Functional aspects of plant secondary metabolites in metal stress tolerance and their importance in pharmacology

Toxic trace metals are ecotoxic due to their high bioaccumulation and toxicity, acting as abiotic stress agents, causing oxidative damage to the plant cells. Plants can recognize these threat signals and activate various defense responses. Enhanced production of secondary metabolites is a vital detoxification mechanism evolved in plants to alleviate the detrimental effects caused by toxic metals. Metal stress tolerance in plants can be increased by manipulating the biosynthesis and accumulation of secondary metabolites. The application of elicitors in plant and cell cultures is an efficient method for triggering the large-scale production of secondary metabolites and has significant importance in pharmaceutical and therapeutic industries. This review analyses the role of secondary metabolites as metal precipitators, antioxidants, and metal chelators in plants growing under toxic metal-contaminated environments. Also, this review focuses on the contemporary progression in understanding the machinery of secondary metabolite biosynthetic pathways and discusses the progress and prospects of improving their production through elicitation.