Tocotrienol rich palm oil extract is more effective than pure tocotrienols at improving endothelium-dependent relaxation in the presence of oxidative stress

Oxidative endothelial dysfunction is a critical initiator of vascular disease. Vitamin E is an effective antioxidant but attempts to use it to treat vascular disorders have been disappointing. This study investigated whether tocotrienols, the less abundant components of vitamin E compared to tocopherols, might be more effective at preserving endothelial function. Superoxide generated by hypoxanthine/xanthine oxidase or rat aorta was measured using lucigenin-enhanced chemiluminescence. The effect of alpha-tocopherol, alpha-, delta-, and gamma-tocotrienols and a tocotrienol rich palm oil extract (tocomin) on levels of superoxide was assessed. Endothelial function in rat aorta was assessed in the presence of the auto-oxidant pyrogallol. Whilst all of the compounds displayed antioxidant activity, the tocotrienols were more effective when superoxide was produced by hypoxanthine/xanthine oxidase whereas tocomin and alpha-tocopherol were more effective in the isolated aorta. Tocomin and alpha-tocopherol restored endothelial function in the presence of oxidant stress but alpha-, delta-, and gamma-tocotrienols were ineffective. The protective effect of tocomin was replicated when the tocotrienols were present with, but not without, alpha-tocopherol. Tocotrienol rich tocomin is more effective than alpha-tocopherol at reducing oxidative stress and restoring endothelium-dependent relaxation in rat aortae and although alpha-, delta-, and gamma-tocotrienols effectively scavenged superoxide, they did not improve endothelial function.