1H-13C HSQC-NMR analysis of cranberry (Vaccinium macrocarpon) juice defines the chemical composition of juice precipitate

Authors: DORRIS, MATTHEW - University Of Wisconsin; Zeller, Wayne; BOLLING, BRADLEY - University Of Wisconsin

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2023
Publication Date: 7/11/2023
Citation: Dorris, M.R., Zeller, W.E., and Bolling, B.W. 2023. 1H–13C HSQC–NMR Analysis of cranberry (Vaccinium macrocarpon) juice defines the chemical composition of juice precipitate. Journal of Agricultural and Food Chemistry. 71(28):10710-10717. https://doi.org/10.1021/acs.jafc.3c01629.
DOI: https://doi.org/10.1021/acs.jafc.3c01629

Interpretive Summary: This study was an investigation of the composition of precipitate from cranberry juice, which is a loss process for soluble polyphenols (including condensed tannins), and generally regarded as a reduction in product quality. Nuclear magnetic resonance (NMR) spectroscopy signals in the mixture corresponded to those of purified fatty acids, carbohydrates, lipids, and proteins, indicating that these biomolecule components were present in the sample in addition to the expected condensed tannins. Qualitative analyses of these samples included the identification of the bonding structure and the subunit composition of the condensed tannins contained within the cranberry precipitate. The NMR method used here allows for qualitative analysis (what biomolecules are present in the sample) as well as providing some information on the amounts of the biomolecules present. This approach could be further refined and applied to a variety of agricultural and natural product samples that are usually complex mixtures to provide a comprehensive, global analysis of the components contained in them. Such an approach could help identify synergistic interactions among the components leading to observed bioactivities and properties of the samples.

Technical Abstract: 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 30 ± 1% 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.