Polyamines are amine-containing, low molecular weight, and ubiquitous polycationic molecules present in almost all cells and free-living microbes, which are formed by aliphatic hydrocarbons replaced with multiple amino groups. They have been considered as a new kind of plant biostimulant, which play vital roles in diverse plant growth and developmental processes, and environmental stress responses. However, little is known regarding the effects of polyamines specifically on the elicitation of bioactive compounds in medicinal plant production. Therefore, in this review, we attempt to cover these gaps of information. Supply of polyamines, whether by exogenous application or through genetic engineering, could positively affect medicinal plant growth, productivity, and stress tolerance; however, these effects depend on type and dose of polyamine application and plant species. Furthermore, polyamines play as precursor for the several groups of alkaloids (pyrrolizidine, tropane, and quinolizidine alkaloids) and phenolamides, so these bioactive compounds could significantly increase the concentration of the above-mentioned natural products.
