The plant-derived chemicals present in the leaf extract of Gymnema sylvestre (LEGS) commonly known as "Gurmer" has been utilized for the synthesis of Gymnema sylvestre conjugated silver nanoparticles (GS-AgNPs) at room temperature without any auxiliary reducing and capping agents. Spherical shaped GS-AgNPs of 26.6 nm average diameters were observed. A selective dose dependent antimicrobial activity of the freshly synthesized GS-AgNPs on both gram-positive Staphylococus aureus and gramnegative Proteus vulgaris strain showed the same minimum inhibitory concentration (MIC) value at 50 µg/mL, as revealed by in-vitro MIC assay. Zone inhibition study carried out by Disk agar diffusion (DAD) test showed that the GS-AgNPs is sensitive on both the bacteria cell having a comparatively better antimicrobial activity towards Gram-negative over Gram-positive bacteria. The synthesized GS-AgNPs showed very low toxic effect in normal human cells. Dichlorodihydrofluorescein diacetate (DCDHFDA) and ethidium bromide-acridine orange (EB-AO) staining studies revealed that the GS-AgNPs mainly produces Reactive Oxygen Species (ROS) by altering its electron transport chain (ETC) system and it leads to cell death or necrosis through apoptosis of bacterial cells.

The antioxidant activity of the leaf extract of Roscoea purpurea Sm. (commonly known as Kakoli) has been studied against a long lived 2,2-diphenyl-1picrylhydrazyl (DPPH) radical at room temperature. Green syntheses of Kakoli Leaf extract conjugated gold and silver nanoparticles at room temperature have been reported.