Detection and identification of small-molecule Δ9-tetrahydrocanabinol pyrolysis products part 1: C3 – C10 compounds

Abstract Background Cannabis is the most widely used psychoactive plant product in the world. As smoking is the most common route of Cannabis consumption, it is of interest to know what products are formed from the pyrolysis of its psychoactive constituent, Δ 9 -THC, at the temperatures achieved upon igniting a cigarette, and to which a user may be exposed through inhalation of Cannabis smoke. This study investigated the C 3 – C 10 products formed from Δ 9 -THC pyrolysis, conducted at temperatures present in a burning cigarette. Methods Δ 9 -THC standards were pyrolyzed from 400 °C – 800 °C, as these temperatures are attained in the “pyrolysis zone” of a lit cigarette. The resulting product mixture was analyzed using two-dimensional gas chromatography – high-resolution mass spectrometry. Cracking products eluting during the first 19 min of a 90-min analysis were identified based on their mass spectral fragmentation patterns, accurate mass analysis, isotope ratios, retention index information, and comparisons of their characteristics with those of authentic standards. Results The pyrolysis resulted in an intricate mixture of compounds whose complexity increased at higher temperatures. A total of 79 cracking products were detected, 75 of which were identified. These compounds included cycloalkanes, alkenes (acyclic and cyclic), an alkyne, aromatic hydrocarbons and heterocycles, an alcohol, phenols, ketones, and a carboxylic acid. Of the identified compounds, 34 have previously been detected in marijuana smoke. Twenty of these have been linked to adverse health effects such as genotoxicity and neurotoxicity. However, several others are reported to have beneficial effects such as anticancer and antimicrobial properties. Conclusions Δ 9 -THC pyrolysis resulted in a complex mixture of 79 cracking products across all five temperatures analyzed. The greatest number of compounds were formed at 700 °C, while the least were formed at 400 °C. Several have been detected previously in Cannabis smoke but not in the plant itself, indicating that they may be derived from the burning of Δ 9 -THC. While a few of the products are reported to have beneficial biological effects, many are well-known carcinogens and neurotoxins.