Remediation of cadmium-contaminated soil using Bacopa monnieri (L.) Wettst. Synergistic role of salicylic and jasmonic acids in Phytostabilisation and neuroprotective bacoside A biosynthesis

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• SA and JA reduced Cd translocation, improving Bacopa phytostabilization. • SA and JA alleviated Cd stress, enhancing growth and chlorophyll content. • SA and JA boosted antioxidant enzymes, lowering oxidative stress in plants. • JA treatment markedly raised bacoside A, enhancing metabolite production. • SA and JA provide dual benefits for phytoremediation and medicinal use. Cadmium (Cd), a toxic trace element, poses a significant threat to plant physiology and secondary metabolite production, with implications for environmental and human health. Bacopa monnieri (BM), a medicinal plant valued for its neuroprotective properties, is highly sensitive to Cd, which reduces shoot biomass by approximately 50 % and chlorophyll content by approximately 30 %. Phytohormones, such as salicylic acid (SA) and jasmonic acid (JA), are recognized stress modulators; however, their combined influence on Cd detoxification and bacoside A production has not been reported. In this study, BM plants were exposed to Cd stress, with SA and JA applied individually and in combination. Cd-induced growth inhibition, pigment loss, and elevated root Cd accumulation were significantly alleviated by phytohormone treatments, with the SA + JA combination exhibiting the greatest effect. Co-treatment improved shoot and root biomass, restored chlorophyll levels, enhanced antioxidant enzyme activities, and reduced root Cd accumulation from 6340 to 3600 µg/g DW, thereby lowering the translocation factor from 0.16 to 0.10. Importantly, JA and SA + JA treatments increased bacoside A content by up to 1.7-fold, demonstrating enhanced secondary metabolite biosynthesis. This study provides the first experimental evidence that exogenous SA and JA synergistically mitigate Cd toxicity, strengthen phytostabilization, and boost bacoside A accumulation. These findings highlight the potential of BM as a dual-purpose candidate for phytoremediation and pharmaceutical exploitation in metal-contaminated ecosystems.