Host metabolite producing endophytic fungi isolated from Hypericum perforatum

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.

Isolation, Characterization and Targeted Metabolic Evaluation of Endophytic Fungi Harbored in 14 Seed-Derived Hypericum Species

“…On the other hand, two-thirds of our Alternaria sp. isolates from H. kalmianum and H. tetrapterum possessing the laccase activity, which was previously mentioned as producers of emodin [26], did not show a positive reaction for the presence of anthraquinones (samples 15LF2-1, 32SF1-2) (▶ Fig. 2).…”

“…The studies on fungal and bacterial endophytes that inhabit the genus Hypericum comprise, to date, only six Hypericum species viz., H. perforatum [12,17,22,24,26], H. mysorense, H. japonicum [25], H. sinaicum [4], H. scabrum [27], and H. silenoides [28]. Here, we present the results of screening for the presence of endophytic fungi in various plant organs of 14 Hypericum host species, from among which only H. perforatum has previously been reported.…”

“…Kusari et al [12] isolated the endophytic fungus T. subthermophila from H. perforatum native to the Himalaya Mountains, which was able to biosynthesize emodin and hypericin in axenic culture fermentations in vitro over several subcultures. Recently, Vigneshwari et al [26] reported the production of hypericin and emodin by the endophytic fungus Epicoccum nigrum isolated from H. perforatum. From among six Alternaria sp.…”

“…To date, there are only a handful of studies conducted on endophytes in Hypericum species [4,12,17,[21][22][23][24][25][26]. Zhang et al [24] reported the antimicrobial properties evaluated in 21 endophytic fungal strains of 5 genera, including Fusarium sp., Mucor sp., Aspergillus sp., Xylaria sp., and Hypocrea sp., isolated from H. perforatum.…”

MALDI-HRMS Imaging Maps the Localization of Skyrin, the Precursor of Hypericin, and Pathway Intermediates in Leaves of Hypericum Species

“…Remarkably, skyrin (7) is typically biosynthesized by fungi belonging to different species and ecological niches and reported to have antimicrobial properties [ 19 , 20 ]. Thus far, the role of plant-associated microorganisms such as endophytes in the production of skyrin (7) is a plausible, open question, particularly since native endophytes harbored in H. perforatum can produce hypericin (6) [ 21 , 22 , 23 ]. Therefore, it is essential to identify the in planta site of localization and the role of skyrin (7) , as well as the related intermediates leading to the production of hypericin (6) .…”