Chemotaxonomy of Veroniceae and its allies in the Plantaginaceae

Abstract

In a chemosystematic investigation of tribe Veroniceae (Plantaginaceae), representatives of Camptoloma, Sibthorpia, Veronica subg. Pentasepalae and subg. Hebe, Veronicastrum, Wulfenia, and the related Ellisiophyllum and Globularia were examined for non-flavonoid glycosides. From the 14 species studied, 28 different iridoid glucosides and 10 caffeoyl phenylethanoid glucosides (CPGs), as well as salidroside and arbutin were isolated and characterized by NMR; of these, five compounds were previously unknown. It was found that the representatives of Veroniceae, as well as Globularia, were characterized by mannitol, aucubin, catalpol and catalpol esters. Each of the three studied species of Veronica subg. Hebe contained at least one of the 6-O-catalpol esters typical for Veronica s. str. (verminoside), supporting the inclusion of Hebe in Veronica. However, their main constituents were esters of 6-O-rhamnopyranosylcatalpol; a CPG, hebeoside (2'-beta-xylopyranosyl-verbascoside) was isolated from V. (Hebe) salicifolia. The two species of Veronicastrum also contained 6-O-rhamnopyranosylcatalpol esters, including the previously unknown 2'',3''- and 3'',4''-dicinnamoyl derivatives and, in contrast to the earlier reports, they lacked 6-O-catalpol esters. The main iridoid constituents in the three investigated species of Wulfenia were 10-O-aucubin and 10-O-catalpol esters (isoscrophularioside or globularin) while baldaccioside (10-O-cinnamoyl asystasioside E) was isolated from W. baldaccii. Globularia vulgaris contained 10-O-catalpol esters (e.g., globularin) and, in addition, asperuloside together with its benzoyl analogue named besperuloside. The representatives of Sibthorpia and Ellisiophyllum were almost completely devoid of iridoids; this, however, together with the CPGs present implied a close relationship between the two genera. Camptoloma lyperiiflorum lacked hexitols but contained esters of 6-O-rhamnopyranosylcatalpol different from those found in Veroniceae but known from Buddleja, Scrophularia and Verbascum (Scrophulariaceae s. str.).

Naturally Occurring Phenylethanoid Glycosides: Potential Leads for New Therapeutics

“…Other studies have also confirmed the utilization of PhGs as taxonomic markers of genus Orobanche [142], Sibthorpia, and Ellisiophyllum (Plantaginaceae) [143]. Findings in chemotaxonomy based on PhGs are expected to provide a valuable measure for chemists to source rare PhGs from related species or genera.…”

Unusual iridoid glycosides in Veronica sects. Hebe and Labiatoides

“…16 or 11), since they apparently always occur together with these. Previously, the parent asystasioside E (17) has been found in the related Wulfenia baldaccii Degen together with its 6-O-cinnamoylester (Taskova et al, 2006).…”

Molecular systematics and phytochemistry of Rehmannia (Scrophulariaceae)

“…The isolated compounds were identified by their 1 H and 13 C NMR spectra by comparison with spectra of known standards (Taskova et al, 2006). Dry leaf material (7 to 11 g) was extracted by blending in EtOH (50 ml).…”