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148.5 |
1 Arkansas Children's Nutrition Center, UAMS, Little Rock, AR
2 Arkansas Children's Nutr. Ctr., Uams, Little Rock, AR
3 Mars SnackFood US, Hackettstown, NJ
4 Arkansas Children's Nutr. Ctr., USDA, ARS, Little Rock, AR
ABSTRACT
Separation of procyanidins using silica-based HPLC suffered from poor resolution for higher oligomers and low sensitivity due to the fluorescence quenching effects of methylene chloride in the mobile phase. Optimization of a published Diol-phase HPLC method resulted in near baseline separation for pentamers to decamers at 29 min to 50 min and the elution of polymers with molecular weights higher than decamers at 66 min. By using excitation and emission wavelengths of 230 nm and 321 nm, the sensitivity was increased by 5 fold. Flavonoids other than proanthocyanidins did not generate signals at these wavelengths. Dimers and trimers in grape seed procyanidins eluted as a cluster of 5 peaks of isomers on normal phase HPLC, whereas they merged into a large peak with shoulders using the Diol-phase HPLC. Hexamers, heptamers, and octamers can be resolved on Diol-phase HPLC but not on normal-phase HPLC. Separation of procyanidins on Diol-phase HPLC was according the degree of polymerization and was not sensitive to isomeric differences for procyanidins of the same degree of polymerization. Proanthocyanidins in foods that contained predominantly procyanidins, such as sorghum, pear, and apple, eluted as well separated oligomers and polymers using Diol-based HPLC.
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