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Số người truy cập: 75,104,053

 Antioxidant Motifs in Flavonoids: O−H versus C−H Bond Dissociation
Tác giả hoặc Nhóm tác giả: Quan V. Vo,*,†,‡ Pham Cam Nam,*,§ Nguyen Minh Thong,∥ Nguyen Tien Trung, ⊥, Cam-Tu D. Phan,⊥ and Adam Mechler
Nơi đăng: ACS Omega; Số: 4;Từ->đến trang: 8935−8942;Năm: 2019
Lĩnh vực: Tự nhiên; Loại: Bài báo khoa học; Thể loại: Quốc tế
TÓM TẮT
Flavonoids provide potential health benefits due to their antioxidant properties. The antioxidant activity of natural flavonoids is primarily exerted by phenolic hydroxyl groups; however, C−H bonds also contribute to these properties. In this study, the contributions of phenolic groupsand C−H bonds to the antioxidant properties of 13 flavonoids were investigated by using the (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) model chemistry in the gas phase and water and ethanol solvents. It was found that the C−H bonds have lower bond dissociation energies than O−H bonds in the 4-carbonyl and/or 3-hydroxyl group containing flavonoids and hence define antioxidant activity. The HOO·radical scavenging of the selected flavonoids is also investigated in detail through the potential energy surface, natural bond orbitals, and kinetic calculations. It was found that the favored radical scavenging mechanism of the flavonoids is hydrogen atom transfer,with the gas phase rate constants in the range of 7.23 × 103 − 2.07 × 109 L·mol −1·s−1. The results suggest that the flavonoids, isomelacacidin, isoteracacidin, melacacidin, and teracacidin, have antioxidant properties as high as typical phenolic compounds such as quercetin, trans-resveratrol, trolox, and ascorbic acid.
ABSTRACT
Flavonoids provide potential health benefits due to their antioxidant properties. The antioxidant activity of natural flavonoids is primarily exerted by phenolic hydroxyl groups; however, C−H bonds also contribute to these properties. In this study, the contributions of phenolic groupsand C−H bonds to the antioxidant properties of 13 flavonoids were investigated by using the (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) model chemistry in the gas phase and water and ethanol solvents. It was found that the C−H bonds have lower bond dissociation energies than O−H bonds in the 4-carbonyl and/or 3-hydroxyl group containing flavonoids and hence define antioxidant activity. The HOO·radical scavenging of the selected flavonoids is also investigated in detail through the potential energy surface, natural bond orbitals, and kinetic calculations. It was found that the favored radical scavenging mechanism of the flavonoids is hydrogen atom transfer,with the gas phase rate constants in the range of 7.23 × 103 − 2.07 × 109 L·mol −1·s−1. The results suggest that the flavonoids, isomelacacidin, isoteracacidin, melacacidin, and teracacidin, have antioxidant properties as high as typical phenolic compounds such as quercetin, trans-resveratrol, trolox, and ascorbic acid.
[ 2019\2019m06d015_21_10_54acsomega.9b00677.pdf ]
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