Torres Ortega, L. R.; Contreras-Aviles, W.; Heuvelink, E.; Marcelis, L. F. M.; van der Hooft, J. J. J.; Kappers, I. F.

Controlled-environment cultivation of medicinal cannabis (Cannabis sativa L.) typically optimizes light conditions to enhance the biosynthesis of pharmaceutically important metabolites such as cannabinoids, but these strategies may also influence other specialized metabolites including terpenoids, flavonoids, and alkaloids. Previous untargeted metabolomics studies of short wavelength conditions such as UV and blue light have shown that terpenoids and prenylated flavonoids in cannabis leaves respond differentially; however, because metabolomic studies in cannabis have largely focused on floral cannabinoids, a comprehensive untargeted study of the cannabis floral metabolome response to short wavelengths is currently lacking. Here, we investigate the impact of short wavelength usage on cannabis specialized metabolism, focusing on the influence of UVB, UVA, and blue light on the floral flavonoid metabolome and associated glycosylation moieties. Cannabis plants were grown under a white background light and exposed to supplemental UVB, UVA, or blue light during the generative phase of the cultivation cycle, and treatments were compared to a reference white background light without UV or blue light. Metabolites from floral tissue were extracted and analyzed via ultra-performance liquid chromatography-tandem mass spectrometry, and a comparative metabolomics workflow was designed to characterize the floral flavonoid metabolome and associated glycosylation moieties. Our results demonstrate that short wavelengths differentially affect the metabolism of natural product compound classes including polyketides and phenylpropanoids/shikimates. Blue light induced flavonoids similarly to UVB, while both UVA and blue light specifically induced flavanone accumulation, and UVB showed the strongest regulatory effect on flavonoid production and glycosylation patterns. UVB reshapes the cannabis floral flavonoid metabolome by selectively stimulating the accumulation and structural modification of flavonoids, making UVB application a useful horticultural strategy to increase inflorescence medicinal quality without affecting cannabinoid levels.