Effect of different NaCl concentrations on secondary metabolites and antioxidant activity in three radish (Raphanus sativus L.) varieties

Salinity, a critical environmental stressor, imposes constraints on field crops' anatomical structure, growth, and physiology. This study has uniquely evaluated the effect of 0 (control), 100, and 200 mM NaCl on phenolic acids (PAs), total anthocyanin content (TAC), chlorophyll, and antioxidant activity in three radish varieties and contributes novel insights to the scientific co community. The salt concentration significantly influenced shoot length (SL), root length (RL), and fresh weight (FW) in radish sprouts. The varying salt concentrations did not affect chlorophyll a, but chlorophyll b and total chlorophyll content (TCC) increased the red and super red varieties. The total phenolic content (TPC) and total flavonoid content (TFC) registered a slight increase in some varieties under 100 mM salt concentration, with the highest accumulation of these secondary metabolites found in the super red variety. Five individual PAs were identified using high-performance liquid chromatography (HPLC) analysis, with salt treatment significantly affecting ferulic acid and trans-cinnamic acid concentrations. The lowest level of anthocyanin was found in all green varieties. Salinity stress of 100 and 200 mM affected the TAC in the red and super red varieties compared to the control. Furthermore, among the three varieties treated with NaCl, the super red IC50 values displayed the highest 2,2,1-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-Azino-bis-3-ethylbenzothiazoline-6-sulfonic Acid (ABTS) free radical scavenging activity compared to the other treatments. These results suggest that a 100 mM NaCl concentration can be used as an inducer to improve the accumulation of phytochemicals in the radish seedlings 12 days after sowing (DAS).