Structural Characterization of New Malvidin 3-Glucoside−Catechin Aryl/Alkyl-Linked Pigments

Abstract

The condensation reaction between malvidin 3-glucoside and catechin mediated by isobutyraldehyde, benzaldehyde, and isovaleraldehyde was conducted in model solutions at two pH values (1.5 and 3.2). The formation of new alkyl/aryl-linked adducts corresponding to the structures malvidin 3-glucoside−isobutylcatechin, malvidin 3-glucoside-benzylcatechin, and malvidin 3-glucoside−3-methylbutylcatechin was respectively observed from each aldehyde. The structural characterization of these new structures has been elucidated by 1D and 2D NMR, mass spectrometry, and UV−vis techniques. These new adducts showed the same λ_max in the visible region at 540 nm, which is bathochromically shifted 15 nm when compared with the original anthocyanin (λ_max = 525 nm). Keywords: Pigment; anthocyanin; catechin; isobutyraldehyde; benzaldehyde; isovaleraldehyde