Investigation into the Effect of Emodin-8-O-β-D-glucoside on Sleep Improvement in a Mouse Experimental Model

Background Poor sleep quality and even insomnia are global problems, especially after the COVID-19 pandemic, and bioactive substances in natural herbal medicines may improve subjective sleep for people with insomnia. However, their active components still need to be isolated, determined, and verified by pharmacological experiments. Purpose To verify the efficacy of emodin-8-O-β-D-glucoside (EG), derived from Caulis Polygoni Multiflori in improving sleep in mice. Methods Hypnotic effect test, hypnotic experiment of sodium pentobarbital at a subthreshold dose, measurement of sleep latency induced by sodium barbital, and extending sodium pentobarbital sleep time experiment were performed in mice after different concentrations of EG were given intragastric administration for 30 days. The concentrations of 5-hydroxytryptamine (5-HT) and gamma-aminobutyric acid (GABA) in mouse brain tissue were determined by enzyme-linked immunosorbent assay. Levels of tryptophan hydroxylase 2 (TPH2) were detected by western blotting analysis and immunofluorescence labeling. Results After 30 days of continuous administration, behavioral experiments showed EG could shorten the time to fall asleep and prolong sleep duration. Tests revealed EG dose-dependently increased the levels of 5-HT in the brain tissue and the cause might be it could increase the expression of TPH2, the rate-limiting enzyme of 5-HT, in nerve cells in the hypothalamus. Conclusion Experimental data confirmed that EG could shorten sleep latency and prolong sleep time to improve sleep, and its mechanism of sleep meliorating is related to the upregulation of TPH2 and 5-HT levels in brain tissue.