Abstract
Cranberry products have long been used to treat urinary tract infections. It is believed that the A-type proanthocyanidins in cranberries contribute to this function. Peanut is one of the other, few food sources that primarily contain A-type proanthocyanidins. The skin on the outside of the peanut kernels (testa), which is treated as an agriculture waste product, contains high levels of A-type proanthocyanidins. In this study, an HPLC diol column separation method and MALDI-TOF MS were used to characterize and compare the proanthocyanidin compositions of peanut skins and cranberries. MALDI-TOF MS in linear mode was able to detect a group of proanthocyanidins with DP (degree of polymerization) 10 in peanut skin extract, but was only able to detect DP 8 in cranberry extract. The reflectron mode showed clusters of clear narrow peaks at DP 7 in peanut skin extract, while the highest DP resolved for cranberry extract was only 3 in reflectron mode. This might be due to the low response intensity of the cranberry samples with the current cleanup method and the matrix. Based on the resolved peaks in reflectron mode, pPeanut skins and cranberries have similar proanthocyanidins composition; they contain both A-type and B-type proanthocyanidins, with the A-type being predominant. This result may inspire future studies on the comparison of biological functions between peanut skins and cranberries and further comparison of their polymeric proanthocyanidin composition.
Highlights
Cranberry proanthocyanidins are well known for their antiUTI properties
Later research showed that cranberries do not alter the pH of urine, and that the prevention effect is not due to change in the physical properties of urine, but to specific compounds that inhibit the adherence of E. coli to uroepithelial cells [6]
The linear mode was able to detect a group of proanthocyanidins with DP 10 in peanut skin extract (Figure 4a) but was only able to detect DP 8 in cranberry (Figure 4b)
Summary
Cranberry proanthocyanidins are well known for their antiUTI (urinary tract infection) properties. Later research showed that cranberries do not alter the pH of urine, and that the prevention effect is not due to change in the physical properties of urine, but to specific compounds that inhibit the adherence of E. coli to uroepithelial cells [6]. Proanthocyanidins with “unique” molecular structures, the A-type interflavan bonds, were isolated from cranberry fruit that exhibited potent bacterial anti-adhesion activity. These proanthocyanidins consisted predominantly of epicatechin units with mainly a DP of 4 and 5 and at least one A-type linkage [8,9]
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