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 center dot radical scavenging activity with overall rate constant values of 2.89 x 10(10) and 3.86 x 10(9) M-1 s(-1). RA is anticipated to exhibit excellent scavenging properties for HOO center dot in an aqueous environment (k(overall) = 3.18 x 10(8) M-1 s(-1), approximate to 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 x 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.