The green synthesis of plasmonic metal nanoparticles
(NPs) has
gained considerable attention among researchers as it is cost-effective,
environmentally friendly, energy-saving, and nontoxic. We have synthesized
silver NPs (Ag NPs) with Oscimum sanctum (holy Tulsi) medicinal plant leaf extract by green synthesis methods.
Further, we investigate the antibacterial, antioxidant, and antidiabetic
activities of the synthesized Ag NPs. Oscimum sanctum leaf extract has secondary metabolites such as phenolic and flavonoid
compounds, which play a significant role in the synthesis of Ag NPs.
Subsequently, these bioactive molecules get adsorbed on the large
surfaces of the synthesized NPs. Spectroscopic techniques such as
X-ray diffraction (XRD), UV–visible absorption, Fourier-transform
infrared, and scanning electron microscopy have been used to study
and characterize the phytosynthesized Ag NPs. The XRD pattern confirms
the formation of crystalline Ag NPs with a high degree of intensity.
UV–visible absorption spectra confirm the surface plasmon resonance
peak in the range of 440–450 nm. A scanning electron microscopy
picture reveals homogeneous growth of Ag NPs with particle sizes of
200–400 nm; however, crystallite size along different planes
has been estimated in the range of 18–23 nm. We have found
that these Ag NPs synthesized with Oscimum sanctum leaf extract show inhibitory activity against α-amylase and
α-glucosidase enzymes in vitro. Our findings further reveal
that these Ag NPs are more effective in inhibiting the growth of Salmonella typhi bacteria as compared to other bacterial
strains.