Acylated anthocyanins from leaves of Oxalis triangularis

Abstract

The novel anthocyanins, malvidin 3-O-(6-O-(4-O-malonyl-a-rhamnopyranosyl)-b-glucopyranoside)-5-O-b-glucopyranoside (2), malvidin 3-O-(6-O-a-rhamnopyranosyl-b-glucopyranoside)-5-O-(6-O-malonyl-b-glucopyranoside) (3), malvidin 3-O-(6-O-(4-Omalonyl- a-rhamnopyranosyl)-b-glucopyranoside)-5-O-(6-O-malonyl-b-glucopyranoside) (4), malvidin 3-O-(6-O-(4-O-malonyl-arhamnopyranosyl)- b-glucopyranoside) (5) and malvidin 3-O-(6-O-(Z)-p-coumaroyl-b-glucopyranoside)-5-O-b-glucopyranoside (6), in addition to the 3-O-(6-O-a-rhamnopyranosyl-b-glucopyranoside)-5-O-b-glucopyranoside (1) and the 3-O-(6-O-(E)-p-coumaroyl- b-glucopyranoside)-5-O-b-glucopyranoside (7) of malvidin have been isolated from purple leaves of Oxalis triangularis A. St. -Hil. In pigments 2, 4 and 5 a malonyl unit is linked to the rhamnose 4-position, which has not been reported previously for any anthocyanin before. The identifications were mainly based on 2D NMR spectroscopy and electrospray MS.