Sliwka Hans-Richard, Melø Thor-Bernt, Foss Bente Jeanette, Abdel-Hafez Shams H, Partali Vassilia, Nadolski Geoff, Jackson Henry, Lockwood Samuel F
Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
Chemistry. 2007;13(16):4458-66. doi: 10.1002/chem.200601527.
The antioxidant activities-expressed as the electron-donating properties-of five hydrophilic carotenoids (carotenoid surfactants) and three related hydrophobic carotenoids were investigated by flash photolysis. The electron-transfer rates of the carotenoids to the triplet state of the sensitizer 2-nitronaphthalene and the energy transfer rates of triplet 2-nitronaphthalene to the carotenoids were determined. The results demonstrate that the electron-donating effects of the hydrophilic and hydrophobic carotenoids were comparable when evaluated in acetonitrile. In the presence of water, however, electron transfer (i.e., antioxidant efficiency) was enhanced by a factor of four for the hydrophilic carotenoids. The increased hydrophilicity of carotenoids, therefore, could expand their antioxidant properties, thus facilitating their use as aqueous-phase radical scavengers. At the same time, it was shown that supramolecular assembly ("aggregation") of the amphiphilic carotenoids prevented electron transfer, thus deactivating the antioxidant function. Modulation of the biophysical properties of carotenoids through synthetic modification is capable of increasing the biological and medical utility of this natural class of predominantly hydrophobic antioxidant compound.
通过闪光光解研究了五种亲水性类胡萝卜素（类胡萝卜素表面活性剂）和三种相关疏水性类胡萝卜素的抗氧化活性（以给电子性质表示）。测定了类胡萝卜素向敏化剂2-硝基萘三重态的电子转移速率以及三重态2-硝基萘向类胡萝卜素的能量转移速率。结果表明，在乙腈中评估时，亲水性和疏水性类胡萝卜素的给电子效应相当。然而，在有水存在的情况下，亲水性类胡萝卜素的电子转移（即抗氧化效率）提高了四倍。因此，类胡萝卜素亲水性的增加可以扩展其抗氧化性能，从而便于其用作水相自由基清除剂。同时，研究表明两亲性类胡萝卜素的超分子组装（“聚集”）会阻止电子转移，从而使抗氧化功能失活。通过合成修饰调节类胡萝卜素的生物物理性质能够提高这类天然的主要为疏水性抗氧化化合物的生物学和医学效用。
