Iridoid glycosides from some butterflies and their larval food plants

Catalpol was the major iridoid glycoside isolated from Penstemon newberryi and P. strictus. Catalpol was found in the butterflies Euphydryas chalcedona and E. anicia whose larvae consume these plant species. P. griffinii, a possible larval host for E. anicia, did not contain catalpol, but contained other iridoid glycosides. Thessalia theona, a butterfly from Costa Rica whose larval food plant is unknown, contained only 6-β-hydroxyipolamide, a type of iridoid glycoside known only from the Verbenaceae, and not previously found in any Lepidoptera. A new iridoid glycoside, 10-bisfoliamenthoylcatalpol, was isolated from P. newberryi.