Butyrolactones from the Fermentation Products of the Endophytic Fungus Aspergillus versicolor

Isochromenes from the Nicotiana tabacum-derived endophytic fungus Aspergillus versicolor and their anti-tobacco mosaic virus activities

Three new isochromenes, (5-methoxy-7-prenyl-1H-isochromen-3-yl)methanol (1), 3-(3-(hydroxymethyl)-5-methoxy-1H-isochromen-7-yl)propan-1-ol (2), and (5-methoxy-7-methyl-1H-isochromen-3-yl)methanol (3), along with three known analogues (4-6) were isolated from the fermentation products of a Nicotiana tabacum-derived endophytic fungus Aspergillus versicolor. Their structures were elucidated by spectroscopic methods, including extensive 1 D and 2 D NMR techniques. Compounds 1-3 and 6 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compound 2 exhibited high anti-TMV activity with inhibition rate of 46.4%, and this rate is higher than that of positive control. Compounds 1, 3, and 6 also showed potential anti-TMV activity with inhibition rates of 28.6, 30.5, and 26.2%, respectively. The IC₅₀ of compounds 1-3 and 6 were also tested, and showed IC₅₀ values of 49.3, 22.4, 42.2, and 54.1 µM, respectively.

Natural product diversity from the endophytic fungi of the genus Aspergillus

The endophytic fungus Aspergillus is considered as an enormous source of chemical leads with promising biological activities. Different Aspergillus species have proved their ability to produce plenty of secondary metabolites including butenolides, alkaloids, terpenoids, cytochalasins, phenalenones, ρ-terphenyls, xanthones, sterols, diphenyl ether and anthraquinone derivatives with diverse biological activities, such as anti-cancer, antifungal, anti-bacterial, anti-viral, anti-inflammatory, antitrypanosomal and antileishmanial activities. From January 2015 until December 2019, three hundred and sixty-one secondary metabolites were reported from different endophytic Aspergillus species. This review discusses the isolated secondary metabolites from different endophytic Aspergillus species reported from January 2015 to December 2019 along with their reported biological activities and structural aspects whenever applicable.

Chemical Investigation Of Secondary Metabolites Produced By Mangrove Endophytic Fungus Phyllosticta Capitalensis

Chemical investigation of endophytic fungus Phyllosticta capitalensis, isolated from the hypocotyls of the Chinese mangrove Bruguiera sexangula led to the isolation of eight known secondary metabolites, including four meroterpenes guignardone A (1), 12-hydroxylated guignardone A (2), guignardone J (3), guignardone M (4), and four polyketides xenofuranone B (5), 6,8-dihydroxy-5-methoxy-3-methyl-1H-isochromen-1-one (6), regiolone (7), 3,4-dihydroxybenzoic acid (8). Their structures were elucidated unambiguously based on the comprehensive spectroscopic analysis and comparison with literature data. This is the first report of these compounds being isolated from this fungal species. All compounds isolated were subjected to antimicrobial and cytotoxic activities evaluation.

Expanding the chemical diversity of an endophytic fungus Bulgaria inquinans, an ascomycete associated with mistletoe, through an OSMAC approach

An endophytic fungus Bulgaria inquinans (isolate MSp3-1), isolated from mistletoe (Viscum album), was subjected to fermentation on solid Czapek medium. Chromatographic workup of the crude EtOAc extract yielded five new natural products (1–5). Subsequent application of the “One Strain, MAny Compounds” (OSMAC) strategy on this strain by the addition of a mixture of salts (MgSO₄, NaNO₃ and NaCl) to solid Czapek medium induced the accumulation of nine additional new secondary metabolites (6–13, 16), with most of them (8, 10–12) not detectable in cultures lacking the salt mixture. The structures of the new compounds were established on the basis of the 1D/2D NMR and HRESIMS data. The TDDFT-ECD method was applied to determine the absolute configurations of the new compounds 1, 4 and 6 as well as of the previously reported bulgarialactone B (14), for which the absolute configuration was unknown so far. The modified Mosher's method was performed to assign the absolute configurations of 12 and 13. TDDFT-ECD analysis also allowed determining the absolute configuration of (+)-epicocconone, which had an enantiomeric absolute configuration in the tricyclic moiety compared to that of bulgarialactone B (14). All the isolated metabolites were evaluated for their cytotoxic activity. Compound 2 was found to possess strong cytotoxic activity against the murine lymphoma cell line L5178Y with an IC₅₀ value of 1.8 μM, while the remaining metabolites were shown to be inactive.

OSMAC approach on endophytic Bulgaria inquinans by addition of a mixture of salts (MgSO₄, NaNO₃ and NaCl) to solid Czapek medium induced the accumulation of new secondary metabolites.