A Comprehensive Study of the Radical Scavenging Activity of Rosmarinic Acid.

Rosmarinic acid ( RA ) is reported in separate studies to be either an inducer or reliever of oxidative stress, and this contradiction has not been resolved. In this study, we present a comprehensive examination of the radical scavenging activity of RA using density functional theory calculations in comparison with experimental data. In model physiological media, RA exhibited strong HO • radical scavenging activity with overall rate constant values of 2.89 × 10 10 and 3.86 × 10 9 M -1 s -1 . RA is anticipated to exhibit excellent scavenging properties for HOO • in an aqueous environment ( k overall = 3.18 × 10 8 M -1 s -1 , ≈2446 times of Trolox) following the hydrogen transfer and single electron transfer pathways of the dianion state. The neutral form of the activity is equally noteworthy in a lipid environment ( k overall = 3.16 × 10 4 M -1 s -1 ) by the formal hydrogen transfer mechanism of the O6(7,15,16)-H bonds. Chelation with RA may prevent Cu(II) from reduction by the ascorbic acid anion (AA - ), hence blocking the OIL-1 pathway, suggesting that RA in an aqueous environment also serves as an OIL-1 antioxidant. The computational findings exhibit strong concurrence with the experimental observations, indicating that RA possesses a significant efficacy as a radical scavenger in physiological environments.