Kaempferitrin from Uncaria guianensis (Rubiaceae) and its potential as a chemical marker for the species

Abstract

Uncaria tomentosa (Willd.) DC. and U. guianensis (Aubl.) Gmel., known as cat's claw, are large woody vines native to the Amazonian and Central American rainforests. The species contain, in different proportions, indole and oxindole alkaloids, triterpenoid glycosides, sterols and proanthocyanidins. U. tomentosa can be chemically identified by its oxindole alkaloid profile and content, whereas U. guianensis has no satisfactorily established chemical markers. This work describes, for the first time, the isolation of kaempferol-3,7-O-(α)-dirhamnoside (kaempferitrin) in Uncaria species. Screening for this compound in leaves, stems or bark of both species through TLC and HPLC-DAD-MS showed the presence of kaempferitrin only in the leaves and stems of U. guianensis, at a ratio almost thirty six times greater in the leaves than in the stems. These results reveal the selectivity of U. guianensis to produce this bioactive flavonoid glycoside, and suggest this compound as a potential chemical marker for the species.