LC-ESI-MS/MS analysis of Quassia amara leaves tea. Is antiplasmodial activity of the tea is due to quassinoids?

Quassia amara L. (Simaroubaceae) leaves tea is a widely used remedy against malaria all over the north-west amazon. Our group has isolated different quassinoids from the leaves and shown that the most active compounds against Plasmodium falciparum were simalikalactones D and E (IC₅₀ 10 and 24 nM respectively). In order to evaluate if the antiplasmodial activity of the traditional preparation is due to these quassinoids, a LC-ESI-MS/MS analysis was performed on teas prepared from both mature fresh and dry leaves of Q. amara. The results showed the presence of phenolic compounds, mainly gallic acid (GA), methyl gallate (MG), a new apiosyl gallate and vitexin (VT). Simalikalactone D was not detected and simalikalactone E was only detected at very low concentration (0.0072% m/m). The quantification (% m/m) of the 3 main compounds revealed concentrations of 15, 4.4 and 10% for GA, MG and VT respectively in the tea prepared from dry leaves and 7.9, 2.2 and 1.7% form GA, MG and VT in the fresh leaves tea. Antiplasmodial IC₅₀ were measured to be 9µg/ml for fresh leaves tea and 1, 17 and 80µg/ml for GA, MG and VT respectively. So, the antiplasmodial activity of Quassia tea is due to gallic acid derivatives.