Isolation and identification of two major acylated anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) by UPLC-QTOF-MS/MS and NMR

In recent years, researches on the isolation and preparation of monomeric anthocyanins have intensified because of the requirements of quantitative and structure-bioactivity relationship analyses. However, simple and effective methods about the scale of monomeric anthocyanins from the natural purple sweet potato powder are rarely reported. In this study, high molecular weight acylated monomeric anthocyanins were isolated from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) via the combination of column chromatography and semi-preparative HPLC technology and identified mainly by ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry/mass spectrometry (UPLC-QTOF-MS/MS) and H-1 and C-13 nuclear magnetic resonance (NMR). Two major acylated anthocyanins were unambiguously determined as peonidin 3-O-(6-O-(E)-caffeoyl-(2-O-(6-O-p-hydroxybenzoyl)--D-glucopyranosyl)--D-glucopyranoside)-5-O-(-D-glucopyranoside) and peonidin 3-O-(6-O-(E)-caffeoyl-(2-O-(6-O-(E)-feruloyl)--D- glucopyranosyl)--D-glucopyranoside)-5-O-(-D-glucopyranoside). The results of this study may help promote the purification of high molecular weight acylated anthocyanins from purple sweet potato as well as from other plant materials in nature.