Phlorotannin-rich fraction from Ishige foliacea brown seaweed prevents the scopolamine-induced memory impairment via regulation of ERK-CREB-BDNF pathway

Ishige foliacea, a species of edible brown algae, contains specific polyphenols called phlorotannins, which have antioxidant, anti-inflammatory, and anticancer properties. We hypothesized that the phlorotannin-rich fraction of I. foliacea (PRFI) is neuroprotective. We investigated the effects of PRFI on scopolamine-induced memory impairment in mice. PRFI (50 or 100 mg/kg) supplementation for 6 weeks improved scopolamine-induced memory impairment symptoms in the Morris water maze and passive avoidance tests. PRFI reduced acetylcholinesterase activity in the brain and significantly decreased lipid peroxidation levels, but increased glutathione levels and superoxide dismutase activity. Additionally, PRFI up-regulated the expression levels of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B, and phosphorylated extracellular signal-regulated kinase (ERK) and cyclic AMP-response element-binding protein (CREB), which are involved in neuroplasticity in the cerebral cortex and hippocampus. Our results suggest that PRFI prevents scopolamine-induced memory impairment, possibly through oxidative scavenging and ERK-CREB-BDNF pathway regulation.