摘要：We previously found that antioxidative activity of liposomes co-encapsulating astaxanthin (Asx) and tocotrienols (T3s) was higher than the calculated additive activity, which results from intermolecular interactions between both antioxidants ( J. Clin. Biochem. Nutr. , 59 , 2016, Kamezaki et al. ). Herein, we conducted experiments to optimize Asx/α-T3 ratio for high antioxidative activity, and tried to elucidate details of intermolecular interaction of Asx with α-T3. Higher activity than calculated additive value was clearly observed at an Asx/α-T3 ratio of 2 : 1, despite two α-T3 would potentially interact with two terminal rings of one Asx. The synthetic Asx used in this study was a mixture of three stereoisomers, 3 R ,3′ R -form (Asx- R ), 3 S ,3′ S -form (Asx- S ) and 3 R ,3′ S - meso form (Asx- meso ). The calculated binding energy of the Asx- S /α-T3 complex was higher than those of Asx- R /α-T3 and Asx- meso /α-T3, suggesting that Asx- S and α-T3 is the most preferable combination for the intermolecular interaction. The optimal Asx- S /α-T3 ratio for antioxidation was shown to be 1 : 2. These results suggest that the Asx stereochemistry affects the intermolecular interaction of Asx/α-T3. Moreover, the absorption spectrum changes of Asx- S upon co-encapsulation with α-T3 in liposomes indicate that the electronic state of Asx- S is affected by intermolecular interactions with α-T3. Further, intermolecular interactions with α-T3 affected the electronic charges on the C9, C10 and C15 atoms in the polyene moiety of Asx- S . In conclusion, the intermolecular interaction of Asx/T3 depends on the Asx stereochemistry, and caused a change in the electronic state of the Asx polyene moiety by the presence of double bond in the T3 triene moiety.
