Dynamic alterations of metabolites in Plectranthus amboinicus (Lour.) Spreng. to encounter drought and Zn toxicity

Abstract

Heavy metal toxicity and drought stresses are two growing concerns of the global population as these have a disastrous effect on the agriculture sector, creating oxidative stress in plants and leads to deleterious effects, which end up causing a major decline in yield. Hence, carving out the best candidate for combating both these stresses have become the prime objective of researchers. Plectranthus amboinicus (Lour.) Spreng., a medicinal plant, is regarded as one such candidate that can tolerate both drought and zinc stressors by the elicitation of metabolic changes. Variation in the composition of primary and secondary metabolites of P. amboinicus was evaluated in the leaf tissues of the plants subjected to drought and ZnSO4 (4\xa0mM) treatments. Drought stress resulted in the accumulation of amino acids and sugars in the leaves of plants exposed to this stress. Similarly, zinc stress exhibited a remarkable impact on the synthesis of secondary metabolites like alkaloids, phenols, and flavonoids. Further, on carrying out GC–MS profiling, the compositional variation of secondary metabolites produced in P. amboinicus implicated its inherent potential to survive environments of these two stresses. Compounds like 2-methoxy-4-ethyl-6-methylphenol, gamma-sitosterol, hexadecanoic acid, alpha-amyrin, and ethyl linalool were some of the major secondary metabolites developed in leaves of plants under drought, whereas during ZnSO4 treatment, the major compounds developed were trans-alpha-bergamotene, squalene, 1,5-dimethyl-1-vinyl-4-hexenyl isovalerate, and spathulenol. This in turn makes the plant more compatible with the stressful environmental conditions, aiding it with better survival and protection. At the same time, the enhancement in the content of these metabolites in this medicinal plant under the influence of these stressors may have applications in the pharmaceutical industry, necessary for the development of novel drugs.