Gas-Phase Ligation of Fe+ and Cu+ Ions with Some Flavonoids

• Published in: Journal of agricultural and food chemistry Vol. 54; no. 22; pp. 8391 - 8396
• Main Authors: Kazazić, Snježana P, Butković, Vjera, Srzić, Dunja, Klasinc, Leo
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.2006
• Subjects: apigenin; Biological and medical sciences; Cations - chemistry; chemical reactions; copper; Copper - chemistry; flavonoids; Flavonols - chemistry; Food industries; Fourier transform mass spectrometers; Fundamental and applied biological sciences. Psychology; gas-phase ligation; iron; Iron - chemistry; kaempferol; luteolin; Mass Spectrometry; metal ions; Molecular Structure; myricetin; naringenin; quercetin; DFT calculation; Polyphenol; Flavonoids; antioxidants and antiradical activity; ligation and fragmentation products with Fe+ and Cu; Ions; FTICR MS; Gas phase; Antioxidant; Flavonoid; Fragmentation
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf061401m

It was assumed that gas-phase ligation of metal monocations by flavonoids might provide some insight on the intrinsic antioxidant activity of the latter. Thus, the ligation of Fe+ and Cu+ ions by apigenin (1), luteolin (2), kaempferol (3), quercetin (4), myricetin (5), and naringenin (6) was investigated in the gas phase in a Fourier transform mass spectrometer (FTMS). Both of the metal ions, which were produced by laser desorption ionization (LDI), bind consecutively to two neutral flavonoid molecules either with or without the simultaneous loss of some part (H, CO, H2O) of the latter. The flavonoids are present in the instrument at steady concentrations. The formation of flavonoid positive ions by charge exchange is also a common observation but is accompanied, in some cases, by a loss of H, CO, or H2O fragments. The reaction paths and observed fragmentations are presented. The results are supported by DFT B3LYP calculations that indicate a preference for metal ion attack at C-ring and not at the B-ring site considered to be mainly responsible for flavonoid antioxidant activity. Keywords: Flavonoids; antioxidants and antiradical activity; DFT calculation; FTICR MS; ligation and fragmentation products with Fe+ and Cu+