Efficient radical trapping at the surface and inside the phospholipid membrane is responsible for highly potent antiperoxidative activity of the carotenoid astaxanthin

Abstract

The effects of the carotenoids beta-carotene and astaxanthin on the peroxidation of liposomes induced by ADP and Fe(2+) were examined. Both compounds inhibited production of lipid peroxides, astaxanthin being about 2-fold more effective than beta-carotene. The difference in the modes of destruction of the conjugated polyene chain between beta-carotene and astaxanthin suggested that the conjugated polyene moiety and terminal ring moieties of the more potent astaxanthin trapped radicals in the membrane and both at the membrane surface and in the membrane, respectively, whereas only the conjugated polyene chain of beta-carotene was responsible for radical trapping near the membrane surface and in the interior of the membrane. The efficient antioxidant activity of astaxanthin is suggested to be due to the unique structure of the terminal ring moiety.

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

“…a-Tocopherol and tocotrienols scavenge radicals by donating hydrogen atoms to lipid peroxyl radicals to form lipid hydroperoxides and tocopherol-or tocotrienol-derived radicals. Astaxanthin scavenges radicals by two mechanisms: by donating the hydrogen atom by its terminal ring, acting as a chain-breaking antioxidant (3,14), and by adding radicals to the double bond of the polyene chain to form a conjugated polyene, carbon-centered radical (15). The a-tocopherol and tocotrienols are located near or at the membrane surface (16).…”

“…The a-tocopherol and tocotrienols are located near or at the membrane surface (16). The polar terminal ring of astaxanthin is oriented to or at the lipid/water interface, and the polyene chain in the interior of the membrane (14). In AAPH oxidation, where the oxidizing radicals attack the membranes from the aqueous phase, a-tocopherol, tocotrienols and astaxanthin cooperate to scavenge the hydrophilic radicals.…”

Scavenging of Hydroxyl Radicals in Aqueous Solution by Astaxanthin Encapsulated in Liposomes

“…1,2) Asx has been reported to be more effective than a representative carotenoid, β-carotene, for prevention of singlet oxygen, as well as lipid peroxidation in biological membranes. [3][4][5][6][7] The direct radical scavenging capability of Asx has been confirmed using the synthetic radical 1,1-diphenyl-2-picrylhydrazyl. 8) Previously, we suggested that the potent antioxidation activity of astaxanthin in biomembranes could be attributable to the conjugated polyene and terminal ring moieties of Asx that trap radicals on the membrane surface and within the membrane, respectively.…”

“…8) Previously, we suggested that the potent antioxidation activity of astaxanthin in biomembranes could be attributable to the conjugated polyene and terminal ring moieties of Asx that trap radicals on the membrane surface and within the membrane, respectively. 6) Moreover, it has been reported that some Asx derivatives could scavenge superoxide anion radical. 9,10) Highly active reactive oxygen species (ROS), such as superoxide anion radical and hydroxyl radical, have been considered causative agents of severe diseases, such as arteriosclerosis and ischemic reperfusion injury.…”

“…Previously, we suggested that Asx penetrates through the membrane of liposomes, and the terminal rings of Asx interact with polar head groups of membrane lipids by hydrogen bonding. 6) With the terminal ring moieties of Asx located at the membrane surface, they would be available to react with exogenous free radicals in the aqueous phase.…”