**3.1 Green chemistry and preparation of silver nanoparticles using natural phenolic compounds**

Silver nanoparticles (AgNPs) exhibit unique chemical and biological properties and thus gained extensive interest in commercial applications including food, textiles, pharmaceuticals, and medical products. Green synthesis is a reliable and eco-friendly process for synthesis of AgNPs, which was reported by FAB-Lab team [24] based on the reducing power of different plant extracts. Forty-two aqueous plant extracts were investigated for their ability to produce AgNPs from aqueous solution of AgNO3. Our study showed that the extracts of *Emblica officinalis* fruit, *Psidium guajava* leaves, and *Lawsonia inermis* leaves were able not only to produce AgNPs but also to stabilize the produced nanoparticle. Phytochemical study showed that these extracts contain tannins, polyphenolics, flavonoids, and naphthoquinones, which are responsible for the bioreduction of silver ions to AgNPs (As shown in **Figure 2**). The transmission electron microscopy (TEM) images revealed that the produced AgNPs are characterized by having a spherical and well-dispersed particles with size range from 5 to 30 nm. Interestingly, the AgNPs prepared by *E. officinalis* fruit, *P. guajava* leaves showed nearly the same cytotoxic activity effect as their plant extract. However, AgNPs capped with *L. inermis* exhibited cytotoxic effect against both colon and breast cancer cell lines. This study suggests that AgNPs synthesized and stabilized with *L. inermis* leaves extract could contribute to the development of an appropriate anticancer medication [24].
