Purpactin B

Penicillium purpurogenum FO-608, a soil isolate, was found to produce a series of new inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). Three active compounds, designated purpactins, A, B and C, were isolated from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography and HPLC. Purpactins inhibit ACAT activity in an enzyme assay system using rat liver microsomes with IC50 values of 121 approximately 126 microM. Purpactin A also inhibited cholesterol ester formation in J 774 macrophages, indicating the inhibition of ACAT activity in the living cells by purpactin A.

The structure of purpactins, novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors, was determined by spectroscopic analyses. Purpactin A was deduced to be 3-1'-acetoxy-11-hydroxy-4-methoxy-9-methyl-3'-methylbutyl-5H, 7H-dibenzo[b,g]-1,5-dioxocin-5-one, purpactin B was 5-1''-acetoxy-6'-hydroxymethyl-4-methoxy-4'-methyl-3''-methylbutyl-spiro [benzofuran-2,1'-cyclohexa-3',5'-diene]-2',3(2H)-dione and purpactin C was 5-1''-acetoxy-6'-formyl-4-methoxy-4'-methyl-3''-methylbutyl-spiro [benzofuran-2,1'-cyclohexa-3',5'-diene]-2',3(2H)-dione. Purpactin A was attributed to 1'-O-acetylpenicillide.