New Trends in the Analysis of Cannabis-Based Products

As one of the first plants to be cultivated by humans, probably since at least 8000–5000 bce, hemp (Cannabis sativa L.) has been for millennia a source of textile, building, writing and food/feed materials, as well as being used for religious and recreational purposes. Only in relatively recent times has this plant been considered in a mostly negative light by state authorities; probably the first documented legislation restricting cannabis was passed in Arabia in the 1300s ce. More recently, international restrictions to cannabis trade were first applied in 1925 (International Opium Convention), but hemp cultivation mainly for fibre use continued both in Europe and in the United States until at least World War II, and primarily for recreational use in several Asian countries. Severe restrictions on cultivation have been applied at least since 1961 (Single Convention on Narcotic Drugs), and widely diffused with the “War on Drugs” in the United States during the 1970s and 1980s. However, since the 1970s, several countries started making hemp cultivation and use easier, both for fibre and recreational purposes. Since then, restricting legislation has been relaxed in several parts of the world, and medical uses for cannabis products have also been found, finding widespread application in the last ten years. Currently, great emphasis is being put on the difference between “fibre-type” (or “hemp-type”) and “marijuana-type” cannabis. The main difference between the two types resides in the different contents of the two main bioactive compounds: Δ9-tetrahydrocannabinol (THC, Figure 5.1a) and cannabidiol (CBD, Figure 5.1b). The former is considered responsible for the pleasant and recreational psychotropic effects of cannabis, while the latter can have muscle-relaxing and antiemetic properties while being devoid of psychotropic activity. Both are formed in the plant and during recreational use by decarboxylation of the corresponding acids, Δ9-tetrahydrocannabinolic acid (THCA; Figure 5.1c) and cannabidiolic acid (CBDA, Figure 5.1d). The United Nations Office on Drugs and Crime (UNODC) (Drugs 2009) and the American Herbal Pharmacopoeia (2013) define hemp-type cannabis as having a “total THC”/“total CBD” ratio (i.e., [THC+THCA]/[CBD+CBDA] ratio) lower than one, marijuana-type cannabis as having a total THC/total CBD ratio higher than one and intermediate cannabis as having a ratio close to one. This renewed interest in traditional and new uses for cannabis also brings with itself the need for suitably accurate and selective analytical methods to certify the quality of hemp products and steer their use according to their detailed composition. In particular, cannabis-derived food and food supplements, beverages, cosmetics and perfumes need to be characterised in detail, since they are intended for relatively widespread use without any recreational overtones. As a consequence, the situation is being reflected in increased interest from the scientific community. Reviews of new trends for the chemical characterisation of natural cannabis products (Leghissa et al. 2018) (Citti et al. 2020) have recently underscored a lack of scientifically reliable data. Among the causes of this situation, which starkly contrasts with the human use of the cannabis plant since time immemorial, restricting legislation (especially in the United States) is cited. Judging from the relative wealth and diversity of new publications in this field, however, the scientific situation seems to be gradually improving. In this chapter, only methods published in the last five years (2016–February 2021) are reported and described.