Monacolins J and L, new inhibitors of cholesterol biosynthesis produced by Monascus ruber.

There is considerable interest in the discovery of hypocholesterolemic drugs whose mode of action is the inhibition of sterol biosynthesis. Culture broths of microorganisms have yielded active compounds that specifically inhibit 3hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase, the rate-limiting enzyme in cholesterol biosynthesis. The first of these to be described was ML-236B (compactin)1). Its isolation from Penicillium citrinum and hypocholesterolemic properties were extensively studied by ENDO and his associates2.3). The clinical efficacy of ML-236B in lowering plasma cholesterol has also been reported2~5). Later, a more potent relative of ML-236B, designated monacolin K (mevinolin), was isolated by ENDO and ALBERTS et a!. from Monascus ruber6,7) and Aspergillus terreus8). Along with these two compounds, several metabolites related to either ML-236B or monacolin K were isolated1,9,10). The present communication describes the isolation, structure and some of the biological properties of two new compounds designated monacolins J and L (Fig. 1). Monascus ruber No. 1005 was grown aerobically in a medium containing glucose 6%, peptone 2.5 %, corn steep liquor (Corn Products Co., U.S.A.) 0.5 %, ammonium chloride 0.5 % at 25°C for 10 days. The culture filtrate (5 liters) was adjusted to pH 3 with HCl and extracted with ethyl acetate (5 liters). The solvent layer was dried over Na2SO4, filtered, and then evaporated to dryness in vacuo. A benzene solution of the oily residue was, after filtration, washed twice with 5 % NaHCO3 (100m]) and then mixed with 100 m] of 0.2 M NaOH. The mixture was stirred at room temperature for 2 hours to hydrolyze the S-lactone ring. The aqueous layer was adjusted to pH 3 with HCI and then extracted twice with ethyl acetate (100 ml). The solvent layers were dried over Na2SO4 and then evaporated to dryness. The resulting oily residue (260 mg) was dissolved in a small volume of benzene; crystals formed were removed by filtration, and purified by chromatography in a silica gel (Wako gel C-200) column (10 g). The column was developed first with 50 ml of dichloromethane, then with 600 ml of dichloromethane ethyl acetate (9: 1) followed by 900 ml of dichloromethane ethyl acetate (8: 2) to elute monacolins L, K and J, respectively. The dichloromethane fraction was evaporated to dryness and applied to a silica gel column (Wako gel C-200, 5 g). The column was washed with 30 ml of n-hexane, then developed with 500 ml of n-hexane acetone (9: 1) to elute monacolin L. The active fraction was evaporated to dryness and dissolved in 10 ml of benzene. The solution was washed twice with 5 ml of 5 % NaHCO3, dried over Na2SO4 and evaporated to dryness, yielding 24 mg (white powder) of monacolin L. The dichlorornethane ethyl acete (8: 2) fraction obtained above was evaporated to dryness, dissolved in 10 m] of benzene and washed twice with 5 ml of 5 % NaHCO3. The benzene soluFig. 1.