Soybean supplementation helps reverse age- and scopolamine-induced memory deficits in mice

Phytoestrogens are nonsteroidal plant compounds that are able to exert estrogenic effects. Soybean is a rich source of phytoestrogens, especially isoflavones. Soy isoflavones are utilized for estrogen replacement therapy. Estrogen is reported to influence several areas of brain that are involved in cognition and behavior. Therefore, the present study was undertaken to examine whether dietary supplementation with soybean improves the cognitive function of mice. Soybean was administered in three different concentrations (2%, 5% and 10% [wt/wt]) in the normal diet to young and mature mice for 60 successive days. The passive avoidance paradigm and the elevated plus maze served as the exteroceptive behavioral models, whereas scopolamine (1.4 mg/kg, i.p.) served as the interoceptive behavioral model. The brain acetylcholinesterase activity (AChE) activity, brain thiobarbituric acid-reactive substances (TBARS), reduced glutathione (GSH), and total blood cholesterol levels were also measured in the present study. The administration of soybean for 60 consecutive days protected (P < .05) the animals from developing memory impairment. Soybean administration also resulted in diminished brain AChE activity, decrease in brain TBARS, and increase in GSH levels, thereby indicating facilitated cholinergic transmission, reduced free radical generation, and enhanced scavenging of free radicals. Thus, soybean appears to be a useful remedy for improving memory and for the management of cognitive deficits owing to its pro-estrogenic, antioxidant, procholinergic, and/or neuroprotective properties.