Pensteminoside, an unusual catalpol-type iridoid from Penstemon gentianoides HBK (Plantaginaceae)

The investigation of Penstemon gentianoides, afforded, in addition to plantarenaloside (2), globularisicin (3), luteolin (4), diosmetin (5), verbascoside (6) and martynoside (7); an unusual catalpol-type iridoid, pensteminoside [8-O-trans-cinnamoyl, 6-hydroxy, 1-[β-D-glucopyranoside-6′-O-((4″-hydroxy)-cinnamoyl)]-catalpol (1)]. Its structure was elucidated by spectroscopic analyses, including high field NMR spectroscopy.