UBC Theses and Dissertations
Chemometrics and metabolomics of Cannabis sativa L. Mudge, Elizabeth Margaret
Cannabis is a domesticated crop that has a long history of medical and recreational use. Strains have been selected through informal breeding programs with undisclosed parentage and criteria. The term ‘strain’ refers to minor morphological differences and grower branding rather than distinct stabilized varieties. Anecdotal evidence suggests that there are significant variations in pharmacological effects of different strains, for which the phytochemicals responsible are unknown. The overall objective of this research was to develop analytical methodologies and metabolomic tools to characterize the phytochemical diversity of Cannabis strains within the Canadian marketplace. The expected outcomes were to understand phytochemical relationships caused by domestication and the varying pharmacological effects of the strains. A method was optimized and validated for the quantitation of ten cannabinoids in Cannabis flowers. With nine test materials, the relative standard deviations ranged from 0.78 to 10.08 % with intermediate precision HorRat values of 0.3 to 2.0. In the thirty-three Canadian market samples, the two cannabinoids Δ9-tetrahydrocannabinolic acid and cannabidiolic acid contents ranged from 0.76 to 20.71% and <MDL to 18.11%, respectively. Five clusters of strains were identified based on the ranges of total THC/CBD in the strains. Using targeted-untargeted metabolomics, the relationships between known and unknown cannabinoids were evaluated to identify CBD correlated cannabinoids, and losses in the phytochemical diversity of strains based on the distribution of cannabinoids across strain clusters. Terpenes were determined by headspace profiling in the strains. In total, 67 terpenes were detected and grouped according to their cannabinoid clusters. There were several terpenes identified in unique clusters, which highlights the impacts of aroma and breeding practices on the losses of phytochemical diversity. A data fusion model and post hoc algorithms were used to identify relationships between all cannabinoids and terpenes. There was a strong indication of a unique biosynthetic pathway for the synthesis of terpinolene, nine additional monoterpenes and three unidentified cannabinoids. Isolation and characterization of the most prominent cannabinoid was identified as THCA-C4 with a butyl sidechain. Another correlated cannabinoid was identified as THCVA. These two cannabinoids are present in higher quantities in the presence of terpinolene suggesting that breeding for increased cannabinoid production, switches on the biosynthesis of terpinolene in some strains. This research provides novel insight into the impacts of breeding, selection and domestication syndrome in Cannabis. There is a loss of phytochemical diversity in many strains that can potentially impact pharmacological activities.
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