The memory-enhancing effects of 7,8,4'-trihydroxyisoflavone, a major metabolite of daidzein, are associated with activation of the cholinergic system and BDNF signaling pathway in mice

Daidzein is one of the dietary isoflavones present in soybean-based products. After ingestion, daidzein is bioconverted into its major metabolite, 7,8,4'-trihydroxyisoflavone (THIF). Given the pharmacological importance of daidzein, 7,8,4'-THIF has also attracted the interest of researchers. However, there are no reports on the effects of 7,8,4'-THIF on cognition and memory with regard to the cholinergic system. Therefore, this study sought to evaluate the memory-enhancing effects of 7,8,4'-THIF in mice. Treatment with 7,8,4'-THIF ameliorated the cognitive impairments induced by scopolamine, a muscarinic acetylcholine receptor antagonist, in the Y-maze and passive avoidance tests. Interestingly, 7,8,4'-THIF treatment also improved cognitive function in normal mice. This treatment was also able to reverse acetylcholinesterase (AChE) and thiobarbituric acid reactive substance (TBARS) activities in the hippocampus. Finally, 7,8,4'-THIF significantly increased the expression levels of the following molecules in the hippocampus: brain-derived neurotrophic factor (BDNF); phospho extracellular signal-regulated kinase (ERK); phospho cAMP response element binding (CREB); and choline acetyltransferase (ChAT). Our data suggest that 7,8,4'-THIF, a metabolized product of daidzein, improves cognitive function by activating the cholinergic system and the BDNF/ERK/CREB signaling pathway in mice.