Three New Isochromans from the Mycelial Culture of a Cylindrocarpon Fungus

Abstract

Three new isochroman derivatives, 1-acetonyl-7-carboxyl-6,8-dihydroxy-3,4,5-trimethylisochroman (1), 7-carboxyl-6,8-dihydroxy-1,1,3,4,5-pentamethylisochroman (2), and 6,8-dihydroxy-3,4,5-trimethylisochroman (3), together with decarboxydihydrocitrinone (4), were isolated from mycelial solid culture of a Cylindrocarpon fungus.Their structures were established by spectroscopic methods.In the course of our continual search for antibacterial and antifungal natural products produced by filamentous fungi collected in South China, we found that the EtOH extract from mycelial solid culture of an Ascomycetes, Cylindrocarpon sp.SC0537, showed potent antibacterial activity against Staphylococcus aureus and antifungal activity against Peronophythora litchii, one of the main pathogens causing litchi (Litchi chinensis Sonn.) fruit rot.We therefore investigated the secondary metabolites of this fungus, and obtained three new isochroman derivatives (1 3) along with a known isochroman, decarboxydihydrocitrinone (4). 1 We herein report the isolation and structure elucidation of these new compounds.The mycelia of the fungus, Cylindrocarpon sp.SC0537, were grown on solid culture for 15 days at 28°C in the dark.The EtOH extract of the mycelial culture was sequentially fractionated with petroleum ether, CHCl 3 and EtOAc.The CHCl 3 -soluble fraction was separated by SiO 2 and Sephadex LH-20 column chromatography to afford the compounds (1-4).