Detection and identification of small-molecule cracking products formed on pyrolysis of cannabidiol part 1: C3 – C10 compounds

BACKGROUND: Cannabidiol (CBD) is one of over 100 naturally occurring phytocannabinoids in Cannabis. While extensive research has evaluated the effects that CBD and other phytocannabinoids have on consumers, less attention has been directed towards studying the health impacts of the compounds formed when cannabinoids are burned. Such an investigation is highly desirable, as smoking remains the most common form of Cannabis consumption. Previous research has investigated the structures of CBD pyrolysis products that are of a molecular mass similar to or greater than CBD. However, studies of the lower molecular weight products formed when CBD is pyrolyzed at the temperatures of a burning cigarette are limited. This work investigated the identities of the small-molecule cracking products formed from the pyrolysis of CBD. METHODS: CBD standards were pyrolyzed within the temperature range of 400 °C - 800 °C and analyzed using two-dimensional gas chromatography - high-resolution mass spectrometry. A combination of mass spectral fragmentation patterns, retention index data, GC retention times, and comparison of the profiles of detected compounds with those of authentic standards were used to identify cracking products that eluted during the first 19 min of a 90-min analysis. RESULTS: This investigation revealed a mixture of pyrolysis products whose complexity increased with increasing temperature. A total of 86 compounds were detected, 81 of which were identified. They spanned the alkane (both cyclic and acyclic), alkene (both cyclic and acyclic), alkyne, substituted benzene, aromatic heterocycle, phenol, and ketone compound classes. Seventy-eight of the identified molecules are reported here for the first time as CBD pyrolysis products. Several are known to have adverse health effects, including genotoxicity and neurotoxicity. Others have been reported to possess health benefits such as anti-inflammatory and antioxidant properties. CONCLUSIONS: cracking products across all five temperatures analyzed. The largest number of compounds were formed at 800 °C, while the smallest number of products was observed at 400 °C. The vast majority of these compounds have not been reported in previous studies of CBD pyrolysis. Many of the identified products are known to have impacts on human health.