Unravelling triterpenoid biosynthesis in plants for applications in bioengineering and large-scale sustainable production

Plants are major factories for the biosynthesis of valuable bioactive compounds having pharmaceutical applications. These phytocompounds are synthesised via the diversion of primary metabolites toward secondary metabolic pathways. The most varied class of metabolites are triterpenoids that are biosynthesized through the MVA-MEP pathways, leading to the production of oxidosqualene followed by cyclization, and enzymatic modifications. Triterpenoids play a significant role in growth, development, reproductive behaviour, plant adaptation, and plant-to-plant communication. Various signals, through the signal transduction mechanism, are transmitted through receptors from cell to cell by a series of molecular events to initiate/ activate the cascade of the triterpenoid biosynthesis network. In this review, different naturally occurring classes of triterpenoids with their medicinal potential have been summarized. Further, this review provides insight into the current status of its synthesis through heterologous gene expression, structure elucidation, biosynthetic regulation via transcriptional regulation, and miRNAs. Recently, triterpenoids are in demand due to their variety of pharmacological importance which requires a fast rate of production. Furthermore, to ramp up the synthesis of these vital triterpenoids, the applications of modern bioengineering technologies and green nanoparticle synthesis, have been also highlighted here, offering sustainable alternatives for their large-scale production.