Toward the prediction of the activity of antioxidants: Experimental and theoretical study of the gas-phase acidities of flavonoids

• Type: Article in International Scientific Journal
• Date: 2004

Authors

Martins, HFP (Author) Other; Leal, JP (Author) Other; Fernandez, MT (Author) Other; Lopes, VHC (Author) Other; Natalia N D S Cordeiro (Author) FCUP

Journal

Title: Journal of the American Society for Mass Spectrometry

Vol. 15

Pages: 848-861

ISSN: 1044-0305

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 50 Citations

Scopus - 54 Citations

Other information

Authenticus ID: P-000-A7D

DOI: 10.1016/s1044-0305(04)00153-9

Abstract (EN): The relative gas-phase acidities were determined for eight flavonoids, applying the kinetic method, by means of electrospray-ion trap mass spectrometry. The experimental acidity order, myricetin > luteolin > quercetin > (+/-)-taxifolin > kaempferol > apigenin > (+)-catechin > (+/-)-naringenin shows good agreement with the order obtained by theoretical calculations at the B3LYP/6-311 + G(2d,2p)//HF/6-31G(d) level. Moreover, these calculations provide the gas-phase acidities of the different OH groups for each flavonoid. The calculated acidity values (Delta(ac)H), corresponding to the most favorable deprotonation, cover a narrow range, 314.8-330.1 kcal/mol, but the experimental method is sensitive enough to differentiate the acidity of the various flavonoids. For all the flavones and the flavanol, catechin, the 4'-hydroxyl group is the most favored deprotonation site whereas for the flavanones studied, taxifolin and naringenin, the most acidic site is the 7-hydroxyl group. On the other hand, the 5-hydroxyl, in flavones and naringenin, and the 3-hydroxyl, in taxifolin and catechin, are always the less acidic positions. The acidity pattern observed for this family of compounds mainly depends on the following structural features: The ortho-catechol group, the 2,3 double bond and the 4-keto group. (C) 2004 American Society for Mass Spectrometry.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14