Antiplasmodial activity and phenolic composition of Brazilian Salix humboldtiana Willd. extract and fractions

Abstract

Salix humboldtianaWilld. (Salicaceae) colonizes Brazilian riverine forests and, besides other congeneric species, is traditionally used to treat fever. In folk medicine, it is even used as a Quinine substitute to treat malaria fever. Although its occurrence worldwide was largely reduced between 2000-2015, in Brazil, the case numbers induced by Plasmodium falciparum have increased. Thus, new tools and strategies are necessary against malaria according to the World-Malaria-Report. In the present study the characterization of flavonoids, phenolic acids, phenolic glycosides, and salicylates detected in the ethanol extract of willow leaves, and the antiplasmodial activity of extract of S. humboldtiana and its fractions are firstly reported. Chromatography, UV-Visible spectroscopy, and mass spectrometry were used to characterize substances, and the antiplasmodial activity was accessed by cellular DNA fluorescence measurement with ethidium bromide on a flow cytometer. Kaempferol, apigenin, salicylic acid, and salicylates were found in the extract among other phenolics. The bioassays revealed that lyophilized extract of S. humboldtiana Willd showed antiplasmodial activity. Hexane, AcOEt, and Methanol fractions were active against P. falciparum at IC 50 of 0.655, 0.929 and 0.688 μg/mL, respectively. Quinine, used as a reference, showed an IC 50 of 0.147 μg/mL. The polyphenols -salicylates and flavonoids, especially kaempferol and catechin, detected in LESh, exhibit biochemical interference on the plasmodial metabolism, as already reported, and they could also promote the antiplasmodial activity detected. This alleged medicinal use has been already reported for some Salix species. Moreover, this work presents scientific evidence for the antiplasmodial activity of S. humboldtiana, which can be helpful in the development of antiplasmodial phytomedicine.