Bioactive natural products of endophytic fungal origin: Production, activity and biotechnology

Abstract

Abstract Recent scientific investigations focused on drug discovery have accelerated the demand for novel pharmaceutical and agricultural products which are closely correlated with industrial applications. So, the present scenario of natural product-oriented research has expanded the combinatorial application of analytical chemistry, bioinformatics, and molecular biology to identify and isolate lead bioactive compounds from unexplored biological resources. The key features of natural selection attribute cumulatively in the functionality of any natural product, so secondary metabolites derived from specific organisms that exhibit exquisite niche specificity are favored over the common organism in ongoing pharmaceutical research. Endophytic fungi are ubiquitous, but their host infestation mechanism is quite interesting and evolutionarily very active, so the metabolic pathway regulating the mutualistic host-endophyte relationship possesses exclusive features and often biological applications. The research includes isolation, identification, and characterization of endophytic fungi as well as qualitative and quantitative estimation, structure elucidation, and screening of the structure-activity relationship of the biologically active compounds. However, biotope specificity and competitive vigor for nutrition, host, and survival of endophytic fungi are largely correlated with their biological activity, and are found to be superior to other microbes such as epiphytes. The precise balance between pathogenicity and mutualism is greatly monitored by the agonistic and antagonistic activity of fungal metabolites. Moreover, the influence of these metabolites boosts the immunological strength of the host and triggers a preventive reaction against herbivory or allelopathy in exchange for nutrients supplied to the microbial population. Interestingly, endophytes serve as a novel resource producing an array of bioactive compounds with great significance in basic research and medicine. Different biosynthetic pathways produce the secondary constituents, and they belong to diverse chemical classes including alkaloids, phenols, terpenes, quinones, isocoumarins, chromones, cytosporones, chalcone, steroids, xanthones, polyketides, and esters screened for a plethora of biological activities, that is, antibacterial, antifungal, insecticidal, and anticancer. Structure-activity relationship studies, key lead-based in vitro and in vivo investigations, and drug-metabolite synergism have largely elucidated the promising characteristics of endophytic fungi-derived metabolites to be the template of safe, economic, and bioactive therapeutics. However, authentication, screening, differentiation, clinical, and preclinical investigations are largely required before ensuring the medicinal efficacy of any metabolite derived from endophytic fungi.