PTPA and Alzheimer disease: Polgala saponins can reduce the expression of Taup-Ser2 protein and PKA in AD model rats, increase the expression of PP2A protein, reduce the hyperphosphorylation of the Ser396 site of tau protein in brain neurons of AD rats, and protect nerve cells from Aβ1-40 toxicity (Chen et al., 2015).Polygala powder can inhibit the phosphorylation of tau protein in the hippocampal CA1 region of model rats in which AD is induced by Aβ1-40, and its mechanism is related to the regulation of the PI3K/AKT/GSK-3β signaling pathway (Xie P. et al., 2020).