الفهرس 
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Abstract
Zinc OxideNanoparticles(ZnONPs)are among those most widelymanufactured on a global scale.They are amongthe top five used NPs that play an important role in a very wide range of applications, ranging from tyres to ceramics, from pharmaceuticals to agriculture and from paints to chemicals.
The nanoparticles have differentphysical andchemicalproperties comparedto their conventionalbulk counterparts,even if they are of the same composition, whichmight alter their bioactivity.Their ability to induce toxicity has been attributed to their increased surface reactivity. The smaller the particles are, the more surface they have per unit mass and the morereactivetheyare inthe cellular environment.
Investigating the potential hazardous effect of ZnONPs on the seminiferous tubules of adult male albino ratshas been a point of interest in the recent research work, asit is well documented that, after their injection or ingestion, ZnONPsare able tocross the blood-testes barrier,depositandbio-accumulate in the testiculartissue.
Oxidative stress has been suggested to be the main mechanism of toxicity caused by the NPs including the ZnO ones. Therefore,using antioxidantsmay play a role in amelioratingtheirpotentialhazardous effects.
Quercetin is categorized as a flavonol, one ofthe sixsubclasses ofthe flavonoid compounds. It has various importantproperties, making it suitable to act as antioxidant, antitoxinand anti-inflammatory agent. It can scavenge free radicals, inactivate ROSand chelate pro-oxidant transition metals,preventing oxidation of membrane lipids, oxidative modification of proteinsandDNA fragmentation.However, to the best of our knowledge,the possible protective role of quercetinagainst ZnO NPs’toxic effects on the seminiferoustubules,wasnot yetinvestigated.