Phenochalasin B

Phomopsis sp. FT-0211, a soil isolate, was found to produce inhibitors of lipid droplet formation in mouse peritoneal macrophages. Structurally related new compounds designated phenochalasins A and B were isolated from the fermentation broth of the producing strain by solvent extraction, ODS column chromatography and preparative HPLC. Phenochalasin A caused a dose-dependent reduction in the number and size of lipid droplets in macrophages without any cytotoxic effect at least up to 20 microm. On the other hand, phenochalasin B showed inhibition of lipid droplet formation with a severe cytotoxic effect on macrophages.

The structures of phenochalasins A and B were elucidated by spectroscopic studies including various NMR measurements. Phenochalasins A and B have the cytochalasan skeleton of the 21,23-dioxa, 17,22-dione moiety containing unique phenyl and O-methyl phenyl residues at the C-10 position, respectively.

Four compounds, daldinone A (1), daldinone B (2), daldiniapyrone (4-methoxy-5-carbomethoxy-6-pentyl-2H-pyran-2-one, 3), and daldinialanone (22R-hydroxylanosta-7,9(11),24-trien-3-one, 4), were isolated from an ethyl acetate extract of fruit bodies of Daldinia concentrica collected in Europe. In addition, 11 known compounds, 4:5:4':5'-tetrahydroxy-1:1'-binaphthyl (5), 3,4,5-trihydroxy-1-tetralone (6), (+)-orthosporin (7), curuilignan D (8), (22E)-cholesta-4,6,8(14),22-tetraen-3-one (9), 3beta,22-dihydroxylanosta-7,9(11),24-triene (10), concentricol (11), concentricol B (12), concentricol C (13), concentricol D (14), and phenochalasin B (15), were obtained. The structures of the new compounds were elucidated by 2D NMR, MS, IR, and UV spectra and by X-ray crystallographic analysis. The absolute configurations of 1 and 4 were determined by CD spectroscopy and the modified Mosher's method, respectively. The chemotaxonomic relevance of the compounds obtained in this investigation is discussed.