Flavan-3-ols from the rhizomes of Drynaria fortunei

Six flavan-3-ols, including one monomer, two monomer glycosides, two dimers, and one trimer were isolated from the rhizomes of Drynaria fortunei (Polypodiaceae). [Display omitted] ► Six flavan-3-ols were isolated from Drynaria fortunei (Polypodiaceae). ► Low temperature NMR spectroscopy was used for identification of flavan-3-ol dimers and trimers. ► Aromatic hydrogen–deuterium exchange was observed during NMR determination of flavan-3-ols. One monomer flavan-3-ol, 4α-carboxymethyl-(+)-catechin methyl ester, two monomer flavan-3-ol glycosides, (+)-afzelechin-3- O- β-allopyranoside, (+)-afzelechin-6- C- β-glucopyranoside, two dimer flavan-3-ols, (−)-epiafzelechin-(4 β → 8)-4 β-carboxymethyl-(−)-epicatechin methyl ester, and -(−)-epiafzelechin-(4 β → 8)-4 α-carboxymethyl-(−)epiafzelechin ethyl ester, and one trimer flavan-3-ol, (−)-epiafzelechin-(4 β → 8)-(−)-epiafzelechin-(4 β → 8)-4 β-carboxymethyl-(−)-epiafzelechin methyl ester, together with thirteen known flavan-3-ols were isolated from the rhizomes of Drynaria fortunei (Kunze) J.Sm (Polypodiaceae). The structures were established by analysis of their HRESIMS, 1D, 2D NMR spectroscopic, and CD data. In order to obtain improved resolution, the high-resolution NMR spectra of the dimers and trimer were measured at −40 °C.