Phytochemistry and the systematics and ecology of Loasaceae and Gronoviaceae (Loasales)

A screening for iridoid compounds of 78 of 315 species from all major group s in Gronoviaceae and Loasaceae has been carried out. The results were comp ared to the systematic concepts in the family and distribution and ecology of the taxa. Iridoids are present in at least some species of all genera sc reened. Some simple, monomeric compounds (e.g.. loganin, sweroside) are fou nd in all major groups of the two families and represent the basic iridoid inventory. Other compounds are restricted to certain taxonomic groups: nine -carbon iridoids (e.g., deutzioside) are restricted to Mentzelia (Loasaceae subfam. Mentzelioideae), hetero-oligomeric iridoids (e.g., tricoloroside m ethyl ester, acerifolioside) are restricted to two Small groups in Loasa (L oasa ser. Macrospermae and ser. Floribundae, Loasaceae subfam. Loasoideae), and oleosides (e.g., 10-hydroxyolcoside dimethyl ester) are restricted to the large genus Caiophora sensu Wiegend). The distribution of certain irido id compounds thus confirms some of the generic limits. Iridoid phytochemist ry does not correlate with systematic entities above the generic level nor does it in any way correlate with the morphological evolution of taxa. Conv ersely, the amount and complexity of iridoid compounds present in taxa corr elate positively with the aridity of their habitat and the extent of mammal ian herbivore pressure.