Postharvest Blue Light Irradiation During Drying Enhances Flavonoid Biosynthesis and Bioactivity in Adenophora triphylla Leaves

Postharvest processing conditions critically influence the phytochemical composition and functional quality of medicinal plants. Emerging evidence suggests that light quality acts as an active regulatory signal capable of modulating secondary metabolism even after harvest. In this study, we examined the effects of light quality during postharvest drying on flavonoid accumulation and associated bioactivities in Adenophora triphylla leaves. Blue light treatment for 24 h significantly enhanced anti-inflammatory and anti-melanogenic activities compared with red or white light, without inducing cytotoxicity. These functional improvements correlated strongly with increased total flavonoid and anthocyanin contents. Gene expression analyses further demonstrated that blue light significantly induced key flavonoid biosynthetic genes, including CHS1, CHS2, DFR, and LDOX, indicating that harvested leaves retain light-responsive transcriptional capacity. Taken together, these results suggest that postharvest blue light exposure can upregulate flavonoid metabolism during drying, thereby improving the pharmaceutical properties of A. triphylla leaves. This study highlights light quality-guided postharvest drying as an effective and scalable approach for enhancing the value and quality consistency of medicinal plant materials.