Palm-tocotrienol rich fraction (TRF) is a more effective inhibitor of LDL oxidation and endothelial cell lipid peroxidation than α-tocopherol in vitro

• Published in: Food research international 2003, Vol.36 (5), p.405-413
• Main Authors: Mutalib, Mohd Sokhini Abdul, Khaza'ai, Huzwah, Wahle, Klaus W.J.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; General pharmacology; Medical sciences; Oxidised LDL; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; TBARS; Tocotrienol rich fraction; α-Tocopherol
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/S0963-9969(02)00173-4

Comparative protective effects of palm tocotrienol rich fractions (TRF) and α-tocopherol on the copper-induced oxidation of plasma low density lipoprotein (LDL) and indices of lipid peroxidation in human umbilical vein endothelial cells (HUVEC) were investigated. LDL (100 μg protein/ml) was incubated at 37 °C with 1 μM CuSO 4 with or without the presence of 50 μM (TRF) or 50 μM α-tocopherol. Aliquots were collected at 0,1,2,3,6,9,12 and 24 h and thiobarbituric acid reactive substances (TBARS) determined. In the absence of antioxidant, TBARS increased significantly in LDL reaching a maximum after 6 h. α-Tocopherol and TRF delayed TBARs formation by 6 h with a maximum effect after 12 h. The rate of TBARs formation with TRF was significantly slower than with α-tocopherol, indicating a higher antioxidant efficacy for TRF. Low density lipoprotein isolated from volunteers consuming low or high polyunsaturated fatty acid (PUFA) diets were similarly incubated with 1 μM CuSO 4 with or without 50 μM TRF or 50 μM α-tocopherol. LDL oxidation was not significantly different between low and high PUFA groups. However, LDL treated with TRF was better protected against copper-induced oxidation than that treated with α-tocopherol. In HUVEC pre-incubated with 100 μM arachidonic acid, 25 μM TRF treatment decreased TBARS by ∼73% compared to ∼50% with 25 μM of α-tocopherol. Higher concentrations of TRF did not further decrease TBARS formation in the medium. However, treatment with higher concentrations of α-tocopherol again increased TBARS formation. Formation of conjugated diene in HUVEC subjected to arachidonic acid (ARA)-induced oxidative stress was decreased equally with either 10 μM TRF or 25 μM α-tocopherol. Results suggest that TRF is a more potent antioxidant than α-tocopherol, at least in vitro.