Comparative Study of NMR Spectral Profiling for the Characterization and Authentication of Cannabis

Abstract

For the authentication of botanical materials, it is difficult to obtain representative reference materials because botanicals vary significantly with respect to cultivation conditions. Chemical profiling of plant extracts or spectral fingerprinting can differentiate botanicals and group them by their chemical profiles. NMR spectroscopy yields a powerful and useful method for profiling plant extracts. Both 500 MHz 1H and 1H-1H correlation NMR spectroscopy coupled with pattern recognition were used to discriminate among Cannabis samples. A rapid method of analysis was achieved by extracting directly into the deuterated solvent. Spectral ranges including or excluding the downfield region were compared to evaluate the effect on classification accuracy by projected difference resolution. Six classification methods-fuzzy rule-building expert system, linear discriminant analysis (LDA), super partial least-squares discriminant analysis, support vector machine (SVM), and SVM classification trees (SVMTrees)-all gave better classification performance for proton NMR spectra than for proton-proton correlation NMR spectra for seven Cannabis samples. Among the classification methods for a set of 25 Cannabis samples, the 0.5-7.2 plus 7.4-13.0 ppm ranges gave higher prediction rates of greater than 96% when compared to the reduced range of 0.5-7.2 ppm that excluded the downfield range. The LDA method had the best prediction accuracy of 99.8 ± 0.4%. SVMTree methods provide a robust tool, and classification trees are amenable to interpretation. Hence, NMR spectroscopy combined with chemometrics could be used as a fast screening method for the authentication of Cannabis samples.

Selective Preparation and High Dynamic-Range Analysis of Cannabinoids in “CBD Oil” and Other Cannabis sativa Preparations

“…Fraction characterization was performed by quantitative 1 H NMR (qHNMR) as the primary quantitation method. Besides structural characterization, NMR has been used previously for both the quantitation of cannabinoids in extracts and the creation of cannabinoid profiles of crude extracts. − Notably, qNMR provides a means of quantitation that is independent of response factors. Here, qHNMR accompanied by HiFSA ( 1 H iterative full spin analysis) was employed for the unambiguous structural dereplication of chemical constituents and in order to afford high reproducibility for future use of the chromatographic and structural data generated.…”

A Metabolomics and Big Data Approach to Cannabis Authenticity (Authentomics)

“…Proton NMR was applied along with chemometrics approaches to differentiate cannabis extracts [38]. Cannabis samples were directly extracted in deuterated chloroform.…”