Heating of consumer cannabis oils can lead to free radical initiated degradation, causing CBD and THC depletion

Commercial cannabis oil products are widely available in Canada even though there is a significant gap in scientific information regarding them. Oils, such as vegetable oils, are known to undergo oxidative changes through free radical mechanisms when they are heated or aged, but the cannabis oils used in this study did not have expiry dates or best-before usage dates. This led to the question of how these products would be affected with time. We hypothesized that cannabis oils would produce increased concentrations of free radicals in aging-simulated conditions, which would be related to a decrease in cannabidiol (CBD) or Δ⁹-tetrahydrocannabinol (THC) content. Cannabis oils and their respective vehicles (oils) were heated using two protocols: One (moderate aging method) used a 2-day heating protocol at 50 °C, and the other (enhanced aging method) used a 14-day heating protocol at 70 °C. We used electron paramagnetic resonance (EPR) spectroscopy for free radical analysis using the spin trapping technique using 200 mM PBN and 0.02 mM CuCl₂ (for peroxide breakdown to free radicals). For active ingredient analysis (CBD, THC), we used LC/MS. Cannabis oils that contained unsaturated oils as their vehicles, such as olive or sunflower oil, all showed varying degrees of free radical formation. In both aged and unaged oils containing CBD or THC, less free radical formation was detected compared to the vehicle controls. Cannabis oils using medium-chain triglycerides (MCT) showed little or no free radical formation. The most significant decrease in CBD or THC was observed in the products using sunflower oil, to a lesser extent in MCT oil, and THC also decreased in olive oil. These findings are important for consumers and policymakers considering using such products in hot beverages or cooking and highlighting the importance of appropriate storage conditions.