Biological evaluation of a siliconized analog of clofibrate [silafibrate] in rodents

Silicon is the element very similar to carbon, and bioactive siliconized compounds have therefore received much attention. Siliconization of a compound enhances its biological activities. In the present study the hypolipidemic effect and toxicity of clofibrate and its siliconized analog, silafibrate, were compared. The experiments were performed in hypercholesterolemic Wistar rats. Animals received high fat diet with 62.75% normal chow, 2% cholesterol, 0.25% cholic acid, 15% lard oil, 10% wheat flour and 10% sucrose. Silafibrate[40 mg/kg/day] produced a predominant reduction in the serum levels of total cholesterol [28.4%, p < 0.001], triglycerides [62%, p < 0.0001] and low-density lipoproteins [27%, p < 0.001] being more effective than the reference drug clofibrate [20%, 40%, 14.5%; p < 0.05]. Similarly, it increased the total antioxidant levels in serum by 40% [p < 0.05]. Simultaneously, treatment with silafibrate also reduced the malondialdehyde [MDA] concentration by 41% [p < 0.05]. LD[50] of silafibrate, given orally, was greater than 2000 mg/kg body weight in albino mice while LD[50] for clofibrate was calculated to be 1220 mg/kg. Thirty-day subacute toxicity was also evaluated with oral daily dose at 25, 50 and 100 mg/kg body weight in Wistar rats. No significant changes in body weight, food intake, behavior, mortality, hematology, blood biochemistry, vital organ weight were detected. The results of this study indicate that the effectiveness and safety of the hypolipidemic drug, clofibrate, were enhanced remarkably by replacing chlorine atom in its phenoxy ring with trimethylsilyl

Synthesis of a novel siliconized analog of clofibrate [silafibrate] and comparison of their anti-inflammatory activities

Fibrates, as hypolipidemic drugs known as agonists of peroxisome proliferator-activated receptors, diminish inflammatory responses. Studies have shown that incorporation of a silicon atom into a drug structure improves its pharmacological potency, modifies its selectivity toward a given target, or changes its metabolic rate, in addition to increasing the lipophilicity of the compounds. A siliconized analog of clofibrate, ethyl-2-methyl-2-[4-[trimethylsilyl]phenoxy]propionate was synthesized, whereby the chlorine atom in the phenoxy ring was replaced by a trimethylsilyl group. The anti-inflammatory effects of the siliconized analog [silafibrate] were evaluated in an air-pouch model of inflammation and compared with those of clofibrate. Oral administration of both drugs produced a significant anti-inflammatory action by reducing carrageenan induced pouch leukocyte recruitment, exudates production, and granulated tissue weight. The silicon isostere of clofibrate has improved anti-inflammatory properties