Evaluation of cytokinin types and LED light spectra for enhanced production of diarylheptanoids in Alnus incana subsp. incana

This study aimed to develop an efficient in vitro propagation system for Alnus incana subsp. incana that enables both vigorous shoot proliferation and enhanced production of bioactive diarylheptanoids. Among the tested cytokinins, 5 µM 6-benzylaminopurine (BA) was most effective for promoting shoot proliferation(1.311 ± 0.070), whereas 10 µM zeatin moderately induced shoots but significantly increased secondary metabolites, with oregonin being 1.82-fold, hirsutenone 1.39-fold, and hirsutanonol 1.25-fold higher than BA 5 µM treatment. In terms of light quality, blue LED irradiation (450 nm) led to the highest antioxidant activity, with 2,2-diphenyl-1-picrylhydrazyl(DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical scavenging values of 48.67 ± 27.33% and 92.78 ± 0.35%, respectively. In contrast, white LED (broad-spectrum) supported both balanced growth (1.133 ± 0.051 shoots per explant under 10 µM zeatin) and elevated metabolite production, including oregonin (108.089 µM) and hirsutanonol (13.203 µM). The combination of 10 µM zeatin and white LED thus provided an optimal compromise between shoot proliferation and secondary metabolite accumulation, offering a sustainable strategy for producing antioxidant-rich A. incana plantlets in vitro.