Abstract
Quantum mechanical calculations at B3LYP/6-31G** level of theory were employed to obtain energy (E), ionization potential (IP), bond dissociation enthalpy (O-H BDE) and stabilization energies (ΔEiso) in order to infer the scavenging activity of dihydrochalcones (DHC) and structurally related compounds. Spin density calculations were also performed for the proposed antioxidant activity mechanism of 2,4,6-trihydroxyacetophenone (2,4,6-THA). The unpaired electron formed by the hydrogen abstraction from the phenolic hydroxyl group of 2,4,6-THA is localized on the phenolic oxygen at 2, 6, and 4 positions, the C3 and C6 carbon atoms at ortho positions, and the C5 carbon atom at para position. The lowest phenolic oxygen contribution corresponded to the highest scavenging activity value. It was found that antioxidant activity depends on the presence of a hydroxyl at the C2 and C4 positions and that there is a correlation between IP and O-H BDE and peroxynitrite scavenging activity and lipid peroxidation. These results identified the pharmacophore group for DHC.
Highlights
Antioxidants are of great interest because of their role in important biological and industrial processes
The purpose of this work was twofold: one is to contribute to a better understanding of the mechanistic features of these processes in 2,4,6,4’-tetrahydroxy-dihydrochalcones and their derivatives against ROS and RNS, and the other is to determine the pharmacophore responsible for antioxidant activity of dihydrochalcones
The stabilization energy (ΔEiso) is used as simple method to predict the ability of antioxidants to trap free radicals of phenolic derivatives
Summary
Antioxidants are of great interest because of their role in important biological and industrial processes. Flavonoids are the most abundant natural antioxidants, as well as abundantly present in green vegetables, fruits, olive, red wine, chocolate, and tea [1]. The chemical structure of flavonoids is based on a fifteen carbon skeleton with a chromane ring bearing a second aromatic ring. The flavonoid subgroups are classified according to the C-ring substitution pattern, in addition to the oxidation state of the heterocyclic ring and the position of B-ring. Examples are: chalcones, flavones 2, flavonols 3, flavanones 4, anthocyanins 5, and isoflavonoids 6 (Figure 1). Chalcones (1,3-diaryl-2-propen-1-ones) are flavonoids lacking a heterocyclic C-ring, and they have a broad spectrum of bioactivities such as anticancer, antifungal, antibacterial, antiviral, antioxidant and anti-inflammatory properties [2,3,4]
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