Usnic acid causes apoptotic-like death in and .

Leishmaniasis, a deadly parasitic infection, threatens many people worldwide. Since the high cost, toxicity, and resistance are drawbacks of current treatment options, it is necessary to find safer and more effective new antileishmanial drugs. The aim of this study was to determine the antileishmanial activity of usnic acid and its apoptotic mechanism on spp. promastigotes. The antileishmanial activity was evaluated by MTT assay and apoptosis-related gene expression was investigated by qRT-PCR. Usnic acid was to be effective against , and promastigotes at IC = 10.76 µg/ml, 13.34 µg/ml, and 21.06 µg/ml, respectively. We also demonstrated a novel mechanism by which usnic acid inhibited proliferation and caused apoptosis; usnic acid upregulated , and gene expression and downregulated the level of gene expression. Accordingly, the expression level of the P53 gene increased in and by 14.4-, 11.8-, and 9.5-fold, respectively, and in contrast, the gene expression decreased in all three leishmaniasis by 0.8-, 0.8-, and 0.7-fold, respectively. The present study, therefore, revealed that usnic acid played a critical role in the usnic acid-induced apoptotic process in species. Usnic acid is easily accessible and an inexpensive agent, and can be considered as an alternative therapeutic agent for infections subject to further tests in animal models.