Plant Based Synthesis of Metal Oxide Nanoparticles: Characterization, Mechanistic Insights, and Biological Functions -A Review

The utilization of plant-based systems for the biosynthetic production of metal oxide nanoparticles (MONPs) has emerged as a prominent and cost-effective over other synthethic systems. The presence of a wide variety of bioactive phytochemicals in plants, such as phenolics, flavonoids, alkaloids, terpenoids, and proteins, acts as natural reducing, capping, and stabilizing agents during MONPs synthesis, thereby creating an eco-friendly synthesis process that does not make use of toxic chemicals and enabling meticulous control over the shape, size, and surface morphology of MONPs. The synthesis of various MONPs (ZnO, TiO2, CuO, NiO, Ag2O, and Fe3O4/Fe2O3) using extracts from various plant parts (leaves, flowers, roots, bark, fruit, etc.) has been reported over the years. The MONPs are characterized using various techniques to determine properties such as size, structure, morphology, surface area, optical properties, etc. which are affected by experimental parameters such as the pH and temperature of the reaction, as well as the concentration of extract employed. This review highlights plant-based approaches for the environmentally friendly and rapid synthesis of MONPs. It discusses diverse synthesis strategies, characterization techniques, and the multifunctional properties of biosynthesized MONPs, supported by selected proof-of-concept studies. Moreover, the biomedical applications of plant-mediated MONPs with a specific emphasis on antimicrobial, antioxidant, anticancer, and anti-inflammatory activities are discussed. At the same time, challenges associated with reproducibility, scalability, and in-depth mechanistic understanding of the synthesis process still require attention. Due to the lack of comprehensive knowledge about the synthesis of MONPs via plant extracts , the present review aims to promote interdisciplinary research endeavors to explore the production of MONPs from natural sources, emphasizing their multifunctionality and diverse biomedical applications.