Neuroprotective effects of isoflavone-enriched soybean leaves (Glycine Max) on scopolamine-induced memory deficits in C57BL/6 mice via antioxidative mechanisms.

INTRODUCTION

This study aimed to investigate the neuroprotective and memory-enhancing effects of isoflavone-enriched soybean leaves (IESLs) against scopolamine-induced cognitive impairment. While soybean leaves (SLs) are naturally rich in kaempferol glycosides and soyasaponins, IESLs are characterized by significantly elevated isoflavone levels through metabolite farming.

METHODS

To assess the efficacy of IESLs, C57BL/6 mice were orally administered IESLs (6.25 and 18.8 mg isoflavones/kg/day) for 5 weeks, with scopolamine (1 mg/kg, i.p.) administered to induce memory impairment. Spatial learning and memory functions were evaluated using the Morris water maze and passive avoidance tests.

RESULTS

Scopolamine-induced behavioral deficits were significantly restored by IESLs administration in a dose-dependent manner. Mechanistically, IESLs treatment reduced the intracellular accumulation of reactive oxygen species and enhanced the antioxidant defense system. Furthermore, IESLs significantly upregulated the expression of brain-derived neurotrophic factor (BDNF) and activated the cAMP response element-binding protein (CREB) via phosphorylation. Histological analysis also revealed that IESLs suppressed the activation of astrocytes and microglia, thereby attenuating neuroinflammation.

DISCUSSION: These findings suggest that IESLs effectively alleviate cognitive impairment by strengthening antioxidant defenses and activating the CREB-BDNF signaling pathway. Consequently, IESLs may serve as a promising therapeutic or preventive candidate for amnesia and neurodegenerative diseases.