The antileishmanial activity assessment of unusual flavonoids from Kalanchoe pinnata

The importance of flavonoids for the antileishmanial activity of Kalanchoe pinnata was previously demonstrated by the isolation of quercitrin, a potent antileishmanial flavonoid. In the present study, the aqueous leaf extract from the medicinal plant K. pinnata (Crassulaceae)afforded a kaempferol di-glycoside, named kapinnatoside, identified as kaempferol 3-O-a-L-arabinopyranosyl (1! 2)a-Lrhamnopyranoside (1). In addition, two unusual flavonol and flavone glycosides already reported, quercetin 3-O-a-L-arabinopyranosyl (1! 2)a-L-rhamnopyranoside (2)and 40,5-dihydroxy-30,8-dimethoxyflavone 7-O-b-D-glucopyranoside (3), have been isolated. Their structures were determined via analyses of mono and bi-dimensional 1H and 13C NMR spectroscopic experiments and HR-MALDI mass spectra. Because of its restricted occurrence and its abundance in K. pinnata, flavonoid (2)may be a chemical marker for this plant species of high therapeutic potential. The three flavonoids were tested separately against Leishmania amazonenis amastigotes in comparison with quercitrin, quercetin and afzelin. The quercetin aglycone - type structure, as well as a rhamnosyl unit linked at C-3, seem to be important for antileishmanial activity.