Phytochemicals offer immense promise for sustainable development and production of nanotechnology-enabled products. In the present study, Olax nana Wall. ex Benth. (family: Olacaceae) aqueous extract was used as an effective stabilizing agent to produce biogenic silver (ON-AgNPs) and gold nanoparticles (ON-AuNPs), which were investigated for biocompatibility and prospective biomedical applications (antibacterial, anticancer, antileishmanial, enzyme inhibition, antinociceptive, and anti-inflammatory activities). Various characterization techniques (XRD, FTIR, SEM, TEM, DLS, EDX, and SAED) revealed efficient biosynthesis of ON-AgNPs (26 nm) and ON-AuNPs (47 nm). In the toxicological assessment, ON-AgNPs and ON-AuNPs were found biocompatible towards human RBCs and macrophages (IC50 > 200 μg/mL). In a concentration range of 62.5–2000 μg/mL, a strong antibacterial effect was produced by ON-AgNPs against Staphylococcus epidermidis (MIC = 7.14 μg/mL) and Escherichia coli (8.25 μg/mL), while ON-AuNPs was only active against Staphylococcus aureus (9.14 μg/mL). At a concentration of 3.9–500 μg/mL, a dose-dependant inhibition of HepG2 cancer cells was produced by ON-AgNPs (IC50 = 14.93 μg/mL) and ON-AuNPs (2.97 μg/mL). Both ON-AgNPs and ON-AuNPs were found active against Leishmania tropica (KMH23) promastigotes (IC50 = 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. In the in vivo antinociceptive (acetic acid-induced abdominal constrictions) and anti-inflammatory (carrageenan-induced paw edema) activities, ON-AgNPs and ON-AuNPs at doses of 40 and 80 mg/kg, significantly attenuated the tonic nociception (P < 0.001) and ameliorated the carrageenan-induced inflammation (P < 0.01, P < 0.001). The results of in vitro and in vivo activities indicated that the biogenic nanoparticles can be used as valuable theranostic agents for further exploration of diverse biomedical applications.
