Quercetin enhances antioxidant capacity and reproductive performance in daphnia pulex

Quercetin is a widely distributed flavonoid found in fruits and vegetables, known for its diverse biological effects. In this study, neonatal Daphnia pulex (within 24 h of birth) were exposed to varying concentrations of quercetin (0, 1, 2.5, 5, and 10 mg/L). At high concentrations, quercetin induced morphological deformities, including concavity on the dorsal surface, which appeared earlier in treated individuals compared to controls. Conversely, low concentrations of quercetin extended the average lifespan, increased molting frequency, and significantly enhanced the net reproduction rate and generation cycle. In contrast, high concentrations significantly reduced both molting frequency and net reproduction rate. Regarding metabolic and antioxidant enzyme activities, quercetin exposure decreased triglyceride (TG) levels. Low concentrations significantly downregulated the activities of acid phosphatase (ACP) and alkaline phosphatase (AKP), while all tested concentrations significantly reduced amylase (AMS) activity. Catalase (CAT) and glutathione (GSH) levels initially increased and then declined with rising quercetin concentrations, a pattern also observed for superoxide dismutase (SOD) activity after 14 days of exposure. Transcriptomic analysis revealed that quercetin treatment significantly upregulated metabolic pathways, followed by cellular processes and genetic information processing. Additionally, quercetin enhanced oxidative phosphorylation and alleviated oxidative stress. These findings suggest that low concentrations of quercetin promote the growth and reproduction of D. pulex, regulates metabolic activity, and enhances antioxidant capacity.