Abstract
Natural antioxidants may help prevent oxidative stress-mediated aging. Astaxanthin (Asx) is a powerful antioxidant that has been used in various dietary supplements and cosmetics. Previously, we reported that combination of Asx with tocotrienol (T3) or capsaicin (Cap) exhibited synergistic antioxidative effects; however, the synergistic increase in activity was unremarkable. Herein, we employed curcumin (Cur) to more effectively enhance the antioxidant activity of Asx. The antioxidative activity of liposomes co-encapsulating Asx and Cur (Asx/Cur-lipo) showed effective synergism (activity increase of ~2). A shift in peak absorption suggested intermolecular interactions between Asx and Cur. Since synthetic Asx is a mixture of various stereoisomers, we examined the effect of Asx stereochemistry on the effective synergism by investigating liposomes prepared with 3R,3'R-form (Asx-R), and 3S,3'S-form (Asx-S). Antioxidative activities of Asx-R/Cur-lipo and Asx-S/Cur-lipo were evaluated. Only Asx-S/Cur-lipo exhibited a synergistic effect; however, the activity increase of Asx-S/Cur-lipo was lower than that of Asx/Cur-lipo. In conclusion, liposomes co-encapsulating a synthetic mixture of stereochemical isomers of Asx and Cur may be most potent in preventing oxidative stress-mediated aging.