Are All THC-Dominant Cannabis Varieties the Same? Comparing the Phytochemistry and Bioactivity of Different THC-Dominant Cannabis Samples

Abstract

Cannabis sativa has a complex history of classification and traditional use. Cannabis sativa ssp. sativa and spp. indica are the two major lineages of cannabis and, through artificial selection, many strains or cultivars are found within each group are bred together to yield hybrid plants. New methods of classification based on Δ⁹-Tetrahydrocannbinol (THC) and Cannabidiol (CBD) content as well as minor cannabinoids and terpenes have emerged as a more effective classification of cannabis. However, the fidelity of cannabis varieties relative to their respective strain names and lineages (indica, sativa and hybrid) based on chemistry has been brought into question. THC and more recently CBD are collectively responsible for the psychoactive and therapeutic effects of cannabis and minor cannabinoids and terpenes are emerging as having their own unique bioactivity or synergistic effects in vitro. Considering the variation in cannabis chemical profile and infidelity to strain names or lineages, we investigated the cannabinoid, terpene and metabolomic profiles of 33 THC-dominant strains (113 samples) to evaluate existing and alternative chemistry-based classification systems using multivariate analyses. Here, we conclude that Indica-Sativa-Hybrid designations are insufficient in describing variation in cannabinoid, terpene and metabolomic data, and that a terpene-based profile classification revealed robust groupings in cannabinoid-terpene data. However, terpene profiles were not discernable in metabolomic data. To investigate how chemical complexity and variability impacts bioactivity, we compared the activity of cannabis extracts to that of pure THC (and CBD) to determine if THC alone is driving activity. THC, CBD, and plant extracts were tested in vitro for cytotoxicity in BEAS-2Bs cells and for cannabinoid receptor signalling activity using a human CB₁-HEK293 cell model. THC did not completely dictate 24-hour toxicity in BEAS-2B cells suggesting that other extract components (beyond THC and CBD) are contributing to cytotoxicity. While CBD alone was 2x more toxic than THC alone, THC:CBD do no predict toxic concentration. THC within extracts appeared to drive efficacy at CB₁ receptors by reducing intracellular cAMP accumulation but did not dictate variation in EC₅₀. THC in extract also appeared to increase percent cAMP reduction in cells regardless of low CBD content but a 1:1 balanced THC/CBD extract revealed reduced percent cAMP reduction. Pure compounds compared to extracts of the same THC/CBD ratio performed very similarly at CB1 receptors besides 1:1 extract preparation having reduced % reduction of cAMP compared to 1:1 pure compounds suggestive of NAM by extract components. Regression modelling of THC within extract revealed a significant positive relationship in % cAMP reduction (Emax) but no significance in TC₅₀ and EC₅₀. This work demonstrates the importance of rigorous analysis of cannabis chemistry as well as evaluation of extracts in bioactivity assays.