Alchemy in Nature: The Role of Lawsonia inermis Extract Choice in Crafting Potent Anticancer Metal Nanoparticles.

Phyto-nanotechnology provides an eco-friendly approach for synthesizing biocompatible metal nanoparticles (NPs) with therapeutic potential. Lawsonia inermis (LI) has been historically valued for its diverse medicinal applications, especially its exceptional biological potency against various skin diseases, attributed to its rich abundance of bioactive compounds. Therefore, herein, plant-based iron and zinc NPs were biofabricated via sustainable and simple methods, using crude extracts of the aerial parts of LI as reducing, coating, and stabilizing agents. Since the extraction method affects the type of extracted phytocompounds, two extraction approaches─aqueous and hydro-alcoholic─were applied to determine the influence of the extraction route on the physicochemical and biological properties of the formed NPs. These properties were characterized via various analytical techniques and assays. The UV-Vis spectra revealed absorption bands ranging from 265 to 270 nm, while FT-IR confirmed the successful coating of the NPs with the extracts' phytochemicals, validating the biofabrication of the proposed NPs. The alcoholic-based NPs displayed higher total phenolic content, total flavonoid content, and antioxidant effect compared to their aqueous-based counterparts, reaching up to 55.13 μg of GAE/1 mg of dry weight (DW), 30.48 μg of QU/1 mg of DW, and IC(50) of 46.02 μg/mL, respectively. All tested samples, except for Fe NPs, displayed significant cytotoxic effects against skin cancer, resulting in a cell viability as low as 1% at 1000 μg/mL. QTOF-LC/MS/MS analyses of LI extracts revealed tentative identification of more than 100 metabolites with phenolic compounds representing the largest share. Orthogonal Projections to Latent Structures Discriminant Analysis modeling revealed a clear separation between both extracts, with more than 40 marker compounds. The results indicated that both extracts were effective for the green synthesis of Fe and Zn NPs for biomedical applications, with the alcoholic extract of LI as a superior coating candidate and the aqueous extract as a stronger reducing agent. This work showcases the influence of extraction protocols on physicochemical and biological characteristics of the resulting nanoparticles.