Biomedicine: 2023; 43(1): 249-258 January-February 2023 DOI: https://doi.org/10.51248/.v43i01.2124 Biomedicine- Vol. 43 No. 1: 2023 Review article The factors affecting optimisation of phytosynthesis of silver nanoparticles using Indian medicinal plant species and their biological applications: A review Sima Sikdar, Mausumi Sikdar (nee Bhakta) Microbiology, Nutrition and Dietetics Laboratory, Physiology Unit, Department of Life Sciences, Presidency University, Kolkata-700073, India (Received: September 2022 Revised: January 2023 Accepted: February 2023) Corresponding author: Mausumi Sikdar (née Bhakta). Email: mausumi.dbs@presiuniv.ac.in ABSTRACT Recently, silver nanoparticles (AgNPs) hold a centre stage in the vast arena of research in nanomedicine. Biological methods of synthesis of nanoparticles are being adopted to avoid the use of chemicals that are toxic and hazardous and used in chemical synthetic methods. The choice of the plant extracts used for the synthesis of AgNPs is based on their phytochemicals and pharmaceutical properties. Another importance of the phytosynthesis method is that it is simple, easy, fast, reliable and cost effective. The phytochemical components of the herbal extracts not only cause reduction of Ag +1 to Ag 0 , but also increase the biological activities of the nanoparticles. This article briefly describes the research on green synthesis of AgNPs using Indian medicinal plant extracts. We aim to provide a systemic depth of information regarding the effect of various reaction factors during the synthesis of AgNPs such as the concentration of silver salt and phytoextract, light intensity, time, temperature, pH of the reaction mixture. The characterizations of nanoparticles are done by X-ray diffraction, ultraviolet- visible spectroscopy, Fourier- transform infrared spectra, transmission electron microscopy, dynamic light scattering and zeta potential analysis. The phytochemicals and pharmaceutical activities present in the plant extracts are also reported here. The articles from 2011 to 2022 were selected and studied in detail to get in-depth knowledge about the phytosynthesis of AgNPs and their biological activities. Keywords: phytosynthesis; silver nanoparticles (AgNPs); Indian medicinal plants; pharmacological activities; biological activity. INTRODUCTION round 20% of the world-wide plant species (45,000 species) are found in the Indian sub- continent and among them 6000- 7000 different plants are used in traditional and documented medicine systems like Siddha, Unani, Ayurveda and Homeopathy. For their unique properties and multipurpose applicability, medicinal plants have been gaining importance in various developing areas of research and development (1). Nanoparticles (NPs) occupy a special place in the modern research arena due to their large surface area and nanoscale dimension (1-100 nm) (2). Nanoparticles can be smaller than the size of human cells, and so, can be used for drug delivery into cells. NPs can be delivered by all established methods of administration and has the ability to go deeper to the cellular nucleus (3). Among the various types of NPs, silver nanoparticles (AgNPs) play a key role in nanoscience and technology, especially in nanomedicine (2). Besides that, AgNPs have increased potential for exposure and interaction with terrestrial and aquatic environments. This may lead to toxicity to human health (4). NPs are synthesized using chemical, physical or biological processes. Physical synthesis is cost effective, whereas, the chemical methods involve the use of toxic chemicals and have adverse effects, as some of these toxic chemicals remain adsorbed on the surface of the NPs (5). To eliminate or reduce the toxicity, various biological processes of AgNPs synthesis have been developed. NPs can be synthesized using microbes, enzymes, fungi and plants. The standardisation of these environment friendly methods for the NPs synthesis, especially that of AgNPs, has emerged as a key discipline of nanotechnology, which has diverse applications (6). The method for the synthesis of AgNPs using plant extracts seems to be the best because the methods are simple, easy, faster, reliable, and cost effective (7). Plant extracts contain phytochemicals- such as flavonoids, phenolics, terpenoids followed by polysaccharide, polymers, enzymes and proteins that mainly act as capping, stabilizing and reducing agents (8). It allows the interaction of the green synthesized NPs with microorganisms and also enhances their antimicrobial activity (9). AgNPs synthesized using Azadirachta indica showed no adverse effect when administered orally at 10 mg/kg up to 28 days (10). In the present article, the phytosynthesis and biological activities of silver nanoparticles utilising Indian medicinal plants are discussed, that could help the researchers in their future work involving the phytosynthesis of AgNPs. Method of phytosynthesis of AgNPs using plant extracts Synthesis of AgNPs using plant extracts have been gaining focus because of the wide range of bioactive A 249