Tocotrienol Rich Palm Oil Extract Is More Effective Than Pure Tocotrienols at Improving Endothelium-Dependent Relaxation in the Presence of Oxidative Stress

Abstract

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 ofα-tocopherol,α-,δ-, andγ-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 andα-tocopherol were more effective in the isolated aorta. Tocomin andα-tocopherol restored endothelial function in the presence of oxidant stress butα-,δ-, andγ-tocotrienols were ineffective. The protective effect of tocomin was replicated when the tocotrienols were present with, but not without,α-tocopherol. Tocotrienol rich tocomin is more effective thanα-tocopherol at reducing oxidative stress and restoring endothelium-dependent relaxation in rat aortae and althoughα-,δ-, andγ-tocotrienols effectively scavenged superoxide, they did not improve endothelial function.