In recent years, the green synthesis of gold (GNPs) and silver (SNPs) nanoparticles has gained great interest among chemists and researchers. The present study reports an eco-friendly, cost-effective, rapid and easy method for the synthesis of gold and silver nanoparticles using the seed extract of Embelia ribes (SEEr) as capping and reducing agent. The synthesised GNPs and SNPs were characterised using the following techniques: UV-vis spectroscopy, DLS, HR-TEM, FT-IR and XRD. The free radical scavenging potential of GNPs and SNPs was measured by DPPH assay and Phosphomolybdenum assay. Further, the antimicrobial activity against two micro-organisms were tested using disc diffusion method and cytotoxicity of GNPs and SNPs was determined against MCF-7 cell lines at different concentrations by MTT assay. Both the GNPs and SNPs prepared from E. ribes comparatively showed promising results thereby proving their clinical importance.

The importance of medicinal plants in traditional health-care practices provides clues to new areas of research and in the biodiversity of conservation. Right from the beginning, the documentation of traditional knowledge, especially on the medicinal uses of plants, has provided many important drugs for the modern day. Even today, this area holds much more hidden treasure as almost 80% of the human population in developing countries depend on plant resources for health care. Keeping this in view, the present study was initiated to document the traditionally used tribal plants and their inborn antimicrobial activity which is enhanced on the synthesis of noble metal nanoparticles.

Green synthesis of silver nanoparticles (AgNPs) is considered to be nature-friendly and risk-free to the ecosystem. India is copious in biodiversity; the traditional medicine consists of the plant as a major component. The tribal people who lived in the rural region are entirely dependent on the tribal plant for their medical emergencies. These tribal plants have attracted the modern drug industry to develop drugs which are economical with minimal side-effects. The present study focuses on the tribal plants such as Aegle marmelos, Andrographis paniculata, Acacia arabica, Ficus religiosa, Cassia auriculata, Punica granatum, and Tinospora cordifolia used by the Bhilla, Irular, Dimasa, Paliyan Sholaga, and Dantewada tribes of India for their antimicrobial activity. Since these tribal plants are well known for its medicinal properties, the AgNPs synthesized from these plants were found to have enhanced antimicrobial activity than the pure plant extract.

Objective: The current study focuses on optimization and ecologically innocuous green synthesis of silver nanoparticles (AgNPs) using tribal plant Caralluma umbellata and to study its potential as an antibacterial and antifungal agent.Methods: The synthesis of AgNPs were confirmed by the colour change of the stem extract from yellow to dark brown and by UV-Visible spectroscopy. The optimum conditions for synthesis of AgNPs were analysed using Response surface methodology (RSM) based Box-Behnken design (BBD) using Design Expert software (7.0.0 trial version). The AgNPs synthesized were characterized by Scanning electron microscope (SEM), Energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis. Further, antibacterial and antifungal activity were performed using well diffusion method for both plant extract and AgNPs.Results: The UV-Visible spectrum of AgNPs revealed characteristic peak at 425.5 nm. The crystalline nature of synthesized AgNPs was confirmed by XRD with average size 26 nm. SEM confirms the spherical shape of AgNPs and by EDX the presence of elemental silver was observed. The ability of the plant to produce both reducing and capping agents were confirmed by FTIR. The optimum conditions for synthesis of AgNPs were found to be 0.55 mmol AgNO3 concentration, 45 °C temperature and 24h reaction time. Both plant sample and synthesized AgNPs exhibited good antimicrobial activity where AgNPs showed superior efficacy as an antimicrobial agent over the other.Conclusion: From the results obtained, it can be deduced that both C. umbellata stem extract and synthesized AgNPs can act as potent antimicrobial agent. But the synthesized AgNPs is more potent against bacteria and fungus.