Virgaricin produced by Virgaria sp. FKI-4860

Abstract

The genus Virgaria was first proposed in 1817 1 and classified in the family Xylariaceae. 2 Virgaria nigra, a type species of Virgaria, is a commonly encountered hyphomycetes and has been illustrated in numerous publications. [3][4][5] However, little work has been done on the chemical constituents of Virgaria species, and only one compound, vinigrol, has previously been isolated from V. nigra. 6 As part of our interest in the presence of novel metabolites in Virgaria sp., we investigated the chemical constituents of a culture broth of a newly discovered Virgaria sp. FKI-4860 that resulted in the isolation of a new compound, virgaricin (1). This compound was found to be an analog of pramanicins and TMC-260. [7][8][9] In this study, we describe the isolation, structure elucidation and antimicrobial activity of 1.Fungal strain FKI-4860 was isolated from a soil sample collected in the Bonin Islands, Tokyo, Japan. It is characterized by olive gray colonies, and solitary, mainly reniform and light brown sympodial conidia. The rDNA internal transcribed spacer (ITS) sequence of strain FKI-4860 was elucidated and deposited at the DNA Data Bank of Japan, with the accession number AB670709. With respect to sequence distances elucidated by the MegAlign programs from the Lasergene 9 package (DNAStar Inc., Madison, WI, USA), FKI-4860 had 90% similarity with the ITS sequences of V. nigra CBS 525.69 (AB670712). From the results of morphological characteristics and sequence analysis, strain FKI-4860 was identified as a novel species of Virgaria. 10 Strain FKI-4860 was grown and maintained on a LcA slant consisting of 0.1% glycerol, 0.08% KH 2 PO 4 , 0.02% K 2 HPO 4 , 0.02% MgSO 4 Á7H 2 O, 0.02% KCl, 0.2% NaNO 3 , 0.02% yeast extract and 1.5% agar (adjusted to pH 6.0 before sterilization). A loop of spores of Virgaria sp. FKI-4860 was inoculated into 10 ml of seed medium, which consisted of 2.0% glucose, 0.2% yeast extract, 0.5% Polypepton (Wako Pure Chemical Industries, Osaka, Japan), 0.05% MgSO 4 Á7H 2 O, 0.1% KH 2 PO 4 and 0.1% agar (adjusted to pH 6.0 before sterilization), in a test tube. The inoculated tube was incubated on a rotary shaker (300 r.p.m.) at 27 1C for 3 days.

Cinatrins D and E, and virgaricin B, three novel compounds produced by a fungus, Virgaria boninensis FKI-4958

“…Chemical constituents of the fungus Virgaria have also previously been studied by Ando et al, 1 but only two compounds had been isolated so far, of which one is identified in our previous study. 2 In the present study, chemical reinvestigation of V. boninensis FKI-4958 has resulted in the isolation of three additional new natural products, cinatrins D (1) and E (2), and virgaricin B (3). V. boninensis FKI-4860 strain produced 4 (but not 1, 2 and 3).…”

“…The structures of these known compounds were confirmed by comparison of their spectroscopic data with those reported in the literature. 2,[6][7][8] Details of the fermentation and isolation of the known compounds from the culture broth of FKI-6621 strain are described in the Supplementary Information.…”

“…1 To the best of our knowledge, our previous chemical investigations of the species V. boninensis constituted the second report of its metabolites by the isolation of virgaricin (4) from a culture of the recently discovered V. boninensis FKI-4860. 2,3 In our continuing search for novel microbial metabolites from strains of V. boninensis, we investigated the chemical constituents of a fermentation broth of another strain of V. boninensis FKI-4958. As a result, we isolated and identified two new hydroxycitric acid lactone derivatives, cinatrin D (1) and cinatrin E (2), and a new γ-lactam, virgaricin B (3), together with virgaricin (4), 2 which we have now renamed virgaricin A.…”

“…2,3 In our continuing search for novel microbial metabolites from strains of V. boninensis, we investigated the chemical constituents of a fermentation broth of another strain of V. boninensis FKI-4958. As a result, we isolated and identified two new hydroxycitric acid lactone derivatives, cinatrin D (1) and cinatrin E (2), and a new γ-lactam, virgaricin B (3), together with virgaricin (4), 2 which we have now renamed virgaricin A. The absolute configurations of 1-4 were elucidated using α-methoxy-α-(trifluoromethyl)phenylacetyl (MTPA) ester and phenylglycine methyl ester (PGME) as chiral anisotropic reagents.…”

Combination cellulose plate (non-agar solid support) and agar plate method improves isolation of fungi from soil

“…18,19 We discovered more than 30 novel compounds (including unpublished) from screening using 1500 fungal strains from 2005 to 2010. [20][21][22] The producers of the novel compounds were classified as species level, and 63% of them were new (or potential) species. 10,17,23 In this study, Trichoderma sp.…”