Singlet oxygen quenching ability of anthocyanins flavylium cations

V. V. DE ROSSO; F.E. MORÁN VIEYRA; A. Z. MERCADANTE; C. D. BORSARELLI

FREE RADICAL RESEARCH

Society for Free Radical Research

Año: 2008 vol. 42 p. 885 - 891

1071-5762

The quenching of singlet molecular oxygen (1O2) by the flavylium cation form of six widespread anthocyanin derivatives: cyanidin 3-glucoside (CG), cyanidin 3-rutinoside (CR), cyanidin 3-galactoside (CGL), malvidin (M), malvidin 3-glucoside (MG), and malvidin 3,5-diglucoside (MDG) was studied in 1% HCl methanol solution by time-resolved phosphorescence detection (TRPD) of 1O2 and photostationary actinometry using perinaphthenone and methylene blue as sensitizers, respectively. The average value of the total (kQ) and chemical (kc) quenching rate constants, were approximately 4x108 M-1s-1 and 3x106 M-1s-1, respectively, indicating the good performance of the studied anthocyanins as catalytic quenchers of 1O2. The quenching efficiency was larger for malvidin than for cyanidin derivatives, probably by the extra electron-donating methoxy group in the ring B of the malvidin derivatives; and it was also dependent on the number and type of glycosylated substitution. As observed for other phenolic-like derivatives, the quenching of 1O2 by anthocyanins was mediated by a charge-transfer mechanism, which was modulated by the total number of –OR substituents that increases the electron-donating ability of these compounds.