This study investigated the effects of supplemental ultraviolet-A (UV-A) radiation on phenolic compounds, antioxidant properties, and agro-morphological characteristics of Rosmarinus officinalis L. Greenhouse plants were exposed to UV-A for 1, 2, and 4 h daily, 40 days. Based on the results, UV-A radiation had no significant effect on agro-morphological traits, while it remarkably altered chlorophyll content, total phenolic and flavonoid contents, as well as radical scavenging activity. Plants exposed to UV-A (4h) had the highest total phenolic and flavonoid contents, antioxidant activity, as well as the content of rosmarinic, carnosic, vanillic, and caffeic acids, and naringin. Conversely, carnosol, cirsimaritin, and hispulin levels decreased in treated plants. Overall, UV-A radiation had a positive effect on the medicinal aspects of R. officinalis L., which is important in the pharmaceutical industry. Therefore, it is suggested application of UV-A emitting LEDs for commercial purposes, with a lower risk level than UV-B and UV-C.
Keywords: Rosmarinus officinalis L.; UV-A; agro-morphological traits; antioxidant properties; phenolic compounds; rosmarinic acid.