1H–13C HSQC–NMR Analysis of Cranberry (Vaccinium Macrocarpon) Juice Defines the Chemical Composition of Juice Precipitate

Shelf-stable cranberry juice precipitate has not been well characterized. Here, we describe using 1H-13C heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) spectroscopy for cranberry juice analysis, focusing on proanthocyanidins and the precipitate. HSQC-NMR cross-peaks from juices were categorized as aliphatic, olefinic, aromatic, carbohydrate backbone, or anomeric signals. An average cranberry juice precipitate had significantly more aromatic and significantly less carbohydrate backbone signals than an average supernatant. The precipitate was a collection of biomolecules held together by a mix of weak and strong intermolecular forces. Proanthocyanidin signals from precipitates of juices showed 22 ± 2 to 29.9 ± 0.7% A-type interflavan linkages and 34 ± 2 to 48 ± 3% of flavan-3-ol units with trans stereochemistry between the C2 and C3 positions. Based on this work, 1H-13C HSQC-NMR is useful to analyze cranberry juice and reveals the complex chemical nature of components in the soluble and insoluble phases.