Studies on Transition Metal-Quercetin Complexes Using Electrospray Ionization Tandem Mass Spectrometry

Molecules

Yuanzhen Liu¹  Mingquan Guo¹ 

[1] Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden of Chinese Academy of Sciences, Wuhan 430074, China; E-Mail:

关键词: flavonoid;    ESI-MSⁿ;    metal complexes;    CID;    fragmentation mechanism;   

DOI  :  10.3390/molecules20058583

来源: mdpi

【 摘 要 】

To systematically study the effects of the number of d electrons of the first transition metal ions (Fe, Co, Ni, Cu and Zn) on the formation and stability of metal flavonoid complexes, we took the quercetin/M²⁺ complex as a model system to investigate the structures and properties of these complexes. Based on considerable structural information obtained through ESI-MSⁿ, all of the first transition metal ions (Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) were found to form different complexes with quercetin, while with the number of chelating flavonoids decreasing along with the reduction of the metal ionic radius. Quercetin forms different complexes with the above metal divalent ions through its 5-OH and 4-carbonyl groups; the complex stability is highly dependent on both the metallic ion and the flavonoid chelator itself. As for the central ion (M²⁺), when chelated with quercetin to form the complex, the stability of the complex decreased in the following order: Cu²⁺ > Ni²⁺ > Co²⁺ > Fe²⁺ > Zn²⁺. With flavonoid: metal stoichiometries at 2:1, the complexes formed between quercetin and metal ions (Fe²⁺, Ni²⁺, Co²⁺ and Zn²⁺) have the similar fragmentation mechanism, while Cu²⁺ displayed different fragmentation mechanism due to the concurrent oxidation.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.