Ursane Triterpenes and Norisoprenoids from Anchusa italica Retz. and Their Chemotaxonomic Significance

A total of 31 compounds were isolated from the ethyl acetate and n-butanol fractions of Anchusa italica Retz., which contained one ursane triterpenoid, 2α,3β,19α-trihydroxy-23-formyl-urs-12-en-28,21β-olide (1), and five norisoprenoids: (2R,6R,9S)-9-hydroxy-4-megastigmen-3-one-2-O-β-D-glucopyranoside (3); (2R,6S,9S)-9-hydroxy-megastigman-4,7-dien-3-one-2-O-β-D-glucopyranoside (4); (+)-isololiolide β-D-glucopyranoside (5); (2S,8R)-loliolide β-D-glucopyranoside (6a); and (2R,8S)-loliolide β-D-glucopyranoside (6b). It also contained 25 known compounds (2 and 7–30). The chemical structures of the compounds, inclusive of their absolute configurations, were ascertained using spectroscopic methods such as NMR, HR-MS, and quantum chemical calculations (computational NMR and ECD), in combination with relevant literature data. Moreover, the chemotaxonomic significance of the isolated substances was discussed, with compounds 1, 2, and 7–13 potentially broadening the application of triterpenes as taxonomic markers for the classification of the genus Anchusa.