Interaction between .ALPHA.-Tocopherol, Tocotrienols and Astaxanthin in Liposomes, Subjected to Lipid Peroxidation

Abstract

Vitamin E is a generic term for a-, b-, g-and d-tocopherols and a-, b-, g-and d-tocotrienols, which have saturated and unsaturated phytyl chains, respectively, and differ in the number and position of the methyl groups on the chroman ring. Studies on vitamin E usually are directed to a-tocopherol, which accounts for 90 % of vitamin E in tissues and is believed to have the greatest biological activity. Nowadays the focus on tocopherols is replaced by that on tocotrienols due to increasing evidence indicating that they have stronger activity than tocopherols. For example, a-tocotrienol, unlike a-tocopherol, shows neuroprotective effects on cells (1). a-, g-and d-tocotrienols, and to a lesser extent d-tocopherol, have potent antiproliferative effects on breast cancer cells (2). Astaxanthin, possessing ketoand hydroxygroups in its terminal rings, shows the highest antioxidant activity among carotenoids (3), and protects against reactive oxygen and nitrogen species, No. 7, 347-352 (2003) Abstract: We studied the cooperative interaction between a-tocopherol, tocotrienols and astaxanthin, incorporated in soybean phosphatidylcholine (PC) multilamellar vesicles (MLV) against 2, 2 -azobis (2-amidinopropane) dihydrochloride (AAPH), 2, 2 -azobis (2, 4-dimethylvaleronitrile) (AMVN), or 1, 3-morpholinosydnonimine hydrochloride (SIN-1) induced lipid peroxidation. Tocotrienols spared a-tocopherol consumption in hydrophilic or lipophylic radicals initiated oxidation. The combination of tocotrienols and astaxanthin had the greatest protective effect on a-tocopherol consumption in MLV, oxidized by the hydrophilic radical initiator. a-Tocopherol and tocotrienols protected astaxanthin against AAPH-, AMVN-, and SIN-1-induced oxidations. In the three oxidations a-tocotrienol was consumed first, followed by a-tocopherol and the tocotrienols in the sequence: b > g > d. Astaxanthin was consumed as fast as g-tocotrienol in AAPH oxidation, as fast as a-tocopherol in AMVN oxidation, and before dtocotrienol in SIN-1 oxidation. In conclusion, a-tocopherol, tocotrienols, and astaxanthin cooperated in protecting against MLV lipid peroxidation. a-Tocotrienol was the most effective antioxidant among them. Astaxanthin was as effective as the chain-breaking antioxidants against lipid peroxidation.

In vitro antioxidant activity of tocopherols and tocotrienols and comparison of vitamin E concentration and lipophilic antioxidant capacity in human plasma

“…The peroxyl radical-scavenging activity detected in our assay depends on the one hand on the degree of methylation and furthermore on the character of the side chain. As observed for a-T and a-T3 by incubation with synthetic peroxyl radical generators (AAPH, AMVN, SIN-1) by Raneva et al [22] the unsaturated vitamin E forms showed a higher activity in our studies, too. The unsaturated ''tail'' of the T3 caused a doubling of the antioxidant activity.…”

“…a-T3 seemed to be several times more active than a-T in lipid peroxidation in membranes [20], because T3 are more mobile within the membrane bilayer and less restricted in interaction with lipid radicals due to their unsaturated side chain [21]. Furthermore, in a system with multi-lamellar vesicles, T3 were more active against the typical synthetic radicals 2,2 0 -azobis-(2-amidinopropane) hydrochloride (AAPH), AMVN, and SIN-1 in the order a>b>g>d [22]. Other articles showed that the relative effectiveness depends on the experimental conditions [14,20,[23][24][25].…”