Endophytic Fungi: A Source of Potential Antifungal Compounds

Abstract

The emerging and reemerging forms of fungal infections encountered in the course of allogeneic bone marrow transplantations, cancer therapy, and organ transplants have necessitated the discovery of antifungal compounds with enhanced efficacy and better compatibility. A very limited number of antifungal compounds are in practice against the various forms of topical and systemic fungal infections. The trends of new antifungals being introduced into the market have remained insignificant while resistance towards the introduced drug has apparently increased, specifically in patients undergoing long-term treatment. Considering the immense potential of natural microbial products for the isolation and screening of novel antibiotics for different pharmaceutical applications as an alternative source has remained largely unexplored. Endophytes are one such microbial community that resides inside all plants without showing any symptoms with the promise of producing diverse bioactive molecules and novel metabolites which have application in medicine, agriculture, and industrial set ups. This review substantially covers the antifungal compounds, including volatile organic compounds, isolated from fungal endophytes of medicinal plants during 2013–2018. Some of the methods for the activation of silent biosynthetic genes are also covered. As such, the compounds described here possess diverse configurations which can be a step towards the development of new antifungal agents directly or precursor molecules after the required modification.

Antifungal Agents in Agriculture: Friends and Foes of Public Health

“…Endophytic fungi have been studied as an alternative and sustainable means of converting the natural compounds in host plants to antifungal compounds, which are not only effective against human pathogens but also against phytopathogens [127]. Endophytic microorganisms are found in plant species of extreme importance [124] and can be classified as competent, optional, obligatory, opportunistic, or passive, depending on their effects on plants [128][129][130][131].…”

“…Another beneficial approach involving endophytic fungi makes use of their production of bioactive secondary metabolites, which represent a group of microorganisms capable of synthesizing new compounds [138] that can target plant pathogens and pests [139]. Deshmukh et al (2018) reported several metabolites produced by endophytic fungi from medicinal plants and their potential as antifungal agents [127]. For example, scleroderma A and B and triterpenoid lanostane are produced by an endophyte basidiomycete fungus associated with the Eucalyptus grandis plant and these compounds were identified as potential fungicides against Candida albicans, C. tropicalis, C. crusei, and C. parapsiosis.…”

“…Xylaria spp., associated with the Azadirachta indica plant from China, are a source of new bioactive compounds, some of which exhibit relevant pharmacological properties for drug discovery [141], presenting with antifungal activities against C. albicans, Aspergillus niger, and Fusarium avenaceum [127,142]. The fungus Mycosphaerella, which is an endophyte of the plant Eugenia bimarginata from Brazil, has been shown to produce two eicosanoid acids that have antifungal activities against C. neoformans and C. gattii [143].…”

“…Basidiomycete fungus [140] Eucalyptus grandis [140] Scleroderma A and B Triterpenoid lanostane [140] Candida albicans C. tropicalis C. grusei C. parapsiosis [140] Xylaria spp. [141] Azadirachta indica [127,142] Bioactive compounds [141] C. albicans Aspergillus niger Fusarium avenaceum [127,142] Mycosphaerella spp. [143] Eugenia bimarginata [143] Eicosanoid acids [143] Cryptococcus neoformans C. gattii [143] Cryptosporiopsis quercina [144] Wood species in Europe [144] Cryptocandin lipopeptide [144] Botrytis cinerea [144] Novel molecular biology approaches have been used for the identification and characterization of genetic elements and metabolites involved in the interactions between plants and endophytic microorganisms [146].…”

Beyond Enzyme Production: Solid State Fermentation (SSF) as an Alternative to Produce Antioxidant Polysaccharides

“…In general, fungal endophytes coexists asymptomatically with their hosts and they represent an underused group of microorganisms for the discovery of new valuable compounds because they can produce diverse metabolites and have the ability to synthesize substances that are only produced and isolated from higher plants [65]. In the same manner, the antioxidant activity of fungal endophytes from medicinal plants has gained recognition in natural product research during the last decades.…”