Both ON-AgNPs and ON-AuNPs were found active against Leishmania tropica (KMH23) promastigotes (IC<sub>50</sub> = 12.56 and 21.52 μg/mL) and amastigotes (17.44 and 42.20 μg/mL), respectively, after exposure to a concentration range of 1-200 μg/mL for 72 h. Preferential enzyme inhibition against urease and carbonic anhydrase II were noted for ON-AgNPs (39.23 and 8.89%) and ON-AuNPs (31.34 and 6.34%), respectively; however, these were found inactive against xanthine oxidase at 0.2 mg/mL.