Background: The emergence of eco-friendly methods for the synthesis of metallic
nanostructures has continued to receive wider acceptance.
Objective: The study investigated the effect of biologically-synthesized ZnO nanoparticles on free
radicals and carbohydrate-hydrolyzing enzymes.
Methods: The characterized nanoparticles, DaZnONPs (Dicoma anomala zinc oxide nanoparticles)
were obtained using ultraviolet-visible spectroscopy, transmission electron microscopy, Fourier-
transform infrared spectroscopy (FTIR), energy dispersive spectroscopy, and X-ray diffraction
technique (XRD). The activity of the synthesized nanostructures against 1,1-diphenyl-2-picrylhydrazyl
(DPPH), 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), metal chelating,
alpha-amylase and alpha-glucosidase was determined using standard methods.
Results: DaZnONPs were observed to be stable, mostly cubical in shape and within the nanometre
size range. Optimum absorption of DaZnONPs was observed at 386 nm. The FTIR analysis indicated
the presence of functional groups arising from alkaloids, flavonoids, tannins, and saponins
(detected in earlier reports) and indicate potential nucleation and stability of the ZnONPs. XRD
result depicted similar patterns of DaZnONPs and standard ZnO spectra, revealing a hexagonal
and crystalline nature of the particles in nanometre range as shown by the obtained peaks.
DaZnONPs inhibited DPPH (0.54 μgmL-1) and alpha-amylase (104.34 μgmL-1) better than quercetin
(349.98 μgmL-1) and acarbose (594. 54 μgmL-1). Meanwhile, the metal chelating effect of
DaZnONPs (30.41 μgmL-1) was observed to be insignificantly (p>0.05) at par with quercetin
(27.81 μgmL-1). The kinetics of alpha-amylase and alpha-glucosidase enzymes by DaZnOnPs was
observed to be non-competitive inhibitions.
Conclusion: DaZnONPs (as against the bulk extract) could be explored as possible antioxidative
and antihyperglycaemic agents mitigating the adverse effects of free radicals and hyperglycaemia.