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Kaempferol Binding to Zinc(II), Efficient Radical Scavenging through Increased Phenol Acidity
Yi Xu1, Ling-Ling Qian1, Jing Yang1
1Department of Chemistry , Renmin University of China , Beijing 100872 , China.
The Journal of Physical Chemistry. B
|October 9, 2018
Summary
Zinc(II) significantly enhances the radical scavenging ability of kaempferol (Kaem) by forming a 1:1 complex. This complex acts as a potent antioxidant, improving the body's defense against oxidative stress.
Area of Science:
- Biochemistry
- Chemical Biology
- Medicinal Chemistry
Background:
- Flavonoids like kaempferol (Kaem) are known for their antioxidant properties.
- The role of metal ions, such as Zinc(II), in modulating flavonoid antioxidant activity is not fully understood.
Purpose of the Study:
- To investigate how Zinc(II) influences the radical scavenging capacity of kaempferol.
- To elucidate the structural and electronic changes in kaempferol upon Zinc(II) complexation and their impact on antioxidant activity.
Main Methods:
- Laser flash photolysis and stopped-flow spectroscopy were used to determine reaction rate constants.
- Density functional theory calculations and UV-vis absorption spectroscopy were employed to study complex formation and electronic properties.
- Cyclic voltammetry was used to assess the reductive potential of the complexes.
Main Results:
- The 1:1 Zn(II)-Kaem complex exhibited significantly enhanced radical scavenging compared to free kaempferol and the 1:2 complex.
- Complexation with Zinc(II) increased the acidity of kaempferol, facilitating proton and electron transfer.
- The 1:1 Zn(II)-(Kaem-2H) complex showed a much higher reductive potential, acting as a stronger antioxidant.
Conclusions:
- 1:1 coordination with Zinc(II) dramatically boosts kaempferol's antioxidant activity by increasing its reducing power.
- This mechanism of enhanced phenol acidity by Zinc(II) coordination may explain its biological antioxidant role.
- The findings suggest potential for designing novel, non-toxic metal-based drugs from natural bioactive molecules.
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