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Similar Hypolipidemic And Antioxidant Properties Of - And -tocotrienols Isolated From Different Rice Cultivars In Experimentally Induced Hyperlipidemic Rats

Jahangir Iqbal, Mohammad Minhajuddin, Zafarul H. Beg

Hypolipidemic and antioxidant properties of tocotrienol rich fraction (TRF), especially g- and d-tocotrienols, isolated from different rice cultivars have not been studied, to our knowledge. The aim of the current study was to evaluate hypolipidemic and antioxidant effects of g- and d-tocotrienols, isolated from different cultivars of rice bran, in experimentally induced hyperlipidemic rats. Hyperlipidemia was induced by feeding of atherogenic diet (5% hydrogenated fat, 0.5% cholic acid and 1% cholesterol) for three weeks. At the end of three weeks, four rats each in normal and hyperlipidemic group were sacrificed to determine time zero levels of various parameters. There was around 3 fold increase in plasma triglyceride levels in hyperlipidemic rats compared to normal control. The level of plasma total cholesterol increased by 2.5 fold and this was mainly because of a 5 fold increase in the level of LDL cholesterol with only a small increase in HDL cholesterol. There was more than 75% reduction in the activity of HMG-CoA reductase in the hyperlipidemic animals, probably due to feed back inhibition. The formation of thiobarbituric acid reactive substances (TBARS) increased by 72% and conjugated dienes increased by 92%. After the induction of hyperlipidemia for three weeks, rats were supplemented with 2.83 mg, 8.23 mg and 3.02 mg of purified TRF isolated from basmati (long grain), mansuri (medium grain), or sarju-52 (short grain), respectively, for one week. The dose of TRF was calculated based on 8 mg equivalent concentration of g- and d-tocotrienols present in refined grade rice bran oil (RBO). TRF supplementation from different rice cultivars equally decreased the lipid parameters in the hyperlipidemic rats. HMG-CoA reductase activity, which was increased after the withdrawal of atherogenic diet, remained significantly decreased during the TRF treatment in all the treatment groups. TRF from different cultivars decreased the levels of TBARS and conjugated dienes significantly. These results suggest that g- and d-tocotrienols in the TRF isolated from different rice cultivars equally modulated various physiological functions including atherogenic lipid profiles and antioxidants in hypercholesterolemia.