A galloylated dimeric proanthocyanidin from grape seed exhibits dentin biomodification potential

Abstract

Grape seeds are a rich source of polyphenols, especially proanthocyanidins (PACs), and are also known for the presence of galloylated oligomeric PACs (OPACs). The present study focuses on the phytochemical methodology for grape seed (O)PACs and their potential role as dentin biomodifiers to be used in restorative and reparative dentistry. A new method using centrifugal partition chromatography (CPC) was developed for the preparative separation of the grape seed (O)PACs. Orthogonal phytochemical profiling of the resulting CPC fractions was performed using C18 and diol HPLC, normal phase HPTLC, and IT-TOF MS analysis. A galloylated procyanidin dimer (1) was isolated from a CPC fraction in order to evaluate its potential to enhance dentin bio-mechanical properties. Moreover, it helped to evaluate the impact of the galloyl moiety on the observed bioactivity. Structure elucidation was performed using ESI-MS, 1D and 2D NMR analyses. For the first time, (1)H iterative full spin analysis (HiFSA) was performed on this type of molecule, enabling a detailed proton chemical shift and coupling constant assignment. The CPC fractions as well as 1 showed promising results in the dentin stiffness bioassay and indicate that they may be used as dental intervention biomaterial.

Keywords: Centrifugal partition and countercurrent chromatography (CPC/CCC); Countercurrent separation (CS); Dentin stiffness and biomodification; Epicatechin-(4β→8)-epicatechin-3-O-gallate (PubChem CID: 15593124); Galloylation; HiFSA; Oligomeric proanthocyanidins (OPACs); Procyanidin B1 (PubChem CID: 11250133); Procyanidin B3 (PubChem CID: 146798).