Abstract
The antioxidant capability of moracin C and iso-moracin C isomers against the OOH free radical was studied by applying density functional theory (DFT) and choosing the M05-2X exchange-correlation functional coupled with the all electron basis set, 6-311++G(d,p), for computations. Different reaction mechanisms [hydrogen atom transfer (HAT), single electron transfer (SET), and radical adduct formation (RAF)] were taken into account when considering water- and lipid-like environments. Rate constants were obtained by applying the conventional transition state theory (TST). The results show that, in water, scavenging activity mainly occurs through a radical addition mechanism for both isomers, while, in the lipid-like environment, the radical addition process is favored for iso-moracin C, while, redox- and non-redox-type reactions can equally occur for moracin C. The values of pKa relative to the deprotonation paths at physiological pH were predicted in aqueous solution.
Highlights
Moracin C Antioxidant Capability functions correlated with oxidative stress (Zelová et al, 2014; Naik et al, 2015; Li et al, 2018; Seong et al, 2018)
When the C=C bond is close to the phenyl ring, the electronic delocalization between the two groups increases, stabilizing the radical that is formed as a result of O–H abstraction reaction
The radicals obtained following the abstraction of the proton by OOH free radical have a spin density that is distributed over almost the entire molecular structure, as it is reported in Figure 4 that the spin density plots of moracin C deprotonated on C1′′ and iso-moracin C deprotonated on C3.′′ In particular, due to the C=C double bond proximity to the phenyl ring, electron delocalization appears to be slightly more extended in iso-moracin C
Summary
2–phenyl–benzofuran-containing molecules, found in a variety of plants (Morus alba, Artocarpus champeden, Erythrina addisoniae, and Calpocalyx dinklagei) (Hakim et al, 1999; Na et al, 2007; Naik et al, 2015; Kapche et al, 2017; Pel et al, 2017), have attracted considerable interest both for their massive use in pharmacology and for their ancient use in traditional medicine in Asia, Africa, and America (Fashing, 2001; Venkatesh and Seema, 2008; Kapche et al, 2009; Kuete et al, 2009). Many of them showed a variety of biological and pharmacological activities and were tested as potent antioxidants (Kapche et al, 2009; Seong et al, 2018), anti-cancer agents (Nguyen et al, 2009), anti-inflammatories, and anti-microbial agents (Kuete et al, 2009; Zelová et al, 2014; Lee et al, 2016). Close to the diffusion limit, the Collins–Kimball theory (Collins and Kimball, 1949) was applied
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