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.

Metabolite fingerprinting, in vitro antimicrobial and antioxidant activities and in-silico docking in Alloteropsis cimicina and its endophytic fungus Penicillium pinophilum.

Endophytic fungal interaction with medicinal plant resulting in the production of bioactive compounds influenced the present study. Endophytic fungus Penicillium pinophilum Hedgc. from Alloteropsis cimicina with high incidence was isolated by incubation methods and characterized by morphological and molecular (ITS rDNA region) methods. Penicillium pinophilum was cultured on PD broth and metabolites of host and endophyte were extracted with ethyl acetate and methanol. Metabolites were assayed for antimicrobial potential by well diffusion and scavenging ability by spectrophotometric and electrochemical methods. Metabolite profiling by Orbitrap High-Resolution Liquid Chromatography-Mass Spectrometry and Fourier-transform infrared spectroscopy and by validation of antimicrobial and antioxidant activities in-silico drug-likeness of spectral compound prediction and molecular docking were performed. Host and P. pinophilum extracts showed strong antimicrobial potential against certain clinical bacterial strains and Fusarium oxysporum. Fungal extracts exhibited higher antioxidant activity than A. cimicina extract. Metabolite profiling indicated 14 and 21 antimicrobial, 10 and 13 antioxidant compounds in A. cimicina and P. pinophilum extracts, respectively. There were eight spectral compounds common to endophyte and host with high binding affinity towards receptors. The present study revealed that P. pinophilum and A. cimicina are natural reservoirs of novel bioactive compounds with antimicrobial and antioxidant properties.

Antimicrobial activity and metabolite profiling of endophytic fungi in Digitaria bicornis (Lam) Roem. and Schult. and Paspalidium flavidum (Retz.) A. Camus.

Endophytic fungal occurrences were studied in aerial regions of Digitaria bicornis and Paspalidium flavidum by three isolation methods: potato dextrose agar (PDA), malt extract agar (MEA), and moist blotters. Seventy species of 29 genera of endophytic fungi in D. bicornis and 71 species of 30 genera in P. flavidum were documented. Endophytic fungal communities were grouped into 40 and 43 anamorphic ascomycetes (21 and 23 genera) and 20 teleomorphic ascomycetes (6 and 7 genera) in D. bicornis and P. flavidum, respectively. PDA supported the expression of larger number of fungal communities than MEA and MB; and P. flavidum hosted more number of endophytic fungi than D. bicornis. Seasons played an important role in supporting the assemblage of fungal endophytes. Endophytic fungal species richness and assemblages in plant regions were determined for alpha, beta, and gamma diversities. The ethyl acetate followed by methanolic extracts of certain fungal species showed good antagonistic and antibacterial activities. Among fungal endophytes, Curvularia protuberata and Penicillium citrinum exhibited high antagonistic and antibacterial activities. The high-resolution orbitrap liquid chromatography-mass spectrometry of ethyl acetate crude extracts of C. protuberata and P. citrinum revealed the presence of antifungal and antimicrobial, besides a host of compounds in the extracts. The present study indicated that grass endophytes are the sources of compounds with antimicrobial and other pharmacological activities.

Antimicrobial and antioxidant activities and chemical profiling of Curvularia tsudae endophytic in Cynodon dactylon (L.) Pers.

There is a growing body of evidence that endophytic fungal metabolites possess important biological activities. Cynodon dactylon (L.) Pers., a well-known grass species with potential medicinal properties, is under-explored for the diversity of endophytic fungal species and their metabolites. We report here the diversity of endophytic fungi in the culm, leaf and inflorescence of Cynodon dactylon when cultured on moist blotter (MB), potato dextrose agar (PDA) and malt extract agar (MEA). Species richness, Shannon and Simpson diversity and evenness indices showed that PDA followed by MEA supported the growth of the largest number of fungal species. Amongst four fungal species tested, Curvularia tsudae was selected for further studies on antimicrobial and antioxidant activities. The mycelial mat (MM) and culture filtrate (CF) of PD broth grown Curvularia tsudae extracted with ethyl acetate and methanol, respectively, were subjected to antimicrobial assay against five bacterial and four fungal test isolates. Results indicated that the ethyl acetate extract of CF had moderate activity against Enterococcus faecalis, Escherichia coli, Pseudomonas fluorescence and Staphylococcus aureus whereas the methanolic MM extract showed high to moderate activity to Aspergillus flavus, A. niger and Fusarium oxysporum. Cyclic voltammetric analysis of ethyl acetate extract showed very good antioxidant activity and the extract contained coumarins when determined by HPLC. High-resolution orbitrap LC-MS of ethyl acetate extract revealed the presence of metabolites with antimicrobial and antioxidant and other biological activities. Finding of the present study suggested that Curvularia tsudae could be exploited for pharmaceutical applications.