On the hydroperoxyl radical scavenging activity of estrogens in lipid and aqueous media: A theoretical study

Despite the evidence on the antioxidant capability of estrogens, little is known about their reaction mechanism involved. According to the above, this work was carried out on the hydroperoxyl radical scavenging activity of three estrogens—estriol (EST), estradiol (ESD), and estrone (ESO)—in lipid and aqueous media by theoretical methodologies employing the DFT. In lipid and aqueous media, hydrogen transfer was the main reaction mechanism on the hydroperoxyl radical scavenging of EST, ESD, and ESO. The reaction rate constants calculated in lipid media were 1.08 × 10⁶, 8.39 × 10⁴, and 6.43 × 10⁴ M⁻¹ s⁻¹ for the EST, ESD, and ESO, respectively. The reaction rate constants calculated in aqueous media were 3.00 × 10⁶, 3.58 × 10^6, and 1.05 × 10⁸ M⁻¹ s⁻¹ on the hydroperoxyl radical scavenging activity of EST, ESD, and ESO, respectively. The results also showed that the EST, ESD, and ESO estrogens could scavenge high reactivity radicals through the SET mechanism in aqueous media. In lipid media, estrogens are moderate antioxidants, whereas in aqueous media, these are good antioxidants. These theoretical results support the intrinsic antioxidant activity of EST, ESD, and ESO estrogens in lipid and aqueous media.