Cytotoxic activity of silver nanoparticles prepared from Psidium guajava L. (Myrtaceae) and Lawsonia inermis L. (Lythraceae) extracts

Purpose: To biosynthesize silver nanoparticles (AgNPs) using Psidium guajava L. and Lawsonia inermis L. leaf extracts, and investigate their antioxidant and cytotoxic activities. Methods: The aqueous extracts were prepared by maceration in distilled H2O followed by partitioning with EtOAc. AgNPs were prepared by treating the extracts with 1 mM AgNO3 and then were characterized by UV-vis and FTIR analyses, and transmission electron microscopy (TEM). MTT cytotoxicity and 2,2`-azinobis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) antioxidant assays were used to assess their cytotoxic and antioxidant properties, respectively. Results: AgNPs from P. guajava and L. inermis extracts exhibited good morphological stability and showed moderate antioxidant activity (68.1 and 71.9%, respectively) compared to their extracts. Equipotent cytotoxicity against HCT-116 and MCF-7 cells was observed for AgNPs derived from P. guajava, while AgNPs derived from L. inermis possessed two-fold cytotoxicity compared to their corresponding extracts. Phytochemical analysis of P. guajava afforded pyrogallol, quercetin, quercetin- 3-O-β-xylopyranoside, quercetin-3-O-β-arabinopyranoside, and quercetin-3-O-α-arabinofuranoside, while L. inermis afforded lawsone and luteolin. Conclusion: Flavonoids and phenolics play a major role in reducing Ag+ ions, surface coating, antioxidant, and cytotoxic activities of AgNPs. The biocompatible AgNPs produced by L. inermis demonstrate promising cytotoxic activity that could contribute to new cancer treatments.