VARIATIONS IN THE HETEROGENEITY OF THE DECAY OF THE FLUORESCENCE IN 6 PROCYANIDIN DIMERS

The decay of the fluorescence has been measured in 1,4-dioxane for six dimers of (2R,3R)-(-)-epicatechin and (2R,3S)-(+)-catechin, hereafter denoted simply epicatechin and catechin. The dimers are epicatechin-(4ß→8)-catechin, epicatechin-(4ß→8)-epicatechin, catechm-(4α→8)-catechin, catechin-(4α →8)-epicatechin, epicatechin-(4ß→6)-epicatechin, and epicatechin-(4ß→8;2ß→0→-7)-epicatechin. The monomers and the bridged dimer have a fluorescence that decays as a single exponential. The remaining five dimers have a heterogeneous decay that can be described by the sum of two exponentials. The heterogeneity is most apparent in the two dimers with 4α→8 interflavan bonds. In view of the molecular origin of the heterogeneous decay in the presence of two rotational isomers at the interflavan bond, polymeric procyanidins with predominantly a stereochemistry for the interflavan bond at C(4) should be more disordered and more compact than those with predominantly ß stereochemistry. © 1990, American Chemical Society. All rights reserved.