An endophytic Penicillium oxalicum isolated from Citrus limon possesses antioxidant and genoprotective potential

Halotolerant and plant growth-promoting endophytic fungus Aspergillus terreus CR7 alleviates salt stress and exhibits genoprotective effect in Vigna radiata

Soil salinity is one of the major environmental stresses that results in reduction of cultivable land and decreased productivity. In the present study, halotolerant and plant growth-promoting endophytic fungi were isolated from Catharanthus roseus, and their effect in mitigating salt stress in Vigna radiata was evaluated. An isolate CR7, identified to be Aspergillus terreus, showing plant growth promotion activities, viz. IAA production (23.43 ± 0.79 μg/ml), phosphate solubilization (133.63 ± 6.40 μg/ml), ACC deaminase activity (86.36 ± 2.70 μmol α-ketobutyrate/h/mg protein) etc. and ability to grow at 15% NaCl was selected for further in vivo studies. Colonization of CR7 was carried out in V. radiata which was subjected to different concentrations of salt (150, 200, and 250 mM NaCl). Under salt stress, A. terreus CR7 inoculated plants showed substantially improved root and shoot length, biomass, chlorophyll content, relative water content, phenolics, protein content, and DPPH scavenging activity. Endogenous IAA level was enhanced by 5.28-fold in treated plants at maximum salt stress. Inoculation of A. terreus CR7 affected oxidative stress parameters, exhibiting an increase in catalase and superoxide dismutase and reduction in proline, electrolyte leakage, and malondialdehyde content. Fluorescent microscopic analysis of roots revealed improved cell viability and decreased levels of glutathione and hydrogen peroxide under salt stress in treated plants. The isolate A. terreus CR7 also protected against DNA damage induced by salt stress which was evaluated using comet assay. A decrease in DNA tail length, tail moment, and olive tail moment to the extent of 19.87%, 19.76%, and 24.81%, respectively, was observed in A. terreus CR7-colonized plants under salt stress. It can be concluded that A. terreus CR7 can be exploited for alleviating the impact of salt stress in crop plants.

Isolation, identification, and antibacterial evaluation of endophytic fungi from Gannan navel orange

Gannan navel orange is a famous brand in China but the isolation of its endophytic fungi was rarely reported. In this study, a total of 54 strains of endophytic fungi were successfully isolated from the pulp, peel, twig, and leaf of Gannan navel orange; they were successfully identified to belong to 17 species of 12 genera. All these strains were fermented using potato-dextrose agar (PDA) medium, and their secondary metabolites were then extracted with ethyl acetate (EtOAc). The antibacterial assays of Escherichia coli (E. coli), methicillin-resistant Staphylococcus aureus (MRSA), and Xanthomonas citri subsp. citri (Xcc) were also performed for the EtOAc extracts of these strains. As a result, the extracts of both Geotrichum sp. (gc-1-127-30) and Diaporthe biconispora (gc-1-128-79) demonstrated significant antibacterial activities against Xcc, and the MIC value for the extract of Colletotrichum gloeosporioides against MRSA was low to 62.5 μg/mL. Moreover, the chemical components of the extracts of Colletotrichum sp., Diaporthe biconispora, and Annulohypoxylon atroroseum were primarily investigated, and they successfully led to the isolation of 24 compounds involving a new botryane sesquiterpene. Among the isolated products, compound 2 showed significant inhibitory activities toward SA, MRSA, E. coli, and Xcc with MIC values of 12.5, 3.1, 125, and 12.5 μg/mL, respectively. This study revealed that the endophytic fungi of Gannan navel orange showed high potency to produce secondary metabolites with significant antibacterial effects.

Isolation and Molecular Characterization of Indigenous Penicillium chrysogenum/rubens Strain Portfolio for Penicillin V Production

Beta (β)-lactam antibiotic is an industrially important molecule produced by Penicillium chrysogenum/rubens. Penicillin is a building block for 6-aminopenicillanic acid (6-APA), an important active pharmaceutical intermediate (API) used for semi-synthetic antibiotics biosynthesis. In this investigation, we isolated and identified Penicillium chrysogenum, P. rubens, P. brocae, P. citrinum, Aspergillus fumigatus, A. sydowii, Talaromyces tratensis, Scopulariopsis brevicaulis, P. oxalicum, and P. dipodomyicola using the internal transcribed spacer (ITS) region and the β-tubulin (BenA) gene for precise species identification from Indian origin. Furthermore, the BenA gene distinguished between complex species of P. chrysogenum and P. rubens to a certain extent which partially failed by the ITS region. In addition, these species were distinguished by metabolic markers profiled by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Secalonic acid, Meleagrin, and Roquefortine C were absent in P. rubens. The crude extract evaluated for PenV production by antibacterial activities by well diffusion method against Staphylococcus aureus NCIM-2079. A high-performance liquid chromatography (HPLC) method was developed for simultaneous detection of 6-APA, phenoxymethyl penicillin (PenV), and phenoxyacetic acid (POA). The pivotal objective was the development of an indigenous strain portfolio for PenV production. Here, a library of 80 strains of P. chrysogenum/rubens was screened for PenV production. Results showed 28 strains capable of producing PenV in a range from 10 to 120 mg/L when 80 strains were screened for its production. In addition, fermentation parameters, precursor concentration, incubation period, inoculum size, pH, and temperature were monitored for the improved PenV production using promising P. rubens strain BIONCL P45. In conclusion, P. chrysogenum/rubens strains can be explored for the industrial-scale PenV production.

Metabolite profiling, in vitro and in silico assessment of antibacterial and anticancer activities of Alternaria alternata endophytic in Jatropha heynei

Fungal endophytes produce a range of structurally diverse metabolites with bioactive principles. In this study, an endophytic fungus Alternaria alternata was isolated from Jatropha heynei and cultured in potato dextrose liquid broth. Culture filtrate of A. alternata was extracted in ethyl acetate and metabolites were characterized by QTOF-HRLCMS. Among compounds detected, spectral compounds such as kigelinone, and levofuraltadone were reported with antibacterial property, while 2-hydroxychrasophanol, isoathyriol, glycophymoline, columbianetin and kaempferol 3-O-β-D- galactoside were reported with cytotoxic properties. Partially purified metabolites of A. alternata showed significant antibacterial activity against tested clinical bacterial strains by agar well diffusion method. High zone of inhibition was recorded against Enterococcus faecalis, Pseudomonas syringae and Klebsiella pneumoniae. In vitro anticancer activity of fungal extract by MTT assay displayed high cytotoxic effect on human lung carcinoma cancer cell line (A549) with IC₅₀ value of 393.52 µg ml^-1, and without any significant cytotoxic effect on human breast cancer cell line (MCF-7). Further, antibacterial and anticancer spectral compounds of A. alternata were subjected to molecular docking analysis with antibacterial target proteins such as tellurite resistance protein (2JXU), indole-3-acetaldehyde dehydrogenase (5IUU) and alkyl hydroperoxide reductase (5Y63), and anticancer target human apoptotic regulator protein (1G5M). The results of the study indicated that kigelinone, levofuraltadone, 2-hydroxychrasophanol and isoathyriol in the fungal extract have significant binding modes, with best binding energy scores with their respective antibacterial and anticancer target proteins. Alternaria alternata resident in J. heynei offers a promising source of broad-spectrum antibacterial and anticancer compounds.

An endophytic Schizophyllum commune possessing antioxidant activity exhibits genoprotective and organprotective effects in fresh water fish Channa punctatus exposed to bisphenol A

BACKGROUND

Oxidative stress is responsible for the onset of several chronic and degenerative diseases. Exogenous supply of antioxidants is reported to neutralize the effects of oxidative stress. Several synthetic antioxidants suffer from various side effects which necessitates the exploration of antioxidant compounds from natural sources. Endophytic fungi residing in the plants are gaining the attention of researchers as a source of novel antioxidants. Majority of the research conducted so far on endophytic fungi has been restricted to the members of phylum ascomycota. Basidiomycota, inspite of their immense bioactive potential remain relatively unexploited. This study aimed to assess the ameliorative effects of an endophytic Schizophyllum commune (basidiomycetous fungus) against oxidative stress associated altered antioxidant levels, genotoxicity and cellular damage to different organs in bisphenol A exposed fresh water fish Channa punctatus.

RESULTS

Good antioxidant and genoprotective potential was exhibited by S. commune extract in in vitro studies conducted using different antioxidant, DNA damage protection, and cytokinesis blocked micronuclei assays. In vivo studies were performed in fresh water fish Channa punctatus exposed to bisphenol A. A significant decrease in the considered parameters for DNA damage (% micronuclei and comet assay) were recorded in fish treated with S. commune extract on comparison with untreated bisphenol A exposed group. The S. commune extract treated fish also exhibited an increase in the level of antioxidant enzymes viz. catalase, superoxide dismutase and glutathione reductase as well as histoprotective effect on various organs. GC-MS analysis revealed the presence of 3-n-propyl-2,4-pentanedione, n-heptadecanol-1, trans-geranylgeraniol, 3-ethyl-2-pentadecanone, 1-heneicosanol and squalene as some of the compounds in S. commune extract.

CONCLUSION

The study highlights the significance of an endophytic basidiomycetous fungus S. commune as a source of antioxidant compounds with possible therapeutic potential.

The endophytic fungus Penicillium oxalicum isolated from Ligusticum chuanxiong Hort possesses DNA damage-protecting potential and increases stress resistance properties in Caenorhabditis elegans

The chemical composition and antioxidant activity of extracts (POE) of Penicillium oxalate isolated from Ligusticum chuanxiong Hort have been investigated. However, the biological activity of POE is limited, and its antioxidant, stress resistance and DNA protection effects in vivo are unclear. The current study aims to explore the beneficial effects of POE on DNA damage protection in pBR322 plasmid and lymphocytes and stress resistance in Caenorhabditis elegans. The results showed that POE increased the survival rate of C. elegans under 35°C, UV and H₂O₂ stress, attenuated ROS and MDA accumulation, and enhanced the activity of some important enzymes (SOD, CTA, and GSH-PX). In addition, the POE-mediated stress resistance involved the upregulation of the expression of the sod-3, sod-5, gst-4, ctl-1, ctl-2, daf-16, hsp-16.1, hsp-16.2, and hsf-1 genes and acted dependently on daf-16 and hsf-1 rather than skn-1. Moreover, POE also reduced lipofuscin levels, but did not prolong the lifespan or damage the growth, reproduction and locomotion of C. elegans. Furthermore, POE showed a protective effect against DNA scission in the pBR322 plasmid and lymphocytes. These results suggested that P. oxalate extracts have significant anti-stress and DNA protection potential and could be potential drug candidates in the pharmaceutical field, thus greatly broadening the understanding of the biological effects of the endophytic fungus P. oxalate.

Assessment of Biological Activities of Fungal Endophytes Derived Bioactive Compounds Isolated from Amoora rohituka

Fungal endophytes have remarkable potential to produce bioactive compounds with numerous pharmacological significance that are used in various disease management and human welfare. In the current study, a total of eight fungal endophytes were isolated from the leaf tissue of Amoora rohituka, and out of which ethyl acetate (EA) extract of Penicillium oxalicum was found to exhibit potential antioxidant activity against DPPH, nitric oxide, superoxide anion and hydroxyl free radicals with EC₅₀ values of 178.30 ± 1.446, 75.79 ± 0.692, 169.28 ± 0.402 and 126.12 ± 0.636 µg/mL, respectively. The significant antioxidant activity of EA extract of P. oxalicum is validated through highest phenolic and flavonoid content, and the presence of unique bioactive components observed through high-performance thin layer chromatography (HPTLC) fingerprinting. Moreover, EA extract of P. oxalicum also displayed substantial anti-proliferative activity with IC₅₀ values of 56.81 ± 0.617, 37.24 ± 1.26 and 260.627 ± 5.415 µg/mL against three cancer cells HuT-78, MDA-MB-231 and MCF-7, respectively. Furthermore, comparative HPTLC fingerprint analysis and antioxidant activity of P. oxalicum revealed that fungal endophyte P. oxalicum produces bioactive compounds in a host-dependent manner. Therefore, the present study signifies that fungal endophyte P. oxalicum associated with the leaf of A. rohituka could be a potential source of bioactive compounds with antioxidant and anticancer activity.

Screening of secondary metabolites and antioxidant potential of endophytic fungus Penicillium citrinum and host Digitaria bicornis by spectrophotometric and electrochemical methods

Perennial grasses are hosts to an extremely diverse assemblage of endophytic fungi, but their significance is still underexplored. In the present study, an endophytic fungus was isolated from the aerial regions of Digitaria bicornis (Lam.) Roem. & Schult. and was characterized by morphological and molecular methods (ITS rDNA region), as Penicillium citrinum Thom. The crude extracts of endophytic fungus and host were recovered and evaluated for their antioxidant potential by spectrophotometric and electrochemical methods. The present study was also an attempt to compare the anti-radical power of extracts by spectrophotometric (2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), hydrogen peroxide and nitric oxide radical scavenging assay) and electrochemical (cyclic voltammetry) methods and suggested that cyclic voltammetry could be used routinely instead of assaying by more number of spectrophotometric methods. The results indicated that the ethyl acetate extract of P. citrinum and methanolic extract of D. bicornis has potential compounds with antioxidant and other pharmaceutical activities. Nine and 17 antioxidant biomolecules, respectively, in P. citrinum and D. bicornis extracts were detected by OHR-LC-MS and the presence of function group of the bioactive compounds was confirmed by FTIR spectroscopy. Finally, the study also reported that the extracts of P. citrinum and D. bicornis have several bioactive compounds with application in commercial pharmaceutical industries.

An endophytic Schizophyllum commune Fr. exhibits in-vitro and in-vivo antidiabetic activity in streptozotocin induced diabetic rats

The present study aimed at isolation of endophytic basidiomycetous fungi and evaluation of their in-vitro and in-vivo antidiabetic potential. Preliminary screening for in-vitro activity was carried out using α-glucosidase inhibition assay. An endophytic isolate Sch1 (isolated from Aloe vera), identified to be Schizophyllum commune Fr. on molecular basis, exhibiting more than 90% α-glucosidase inhibitiory activity was selected for further studies. Detailed in-vivo investigations for antidiabetic potential of ethyl acetate extract of S. commune (Sch1), at two different doses, were carried out in streptozotocin induced diabetic Wistar rats. Treatment of diabetic rats with S. commune extract caused significant decrease in blood glucose level and increase in body weight after 14 days experimental period. It significantly restored renal parameters including creatinine, blood urea nitrogen, fractional excretion of sodium, and potassium level in diabetic rats. Improvement in lipid profile and level of antioxidant parameters viz. reduced glutathione, thiobarbituric acid reactive species, and superoxide anion generation was also observed after treatment. Liver enzymes (serum glutamic pyruvic transaminase, serum glutamic-oxaloacetic transaminases, and alkaline phosphatase) homeostasis was found to be markedly improved in diabetic rats administered with S. commune extract. The effects were more pronounced at higher concentration and comparable to acarbose which was used as positive control. Phytochemical analysis revealed the presence of phenolics and terpenoids in the ethyl acetate extract. This is the first report highlighting the therapeutic potential of an endophytic S. commune in the management of diabetes.

Applications of endophytic microbes in agriculture, biotechnology, medicine, and beyond

Endophytes are emerging as integral components of plant microbiomes. Some of them play pivotal roles in plant development and plant responses to pathogens and abiotic stresses, whereas others produce useful and/or interesting secondary metabolites. The appreciation of their abilities to affect plant phenotypes and produce useful compounds via genetic and molecular interactions has paved the way for these abilities to be exploited for health and welfare of plants, humans and ecosystems. Here we comprehensively review current and potential applications of endophytes in the agricultural, pharmaceutical, and industrial sectors. In addition, we briefly discuss the research objectives that should be focused upon in the coming years in order for endophytes and their metabolites to be fully harnessed for potential use in diverse areas.