Mikhail V. Pivkin

Metabolites of the marine fungus Humicola fuscoatra KMM 4629

A new sesquiterpene of the caryophyllene series, fuscoatrol A (1), and known compounds, 11-epiterpestacin (2) and β-nitropropionic acid (3), were isolated from the marine fungus Humicola fuscoatra (Traaen) KMM 4629 associated with the Kuril colonial ascidium. The structure of 1 was established on the basis of X-ray diffraction data and 2D NMR spectroscopy. The antimicrobial and cytotoxic activities of compounds 1–3 were studied.

A lectin with antifungal activity from the mussel Crenomytilus grayanus

Lectins (carbohydrate-binding proteins) are well known to actively participate in the defense functions of vertebrates and invertebrates where they play an important role in the recognition of foreign particles. In this study, we investigated of in vitro antifungal activity of lectin from the mussel Crenomytilus grayanus (CGL). Enzyme-linked immunosorbent assay indicated that CGL was predominantly detectable in tissues of mantle and to a lesser degree in the tissues of muscle, hepatopancreas, gill and hemocytes. After challenged by Pichia pastoris the level of CGL was upregulated and reached the maximum level at 12 h post challenge and recovered to the original level at 24 h. The lectin was capable of inhibiting the germination of spores and hyphal growth in the fungi. All these results indicated that CGL is involved in the innate immune response in mollusc animals.

А new Gal/GalNAc-specific lectin from the mussel Mytilus trossulus: Structure, tissue specificity, antimicrobial and antifungal activity

In the present study, a new Gal/GalNAc specific lectin from the mussel Mytilus trossulus (designated as MTL) was identified, and its expression levels, both in tissues and toward pathogen stimulation, were then characterized. The MTL primary structure was determined via cDNA sequencing. Deduced sequence of 150 amino acid residues showed 89% similarity to lectins from the mussels Crenomytilus grayanus and Mytilus galloprovincialis that were the first members of a new family of zoolectins. The results indicated that the MTL might be involved in immune response toward pathogen infection, and it might perform different recognition specificity toward bacteria or fungi.

New diterpene glycosides of the fungus Acremonium striatisporum isolated from a sea cucumber.

Three new diterpene glycosides, virescenosides V (1), W (2), and X (3) have been isolated from a marine strain of Acremonium striatisporum KMM 4401 associated with the holothurian Eupentacta fraudatrix. Their structures have been elucidated on the basis of high resolution mass spectrometry, 1D and 2D NMR (1H, 13C, DEPT, COSY 45, COSY RCT, HSQC, HMBC, and NOESY spectra) as 19-O-β-D-altropyranosyl-7-oxo-isopimara-8(14),15-diene-2α,3β-diol (1), 19-O-β-D-altropyranosyl-isopimara-7,15-diene-2α,3β,6α-triol (2), and 19-O-β-D-altropyranosyl-isopimara-8,15-diene-2α,3β,7α-triol (3).

Asperpentyn from the Facultative Marine Fungus Curvularia inaequalis

Marine micromycete fungi are rich sources of new compounds that often exhibit strong biological activity. Fungi of the genus Curvularia were also described several times as producers of such compounds [1, 2]. The isolate of C. inaequalis, which was reported earlier by us as a producer of several known polyketides, was isolated during research on fungal metabolites from strains in the oceans of the Russian Far East [3]. Fungi were cultivated for 21 d in five 1-L Pyrex flasks, each of which contained medium consisting of malt extract (50 mL), agar (5 g), and seawater (200 mL). Mycelium together with medium was extracted twice with EtOAc. The extract was evaporated. The residue (0.4 g) was chromatographed over a column of silica gel (2 10 cm) with elution successively by hexane and hexane–EtOAc (stepwise gradient, 25:1 10:1). The fraction eluted by the 10:1 system (24 mg) was separated using HPLC over a ChiraDex chiral column and MeOH–H2O (40:60) to afford pure (–)-asperpentyn (1.5 mg).

Isochromene metabolite from the facultative marine fungus Penicillium citrinum

Facultative and obligative marine microscopic fungi are known to be promising sources of various types of biologically active compounds [1, 2]. Under the auspices of a program for discovery of biologically active compounds in extracts of isolates of marine microscopic fungi, we isolated the strain Penicillium citrinum Thom. from sediment collected during core drilling of methane gas hydrates at a depth of 645 m in the Okhotsk Sea. The fungus was cultivated for 21 d at 22°C in a 1-L flask containing medium of composition sodium tartrate, 0.005 g; yeast extract, 0.01 g; rice, 10 g; KH2PO4, 0.005 g; and seawater, 20 mL. Fungal mycelium with medium was extracted twice with EtOAc. The extract was evaporated. The solid was dissolved in EtOH:H2O (1:4). The resulting solution was extracted successively by hexane, EtOAc, and BuOH. The EtOAc extract was evaporated in vacuo. The dry solid (300 mg) was chromatographed over a column (25 2 cm) of silica gel with elution by hexane:EtOAc (95:5) to afford a compound (8 mg). The compound was identified by MS and 2D NMR spectroscopy (Table 1) and comparison with the literature [3] as (3S)-3,5-dimethyl-8-methoxy-3,4-dihydro-1H-isochromen-6-ol (1).

Asperindoles A–D and a p-Terphenyl Derivative from the Ascidian-Derived Fungus Aspergillus sp. KMM 4676

Four new indole-diterpene alkaloids asperindoles A–D (1–4) and the known p-terphenyl derivative 3″-hydroxyterphenyllin (5) were isolated from the marine-derived strain of the fungus Aspergillus sp., associated with an unidentified colonial ascidian. The structures of 1–5 were established by 2D NMR and HRESIMS data. The absolute configurations of all stereocenters of 1–4 were determined by the combination of ROESY data, coupling constants analysis, and biogenetic considerations. Asperindoles C and D contain a 2-hydroxyisobutyric acid (2-HIBA) residue, rarely found in natural compounds. Asperindole A exhibits cytotoxic activity against hormone therapy-resistant PC-3 and 22Rv1, as well as hormone therapy-sensitive human prostate cancer cells, and induces apoptosis in these cells at low-micromolar concentrations.

Zosteropenillines: Polyketides from the MarineDerived Fungus Penicillium thomii

Twelve new polyketides, zosteropenillines A–L (1–12), together with known polyketide pallidopenilline A (13), were isolated from the ethylacetate extract of the fungus Penicillium thomii associated with the seagrass Zostera marina. Their structures were established based on spectroscopic methods. The absolute configuration of zosteropenilline A (1) as 4R, 5S, 8S, 9R, 10R, and 13S was determined by a combination of the modified Mosher’s method, X-ray analysis, and NOESY data. Absolute configurations of zosteropenillines B–D (2–4) were determined by time-dependent density functional theory (TD-DFT) calculations of ECD spectra. The effect of compounds 1–3, 7, 8, 10, and 11 on the viability of human drug-resistant prostate cancer cells PC3 as well as on autophagy in these cancer cells and inhibitory effects of compounds 1, 2, and 8–10 on NO production in LPS-induced RAW 264.7 murine macrophages were examined.

Metabolites of the Marine Fungus Aspergillus candidus KMM 4676 Associated with a Kuril Colonial Ascidian

Marine fungi and micromycetes are reported to produce a large variety of low-molecular-mass secondary metabolites [1, 2]. The separate ecological groups of marine fungal metabolites remain practically unstudied by chemists despite the fact that they have been known for almost 20 years. One such group comprises fungi associated with ascidians [3]. Currently, about 20 pure compounds have been isolated from such fungi [4]. A search for new producers of biologically active compounds among fungi preserved at the Collection of Marine Microorganisms (KMM), PIBOC, FEB, RAS, led us to investigate Aspergillus candidus KMM 4676 that was isolated during the 21st cruise of the RS Academician Oparin as an unidentified colonial ascidian (Shikotan Is.). The fungus was cultivated for 21 d at 22°C in 14 1-L Ehrlenmeyer flasks, each of which contained rice medium (60 g) [5]. Mycelium together with medium was extracted (2 ) with EtOAc. The extract was evaporated. The residue was dissolved in EtOH–H2O (1:4) and extracted sequentially with hexane, EtOAc, and BuOH. The EtOAc fraction was separated by column chromatography over SiO2 and by HPLC over SiO2 and C18-SiO2 to afford 1 (10.5 mg), 2 (2.8), 3 (13.8), 4 (22.2), 5 (1.9), and 6 (1.3).

New Kipukasin from Marine Isolate of the Fungus Aspergillus flavus

A new aromatic nucleoside kipukasin J (1) and two known compounds decumbenone B (2) and cyclopenol (3) were separated from marine isolate of the fungus Aspergillus flavus. The structure of kipukasin J was elucidated using NMR spectroscopy and high-resolution mass spectrometry. The antimicrobial activity of the separated compounds was investigated.