Inuloxin E, a New Seco-Eudesmanolide Isolated from <i>Dittrichia viscosa</i>, Stimulating <i>Orobanche cumana</i> Seed Germination

Abstract

A new sesquiterpenoid belonging to the subgroup seco-eudesmanolides and named inuloxin E was isolated from Dittrichia viscosa, together with the already known sesquiterpenoids inuloxins A−D and α-costic acid. Inuloxin E was characterized by spectroscopic data (essentially NMR and ESI MS) as 3-methylene-6-(1-methyl-4-oxo-pentyl)-3a,4,7,7a-tetrahydro-3H-benzofuran-2-one. Its relative configuration was determined by comparison with the closely related inuloxin D and chemical conversion of inuloxin E into inuloxin D and by the observed significant correlation in the NOESY spectrum. Both inuloxins D and E induced germination of the parasitic weed Orobanche cumana, but were inactive on the seeds of Orobanche minor and Phelipanche ramosa. The germination activity of some hemisynthetic esters of inuloxin D was also investigated.

Keywords

• <i>dittrichia viscosa</i>
• <i>orobanche cumana</i>
• sesquiterpenoids
• inuloxin e
• inuloxin d derivatives
• broomrapes seed germination stimulants