Neuroprotective effect of methanolic extract of brown algae Sargassum tenerrimum in a scopolamine-induced memory impairment adult zebrafish model

Sargassum tenerrimum is a brown polysaccharide-rich seaweed known for its antioxidant, anti-inflammatory and antimicrobial properties. This study evaluated the neuroprotective capability of the methanolic extract of Sargassum tenerrimum (MEST) in adult zebrafish (Danio rerio) using a scopolamine-induced memory impairment model. Initially, after acclimatisation, zebrafish were divided into six groups. To analyse the behaviours, the T-maze test and the conditioned inhibitory avoidance test were performed. To analyse the behaviours, the T-maze test and the conditioned inhibitory avoidance test were performed. To validate the behavioural activity, brain samples were collected and biochemical assays of antioxidant and anti-inflammatory properties were performed. The behaviour results from the T-maze test showed that after the fish were treated with MEST, there was a significant increase in time spent in the green arm (p < 0.01) and a decrease in latency to reach the red arm (p < 0.01). In the condition inhibitory avoidance test, there is also a significant decrease in the latency to reach the dark compartment. Additionally, biochemical study showed a significant increase in antioxidant enzymes (superoxide dismutase (SOD), p < 0.01; glutathione S-transferase (GST), p < 0.0001; lipid peroxidation (LPO), p < 0.001) and a significant decrease in anti-inflammatory cytokinin levels (tumour necrosis factor-α (TNF-α), p < 0.01; interleukin-1β (IL-1β), p < 0.0001). Furthermore, a significant decrease in acetylcholinesterase (AChE) (p < 0.0001) is observed, which prevents the breakdown of acetylcholine. These results indicate that the MEST provides strong neuroprotection in a zebrafish scopolamine-induced amnesia model, probably through antioxidant and anti-inflammatory mechanisms. Further investigations to determine dose-dependent effects and active constituents of these algae should be carried out in a higher vertebrate mammalian model.