Purpose: Synthetic Cannabinoid Agonists (SCA) (Spice) are potent binders to cannabis CB1 and CB2 receptors, at the former producing strong psychoactive effects. The first generation of SCA were based on medicinal chemistry compounds intended to exploit the pathological implications of CB receptors in many diseases, but they got side-tracked into the illicit clandestine drug market. Fluorinated SCAs are now increasingly prevalent. In 2013, ~90% of seized SCAs had at least one fluorine. This research aims to develop a fast and accurate quantitative analytical method for fluorinated SCA, e.g., 5F-ADB, AM-694, in seized samples with cross-method validation.
Methods: Deuterated solvents were purchased from Cambridge Isotopes Laboratories (Goss Scientific, UK), NMR internal standards (IS) 2-chloro-4-fluorotoluene, dimethyl sulfone (DMS), and maleic acid (MA) were TraceCERT purchased from Sigma-Aldrich (UK). 5F-ADB, AM-694, and JWH-018 were purchased from LGC (Teddington, UK). 19F q-NMR pulse sequence: SW of 241 ppm, (O1P) -160 ppm, 6k data points, AQ 0.7s, 16 scans, D1 30s, 90° pulse angle was performed on a Bruker AVANCE III 500 MHz spectrometer. UHPLC analyses were on a Dionex Ultimate 3000 UHPLC equipped with an Acquity UPLC BEH C18, 1.7 µM, 2.1 x 50 mm RP-column.
Results: 5F-ADB 19F-q-NMR spectroscopic analysis using coupled and decoupled inverse-gated methods resulted in agreement with 1H NMR data using MA as IS. Uniform excitation across the spectrum is essential to ensure that all signals receive the same magnetization in the pulse sequence, making the centre point of the spectra (O1P) a critical parameter to obtain quantitative results. AM-694 19F-q-NMR analysis was validated using UHPLC.
Conclusion: 19F NMR spectroscopy has been applied for the first time to seized Spice herbal blends containing fluorinated SCA, 5F-ADB and AM-694 (Fig. 1) to provide a fast (~8 min), accurate and robust quantitative analytical method with no background interference from the matrix (plant material) component. The analytical technique requires the NMR acquisition parameters, but no method development compared to chromatographic methods. 2-Chloro-4-fluorotoluene was used as an IS in 19F q-NMR, resulting in a method with close agreement to 1H q-NMR results using two different IS and cross-method validation using UHPLC. We thank the Government of Kuwait for a scholarship (to HAN) and DEAT, the Avon and Somerset Constabulary, for the seized samples.
Timothy Woodman– Lecturer in the Department of Pharmacy and Pharmacology, University of Bath
Stephen Husbands– Head of Medicinal Chemistry at the dept of Pharmacy and Pharmacology University of Bath, University of Bath
Ian Blagbrough– Senior lecturer in the department of pharmacy and pharmacology, University of Bath