Triterpenoids as major components of the insect-trapping glue of Roridula species

Roridula dentata and R. gorgonias, two South African plants that were formerly believed to be carnivorous, exhibit an extremely sticky exudate at the tips of secretory trichomes. Unlike the trapping mucilage of Droseraceae, it does not consist of acidic polysaccharides. The Roridula trapping glue was found to be a mutual solution of mainly dihydroxytriterpenoids, instead. All samples contain two isomers of ring A dihydroxyolean-12-enes and dihydroxyurs-12-enes. The difference between the two species is the additional presence of taraxeradiol in the glue of R. gorgonias. The absolute chemical structures of the reported triterpenoids still need confirmation.