The chemotaxonomic significance of laricytrin and medicagenic acid in the tribe Trigonelleae

Abstract

Flavonoids from fresh flowers of 35 species and medicagenic acid from leaf tissue of 44 species of the tribe Trigonelleae Schulz (Fabaceae) were examined using thin-layer chromatography. Moreover, medicagenic acid glycosides in the leaf tissue were also analyzed by the hemolytic test. Compounds tentatively identified as kaempferol, quercetin, myricetin, laricytrin, and medicagenic acid were present in hydrolysates of all species of the genus Medicago, including five species of debated taxonomic position, M. radiata, M. hybrida, M. cretacea, M. arborea, and M. lupulina. Laricytrin and medicagenic acid, while rarely occurring in the plant kingdom, may be regarded as chemical markers that distinguish the genus Medicago in Trigonelleae and may further support the placement of the five questionable species into Medicago. Laricytrin and medicagenic acid were also found in hydrolysates of three species of the section Buceras of the genus Trigonella (T. monantha, T. monspeliaca, and T. polyceratia) and were not found in any of the remaining tested species of Trigonella or in the genus Melilotus. This chemical affinity of the three Trigonella species to Medicago gives further support to the placement of these species in genus Medicago.