Secondary metabolites in orchids: Biosynthesis, medicinal uses, and biotechnology

Abstract Orchidaceae has been considered as the second largest family among the angiosperms. It is commercially important in the cut-flower industry and many of its members also possess medicinal properties to cure innumerable ailments. Among them, Anoectochilus and Dendrobium are the prime genera of medicinally important orchids. A greater number of such orchid species are commercially being used as major sources of main-stream pharmaceutical products. In nature, the population of medicinal orchids is at risk, mainly due to deforestation. In orchid propagation, the conventional methods suffer from several shortcomings such as slow growth, poor germination, susceptibility to pests, and nutritional deficiencies. Therefore, interventions of biotechnological tools and techniques become quite crucial for the improvements in the propagation process and simultaneously, the production of secondary metabolites. In this context, knowledge of biosynthetic pathways of the key secondary metabolites from different medicinal orchid species becomes imperative in order to enhance their production via in vitro biotechnological approaches. This review addresses the availability of secondary metabolites in medicinal orchids, their biosynthetic pathways, pharmacological applications and it is further entwined with the success and shortcomings of the in vitro strategies that have been applied to medicinal orchids in order to enhance their propagation, conservation and secondary metabolites production. Eventually, this in vitro biotechnology-based review will provide a promising platform to construct innovative ideas to harness the commercial production of pharmaceutically important secondary metabolites available in medicinal orchids.