Introduction: Quercetin is a polyphenolic flavonoid which has been used in traditional Chinese medicine as a natural therapeutic agent with a broad spectrum of activities (antioxidant, anticancer, neuroprotective, anti-inflammatory, antiviral and antibacterial). The aim of this study was to develop and validate a rapid and simple ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method for the determination of quercetin in milk. Material and Methods: Sample preparation was based on a liquid-liquid extraction with 0.5% formic acid in acetonitrile. The chromatographic separation was performed on a ZORBAX SB-C18 column with methanol and 0.5% formic acid as a mobile phase. Results: The procedure was successfully validated. The mean recovery of the analyte was 98%, with the corresponding intra- and inter-day variation less than 10% and 15%, respectively, and the repeatability and reproducibility were in the range of 3%–7.2% and 6.1%–12%, respectively. The lowest level of quantification was 1.0 μg/kg. Conclusion: The proposed method was successfully applied in evaluating the pharmacokinetics of quercetin in milk obtained from dairy cows with clinical mastitis after intramammary administration.

Metalaxyl, a benzenoid fungicide, has hazardous effects on mammalian animals. Exposure to metalaxyl causes oxidative stress as well as clear toxicity. The possible protective impact of quercetin or rosemary extract against liver damage caused by the fungicide metalaxyl in rats were evaluated. Twenty-eight male albino rats split into four equal groups. G1 (control group); Rats were received distilled water. G2 (metalaxyl): Rats were administered oral dosages of metalaxyl (130 mg/kg b.wt) 1/10 LD50 three times a week for six weeks. G3 (metalaxyl + quercetin): Rats were given 50 mg/kg b.wt/day of quercetin in addition to (130 mg/kg b.wt) of metalaxyl. G4 (metalaxyl + Rosemary extract): Rats were given (200 mg/kg b.wt/day) of Rosemary extract in addition to 130 mg/kg b.wt of metalaxyl. The findings showed that rats exposed to metalaxyl had markedly elevated levels of liver marker enzymes and clearly up-regulation of Caspase-3 gene expression. However, rats exposed to metalaxyl showed a considerable downregulation of the expression of the liver HO-1, Nrf2, and Bcl-2 genes. Conversely, Quercetin or Rosmary extract co-treatment with metalaxyl induce significant decreases in serum liver enzymes along with downregulation in caspase 3, while up-regulation of HO-1, Nrf2 and Bcl-2 gene expression in hepatocytes of treated rats. These results suggest that quercetin and rosemary extract may have a potential protective role as strong hepatoprotective, anti-inflammatory and anti-apoptotic properties, mitigate oxidative stress caused by metalaxyl toxicity induced -liver damage by inhibiting caspase 3 mediated initiation of HO-1, Nrf2 and Bcl-2 genes.

Manganese (Mn) is a necessary trace mineral, but imbalanced levels in the body can lead to neurotoxicity. The neurotoxicity of manganese chloride (MnCl2) is associated with dopaminergic neurodegeneration, oxidative damage and neuro-inflammation. This study was conducted to assess the neuroprotective effects of quercetin or rosemary extract on neurotoxicity induced by MnCl2 in rats. Twenty-eight male albino rats were separated into four identical groups.  G1(normal control): Rats were provided with purified water. G2 (MnCl2): Rats were orally administered MnCl2 at a dose of 1/25 LD50 (59.36 mg/kg b.wt) five times a week for six consecutive weeks. G3 (MnCl2+ Quercetin): Rats were given MnCl2 (59.36 mg/kg b.wt) along with Quercetin (50 mg/kg b.wt/day).   G4 (MnCl2+ Rosemary extract): Rats were given MnCl2 (59.36 mg/kg b.wt) along with Rosemary extract (200 mg/kg b.wt/day). Results indicated that a significant upregulation of HAT1, HDAC1, and Phosphatidylinositol 3 kinase (PI3K) gene expression with Global DNA hyper-methylation were observed in brain of MnCl2 exposed rats. Meanwhile, Quercetin or Rosmary extract co-treatment with MnCl2 induce significant downregulation of HAT1,HDAC1 and PI3K  expression with major Global DNA hypo-methylation in the brain of rats. Additionally, treating manganese-exposed rats with quercetin or Rosemary extract also resulted in the preservation of the brain's histological structure. This results suggest that quercetin and rosemary can modulate alterations in histone acetylation in rats brain cells when exposed to manganese through their antioxidant, anti-inflammatory, and anti-apoptotic properties.