Effects of hydroalcoholic, methanolic, and hexane extracts of brown algae Sargassum angustifolium on scopolamine-induced memory impairment and learning deficit in rodents

Properties of Alzheimer's disease, can be caused by several reasons and there is no definite treatment for it. We aimed to study the effect of the hydroalcoholic extract, methanolic and n-hexane fractions of brown algae Sargassum angustifolium on memory impairment in mice and rats. 

Experimental approach:

 Hydroalcoholic extract (25, 50, 100, 200 mg/kg), methanolic (20 and 40 mg/kg) and n-hexane (40 and 60 mg/kg) fractions of S. angustifolium were administered for 21 days intraperitoneally before scopolamine injection (2 mg/kg) on day 21. Rivastigmine was administered for 3 weeks intraperitoneally as well. Then, cognitive function was evaluated by three behavioral tests: passive avoidance, object recognition, and the Morris Water Maze test.

Scopolamine induced memory impairment and rivastigmine significantly reversed the memory dysfunction in all three tests. Hydroalcoholic extract and methanolic fraction significantly reversed scopolamine-induced memory impairment in passive avoidance by 64% and 55% and enhanced the recognition index in the object recognition test. In the Morris water maze test probe trial and training session, on days 3 and 4, the hydroalcoholic extract showed a significant decrease in time spent in the target quadrant and path length, respectively. Also, hydroalcoholic extract and methanolic fraction decreased escape latency time in training sessions on days 3 and 4, by 50% and 31% in comparison to scopolamine. N-hexane fractions had no significant effect on scopolamine-induced cognitive impairment. 

Conclusion and implications:

 Although the n-hexane fraction wasn’t effective, the administration of hydroalcoholic extract and the methanolic fraction of S. angustifolium enhanced scopolamine-induced memory impairment.