Inhibitory Activity of Bauhinia forficata Link against Leishmania

Abstract Bauhinia forficata is a Brazilian medicinal plant, named “cow's paw”. Aqueous leaf, seed and stem extracts were prepared and their protein content, and protease inhibitor (PI) activities were assessed. The highest protein concentration was observed in aqueous stem (BF-CA) and tris seed (BF-ST) extracts. Only stem and seed extracts inhibited trypsin, papain and pepsin. All extracts reduced the protease activity of Leishmania amazonensis extracellular fraction, and the greatest inhibition was observed for BF-CA. Thus, BF-CA was elected for the study of secondary metabolite composition by liquid chromatography-mass spectrometry analysis, toxicity against insect larvae and cytotoxicity to erythrocytes, macrophages and promastigote and amastigote from L. amazonensis, since good inhibitors of Leishmania proteases killed parasites in vitro, with future objectives to develop a sustainable formulations prototype to the treatment of cutaneous leishmaniasis. Quercetin and kaempferol glycosylated derivatives were the main metabolites of BF-CA, which showed very low cytotoxicity against erythrocytes, were nontoxic to Tenebrio molitor larvae and had low cytotoxicity against RAW macrophages (CC50 = 166.5 ± 8.61 µg of protein/mL). Regarding L. amazonensis, the half maximal inhibitory concentration (IC50) of BF-CA was 68.96 ± 9.91 µg of protein /mL for promastigotes and 34.61 ± 3.27 µg of protein /mL for amastigotes. Our results suggested that the combination of PIs and flavonoids was responsible for the significant leishmanicidal effects and low toxicity of B. forficata extract, associated with the reduced cost of this extract production, making an attractive and accessible adjuvant agent for leishmaniasis treatment.