HPLC Separation of Vitamin E and Its Oxidation Products and Effects of Oxidized Tocotrienols on the Viability of MCF-7 Breast Cancer Cells in Vitro

摘要

Tocotrienols, a vitamin E subgroup, exert potent anticancer effects, but easily degrade due to oxidation. Eight vitamin E reference compounds, alpha-, beta-, gamma-, or delta-tocopherols or -tocotrienols, were thermally oxidized in n-hexane. The corresponding predominantly dimeric oxidation products were separated from the parent compounds by diol-modified normal-phase HPLC-UV and characterized by mass spectroscopy. The composition of test compounds, that is, alpha-tocotrienol, gamma-tocotrienol, or palm tocotrienol-rich fraction (TRF), before and after thermal oxidation was determined by HPLC-DAD, and MCF-7 cells were treated with both nonoxidized and oxidized test compounds for 72 h. Whereas all nonoxidized test compounds (0-100 mu M) led to dose-dependent decreases in cell viability, equimolar oxidized alpha-tocotrienol had a weaker effect, and oxidized TRF had no such effect. However, the IC50 value of oxidized gamma-tocotrienol was lower (85 mu M) than that of nonoxidized gamma-tocotrienol (134 mu M), thereby suggesting that gamma-tocotrienol oxidation products are able to reduce tumor cell viability in vitro.