Oligomeric Proanthocyanidins from the barks of Cinnamomum verum and their dentin enhancement properties
Proanthocyanidins (PACs) are one of the major classes of polyphenols which represent the condensed tannins consisting of oligomeric or polymeric flavan-3-ols. Dentin is a complex mineralized internal tissue of teeth. Intermolecular crosslinks between dentin and the proanthocyanidins enhance the biomechanical properties of the dentin. This study investigates the constituents of Cinnamon bark as a dentin biomodifier. After selecting a PAC oligomer fraction via a detailed bioassay-guided process, the phytochemical studies resulted in the isolation of a new A-type tetrameric PAC, epicatechin-(2β→O→7,4β→8)-epicatechin-(4β→6)-epicatechin-(2β→O→7,4β→8)-catechin (1) and the known trimer, epicatechin-(2β→O→7,4β→8)-epicatechin-(4β→8)-epicatechin (2). The structures of proanthocyanidins were assigned by a combination of HRESIMS, ECD, 1D and 2D NMR, and 1H iterative Full Spin Analysis (HiFSA). HiFSA of this compound class was performed for the first time to enable rapid identification of congeneric compounds.