9955), CBD (0.9990), THCV (0.9999), CBN (0.9948), and Δ 9 -THC (0.9977) (Figure 4), and Δ 8 -THC (0.999), CBL (0.9975), CBC (0.9996), and THCAA (0.9998) (Figure 3). Accuracy. Accuracy was determined through a spike study, and the average recovery for individual cannabinoids was 90.0% for CBDA (RSD 0.97%), 90.96% for CBD (1.05%), 91.75% for THCV (0.96%), 93.16% for CBN (0.19%), 89.67% for Δ 9 -THC (1.91%), % for CBL (6.32%), 94.11% for CBC (1.97%), and 91.49% for THCAA (1.2%). It was 84.7% (2.8%), 84.2% (2.58%), and 67.7% (4.96%) for the minor constituents CBGA, CBG, and Δ 8 -THC, respectively. Precision. The intraday precision was assessed by applying the procedure repeatedly to multiple samplings (n = 6) of a homogeneous sample. RSD was calculated for CBD (0.6%), CBGA (0.9%), CBDA (0.7%), Δ 9 -THC (0.7%), and THCAA (1.2%). The interday precision was determined by applying the procedure repeatedly to the same sample on 6 different days. RSD was calculated for CBD (2.0%), CBGA (2.0%), CBDA (6.6%), Δ 9 -THC (3.2%), and THCAA (1.7%). The procedure was stable after minor changes were made followed by reinjection of the same sample preparation (intermediate precision). LOD and LOQ. LOD and the LOQ of the 11 cannabinoids are listed in Table 1. Sample Results This method was used to analyze plant samples submitted to our laboratory for potency monitoring by the DEA. Results are listed in Table 2. Conclusions An accurate and reliable analytical method was developed and validated for the simultaneous identification and quantification of the 11 main cannabinoids in biomass and extracts of different varieties of cannabis. HPLC coupled with a photodiode array detector was used. The method is currently being used for routine analysis of cannabis in our laboratories. Acknowledgments The project described was supported in part by the National Institute on Drug Abuse, Contract No. N01DA The authors acknowledge the technical assistance of Candice Tolbert. References (1) Kriese, U., Schumann, E., Weber, W.E., Beyer, M., Brühl, L., & Matthäus, B. (2004) Euphytica 137, org/ /b:euph (2) Merlin, M.D. (2003) Econ. Bot. 57, org/ / (2003)057[0295:aeftto]2.0.co;2 (3) Small, E., & Marcus, D. (2002) in Trends in New Crops and New Uses, J. Janick & A. Whipkey (Eds), ASHS Press, Alexandria, VA, p. 204 (4) ElSohly, M.A., & Gul, W. (2014) in Handbook of Cannabis, R.G. Pertwee (Ed.), Oxford University Press, New York, NY, pp (5) Upton, R., Dayu, R.H., Craker, L., ElSohly, M., Romm, A., Russo, E., & Sexton, M. 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