Introduction: Several studies have found that cannabinoids, particularly delta-9-tetrahydrocannabinol and cannabidiol (CBD), have the ability to reduce cancer cell viability. An ongoing debate regarding the use of medical Cannabis revolves around the effectiveness of pure compounds versus intact plant material for treatment. Proponents for the use of intact plant material or botanical extracts argue that there is a synergistic effect between the different cannabinoids, terpenoids, and flavonoids; this is commonly referred to as the “entourage effect.” Our study was designed to test the validity of the proposed entourage effect in a narrow application using a cancer cell viability model. Materials and Methods: Six cancer cell lines, from 3 different types of human cancer were treated with 10 μM pure CBD or 10 μM CBD from hemp (Cannabis sativa) oil (obtained from 3 different commercial sources) for 48 h, and cell viability was measured with the MTS assay. Dose-response curves were then performed to compare the potencies of pure CBD to CBD oils. CBD concentrations were independently confirmed in the commercial oils, and cannabinoid and terpene composition were also compared. Results: CBD (10 μM) was able to reduce cell viability in 3 of the 6 cell lines tested, and this was found to be cell line specific and not specific to select cancers. None of the CBD oils tested were able to reduce viability to a greater extent than that of pure CBD. Additionally, dose-response curves found lower IC50 values for pure CBD compared to the most potent CBD oil tested. Interestingly, some oils actually appeared to protect cancer cells from the effects of CBD. Conclusions: We found that pure CBD was as potent or more potent at reducing cancer cell viability as the most potent oil tested, suggesting that there is no “entourage” effect under these specific in vitro conditions.
