Martynoside and the Novel Dimeric Open-Chain Monoterpene Glucoside Digipenstroside from Penstemon digitalis

Abstract

From the leaves of Penstemon digitalis Nutt. a novel dimeric open-chain monoterpene glucoside, digipenstroside, in addition to the known phenylpropanoid glycoside martynoside has been isolated. The structure of digipenstroside was elucidated by spectroscopic means (FD-MS, ¹H-, ¹³C-, and 2D-NMR spectroscopy) as 1-(β-D-glucopyranosyl)-8-[8″-hydroxy-2″-6″-dimethyl-oct-2″(E),6″(E)-dienoyl]-5,8-dihydroxy-2,6-dimethylocta-2(E),6(E)-dienoate. Therefore digipenstroside belongs to a new type of natural compounds, comprising of two geraniol-type monoterpenes and glucose linked by esterification. The occurrence of such compounds together with intact iridoid glycosides might be of interest from the biogenetic point of view.