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-(beta-glucopyranosyl)-6-O-(trans-p-coumaroly)-beta-glucopyranside] 5-O-(6-O-malonyl-beta-glucopyranoside) and pelargonidin 3-O-[2-O-(beta-glucopyranosyl)-6-O-(trans-feruloyl)-beta-glucopyranoside] 5-O-(6-O-malonyl-beta-glucopyranoside), were characterized. Two other monoacylated anthocyanins were determined to be pelargonidin 3-O-[2-O-(beta-glucopyranosyl)-6-O-(trans-p-coumaroyl)-beta-D-glucopyranoside] 5-O-(beta-glucopyranoside) and pelargonidin 3-O[2-O-(beta-glucopyranosyl)-6-O-(trans-feruloyl-beta-D-glucopyranoside] 5-O-(beta-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.