Modulation of Phytochemical Composition and Antioxidant Capacity in Basil Microgreens by Light Intensity and Nutrient Solution

Basil (Ocimum basilicum L.) microgreens are valued for their high phenolic content and antioxidant capacity, which can be modulated under controlled environment agriculture (CEA). This study investigated the combined effects of three light-emitting diode (LED) light intensities (200, 250, and 300 &micro:mol m&minus:2 s&minus:1) and three nutrient solution concentrations (basic, enriched, and diluted) on biomass accumulation, phytochemical composition, antioxidant activity, and photosynthetic pigments in basil microgreens. The fresh weight (FW), dry weight (DW), dry matter content (DM), total phenolic content (TPC), antioxidant capacity (DPPH, ABTS, FRAP), and pigment levels were evaluated across nine treatment combinations. Biomass accumulation was primarily driven by nutrient availability: the highest FW (18.23 g 100 cm&minus:2) was recorded under low light with elevated nutrients and was 133% higher than under high light combined with reduced nutrient supply. In contrast, the DM content increased under high light and low nutrients, reaching about 9%, which was 112% higher than in the lowest DM treatment. Increasing light intensity markedly resulted in phenolic accumulation and antioxidant activity. The highest TPC (28.39 mg g&minus:1 DW) observed under 300 &micro:mol m&minus:2 s&minus:1 with reduced nutrients was approximately 97% higher than that under 200 &micro:mol m&minus:2 s&minus:1 with basic nutrition. Under the same conditions, DPPH, ABTS, and FRAP antioxidant activities increased by 54%, 54%, and 81%, respectively. Photosynthetic pigment responses to light and nutrient treatments were limited, with statistically significant differences observed mainly for chlorophyll b and the chlorophyll a/b ratio, while chlorophyll a and carotenoids remained largely unchanged. Principal component analysis separated high-light treatments by elevated phenolic&ndash:antioxidant profiles and low-light treatments by higher biomass and pigment levels. Overall, high light combined with moderate nutrient limitation promotes phenolic and antioxidant enrichment in basil microgreens, representing a quality-modulating strategy rather than a fully optimized cultivation regime.