Conformational preferences of cocoa oligomeric proanthocyanidins and their influence on polarity.

Proanthocyanidins (OPACs) are the second largest class of plant metabolites after lignans. Although knowledge of their 3D conformations would add greatly to our understanding of their biological properties, very little has been published on the conformations of OPACs with a degree of polymerization (DP) above 4. We investigated the conformations of the linear epicatechin oligomers, prominent representatives of OPACs prevalent in apples and cocoa, where the epicatechin units are interconnected through the 4β-8 bonds.

Isolation of Echimidine and Its C-7 Isomers from L. and Their Hepatotoxic Effect on Rat Hepatocytes.

Echimidine is the main pyrrolizidine alkaloid of L., a plant domesticated in many countries. Because of echimidine's toxicity, this alkaloid has become a target of the European Food Safety Authority regulations, especially in regard to honey contamination.

Isolation of 1-(3',4'-Dihydroxyphenyl)-3-(2″,4″,6″-trihydroxyphenyl)-propan-2-ol from Grape Seed Extract and Evaluation of its Antioxidant and Antispasmodic Potential.

HPLC profiling of phenolics in grape seed extracts revealed a prominent peak of an unknown substance with concentrations up to 5.3%. Spectroscopic data allowed the identification of the compound as 1-(3',4'-dihydroxyphenyl)-3-(2″,4″,6″-trihydroxyphenyl)-propan-2-ol.

Ion mobility-mass spectrometry for the separation and analysis of procyanidins.

Procyanidins are polymeric flavan-3-ones occurring in many plants with antioxidant and other beneficial bioactivities. They are composed of catechin and epicatechin monomeric units connected by single carbon-carbon B-type linkages or A-type linkages containing both carbon-carbon and carbon-oxygen-carbon bonds. Their polymeric structure makes analysis of procyanidin mixtures always difficult.

Trimeric and Tetrameric A-Type Procyanidins from Peanut Skins.

Peanut skins are a rich source of oligomeric and polymeric procyanidins. The oligomeric fractions are dominated by dimers, trimers, and tetramers. A multistep chromatographic fractionation led to the isolation of four new A-type procyanidins of tri- and tetrameric structures.

Conformational equilibria in selected A-type trimeric procyanidins.

A-type procyanidin trimers cinnamtannin B-1, cinnamtannin D-1, lindetannin, and aesculitannin B were studied in terms of their conformation and interaction with four solvents: methanol, acetone, DMSO and pyridine. The experiments demonstrated that for each trimer there are two principal conformers observable in the NMR. The ratio of the conformers (rotamers) depends on the structure of a given trimer as well as on the solvent used for NMR measurements.