Elucidation of the Structure and Conformation of Red Radish (Raphanus sativus) Anthocyanins Using One- and Two-Dimensional Nuclear Magnetic Resonance Techniques

Different one- and two-dimensional NMR techniques were used to elucidate the structural conformation of purified anthocyanins obtained from red radish (Raphanus sativus). Two novel diacylated anthocyanins, pelargonidin 3-O-[2-O-(β-glucopyranosyl)-6-O-(trans-p-coumaroyl)-β-glucopyranoside] 5-O-(6-O-malonyl-β-glucopyranoside) and pelargonidin 3-O-[2-O-(β-glucopyranosyl)-6-O-(trans-feruloyl)-β-glucopyranoside] 5-O-(6-O-malonyl-β-glucopyranoside), were characterized. Two other monoacylated anthocyanins were determined to be pelargonidin 3-O-[2-O-(β-glucopyranosyl)-6-O-(trans-p-coumaroyl)-β-d-glucopyranoside] 5-O-(β-glucopyranoside) and pelargonidin 3-O-[2-O-(β-glucopyranosyl)-6-O-(trans-feruloyl)-β-glucopyranoside] 5-O-(β-glucopyranoside). Three-dimensional conformation of the molecule was investigated using NOESY techniques, which showed proximity between hydrogens from the cinnamic acid acylating group and the C-4 of the pelargonidin. Keywords: Anthocyanins; red radish (Raphanus sativus L.); 1D and 2D NMR; pelargonidin derivatives