Prospective Leads from Endophytic Fungi for Anti-Inflammatory Drug Discovery

Discovery of metabolite from the insect-derived endophytic Penicillium chrysogenum and their COX-2 inhibitory activity

Three new N-alkylated amino acid derivatives, penichrysoamides A-C (1-3), along with a new citric acid derivative, penichrysoacid A (4), a new chromanone lactone penichrysoacid B (5), and a new amide derivative, penichrysoamide D (6), as well as seven known benzamide derivatives (7-13), were isolated from the endophytic fungus Penicillium chrysogenum derived from the insect Periplaneta americana. The structures of these compounds, including their absolute configurations, were elucidated using spectroscopic and computational techniques. Biological evaluation revealed that compounds 8-13 exhibited significant COX-2 inhibitory activity, with IC50 values ranging from 275 nM to 1350 nM.

Fungal Endophytes: Microfactories of Novel Bioactive Compounds with Therapeutic Interventions; A Comprehensive Review on the Biotechnological Developments in the Field of Fungal Endophytic Biology over the Last Decade

The seminal discovery of paclitaxel from endophytic fungus Taxomyces andreanae was a milestone in recognizing the immense potential of endophytic fungi as prolific producers of bioactive secondary metabolites of use in medicine, agriculture, and food industries. Following the discovery of paclitaxel, the research community has intensified efforts to harness endophytic fungi as putative producers of lead molecules with anticancer, anti-inflammatory, antimicrobial, antioxidant, cardio-protective, and immunomodulatory properties. Endophytic fungi have been a valuable source of bioactive compounds over the last three decades. Compounds such as taxol, podophyllotoxin, huperzine, camptothecin, and resveratrol have been effectively isolated and characterized after extraction from endophytic fungi. These findings have expanded the applications of endophytic fungi in medicine and related fields. In the present review, we systematically compile and analyze several important compounds derived from endophytic fungi, encompassing the period from 2011 to 2022. Our systematic approach focuses on elucidating the origins of endophytic fungi, exploring the structural diversity and biological activities exhibited by these compounds, and giving special emphasis to the pharmacological activities and mechanism of action of certain compounds. We highlight the tremendous potential of endophytic fungi as alternate sources of bioactive metabolites, with implications for combating major global diseases. This underscores the significant role that fungi can play in the discovery and development of novel therapeutic agents that address the challenges posed by prevalent diseases worldwide.

New natural pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and iNOS inhibitors identified from Penicillium polonicum through in vitro and in vivo studies

Overexpression of pro-inflammatory cytokines and iNOS have been found to be concomitant with several chronic inflammatory diseases and hence targeting their inhibition would be a useful therapy for inflammation. In view of this, study on discovery of natural pro-inflammatory cytokines inhibitory lead molecules from Penicillium polonicum, an endophytic fungus isolated from the fresh fruits of Piper nigrum was performed. When the culture broth extract of P. polonicum (EEPP) was subjected to LPS-induced cytokines expression (ELISA in RAW 264.7 cells), it exhibited inhibition of TNF-α, IL-6 and IL-1β and this encouraged us to do chemical investigation on EEPP to explore the bioactive components. Four compounds isolated and characterised as 3,5-di-tert-butyl-4-hydroxy-phenyl propionic acid (1), 2,4-di-tert-butyl phenol (2), indole 3-carboxylic acid (3) and tyrosol (4) were tested for their effect on the production of TNF-α, IL-1β and IL-6 in RAW 264.7 cells (ELISA). All the compounds exhibited a highly significant (P < 0.0001) inhibition effect, particularly against IL-1β (IC₅₀: 4-0.91 μM, 1-2.81 μM, 3-4.38 μM, and 2-5.54 μM). Tyrosol (4) was most active with IC₅₀ values of 0.91, 2.67 and 4.60 μM against IL-1β, IL-6 and TNF-α, respectively. On observing the potential activity of the compounds, two compositions C1 and C2 were prepared by mixing equimolar concentrations of compounds 1, 2, 3 & 4 (C1) and compounds 1, 2, 3, 4 & piperine (C2) in equal ratio. A synergistic effect was observed with C1 exhibiting potential suppression of IL-6 secretion (IC₅₀ 1.91 μM) and C2 against IL-1β (IC₅₀ 5.98 μM). Also, the individual compounds and C1 were effective in controlling iNOS expressions in RAW 264.7 cells (RTPCR). Further, the in vivo performance of the compounds and compositions were studied under two in vivo inflammatory models (LPS-induced endotoxaemia and carrageenan-induced paw oedema). Compounds 1, 2, 3, 4, C1 and C2 at 50 mg/kg oral dose showed a significant control over the LPS-stimulated TNF-α, IL-1β and IL-6 levels in plasma. C1, C2 and 1 exhibited > 50% pan-cytokine inhibition effect. Under the carrageenan-induced anti-inflammatory model, a significant reduction in the paw oedema measured in terms of the difference in the paw thickness was observed. Further, attenuation of pro-inflammatory cytokines levels following ELISA and RT-PCR experiments in the paw tissue homogenate was in agreement with paw thickness results. All compounds and C1 decreased the iNOS gene expression levels, and also the MPO activity and NO production in the paw tissue homogenate with tyrosol (4) as the most active molecule. Further, the mechanism of action was explored by testing the effect of the compounds on the expression of inflammatory markers using western blot analysis (in vitro). They were found to regulate the expression of pro-form and matured-form of IL-1β by inhibiting NFκB. Also, the compounds reduced the translocation of the NF-κB subunit p65 to the nucleus. Thus, compounds 3,5-di-tert-butyl-4-hydroxy-phenyl propionic acid (1), 2,4-di-tert-butyl phenol (2), indole 3-carboxylic acid (3) and tyrosol (4) are reported as new natural multiple pro-inflammatory cytokines inhibitory leads. The interesting results of C1 might lay a footing for the development of a new anti-inflammatory composition.

A New Lignan (Polonilignan) and Inhibitors of Nitric Oxide Production from Penicillium polonicum, an Endophytic Fungi of Piper nigrum

Inhibiting nitric oxide (NO) or its production is found to be of therapeutic benefit. To discover natural small molecule inhibitors of NO production, a bioassay- and LC/MS-guided chemical investigation was done on the metabolites of endophytic fungus isolated from fresh Piper nigrum fruits. The isolated pure strain was identified as Penicillium polonicum by 16S rDNA sequence comparison. The culture broth extract of P. polonicum (EEPP) exhibited a significant reduction of NO production (Griess method) in LPS-stimulated RAW 264.7 cells (P<0.0001). To understand the chemical constituents of bioactive EEPP, column chromatography and p-TLC studies were carried out, which yielded eight pure compounds. They were characterised as botryosphaeridione (1), 3-(3,5-di-tert-butyl-4-hydroxy)phenylpropionic acid (2), variabilone (3), 2,4-di-tert-butylphenol (4), indole-3-carboxylic acid (5), tyrosol (6), ethyl ferulate (7) and a new lignan (8) based on the spectral analysis. The structure elucidation of the new lignan, named polonilignan (8), was based on HR-MS, 1 H- & 13 C-NMR, H-H COSY, HSQC and HMBC spectra. Compounds 2, 4, 5 and 6 showed a significant decrease (P<0.0001) in the production of NO in LPS-induced RAW 264.7 cells. Tyrosol (6) and indole-3-carboxylic acid (5) controlled nitrite release with IC50 values of 22.84 and 55.01 μM, respectively. This is the first report of (i) P. polonicum as an endophytic fungus of pepper fruits, (ii) isolation of compounds 1-8 except 6 from P. polonicum culture broth extract and (iii) NO inhibition effect of 2, 4, 5 and 6.

Screening for broad-spectrum antimicrobial endophytes from Rosa roxburghii and multi-omic analyses of biosynthetic capacity

Plants with certain medicinal values are a good source for isolating function-specific endophytes. Rosa roxburghii Tratt. has been reported to be a botanical source of antimicrobial compounds, which may represent a promising candidate for screening endophytic fungi with antimicrobial potential. In this study, 54 endophytes were isolated and molecularly identified from R. roxburghii. The preliminary screening using the plate confrontation method resulted in 15 different endophytic strains showing at least one strong inhibition or three or more moderate inhibition against the 12 tested strains. Further re-screening experiments based on the disc diffusion method demonstrated that Epicoccum latusicollum HGUP191049 and Setophoma terrestris HGUP190028 had excellent antagonistic activity. The minimum inhibitory concentration (MIC) test for extracellular metabolites finally indicated that HGUP191049 had lower MIC values and a broader antimicrobial spectrum, compared to HGUP190028. Genomic, non-target metabolomic, and comparative genomic studies were performed to understand the biosynthetic capacity of the screened-out endophytic fungus. Genome sequencing and annotation of HGUP191049 revealed a size of 33.24 megabase pairs (Mbp), with 24 biosynthetic gene clusters (BGCs), where the putative antimicrobial compounds, oxyjavanicin, patulin and squalestatin S1 were encoded by three different BGCs, respectively. In addition, the non-targeted metabolic results demonstrated that the strain contained approximately 120 antimicrobial secondary metabolites and was structurally diverse. Finally, comparative genomics revealed differences in pathogenicity, virulence, and carbohydrate-active enzymes in the genome of Epicoccum spp. Moreover, the results of the comparative analyses presumed that Epicoccum is a promising source of antimicrobial terpenes, while oxyjavanicin and squalestatin S1 are antimicrobial compounds shared by the genus. In conclusion, R. roxburghii and the endophytic HGUP191049 isolated from it are promising sources of broad-spectrum antimicrobial agents.

Polyketide Derivatives from the Endophytic Fungus Phaeosphaeria sp. LF5 Isolated from Huperzia serrata and Their Acetylcholinesterase Inhibitory Activities

The secondary metabolites of Phaeosphaeria sp. LF5, an endophytic fungus with acetylcholinesterase (AChE) inhibitory activity isolated from Huperzia serrata, were investigated. Their structures and absolute configurations were elucidated by means of extensive spectroscopic data, including one- and two-dimensional nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) analyses, and calculations of electronic circular dichroism (ECD). A chemical study on the solid-cultured fungus LF5 resulted in 11 polyketide derivatives, which included three previously undescribed derivatives: aspilactonol I (4), 2-(1-hydroxyethyl)-6-methylisonicotinic acid (7), and 6,8-dihydroxy-3-(1′R, 2′R-dihydroxypropyl)-isocoumarin (9), and two new natural-source-derived aspilactonols (G, H) (2, 3). Moreover, the absolute configuration of de-O-methyldiaporthin (11) was identified for the first time. Compounds 4 and 11 exhibited inhibitory activity against AChE with half maximal inhibitory concentration (IC₅₀) values of 6.26 and 21.18 µM, respectively. Aspilactonol I (4) is the first reported furanone AChE inhibitor (AChEI). The results indicated that Phaeosphaeria is a good source of polyketide derivatives. This study identified intriguing lead compounds for further research and development of new AChEIs.

Multigene Phylogeny, Diversity and Antimicrobial Potential of Endophytic Sordariomycetes From Rosa roxburghii

Rosa roxburghii Tratt. is widely applied in food, cosmetics, and traditional medicine, and has been demonstrated to possess diverse bioactivities. Plant endophytic fungi are important microbial resources with great potential for application in many fields. They not only establish mutualistic symbiosis with host plants but also produce a variety of bioactive compounds. Therefore, in the present study, endophytic fungi were isolated from R. roxburghii, the diversity and antimicrobial activities were evaluated. As a result, 242 strains of endophytic Sordariomycetes were successfully isolated. Multigene phylogenetic analyses showed that these isolates included eight orders, 19 families, 33 genera. The dominant genera were Diaporthe (31.4%), Fusarium (14.4%), Chaetomium (7.9%), Dactylonectria (7.0%), Graphium (4.5%), Colletotrichum (4.1%), and Clonostachys (4.1%). For different tissues of R. roxburghii, alpha diversity analysis revealed that the diversity of fungal communities decreased in the order of root, fruit, stem, flower, leaf, and seed, and Clonostachys and Dactylonectria exhibited obvious tissue specificity. Meanwhile, functional annotation of 33 genera indicated that some fungi have multitrophic lifestyles combining endophytic, pathogenic, and saprophytic behavior. Additionally, antimicrobial activities of endophytic Sordariomycetes against Lasiodiplodia theobromae, Botryosphaeria dothidea, Colletotrichum capsici, Pyricularia oryzae, Rhizoctonia solani, Fusarium oxysporum, Pseudomonas syringae, Pantoea agglomerans, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa were screened. Dual culture test assays showed that there were 40 different endophytic species with strong inhibition of at least one or moderate inhibition of two or more against the 12 tested strains. The results from the filter paper diffusion method suggested that extracellular metabolites may be more advantageous than intracellular metabolites in the development of antimicrobial agents. Eleven isolates with good activities were screened. In particular, Hypomontagnella monticulosa HGUP194009 and Nigrospora sphaerica HGUP191020 have shown promise in both broad-spectrum and intensity. Finally, some fungi that commonly cause disease have been observed to have beneficial biological activities as endophytic fungi. In conclusion, this study showed the species composition, alpha diversity, and lifestyle diversity of endophytic Sordariomycetes from R. roxburghii and demonstrated these isolates are potential sources for exploring antimicrobial agents.