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

A total of 31 compounds were isolated from the ethyl acetate and <i>n</i>-butanol fractions of <i>Anchusa italica</i> Retz., which contained one ursane triterpenoid, 2<i>α</i>,3<i>β</i>,19<i>α</i>-trihydroxy-23-formyl-urs-12-en-28,21<i>β-</i>olide (<b>1</b>), and five norisoprenoids: (2<i>R</i>,6<i>R</i>,9<i>S</i>)-9-hydroxy-4-megastigmen-3-one-2<i>-O-β-</i>D-glucopyranoside (<b>3</b>); (2<i>R</i>,6<i>S</i>,9<i>S</i>)-9-hydroxy-megastigman-4,7-dien-3-one-2<i>-O-β-</i>D-glucopyranoside (<b>4</b>); (+)-isololiolide <i>β-</i>D-glucopyranoside (<b>5</b>); (2<i>S</i>,8<i>R</i>)-loliolide <i>β-</i>D-glucopyranoside (<b>6a</b>); and (2<i>R</i>,8<i>S</i>)-loliolide <i>β-</i>D-glucopyranoside (<b>6b</b>). It also contained 25 known compounds (<b>2</b> and <b>7-30</b>). 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 <b>1</b>, <b>2</b>, and <b>7-13</b> potentially broadening the application of triterpenes as taxonomic markers for the classification of the genus <i>Anchusa</i>.