Two oxazolyl compounds and a monosubstituted alpha-pyrone as free-radical scavengers isolated from a fungus

In the course of our screening for free radical scavengers, (1'E)-erythro-4-(3',4'-dihydroxypentenyl)oxazole (1) (1'E,4'S)-4-(3'-oxo-4'-hydroxypentenyl)oxazole (2) and 6-pentyl-alpha-pyrone (3) were isolated from an unidentified fungal metabolite. These compounds, especially novel oxazolyl compound 2, inhibited the bactericidal effect of the Fenton reagent toward Bacillus subtilis. They and their acetylated compounds (diAc-1 and Ac-2) also showed inhibitory activity against linoleate autoxidation. Furthermore, 1-3 inhibited oxidative enzymes (soybean lipoxygenase and mushroom tyrosinase). To investigate the radical scavenging mechanism of 3, two oxidized products (4 and 5) were isolated from the reaction mixture of 3 and the Fenton reagent. Compounds 4 and 5 seemed to be derived from 3 by scavenging the hydroxyl radical.