Ultraviolet (UV) light-induced geometrical isomerization of cinnamic acid containing molecules: A plausible, non-enzymatic approach to modify metabolite composition of plant extracts

Abstract

• UV light can be used to enhance the cinnamic acid containing-metabolite composition of a plant. • LC-MS in combination with multivariate statistics can be used to probe for the presence of photo-induced metabolites in plant extracts. • UV-irradiated plant extracts have a coherent metabolite composition as compared to naturally growing plants. Cinnamic acid containing molecules are widely distributed in plants, and they are known to possess several pharmacological properties. Structurally, these molecules consist of C 6 C 3 skeletal backbone, with an olefin functional group on the C 3 part . Naturally, plants produce a broad spectrum of cinnamic acid derivatives with a trans configuration, however, cis isomers are formed due to excessive UV-light exposure, thereby increasing the already complex metabolomes of plants containing these compounds. In high sunlight intensive areas, the prevalence of the cis isomers of cinnamic acid containing molecules is becoming more prevalent and synonymous with extracts of many plants. It is therefore imperative to develop analytical and data handling strategies to account for the presence of these molecules, which can serve as a template for rational design of pharmacologically active plant extracts or smart photo-switchable drugs. Herein, we show that a combination of ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS) and principal component analysis (PCA) allows differentiation of plants extracts of which metabolome modification through UV-radiation has been carried out. The results of the current study show that geometrical isomerism is a feasible, non-enzymatic approach to modify metabolite composition of plants. This simple method can be used to create “super” extracts of plants containing structurally diverse metabolites to be evaluated for various pharmacological properties in the future.