Natural flavonoids are the most plentiful form of polyphenols. Given the anti-inflammatory and antioxidant properties of flavonoids, researchers discovered that it might be effective in treating depression and anxiety. The effect of flavonoids on depression and anxiety was investigated by a meta-analysis and systematic review. We searched PubMed, Embase, and Medline databases up to October 15, 2021. We selected 11 studies, among them, 10 studies were chosen to evaluate the depression effects of flavonoids and 7 studies were used to assess anxiety disorder. The meta-analysis showed that flavonoids have an overall significant effect on depression (p = 0.004, Hedge's g = -0.487, 95% CI -0.814 to -0.160) and anxiety (p = 0.006, Hedge's g = -0.741, 95% CI -1.266 to -0.217). Subgroup analysis indicated that the symptoms of depression were significantly improved in the studies when the dose of flavonoids was 50-100mg/day or the treatment duration was >= 8weeks. Anxiety symptoms were improved in the studies with the dose of flavonoids was >= 50mg/day. There was no evidence of publication bias. Our findings suggest that flavonoids might improve symptoms of depression and anxiety. However, a small number of participants and studies were included in this meta-analysis. Therefore, the results should be interpreted with caution.

Cadmium (Cd) is known to cause damage to the liver. In this study, metabolomics technology was used to investigate the effect of quercetin (QE) on Cd-induced hepatotoxicity. A total of 60 male SD rats were randomly divided into the following six groups: control group (C), low and high-dose QE group (Q1: 10 mg/kg·bw, Q2: 50 mg/kg·bw), Cd group (D), low and high-dose QE and Cd combined intervention group (DQ1, DQ2). The rats were given Cd chloride (CdCl2) at a concentration of 40 mg/L through free drinking water. After 12 weeks of treatment, liver samples of rats were collected for metabonlomic analysis. A total of 12 metabolites were identified, the intensities of PC (18:0/14:1(9Z)) and arachidonate acid were decreased in the Cd-treated group (p < 0.01), whereas the intensities of chenodeoxyglycocholic acid, cholic acid, taurochenodesoxycholic acid, glycocholic acid, prostaglandin D2, 15-deoxy-d-12,14-PGJ2, oxidized glutathione, cholesterol, protoporphyrin IX, bilirubin were increased significantly in the Cd-treated group compared with group C (p < 0.01). When rats were given high doses of QE and Cd at the same time, the intensity of the above metabolites was significantly restored in group DQ2. Results suggest that the protective effect of QE on Cd-induced liver injury is associated with antioxidant activity of QE, as well as QE can regulates hepatic bile acid metabolism by affecting FXR and BSEP, and regulates AA metabolism by inhibiting Cd-induced activities of COX-2 and PLA2.