Cannabis chemistry, post-harvest processing methods and secondary metabolite profiling: A review

Differences in cannabis (Cannabis sativa L.) plant chemistry between strains are influenced by genetics, plant growth and development, in addition to environmental conditions such as abiotic and biotic stress. Resulting secondary metabolite profiles are further altered post-harvest by drying and extraction, all of which present sizable challenges to industrial scale producers of pharmaceutical grade products in Canada and elsewhere. Consistent quantity and quality of cannabis extracts, demonstrated by preferred cannabinoid ratios and other secondary metabolites present are important, particularly as the list of therapeutic uses for medical cannabis is expanding. As more countries contemplate the legalization and licensure of medical cannabis, the number of cannabis extraction and testing laboratories is increasing to keep up with demand. However, it is not always known what standards are adhered to, resulting in numerous non-validated methods. In this review, a summary of cannabis chemistry and biosynthesis of secondary compounds is provided, and post-harvest processing practices occurring along the cannabis product value chain that might affect cannabis phytochemistry, potency and volatility are presented. An emphasis is placed on improved drying and extraction methods for plant material suitable for the cannabis industry. Finally, new approaches to secondary metabolite profiling for cannabis products are compared.