Hort. Sci. (Prague), X:X | DOI: 10.17221/105/2025-HORTSCI

Pre-harvest UV-B radiation during the dark period enhances phenolic compounds in Agastache rugosa cultivated in a plant factory with artificial lightingOriginal Paper

Jaewook Shin ORCID...¹, Sehee Kang ORCID...¹, Meiyan Cui ORCID...², Nakhyun Lee ORCID...¹, Hyein Lee ORCID...¹, Jeesang Myung ORCID...¹, Changhoo Chun ORCID...^1,2

¹ Department of Agriculture, Forestry and Bioresources, Seoul National University, Seoul, Korea

² Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Korea

Abstract: Agastache rugosa Kuntze is an aromatic medicinal plant valued for its phenolic compounds in East Asia. To address the limitations of field cultivation, this study evaluated the interactive effects of photosynthetic photon flux density (PPFD), electrical conductivity (EC), and nutrient solution types on A. rugosa growth, to explore its introduction into controlled environments. After determining conditions for a stable yield, specifically 250 μmol/m2/s PPFD and 2.5 dS/m EC using Hoagland solution, the effects of pre-harvest ultraviolet B (UV-B) radiation on secondary metabolite accumulation were examined. UV-B was applied during the dark period starting one week prior to harvest at 0.2 W/m2 (4 or 8 h/day) or 0.4 W/m2 (2 or 4 h/day), along with a control. Leaf rosmarinic acid (RA) content significantly increased in all UV-B treatments, with levels 44–66% higher than in the control, whereas tilianin and acacetin decreased by 17–25% and 61–73% under higher UV-B intensity or longer duration. Growth characteristics remained largely unaffected. These findings demonstrate the potential of UV-B radiation at 0.2 W/m2 for 4 h/day during the dark period for enhancing RA content. Overall, this study highlights the feasibility of a pre-harvest UV-B application to enhance phenolic compounds in A. rugosa under optimized cultivation conditions.

Keywords: controlled environment agriculture; hydroponic production; nocturnal irradiation; rosmarinic acid; secondary metabolites

Received: September 18, 2025; Revised: February 10, 2026; Accepted: February 12, 2026; Prepublished online: October 13, 2026