biostudies-literatureTruong DHNational Foundation for Science and Technology Development1499-1514https://www.ebi.ac.uk/biostudies/studies/S-EPMC8978883biostudies-literatureUnknown12(3)Direct and indirect antioxidant activities of rosmarinic acid (RA) based on HOO˙/CH₃OO˙ radical scavenging and Fe(iii)/Fe(ii) ion chelation were theoretically studied using density functional theory at the M05-2X/6-311++G(2df,2p) level of theory. First, four antioxidant mechanisms including hydrogen atom transfer (HAT), radical adduct formation (RAF), proton loss (PL) and single electron transfer (SET) were investigated in water and pentyl ethanoate (PEA) phases. Regarding the free radical scavenging mechanism, HAT plays a decisive role with overall rate coefficients of 1.84 × 10³ M^-1 s^-1 (HOO˙) and 4.49 × 10³ M^-1 s^-1 (CH₃OO˙) in water. In contrast to PL, RAF and especially SET processes, the HAT reactiRSC advancesNew insights into the competition between antioxidant activities and pro-oxidant risks of rosmarinic acid.PMC8978883103.01-2019.380Ngo TCQuang DTNhung NTANguyen TLALouis FDao DQTruong DHEl Bakali AKhiri DTaamalli SfalseNew insights into the competition between antioxidant activities and pro-oxidant risks of rosmarinic acid.Direct and indirect antioxidant activities of rosmarinic acid (RA) based on HOO˙/CH₃OO˙ radical scavenging and Fe(iii)/Fe(ii) ion chelation were theoretically studied using density functional theory at the M05-2X/6-311++G(2df,2p) level of theory. First, four antioxidant mechanisms including hydrogen atom transfer (HAT), radical adduct formation (RAF), proton loss (PL) and single electron transfer (SET) were investigated in water and pentyl ethanoate (PEA) phases. Regarding the free radical scavenging mechanism, HAT plays a decisive role with overall rate coefficients of 1.84 × 10³ M^-1 s^-1 (HOO˙) and 4.49 × 10³ M^-1 s^-1 (CH₃OO˙) in water. In contrast to PL, RAF and especially SET processes, the HAT reacti2022-01-01T00:00:00Z2022 Jan2025-04-04T23:16:42.306Z2025-04-04T23:16:42.306ZS-EPMC89788833542518510.1039/d1ra07599c