Contributed
The effect of lighting on growth parameters, secondary metabolite composition and biological activity of cannabis sativa inflorescences

Cannabis sativa contains over 500 phytochemicals, some of which possess biological activity on the human body. Agricultural growth conditions are expected to alter the relative and absolute content of the various phytochemicals produced by the plant. However, little is known about the effects of different light regimes on the composition of C. sativa secondary metabolites and their biological activity. In this study, combining novel agricultural studies and advanced chemical analysis, plant growth and blooming were carried out at different illumination conditions, utilizing light-emitting diode (LED) fixtures vs. conventional fluorescent and high-pressure sodium (HPS) lamps. Inflorescences were sampled at different time points along the blooming. Extract compositions were analyzed using High Performance Liquid Chromatography (HPLC) and Gas Chromatography coupled with Mass Spectrometry (GC-MS), and the biological activity of the extracted material was assessed using cell viability assays. We found that growth and blooming under LED illumination considerably changed shoot architecture and inflorescence mass. Moreover, the content of cannabinoids, terpenes and alkanes were altered in the inflorescences of LED-grown plants during the flowering period as well as in the harvested flowers. Notably, the cytotoxic activities of extracts derived from plants grown under the different illumination regimes were different, with extracts from LED-grown plants possessing higher cytotoxicity along the flowering stage. . This novel approach is possible due to the available agricultural facilities, combined with cutting-edge analytical capabilities and biological assays utilization. Our results indicate that the transition to indoor growth of C. sativa under LED lighting, which can have significant impacts on cannabinoid and terpene content, and thus on the bioactive properties of the plant extracts, should proceed with thorough consideration.