Dose-Dependent Cholesterolemic Activity of Tocotrienols and α-Tocopherol

Tocotrienols and tocopherols are isoforms of vitamin E. Vitamin E may exhibit antioxidant, prooxidant and non-antioxidant activities depending upon circumstances. In this study, the effect of tocotrienols and α-tocopherol on the activities of HMG CoA reductase and cholesterol 7 α-hydroxylase was investigated. Pure tocotrienols were isolated from palm fatty acid distillate and pure α-tocopherol was obtained commercially. Guinea pigs were treated with different dosages of tocotrienols and α-tocopherol. After the treatment period, animals were sacrificed and liver microsomes were prepared. HMG CoA reductase and cholesterol 7α-hydroxylase were assayed using tracer techniques. Our results showed that the effects of tocotrienols and α-tocopherol on the activities of both the enzymes were dose-dependent. At low dosages, both tocotrienols and α-tocopherol exhibited an inhibitory effect on both the enzymes. Moreover, tocotrienols were a much stronger inhibitors than α-tocopherol. At high dosages, on the other hand, tocotrienols and α-tocopherol showed opposite effects on the enzymes. While tocotrienols continued to exhibit an inhibitory effect, α-tocopherol actually exhibited a stimulatory effect on both the enzymes. A possible explanation for this observation is suggested

The Digestion, Absorption and Utilization of Refined Palm Oil, Palm Olein and Palm Stearin in the Rat

A nutritional evaluation of refined, bleached and deodorised (RBD) palm oil and its fractionation products, RBD palm olein and RBD palm stearin in terms of their digestibility, rate of absorption and food efficiency in rats, shows that RBD palm olein is a better oil by these criteria than RBD palm stearin and the unfractionated RBD palm oil. Nevertheless, the nutritional indices reported for RBD palm oil and RBD palm stearin are well within the range reported for most cooking oils and fats. The digestibility and food efficiency of RBD palm olein are comparable to that of soybean oil, being 97% and 98% respectively of the values found for the latter oil, although the absorption rate of RED palm olein is 10% less than that obtained for soybean oil