Zaragozic acids: a family of fungal metabolites that are picomolar competitive inhibitors of squalene synthase.

Abstract

Three closely related fungal metabolites, The mammalian isoprenoid pathway not only produces sterols but also produces dolichol, ubiquinone, the farnesyl group of heme A, the farnesyl and geranylgeranyl groups of prenylated proteins, and the isopentenyl side chain of isopentenyl adenine. The pathways for the synthesis of these other isoprenoids diverge from the synthesis ofcholesterol either at or before the farnesyl diphosphate (FPP) branch point. Thus, squalene synthase, which catalyzes the reductive dimerization of 2 mol of FPP to 1 mol of squalene (2, 3), is the first committed step in sterol synthesis. A specific inhibitor of squalene synthase should serve to inhibit cholesterol synthesis and not adversely affect the synthesis of other isoprenoids. FPP, the substrate for squalene synthase, is water soluble and may be readily metabolized (4). Thus, squalene synthase offers a potential target for the safe and specific inhibition of cholesterol synthesis.In this report we describe the isolation, structure, physical characterization, and biological properties of three structurally similar fungal metabolites that are potent inhibitors of squalene synthase. These metabolites, zaragozic acid A (5-7), zaragozic acid B (8, 9), and zaragozic acid C (10-12), had been reported previously only in the patent literature; however, during the review process of this manuscript, three manuscripts (13-15) appeared on the squalestatins: squalestatin I is identical with zaragozic acid A, squalestatin II is des-4'-acetylzaragozic acid A, and squalestatin III is des-6-acylzaragozic acid A. This class of squalene synthase inhibitors has potential utility as cholesterol-lowering agents. MATERIALS AND METHODSZaragozic Acid A, Cultures, and Media. An unidentified sterile fungal culture, ATCC 20986, isolated from a water sample taken from the Jalon river in Zaragoza, Spain (hence the name zaragozic acids), was used to produce zaragozic acid A. The culture was maintained at 25°C on medium B agar slants composed of 4 g of yeast extract, 10 g of malt extract, 4 g of dextrose, and 20 g of agar per liter at pH 7.0.Zaragozic acid A was produced in a two-tiered fermentation process consisting of mycelial growth and development in medium A of ref. 1 and product formation in medium C. Medium C contained 5 g of malt extract, 1 g of peptone, 15 g of dextrose, 1 g of KH2PO4, and 0.5 g of MgSO4 7H20 per liter. Fermentations consisted of mycelial growth in medium A for 72 hr at 250C with agitation, followed by inoculation (5-10%) of medium C. Maximum product was obtained from 14-day agitated fermentations at 250C.Isolation of Zaragozic Acid A. To isolate zaragozic acid A, 23 liters of harvested broth was filtered through Celite, and the mycelial cake was extracted twice with 7 liters of 50%o aqueous methanol. The filtrate was combined with the extracts, diluted with water to a final composition of 25% methanol, and adsorbed on a 1.5-liter column of Mitsubishi HP-20 resin. After a column wash with 6 liters of4:6 (vol/vol) methanol/water, crud...

Search Method for Inhibitors of Staphyloxanthin Production by Methicillin-Resistant Staphylococcus aureus

“…From the natural product library (about 300 compounds), four compounds, cerulenin, 10) dihydrobisvertinol, 11) xanthohumol 13) and zaragozic acid, 15) were selected ( Table 3). All of these compounds have been reported as inhibitors of lipid metabolism; [10][11][12][13][14][15] however, among inhibitors of lipid metabolism, lovastatin and triclosan had no effect on yellow pigment production.…”

“…9) Based on this new concept, we established convenient assay systems to observe staphyloxanthin production by MRSA and started to search for inhibitors of staphyloxanthin production from natural sources. During this screening program, cerulenin (an inhibitor of fatty acid synthase), 10) dihydrobisvertinol, 11,12) xanthohumol (an inhibitor of diacylglycerol acyltransferase) 13,14) and zaragozic acid (an inhibitor of squalene synthase) 15) (Fig. 1), which are known as inhibitors of lipid metabolism, were selected from our natural product library.…”

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Brain-Derived Neurotrophic Factor Regulates Cholesterol Metabolism for Synapse Development

“…4 A, SQS) (Bergstrom et al, 1993), on the BDNF-induced increase in cholesterol. Treatment with zaragozic acid (100 M; 3 d) completely blocked the BDNF effect (Fig.…”