Application of 1H-NMR-based metabolomics to the analysis of cranberry (Vaccinium macrocarpon) supplements

Abstract

Introduction: Commercial cranberry supplements provide a low-sugar alternative to juices and sweetened fruit consumed for health benefits, but their phytochemical composition and associated biological activity varies depending on the source material and post-harvest processing. Proton nuclear magnetic resonance (1H-NMR) is a rapid and environmentally friendly method of generating metabolic profiles of plant materials that may be used to authenticate cranberry products. Objective: The 1H NMR-based chemometrics were used to characterise variations in metabolic profiles of cranberry supplements in comparison to a whole cranberry powder reference standard. Materials and Methods: The secondary metabolite profiles of nine commercial cranberry supplements were compared to a whole cranberry powder reference standard, using 1H-NMR with Bruker AssureNMR software and principal component analysis (PCA). Content of selected triterpenoids and organic acids was determined by quantitative NMR. Total proanthocyanidins and anthocyanins were determined by established methods. Results: PCA of 1H-NMR spectra showed overlap between the cranberry standard and three supplements, but most products varied substantially in metabolic profile. Metabolites contributing to the observed variance include citric acid and cranberry peel constituents ursolic acid, oleanolic acid and hyperoside. Ursolic, oleanolic, citric, quinic and malic acids were readily determined by quantitative 1H-NMR in the whole cranberry standard, but were below detection limits in many supplements. Proanthocyanidin and flavonoid content in several products was minimal or below detection limits. Conclusion: The 1H-NMR chemometrics found significant variation in composition of characteristic cranberry metabolites among commercial preparations, reinforcing the need for reliable industry standards.