Bioprospecting of fungal endophytes from Oroxylum indicum (L.) Kurz with antioxidant and cytotoxic activity.

Oroxylum indicum (L.) Kurz, a medicinal plant, shows numerous pharmacological properties which may be attributed to the bioactive compounds produced by O. indicum or due to associated endophytes. In the present study, leaf of O. indicum was evaluated for the presence of associated fungal endophytes, and antioxidant and cytotoxic activities of bioactive compounds produced from them. Using culture-dependent approach, eight fungal endophytes belonging to five different genera were identified. Two endophytes Daldinia eschscholtzii and Ectophoma multirostrata have been reported for the first time from the leaf of O. indicum plant. High-performance thin-layer chromatography (HPTLC) of ethyl acetate (EA) extract of isolated fungal endophytes showed a distinct fingerprinting profile in EA extract of Colletotrichum gloeosporioides. Among identified endophytes, EA extract of C. gloeosporioides showed significant antioxidant activity against DPPH free radical, superoxide anion radical, nitric oxide radical and hydroxyl radical with EC50 values of 22.24±1.302 µg/mL, 67.46±0.576 µg/mL, 80.10±0.706 µg/mL and 61.55±1.360 µg/mL, respectively. EA extract of C. gloeosporioides exhibited potential cytotoxicity against HCT116, HeLa and HepG2 cancer cell lines with IC50 values of 76.59 µg/mL, 176.20 µg/mL and 1750.70 µg/mL, respectively. A comparative HPTLC fingerprinting and the antioxidant activity of C. gloeosporioides associated with two different hosts (leaf of O. indicum and dead twigs of other plant) showed that C. gloeosporioides produces bioactive compounds in a host-dependent manner.

The plant endosphere-hidden treasures: a review of fungal endophytes.

The endosphere represents intracellular regions within plant tissues colonize by microbial endophytes without causing disease symptoms to host plants. Plants harbor one or two endophytic microbes capable of synthesizing metabolite compounds. Environmental factors determine the plant growth and survival as well as the kind of microorganisms associated with them. Some fungal endophytes that symbiotically colonize the endosphere of medicinal plants with the potential of producing biological products have been employed in traditional and modern medicine. The bioactive resources from endophytic fungi are promising; biotechnologically to produce cheap and affordable commercial bioactive products as alternatives to chemical drugs and other compounds. The exploration of bioactive metabolites from fungal endophytes has been found applicable in agriculture, pharmaceutical, and industries. Thus, fungal endophytes can be engineered to produce a substantive quantity of pharmacological drugs through the biotransformation process. Hence, this review shall provide an overview of fungal endophytes, ecology, their bioactive compounds, and exploration with the biosystematics approach.

Host metabolite producing endophytic fungi isolated from Hypericum perforatum.

In the present study, endophytic fungi have been isolated from various parts of the medicinal herb Hypericum perforatum (St. John's Wort), which is known as a source of medically important metabolites. The isolated strains were cultured in liquid media and their ability to synthesize hypericin, the secondary metabolite of the host and its suspected precursor, emodin was tested analyzing the extracts of the fermentation broth and the mycelia. The HPLC-UV analysis of the chloroform/methanol extracts of the mycelia revealed that three isolates were able to produce emodin (SZMC 23771, 19.9 ng/mg; SZMC 23772, 20.8 ng/mg; SZMC 23769, 427.9 ng/mg) and one of them also could synthesize hypericin (SZMC 23769, 320.4 ng/mg). These results were also confirmed via UHPLC-HRMS technique both in full scan and MS/MS mode. The strains producing only emodin belong to the section Alternata of the genus Alternaria, while the isolate producing both metabolites was identified as Epicoccum nigrum. The mycelial extracts of E. nigrum and the Alternaria sp. SZMC 23772 showed higher inhibitory activities in the antimicrobial tests against the six selected bacteria compared to the hypericin and emodin standards in the applied concentration (100 µg/mL), while in case of the Alternaria sp. SZMC 23771 lower inhibition activities were observed on Staphylococcus aureus and Streptomyces albus than the pure compounds.

Characterization of secondary metabolites of an endophytic fungus from Curcuma wenyujin.

Endophytic fungi are ubiquitous in the plant kingdom and they produce a variety of secondary metabolites to protect plant communities and to show some potential for human use. However, secondary metabolites produced by endophytic fungi in the medicinal plant Curcuma wenyujin are sparsely explored and characterized. The aim of this study was to characterize the secondary metabolites of an active endophytic fungus. M7226, the mutant counterpart of endophytic fungus EZG0807 previously isolated from the root of C. wenyujin, was as a target strain. After fermentation, the secondary metabolites were purified using a series of purification methods including thin layer chromatography, column chromatography with silica, ODS-C18, Sephadex LH-20, and macroporous resin, and were analyzed using multiple pieces of data (UV, IR, MS, and NMR). Five compounds were isolated and identified as curcumin, cinnamic acid, 1,4-dihydroxyanthraquinone, gibberellic acid, and kaempferol. Interestingly, curcumin, one of the main active ingredients of C. wenyujin, was isolated as a secondary metabolite from a fungal endophyte for the first time.