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Updated: Jan 24, 2026

Isolation, Characterization, and Total DNA Extraction to Identify Endophytic Fungi in Mycoheterotrophic Plants
Published on: May 5, 2023
Host metabolite producing endophytic fungi isolated from Hypericum perforatum
Aruna Vigneshwari1,2, Dávid Rakk1, Anikó Németh3
1Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary.
Abstract:
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.
Insights
Endophytic fungi isolated from St. John's Wort produce hypericin and emodin. Epicoccum nigrum and Alternaria species showed significant antimicrobial activity, outperforming pure compounds.
Area of Science:
- Mycology
- Natural Products Chemistry
- Pharmacology
Background:
- Hypericum perforatum (St. John's Wort) is a medicinal herb containing valuable metabolites.
- Endophytic fungi residing within medicinal plants are a potential source of bioactive compounds.
Purpose of the Study:
- To isolate endophytic fungi from Hypericum perforatum.
- To investigate the ability of these fungi to produce hypericin and emodin.
- To evaluate the antimicrobial activity of the fungal isolates and their metabolites.
Main Methods:
- Isolation and culturing of endophytic fungi from Hypericum perforatum.
- High-Performance Liquid Chromatography with Ultraviolet detection (HPLC-UV) and Ultra-High-Performance Liquid Chromatography with High-Resolution Mass Spectrometry (UHPLC-HRMS) for metabolite analysis.
- Antimicrobial assays against selected bacteria.
Main Results:
- Three fungal isolates produced emodin, with one isolate (Epicoccum nigrum SZMC 23769) also producing hypericin.
- Epicoccum nigrum and Alternaria sp. SZMC 23772 exhibited superior antimicrobial activity compared to hypericin and emodin standards.
- Alternaria sp. SZMC 23771 showed varied antimicrobial activity against specific bacterial strains.
Conclusions:
- Endophytic fungi, specifically Epicoccum nigrum and Alternaria species, can biosynthesize key metabolites like hypericin and emodin.
- These fungal endophytes possess significant antimicrobial properties, offering potential for novel therapeutic agents.
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