Evaluation of antimicrobial, antioxidant and antidiabetic properties of green synthesized selenium nanoparticles from Catharanthus roseus

The bio-reduction of selenite (Se (IV)) generates nanoparticles with sizes ranging between 30 and 300 nm. Biological properties of Se nanoparticles are dependent on the nanoparticle size; smaller particles have greater activity. The green SeNPs (selenium nanoparticles) are prepared by mixing of plant leaves methanolic extracts of Centella asiatica, Azadirachta indica, Ocimum tenuiflorum, Murraya koenigii and Catharanthus roseus with sodium selenite. This mixture was stirred which gave a dispersion of SeNPs conjugated with plants phytoconstituents. Among these plants, C. roseus showed high yield of SeNPs and purification of the nanoparticles was performed by alkaline lysis. The visualization and characterization of nanoparticles were performed by UV-Visible spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The antioxidant activity of nanoparticles was determined by ABTS, DPPH and FRAP assays. The anti-bacterial activity was carried out for Streptococcus mutans, Staphylococcus aureus and Escherichia coli and anti-fungal activity was carried out for Candida albicans, Aspergillus niger and Aspergillus flavus using well diffusion method. The suspension solution confirms the formation of SeNPs showed (285 nm) by UV analysis. Screening analysis showed enormous phytoconstituents in leaves methanolic extract and simultaneously, the synthesized SeNPs by FT-IR spectrum confirmed the presence of functional groups which were associated with bioactive molecules. XRD study exhibits the nano-crystalline nature of SeNPs. SEM analysis revealed that the biosynthesized selenium nanoparticles were oval with size range of 195 nm. Green synthesized SeNPs were found to possess significant antioxidant activity (IC50 403.571, 477.48 and 60.090 µg/mL) and SeNPs showed strong antimicrobial action, with A. flavus showing the lowest zone of inhibition (9 mm) and S. mutans showing the highest zone of inhibition (35 mm). The synthesis of thermodynamically stable aqueous SeNPs has been aided by the active phytoconstituents found in C. roseus leaves extract, which are effective reducing agents. The present results support the advantages of green method to produce Se NPs having potential activities.