In vitro antileishmanial activity of sustainable anacardic acid and cardol based silver nanoparticles on L. braziliensis

The search for effective and less toxic drugs for the treatment of Cutaneous Leishmaniasis (CL) is desirable due to the emergence of resistant parasites. The present study shows the preparation, characterization and in vitro antileishmanial activity of green-based silver nanoparticles (AgNPs) with Cashew Nutshell Liquid (CNSL, main constituents: anacardic acid (AA) and cardol (CD). The synthesis of silver nanoparticles was achieved by reduction with sodium borohydride in the presence of anacardic acid or cardol under microwave irradiation (400 W, 60 °C, 5 min) resulting in AgAA and AgCD. In vitro assay showed opposite effects for AgAA and AgCD. While AgAA is highly toxic to macrophages (CC50 = 6.910 µg mL-1) and almost non-toxic for L.braziliensis (IC50 = 86.61 µg mL-1), AgCD results very selective toward killing the parasite (CC50 = 195.0 µg mL-1, IC50 = 11.54 µg mL-1). AA's higher polarity and conical shape easily promote cell lysis by increasing cell permeability, while CD has a protective effect: for that reason, AA and AgAA were not further used for tests. CD (EC50 = 2.906 µg mL-1) had higher ability to kill intracellular amastigotes than AgCD (EC50 = 16.00 µg mL-1), however, less intact cells were seen on isolated CD tests. In addition, considering that NO is one of the critical molecular species for the intracellular control of Leishmania, we used Griess colorimetric test to analyze the effect of treatment with AgCD and CD. Overall, the in vitro antileishmanial tests indicate that AgCD should be further explored as a promising non-toxic treatment for CL.