Green Synthesis and Characterization of Silver Nano-conjugates Using Heliotropium indicum and Glycosmis pentaphylla Leaf Aqueous Extracts

Heliotropium indicum Linn. (Family Boraginaceae), an annual herbaceous medicinal plant, is usually known as Indian heliotrope. Glycosmis pentaphylla (Retz.) DC (Family Rutaceae) is a perennial shrub, commonly known as orange-berry. These traditionally used medicinal plants originate from tropical and temperate parts of the world along with India, Southeast Asia, Northern Australia, and some other African countries. Extensive literature studies suggested that the different parts of the plant are reported to have vast medicinal properties. The present research study deals with phytochemical screening and evaluation of antioxidant activity of Heliotropium indicum (HI) and Glycosmis pentaphylla (GP) leaf aqueous extracts, and synthesis of silver nanoconjugates in green route using those extracts. The synthesized nanoconjugates were characterized using UV-Vis, DLS, and FT-IR techniques. Finally, antimicrobial activity of the nanoconjugates was evaluated. Results highlighted that Heliotropium indicum has more phenolics (131.63±4.05 mg GAE/g of dry plant material) and flavonoids (50.79±0.98 mg QE/g of dry plant material) content as well as it was showed higher free radical scavenging activity (77.81±0.52%) than Glycosmis pentaphylla. I t was observed that GP-conjugated silver nanoparticles showed antibacterial properties against gram-negative bacteria Escherichia coli (zone of Inhibition=11 mm) and gram-positive bacteria Staphylococcus aureus (zone of Inhibition=2.5 mm), as evident from Kirby-Bauer Disc Diffusion Assay. Though phytochemical concentration was higher in HI with respect to GP, but GPAgNPs showed only antimicrobial activity. Keywords: Antimicrobial, antioxidants, flavonoids, Glycosmis pentaphylla, Heliotropium indicum, nanoconjugates, phenolics