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. 2017 Feb 6:7:42008.
doi: 10.1038/srep42008.

Fungal endophyte-derived Fritillaria unibracteata var. wabuensis: diversity, antioxidant capacities in vitro and relations to phenolic, flavonoid or saponin compounds

Feng Pan  1 , Tian-Jiao Su  1 , Shi-Mei Cai  1 , Wei Wu  1
Affiliations

Fungal endophyte-derived Fritillaria unibracteata var. wabuensis: diversity, antioxidant capacities in vitro and relations to phenolic, flavonoid or saponin compounds

Feng Pan et al. Sci Rep. .

Abstract

Diverse fungal endophytes are rich fungal resources for the production of an enormous quantity of natural products. In the present study, 53 fungal endophytes were isolated from the bulbs of Fritillaria unibracteata var. wabuensis (FUW). Of these, 49 strains were identified and grouped into 17 different taxa, and priority was conferred to the Fusarium genus. All fungal fermented filtrates displayed antioxidant activities. The DPPH activity, total antioxidant capacities (ABTS), reduction power (FRAP), total phenolic content (TPC), total flavonoid content (TFC) and total saponin content (TSC) were evaluated using petroleum ether, ethyl acetate, n-butyl alcohol and ethanol fractions extracted from five representative fungal cultures. The last three fractions showed more potent antioxidant activity than the first fraction. Significant positive correlations were found between the compositions (TPC, TFC and TSC) and antioxidant capacities (DPPH, ABTS and FRAP). In addition, multifarious natural antioxidant components were identified from the fungal extracts, including gallic acid, rutin, phlorizin, 2,4-di-tert-butylphenol and 2,6-di-tert-butyl hydroquinone; these were determined preliminarily by TLC-bioautography, HPLC and GC-MS analysis. This study showed abundant fungal resources in FUW. Phenolics, flavonoids and saponins are crucial bioactive constituents in these abundant fungal endophytes and can be viewed as new potential antioxidant resources.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Neighbour-joining method analysis of ITS1-5.8S rDNA-ITS2 sequences from the endophytic fungi of Fritillaria unibracteata var. wabuensis.
The tree was derived from the sequences of 49 endophytic fungi (marked with symbols) and 41 sequences retrieved from GenBank. The percentage of replicate trees in which associated taxa were clustered together in the bootstrap test (1000 replicates, values below 50% are not shown) are shown next to the branches. Phylogeny analyses were conducted in MEGA5.1 software.
Figure 2
Figure 2. Antioxidant assays of petroleum ether (PE, 30–60 °C), ethyl acetate (EA), n-butyl alcohol (BA) and ethanol absolute (ET) fractions extracted from five representative fungal endophytes (4WBY1, 6WBY3, 7WBY2, WBS019 and WBS020).
(A) Total antioxidant capacities (ABTS assay), (B) DPPH free radical-scavenging activity and (C) ferric-reducing antioxidant power.
Figure 3
Figure 3. The total phenolic (TPC), total flavonoid (TFC) and total saponin (TSC) contents in the petroleum ether (PE, 30–60 °C), ethyl acetate (EA), n-butyl alcohol (BA) and ethanol absolute (ET) extracts from five fungal endophyte isolates (4WBY1, 6WBY3, 7WBY2, WBS019 and WBS020).
The values are the mean ± SD (n = 3).
Figure 4
Figure 4. TLC photography of fungal endophytic extractions.
The petroleum ether (PE, 30–60 °C) and ethyl acetate (EA) fractions extracted from strains 4WBY1 (1 and 6), 6WBY3 (2 and 7), 7WBY2 (3 and 8), WBS019 (4 and 9) and WBS020 (5 and 10). These fractions were developed in a preselected solvent system containing trichloromethane/toluene/ethanol/formic acid (4:4:0.5:0.1, by volume) and visualised using several methods, namely, ultraviolet lamps at 365 nm (A), heating for 3 min at 105 °C after spraying with vanillin sulphuric acid (B), ultraviolet lamps emitting at 365 nm after spraying with 2% aluminium chloride solution (C) and 0.04 mg·mL−1 DPPH in ethanol (D).
Figure 5
Figure 5. The phenolic antioxidant contents of petroleum ether (PE, 30–60 °C), ethyl acetate (EA), n-butyl alcohol (BA) and ethanol absolute (ET) fractions extracted from five representative fungal endophytes (4WBY1, 6WBY3, 7WBY2, WBS019 and WBS020).
See this image and copyright information in PMC

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