Biogenic Silver Nanoparticles of Clinacanthus nutans as Antioxidant with Antimicrobial and Cytotoxic Effects

Abstract

Silver nanoparticles (AgNPs) previously synthesised using leaf (AgNP-L) and stem (AgNP-S) extracts of <i>Clinacanthus nutans</i> (<i>C. nutans</i>) were tested to evaluate antimicrobial, antioxidant, and cytotoxicity activities. The AgNPs showed good inhibition against bacteria, but not fungi. The inhibition results showed the highest activity against <i>Staphylococcus aureus</i> (<i>S. aureus</i>) with 11.35 mm (AgNP-L) and 11.52 mm (AgNP-S), while the lowest inhibition was against <i>Escherichia coli</i> (<i>E. coli</i>) with 9.22 mm (AgNP-L) and 9.25 mm (AgNP-S) in the disc diffusion method. The same trend of results was noted in the well diffusion method. The IC₅₀ of AgNP-L and AgNP-S in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays was 417.05 <i>μ</i>g/mL and 434.60 <i>μ</i>g/mL, as well as 304.31 <i>μ</i>g/mL and 326.83 <i>μ</i>g/mL, respectively. Ferric reducing power (FRAP) assay showed that AgNP-L [872.389 <i>μ</i>mol/L Fe(II)] and AgNP-S [612.770 <i>μ</i>mol/L Fe(II)] exhibited significantly (<i>p</i> < 0.05) greater antioxidant activities than leaf extract (CNL) [152.260 <i>μ</i>mol/L Fe(II)] and stem extract (CNS) [110.445 <i>μ</i>mol/L Fe(II)] of <i>C. nutans</i>. The AgNPs were also proven to possess cytotoxic effects on the breast (MCF-7), cervical (HeLa), and colon (HT-29) cancer cells in a dose-dependent manner. AgNP-S and AgNP-L showed significantly (<i>p</i> < 0.05) higher cytotoxicity against MCF-7 (117.43 <i>μ</i>g/mL) and HT-29 (78.47 <i>μ</i>g/mL), respectively. In conclusion, the biosynthesised AgNPs from aqueous extract leaves and stem of <i>C. nutans</i> have demonstrated promising potential towards antioxidant, antimicrobial, and cytotoxicity activities.