Seasonal Metabolic Adaptations and Antioxidant Defense Mechanisms in the Resilience of Rhynchosia minima and Senna italica Legumes in Arid Region

Plants survive the extreme seasonal and environmental conditions by developing various bioactive compounds. These compounds support their survival in harsh environments. This study examines how seasonal shifts influence the metabolic profiles and antioxidant responses of Rhynchosia minima and Senna italica, shedding light on their metabolic adaptation strategies to arid environments. Both species exhibited significant seasonal variations in total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity. Notably, R. minima displayed a 4.8% (0.05-fold) increase in TPC and a more pronounced 1.5-fold increase in TFC during winter compared to summer, while S. italica showed a 2.5-fold increase in TFC. Antioxidant activity was significantly higher in winter; R. minima exhibited a reduction from 98.34 μg/mL (summer) to 68.47 μg/mL (winter), and S. italica showed a decrease from 144.89 μg/mL (summer) to 84.25 μg/mL (winter), indicating enhanced bioactivity under cold stress. Although both species activate common cold stress metabolic pathways involving amino acids, lipids, and carbohydrates, they exhibit unique metabolic seasonal and species-specific patterns. Unique winter phenolic compounds from R. minima include epigallocatechin and 6-hydroxyflavone-β-D-glucoside, while cis-resveratrol and quercetin were unique to S. italica. R. minima demonstrates broader metabolic adaptations, with enriched metabolic pathways, such as glutathione metabolism, whereas S. italica relies on ubiquinone and α-linolenic acid metabolism. These findings provide insights into the intricate links between environmental stress, phytochemical adaptation, and ecological resilience of legume survival in the arid region, with a direction to antioxidant use in human health.