Biphasic Effect of Curcuminoids on Oxidation of Postprandial Chylomicrons

Chylomicrons are large, triglyceride-rich lipoproteins that transport dietary lipids and lipophilic micronutrients through the lymphatic system and into the venous circulation. They therefore represent a valuable means of investigating the bioavailability of a range of bioactive molecules. Curcuminoids have a complex reputation, with most in vitro studies suggesting a beneficial effect (e.g., as an antioxidant), while in vivo work is often, at best, equivocal. We have prepared a curcuminoid extract from fresh turmeric and investigated the transfer of curcuminoids to chylomicrons by rapid ultracentrifugation. We subsequently characterized the chylomicrons in terms of their susceptibility to oxidation. There was a dose-dependent relationship between the curcuminoid level in chylomicrons and decreased levels of preformed lipid hydroperoxides (P < .05), which was broadly mirrored by paraoxonase arylesterase activity. At lower dosages (1000-3000 mg), curcuminoids protected chylomicrons against copper(II)-mediated oxidation, but at higher levels (4000-5000 mg), a pro-oxidant effect was observed. In conclusion, we report a clear biphasic (hormetic) effect of curcuminoids on lipid oxidation, which supports the theory that low dosages of bioactive compounds can have beneficial effects, while higher dosages may have an equivocal or negative impact on the disease.