Improved LC-MS library for detection and identification of rare cannabinoids

Cannabis sativa is a well-known plant with rising medical applications. The plant`s inflorescences contain high levels of cannabinoids, specialized metabolites attributing to the cannabis`s health benefits and intoxicating effects. Cannabinoids are a large group of terpenophenolic compounds found in some flowering plants, liverworts, and fungi but are most abundant in C. sativa. Although more than 113 cannabinoids have been isolated from cannabis, chemical standards are only available for a handfull of them.

To better understand the chemical diversity of cannabinoids in C. sativa, we developed a UPLC–qTOF based mass spectral library. Other than using spectra of standards, the metabolites were putatively identified by calculating elemental composition and comparing fragmentation patterns to published data and known cannabinoids. The library includes the name, formula, retention time, and spectra from MS-MS data for 36 acidic cannabinoids. We further used the library to examine flowers, leaves, and roots of 23 cannabis varieties; among them are many medical strains, CBGA-only strain, and hemp. We found two new putative cannabinoids and relatively higher levels of cannabinoids in the roots of some varieties. Our results demonstrate the great chemical diversity between the plants, as well as in between tissues.

In summary, this work provides a tool for the identification of less abundant and characterized cannabinoids, allowing a more complete approach to cannabis research. It also highlights the metabolite content of tissues other than the cannabis inflorescences, tissues that remain mostly unexploited so far.