Integrative Physiological and Molecular Insights into Drought–Induced Accumulation of Bioactive Compounds in Clinacanthus nutans (Burm.f.) Lindau Leaves

Clinacanthus nutans (Burm.f.) Lindau is a medicinal plant known for its antioxidant, anti–inflammatory, and antiviral properties. Drought is a major abiotic stress affecting plant physiology and secondary metabolite biosynthesis. This study investigated the physiological and biochemical responses of C. nutans under drought stress. Relative water content declined with prolonged drought, while hydrogen peroxide and proline levels increased, indicating oxidative and osmotic stress. Antioxidant activities (DPPH and ABTS) peaked at days 4–8 and showed positive correlations with phenolic and flavonoid contents and triterpenoids, particularly schaftoside and lupeol. Molecular docking supported the bioactivity of drought–induced metabolites, with schaftoside and lupeol showing favorable interactions with inflammation–related targets. Multivariate analysis revealed that short–term drought enhanced stress tolerance and secondary metabolite accumulation, whereas prolonged stress reduced biosynthetic capacity and survival. These findings suggest that controlled drought exposure can enhance bioactive compound levels in C. nutans, supporting its potential for drought–adaptive cultivation for medicinal use.