A study conducted at the Zhejiang University, China, concluded that quercetin inhibited oxidative damage in spermatogonial cells exposed to 3-methyl-4-nitrophenol, a toxic found in diesel exhaust . The team of scientists lead by Zhang analyzed the intracellular antioxidant system of cells from embryonic chickens after treatment with 3-methyl-4-nitrophenol. The found that the toxin induced condensed nuclei and vacuolated cytoplasm, a decreased testicular cell viability, spermatogonial cell numbers and induced lipid peroxidation. Supplementation with quercetin restored these parameters and showed antitox effects.
Quercetin pre-treatment of liver cells provides protection against ethanol-induced oxidative stress and may be used as a new agent for the prevention and treatment of alcoholic liver disease. This was the conclusion of study at Huazhong University of Science and Technology, China . The researchers intoxicated liver cells with ethanol and measured different parameters of cell damage and antioxidant state (lactate dehydrogenase, aspartate transaminase , malondialdehyde, glutathione, superoxide dismutase and catalase). Pre-treatment with quercetin returned all these parameters to the level of the control group.
Abdel-Raheem and colleagues at the Al-Azhar University, Egypt, found that quercetin protected kidney tissue against the nephrotoxic effects of the antibiotic gentamicin . The clinical use of antibiotic is limited by its nephrotoxicity. The researchers theorized that gentamicin acted by forming free radicals and that the antioxidant quercetin protects the cells against these free radicals. They found that injection of rats with quercetin ameliorated histopathological changes and normalized biochemical parameters of the kidneys. Another study by Mexican scientists demonstrated a protective effect of quercetin against liver damage by the toxin diethylnitrosamine. Vásquez-Garzón and colleagues found that pre-treatment with quercetin reduced diethylnitrosamine-induced lesions by up to 70 per cent and inhibited levels of lipid peroxidation by 40 per cent. They concluded that antitoxic action of quercetin is due to the promotion of the enzymatic and non-enzymatic antioxidant defense system during the initiation of hepatocarcinogenesis.
 Quercetin protects embryonic chicken spermatogonial cells from oxidative damage intoxicated with 3-methyl-4-nitrophenol in primary culture. Toxicol Lett. 2009 Jul 8.
 Quercetin protects against ethanol-induced oxidative damage in rat primary hepatocytes. Toxicol In Vitro. 2009 Mar 25.
 Protective effect of quercetin against gentamicin-induced nephrotoxicity in rats. Biol Pharm Bull. 2009 Jan;32(1):61-7.
 Inhibition of reactive oxygen species and pre-neoplastic lesions by quercetin through an antioxidant defense mechanism. Free Radic Res. 2009 Feb;43(2):128-37.