Abstract

Background

Controlled-environment cultivation of medicinal cannabis (Cannabis sativa L.) typically optimizes light condi-tions to enhance the biosynthesis of pharmaceutically important metabolites like cannabinoids. Such experimental strategiesmay also influence other specialized metabolites like terpenoids, flavonoids, alkaloids, among others. Previous untargetedmetabolomics studies testing short-wavelength conditions like UV and blue light have shown that terpenoids and prenylatedflavonoids in cannabis leaves respond differentially. However, since metabolomic studies in cannabis have so far mostlyfocused on floral cannabinoids, a comprehensive untargeted study into cannabis’ floral metabolome response to short wave-lengths is currently lacking.

Objectives

Our study investigates the impact of short-wavelength usage on cannabis specialized metabolism, and in par-ticular the influence of UVB, UVA, and blue light on the cannabis floral flavonoid metabolome and associated glycosylationmoieties.

Methods

Cannabis plants were grown under a white background light and exposed to supplemental UVB, UVA, or bluelight during the generative phase of the cultivation cycle. Treatments were compared to a reference white background lightwithout UV or blue light. Metabolites from floral tissue were extracted and analysed via ultra-performance liquid chromatog-raphy-tandem mass spectrometry. A comparative metabolomics workflow was designed and used to characterize the floralflavonoid metabolome and associated glycosylation moieties.

Results

Our results demonstrate how short wavelengths differentially affect the metabolism of natural product compoundclasses including polyketides and phenylpropanoids/shikimates. Blue light induced flavonoids similarly to how UVB did,while both UVA and blue light specifically induced flavanones accumulation. UVB showed the strongest regulatory effecton flavonoids production and glycosylation patterns.

Conclusions

UVB reshapes the cannabis floral flavonoid metabolome by selectively stimulating the accumulation and struc-tural modification of flavonoids. Therefore, UVB represents a potential horticultural strategy to enhance flavonoid-relatedaspects of medicinal cannabis inflorescence phytochemical quality, without affecting cannabinoid levels.