The use of UV-A radiation for biofortification of lettuce and basil plants with antioxidant phenolic and flavonoid compounds

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Stable plant production is a crucial concern of modern agriculture facing increasing food demands and the risk of less predictable weather conditions in the open field. Alternative approaches for plant production are greenhouses and indoor farming. Modern LED-based artificial lighting indoor facilities allow not only to fill the gap in the supply chain of food production, but to produce plants characterized with higher concentration of essential phytochemicals. Thus, in this study, we attempt to analyse the efficiency of short-term supplementation of spectrum within ultraviolet A light (UV-A, 365 nm) to increase the antioxidant potential of leafy plants, assessed by total phenolic (TPC) and flavonoid (TFC) content. To this end, two distinct cultivars of baby leaf lettuce (Lactuca sativa var. crispa L.) and microgreens basil (Ocimum basilicum L.) plants were grown under red-green-blue spectrum supplemented prior to harvest with low doses of UV-A radiation. Analyses showed that UV-A exposition enhanced TPC and TFC with green leaf cultivars, compared to dark-pigmented ones. The analysis also proved that plants exposed to UV-A presented higher overall antioxidant potential measured with 1,1-diphenyl-2-picrylhydrazil (DPPH). Results are crucial for better understanding the potential of UV-A supplementation to produce functional plants which are natural sources of dietary antioxidants.