Enhanced secondary metabolites production and antioxidant activity in postharvest Lonicera japonica Thunb. in response to UV radiation

Enhanced UV radiation can change plant biology, especially secondary metabolites, yet the effects on postharvest medicinal plant tissues are now rarely researched. Therefore, our study was aimed to explore changes of secondary metabolites and pharmacological activities involved in the response to enhanced UV-A and UV-B radiation induction in freshly collected flower buds of Lonicera japonica Thunb. We found that after UV-A and UV-B radiation, the content of seven compounds dramatically increased. We identified these compounds by HPLC–MS, which were four kinds of iridoid and three kinds of isochlorogenic acid. Antioxidant experiment showed that the antioxidant power of methanol extracts from the flower buds represented enhancement to a certain extent after UV-A and UV-B radiation, compared to control group. Featured by the shorter period required, the fewer experimental costs as well as the easier procedures to carry out, UV radiation would be a novel and feasible method to increase the health-related compounds of fresh postharvest medicinal plant tissues.Industrial relevanceOur study examined the feasibility of short-term and enhanced UV radiation application as emerging technology for enhancing health-promoting phytochemicals in freshly postharvest Lonicera japonica Thunb. Comparing with some other biotic factors, like cell engineering which is also an effective way to stimulate secondary metabolic compounds, UV radiation stimulating plant organs has several advantages. For example, shorter period required, the easier procedures to carry out and the fewer experimental costs are featured. Our study showed that short-term and enhanced UV radiation could be applied to enhance the phytochemical compounds in freshly postharvest Lonicera japonica Thunb. In addition, the convenient and feasible method to enhance the phytochemical concentration in fresh nature products could be used as both postharvest treatment of crops or medical plants and pretreatment of processing industry to obtain the concentration of health-related compounds.

► We find that UV-A and UV-B have effects on postharvest Lonicera japonica Thunb.
► After radiation, contents of seven compounds in buds increased dramatically.
► They are identified as three isochlorogenic acids and four iridoids by HPLC-MS.
► Compared to control, antioxidant powers of induction groups represent enhancement.