Comparative efficacy of oligonol, catechin and (-)-epigallocatechin 3-O-gallate in modulating the potassium bromate-induced renal toxicity in rats

Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen. Oligonol is a product emanating from the oligomerization of polyphenols, typically proanthocyanidin from a variety of fruits (grapes, apples, persimmons, etc.) and contains catechin-type monomers and proanthocyanidin oligomers. In this study, the ability of oligonol derived from grape seeds, grape seeds extracts (Product A, containing biologically active flavonoids and the oligomeric proanthocyanidin) and pine bark extracts (Product B, composed of flavan-3-ol derivatives) to modulate the KBrO(3)-induced renal toxicity was compared with (+) catechin and (-)-epigallocatechin 3-O-gallate (EGCG). In the Trolox equivalent antioxidant capacity (TEAC) assay, the order of the antioxidant activity was EGCG>catechin>oligonol>Product A>Product B. However, oligonol elicits the strongest antioxidant capacity following in vivo supplementation to rats, with the order of efficacy of oligonol>Product A> or =Product B>EGCG>catechin. Blood levels of lipid peroxidation products (LPO), urea nitrogen (BUN) and creatinine were elevated by KBrO(3) treatment. Oligonol significantly restored LPO to the level in the untreated rats and had the strongest potency when compared with the effects of Products A and B. The five materials lowered KBrO(3)-induced BUN level, but this was not statistically significant. Oligonol significantly reduced the increased level of the creatinine, seconded by Product A, Product B and EGCG. Catechin had the lowest effect in both the BUN and creatinine levels. That oligonol was able to modulate KBrO(3)-induced lipid peroxidation and the levels of blood urea nitrogen and creatinine suggests potential chemopreventive function and application in mitigating toxicity due to long-term exposure to KBrO(3) in public drinking water.