Modulation of Metabolic Profiles and Bioactivities Under Four LED Light Qualities in Fenugreek Microgreens

Microgreens are attracting attention in controlled-environment agriculture systems due to their short growth cycle and accumulation of functional metabolites. However, the effects of light quality on phytochemical accumulation and antioxidant-related properties have not been fully characterised in fenugreek (Trigonella foenum-graecum L.) microgreens. This study investigated the effects of four LED spectra (white, blue, red, and red + blue) on the growth characteristics, phytochemical accumulation, and antioxidant properties of fenugreek microgreens. LED treatments had limited effects on biomass production but significantly altered specific growth traits and metabolite accumulation. Blue LEDs resulted in the longest root length, whereas the red + blue LED was confirmed to have the shortest shoot and root lengths. Diosgenin content increased significantly under blue and red + blue LED treatments (6.92 ± 0.18 and 7.19 ± 0.15 mg/g DW, respectively) compared to white and red LED treatments (6.43 ± 0.13 and 5.6 ± 0.32 mg/g DW, respectively). Several carotenoids also showed higher accumulation under blue and red + blue LED treatments, while individual phenolic compounds exhibited LED spectra-dependent responses. Multivariate analyses, including PCA, PERMANOVA, and PLS-DA, indicated treatment-associated variation in metabolic profiles, although the overall separation among LED treatments was limited. Correlation analysis further showed significant associations of selected phenolic compounds and carotenoids with antioxidant activities. Notably, the red LED exhibited relatively high antioxidant activity despite its lower TPC and TFC. These findings demonstrate that LED spectral quality can be used for target-specific modulation of phytochemical composition and antioxidant-related properties in fenugreek microgreens under controlled-environment conditions.