Green synthesis of nanoparticles is superior to physical and chemical methods as it is environment-friendly and cost-effective. The present study was carried out for inducing nanoparticles synthesis by zinc nitrate in the leaves extracts of olive. Further leaves extracts were evaluated for antiradical scavenging activity by 1, 1-diphenyl-2-picryl-hydrazyl assay. Morphological and structural properties of the synthesised ZnO nanoparticles have been characterised using UV-Vis spectrophotometer, FTIR, TEM, XRD and dynamic light scattering (DLS) analysis. Further, zinc oxide nanoparticles were evaluated for antiradical scavenging activity by capacity of total antioxidant assay. Synthesised ZnO nanoparticles were confirmed by the absorption maxima at the wavelength of 370 nm. TEM image revealed that ZnO nanoparticles were spherical with average size 41 nm. FTIR investigation suggested that the flavonoids, glycosides, proteins and phenols molecules can play an important role in the stabilisation of ZnO nanoparticles.

The interaction between nanoparticles and plants is inevitable. In this study, the effect of different concentrations of ZnO nanoparticles synthesised using olive extract on the soybean was studied. The soybean seeds were cultured in a Hoagland medium containing agar which was treated different concentrations (0, 200 and 400 ppm) of ZnO nanoparticles. After 21 days, the plants were harvested and the parameters of proline, anthocyanin, malondialdehyde (MDA), hydrogen peroxide (H 2 O 2), chlorophyll and carotenoid contents and phenylalanine ammonia-lyase (PAL) and catalase (CAT) activity in soybeans (Glycine max) were measured. The results showed that the levels of chlorophyll a and b and carotenoid at concentrations of 200 and 400 ppm in comparison with control decreased, while carotenoid content at 200 ppm concentration at a concentration of 400 ppm was not significant. The level of anthocyanin and PAL activity increased with increasing concentration of nanoparticles, while proline content decreased. By increasing the concentration of ZnO nanoparticles, the content of MDA and hydrogen peroxide increased compared to control but CAT activity did not change significantly. This research suggests that ZnO nanoparticles synthesised using olive extract in soybean plants may be toxic by reactive oxygen species production.

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The size of the nanoparticles is between 1 and 100 nm. Nanoparticles are widely used in consumer and medical products, as well as in agricultural and industrial applications. The excessive use nanoparticles increases its release into the environment. Plants are an important part of the environment that is affected by nanoparticles. Studies have examined the effect of nanoparticles on plants. The results showed that high concentrations of nanoparticles showed a negative effect. Reactive oxygen species generation is a toxicological mechanism of nanoparticles in plants. When the production of radicals is greater than its removal, oxidative stress occurs. The key indicator of oxidative stress is lipid peroxidation. The unsaturated fatty acids in the cell membrane are a major target for radicals. Radical absorbs hydrogen from unsaturated fatty acids to form water. Therefore, the fatty acid has a non-coupled electron, which is then able to capture oxygen and form a peroxyl radical. Lipid peroxyl radical can lead to a chain of radical production. Enzymatic and nonenzymatic systems exist for the removal of radicals in plants. Enzymatic systems include catalase, guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase, glutathione reductase, and dehydroascorbate reductase. Nonenzymatic systems include ascorbate and carotenoids, glutathione, tocopherol, and phenolic compounds.