Inhibitors of blood platelet aggregation. Effects of some 1,2-benzisothiazol-3-ones on platelet responsiveness to adenosine diphosphate and collagen.

A series of substituted 1,2-benzisothiazol-3-ones was synthesized, and the compounds were tested for ability to inhibit platelet aggregation induced by adenosine diphosphate and collagen in rats and guinea pigs ex vivo. Alkyl substituents at the 2-position bearing a basic group were necessary for ex vivo activity. Several of the compounds were potent inhibitors of adenosine diphosphate induced first-phase aggregation, but adverse toxicological findings terminated their further development. Preliminary studies suggested that inhibition of aggregation was not attributable to inhibition of prostanoid synthesis or to raised levels of cyclic 3',5'-adenosine monophosphate.

Xenobiotic cholesteryl ester formation.

1. When the novel hypolipidaemic compound 1-(4-carboxyphenoxy)-10-(4-chlorophenoxy) decane (CCD) was administered orally (250 mg/kg body weight for seven days) to rats, a lipophilic cholesterol-containing metabolite accumulated in the liver. 2. Analysis by n.m.r. spectroscopy and mass spectrometry identified the metabolite as the cholesterol conjugate of CCD. This structure was confirmed by comparison with reference material synthesized in our laboratories. 3. The xenobiotic cholesteryl ester was not further metabolized and, unlike the natural counterparts, was not transported by lipoproteins. 4. When added in vitro, the xenobiotic cholesteryl ester appeared to enhance the activity of hepatic lysosomal cholesteryl ester hydrolase and thus may contribute to the hypocholesterolaemic activity of CCD.

The participation of ethyl 4-benzyloxybenzoate (BRL 10894) and other aryl-substituted acids in glycerolipid metabolism.

Investigation into the mechanism of action of BRL 10894 (ethyl 4-benzyloxybenzoate), a compound possessing hypolipidemic activity in the rat, disclosed participation in glycerolipid metabolism. In the presence of BRL 10894, an abnormal metabolite was synthesized in vitro using liver slices or rings of small intestine with glycerol, palmitate, or monoolein as substrate, and using adipose tissue with pyruvate as substrate. Esters related chemically to BRL 10894 and other pharmacologically active acids (e.g., ibuprofen) also produced abnormal metabolites in vitro. With BRL 10894 in the diet, a similar metabolite was produced in vivo in rats and accumulated in adipose tissue. Chemical characterization of the material synthesized in vivo showed that the metabolite was a triglyceride in which one fatty acid moiety was substituted by the acid of BRL 10894. Additional proof of this structure was obtained by comparison with reference material synthesized in our laboratories. The study of the initimate involvement of exogenous acids in glycerolipid turnover is of value in the characterization of pharmacologically important acids and may be of use in achieving a greater understanding of certain aspects of lipid metabolism.

Hypolipidemic analogues of ethyl 4-benzyloxybenzoate.

A series of compounds related to ethyl 4-benzyloxybenzoate was synthesized and evaluated for potential hypolipidemic activity in rats. Structure--activity relationships are discussed in terms of cholesterol-lowering activity together with effects on weight gain and liver lipids. A number of the compounds inhibited cholesterol and free fatty acid biosynthesis from [1-14C]acetate in rat liver slices in vitro. Ethyl 4-benzyloxybenzoate, ethyl-4-benzyloxybenzoic acid, ethyl 4-p-bromobenzyloxybenzoates, and 4-o-methoxybenzyloxyphenyl acetate exhibited the most favorable spectrum of activity.

Tetronic 701-a novel hypocholesterolaemic agent.

The Tetronic series of polymeric surface-active agents were screened for hypocholesterolaemic activity in rats fed on a semi-synthetic hypercholesterolaemic diet. Only Tetronics 701 and 702 were active and the former was further investigated. Tetronic 701 lowered serum and liver cholesterol in rats fed on a semi-synthetic diet, with or without cholesterol, but not in rats fed on stock laboratory diet. A dose-related growth depression was observed. The compound was hypocholesterolaemic in chicks and rabbits fed on cholesterol-containing diets. The uptake of a single dose of cholesterol into liver and serum was inhibited in rats given Tetronic 701. Tetronics 701 and 702 were effective in precipitating cholesterol from mixed micelles in vitro. Non-hypocholesterolaemic Tetronics were inactive in this respect. A series of tetraesters of tetronic 701 were prepared and tested in rats fed on a semi-synthetic hypercholesterolaemic diet. Several were hypocholesterolaemic and the tetrabenzoate was of especial interest in that it depressed growth less than did Tetronic 701 itself.

Hypolipidemic imidazoles.

A series of analogs of N-benzylimidazole was prepared and tested for hypolipidemic activity. Both plasma cholesterol and triglyceride-lowering activity were found in several members of the series. The most active compounds were N-3-methoxy-, N-4-methoxy-, and N-4-methylbenzylimidazole. Structure-activity relationships are discussed.

The isolation of 2,3-oxidosqualene from the liver of rats treated with 1-dodecylimidazole, a novel hypocholesterolaemic agent.

1. Non-saponifiable lipid from the livers of rats treated with 1-dodecylimidazole contained an unidentified compound that was not present in the livers from untreated animals. 2. Treated rats had lower serum cholesterol concentrations than control rats. 3. 1-Dodecylimidazole, when added to rat liver slices, inhibited the incorporation of [1-(14)C]acetate and [2-(14)C]mevalonate into digitonin-precipitable sterols and resulted in the accumulation of a labelled compound, which was chromatographically identical with the unknown compound described in 1 above. 4. Rats treated with 1-dodecylimidazole incorporated less [(14)C]mevalonate into liver digitonin-precipitable sterols than untreated animals and accumulated the unknown compound as a labelled intermediate. 5. The unknown intermediate had the same chromatographic properties, n.m.r. and mass spectra as authentic 2,3-oxidosqualene. 6. The identity of the intermediate as 2,3-oxidosqualene was further established by showing that it was incorporated into sterols by rat liver homogenates under anaerobic conditions. In addition, incubation of [(14)C]squalene with rat liver homogenates resulted in trapping of the radioactivity by the added intermediate. 7. It is suggested that the hypocholesterolaemic activity of 1-dodecylimidazole results in part from the inhibition of cholesterol biosynthesis at the level of 2,3-oxidosqualene sterol cyclase.