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

Abstract

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 <i>Rhynchosia minima</i> and <i>Senna italica</i>, 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, <i>R. minima</i> 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 <i>S. italica</i> showed a 2.5-fold increase in TFC. Antioxidant activity was significantly higher in winter; <i>R. minima</i> exhibited a reduction from 98.34 μg/mL (summer) to 68.47 μg/mL (winter), and <i>S. italica</i> 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 <i>R. minima</i> include epigallocatechin and 6-hydroxyflavone-β-<i>D</i>-glucoside, while cis-resveratrol and quercetin were unique to <i>S. italica</i>. <i>R. minima</i> demonstrates broader metabolic adaptations, with enriched metabolic pathways, such as glutathione metabolism, whereas <i>S. italica</i> 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.