A microplate assay and a thin-layer chromatography (TLC) "in situ" assay based on the Ellman assay was used to screen for acetylcholinesterase inhibitors from ethyl acetate and methanol extracts of Brazilian medicinal plants of families that, according to the literature, have traditional uses that might be connected with acetylcholinesterase inhibition. Eighteen species belonging to Convolvulaceae, Crassulaceae, Euphorbiaceae, Leguminosae, Malvaceae, Moraceae, Nyctaginaceae and Rutaceae families were tested. The most active plants were Ipomoea asarifolia (IC50 = 0.12 mg/mL), Jatropha curcas (IC50 = 0.25 mg/mL), Jatropha gossypiifolia (IC50 = 0.05 mg/mL), Kalanchoe brasiliensis (IC50 = 0.16 mg/mL) and Senna alata (IC50 = 0.08 mg/mL). The most promising extracts were the Jatropha gossypiifolia and Senna alata species assuming there were compounds with a similar activity to galanthamine, which should contain about 1% of an active compound, or if present at lower levels even more active compounds than galanthamine (IC50 = 0.37 x 10-3 mg/mL) should be present.
Brazilian medicinal plants; Alzheimer's disease; acetylcholinesterase inhibitors; microplate assay
