Chemotaxonomy of the pantropical genus Merremia (Convolvulaceae) based on the distribution of tropane alkaloids.

The occurrence and distribution of tropane and biogenetically related pyrrolidine alkaloids in 18 Merremia species of paleo-, neo-, and pantropical occurrence have been studied. The extensive GC-MS study included members of almost all sections of the genus and has been carried out with epigeal vegetative parts as well as with roots. It comprises altogether 74 tropanes and 13 pyrrolidines including nicotine.

Calystegines as chemotaxonomic markers in the Convolvulaceae.

An extended GC-MS study of 129 convolvulaceous species belonging to 29 genera (all 12 tribes) including the results of a previous survey (65 spp.) revealed the occurrence of one to six polyhydroxy alkaloids of the nortropane type (calystegines) in 62 species belonging to 22 genera of all tribes except the unique parasitic Cuscuteae. The large genus Ipomoea turned out to comprise calystegine-positive species in at least eight out of ten sections checked.

Antiplasmodial activity of sesquilignans and sesquineolignans from Bonamia spectabilis.

Phytochemical re-investigation of the aerial parts of Bonamia spectabilis (Convolvulaceae) led to the isolation of four minor tetrahydrofuran-type sesquilignans (bonaspectins E-H) together with the known neolignan virolongin A and the known lignan rel-(7S,8R,7'R,8'R)-3,3',4,4',5,5'-hexamethoxylignan. Their structures were established on the basis of spectral data. These six compounds as well as further seven lignanoids from B.