Clarifying the Identity of the Main Ellagitannin in the Fruit of the Strawberry, Fragaria vesca and Fragaria ananassa Duch.

Abstract

Although the composition of strawberry fruit has been extensively studied, especially for the most abundant phenolic compounds, agrimoniin has never been univocally identified as one of the most abundant phenolic compounds in the fruit. In this study agrimoniin was isolated in the fruit of Fragaria vesca and its structure characterized. Furthermore, its presence was definitively established to be the main ellagitannin in both F. vesca and Fragaria ananassa D. fruit. The presence of sanguiin H-6 and lambertianin C as minor compounds was confirmed in both F. vesca and F. ananassa D. samples. For the first time here is reported the full NMR assignments for agrimoniin. These data should represent a point of reference for NMR analysis of this and other structurally related ellagitannins. Finally, the establishment of an HPLC protocol for separation provided information making it possible to avoid confusion with sanguiin H-6, the main ellagitannin in Rubus species, which is also present in strawberries but at a much lower concentration.

Distribution and content of ellagitannins in Finnish plant species

“…Laevigatins have originally been identified from Rosa laevigata (Yoshida et al, 1989a(Yoshida et al, , 1989b, but based on the structural characteristics which laevigatins have with agrimoniin (monomers are glucopyranosebased and the linkage between two monomers comprising the corresponding dimer is m-GOG group), it is possible that laevigatins are present in the studied plant species. We were not able to detect sanguiin H-6 (43) or lambertianin C (53) from strawberry (nor from any other of the Potentilla, Alchemilla or Comarum) samples, although previously such observations have been reported (Gasperotti et al, 2013;Vrhovsek et al, 2012). Monomeric ETs were only found in trace amounts and included compounds such as pedunculagin (1), tellimagrandin I (2), isostrictinin (6) (also its isomer 7) and possibly agrimonic acid A/B (28/29) (Yoshida et al, 1989a(Yoshida et al, , 1989b.…”

Nutrient and polyphenolic composition of industrial strawberry press cake

“…This wide range may be due to the juice production conditions, including the dose and type of enzyme and the intensity of pulp pressing and extraction, which usually depend on the price and availability of the raw material. The average energy value of 100 g of dried industrial strawberry press cake calculated on the basis of the content of proteins, fats, dietary fiber, and carbohydrates in accordance with the Commission Directive 2008/100/EC amounts to 309 kcal/100 g and is almost 10 times higher than the energy value of strawberry Assignments based on Vrhovsek U. et al [14] fruits (32 kcal/100 g) [2,38]. This results from the fact that water is removed from press cake, as opposed to proteins and fats.…”

“…The 1 H NMR assignments for both substances are identical, which confirm agrimoniin to be the main strawberry ellagitannin. The zoom of NMR spectrum of agrimoniin (at the same range as presented by Vrhovsek et al [14]) is shown on Fig. 1.…”

“…Proton spectrum was referenced internally to the residual signal of protonated acetone δ H 2.05 ppm. The comparison of NMR spectra of main ellagitannin isolated from strawberry press cake and agrimoniin characterized by Vrhovsek et al [14] is presented in Table 1. The 1 H NMR assignments for both substances are identical, which confirm agrimoniin to be the main strawberry ellagitannin.…”

“…Moreover, dried strawberry press cake, and especially its seedless fraction (ESF), despite substantial contamination with sand, may be used as rich and widely available raw material for the extraction of proanthocyanidins and/or ellagitannins, and especially dimeric agrimoniin. According to many researchers, the main ellagitannin identified in strawberry fruits is sanguiin H-6; however, the research of Vrhovsek et al [14] proved at the base of NMR spectroscopy that agrimoniin, not sanguiin H-6 is the compound. The error resulted from the same mass spectrum of two compounds and the lack of standards of known, documented structure.…”