Oral administration of evening primrose leaf extract improves cognitive impairment in 5xFAD transgenic mice

This study investigated the cognitive benefits of Oenothera biennis L. (evening primrose) leaf (EPL) ethanolic extract in 5xFAD mice, a transgenic model of Alzheimer's disease (AD). Starting at two months of age, mice orally received EPL extract (100 or 200 mg/kg BW per administration), three times per week for 14 weeks. Cognitive performance was assessed using the passive avoidance, Morris water maze, and Y-maze tasks. EPL-treated mice showed significant improvements in associative and spatial learning and memory, although working memory was unaffected. EPL also reduced plasma levels of pro-inflammatory mediators, including tumor necrosis factor-alpha (TNFα) and nitric oxide, and suppressed TNFα, interleukin-6 mRNA, and cyclooxygenase-2 expression in the brain. Histological analysis revealed reduced amyloid-beta (Aβ) plaque accumulation in AD-vulnerable hippocampal regions. These results suggest that chronic EPL supplementation may alleviate neuroinflammation and Aβ burden while enhancing cognitive function, highlighting its potential as a natural dietary intervention for AD prevention or management.