Differential neuritogenic activities of two edible brown macroalgae, Undaria pinnatifida and Saccharina japonica.

Undaria pinnatifida (Harvey) Suringar and Saccharina japonica Areschoug are two common seaweeds, and both are known to have numerous pharmacological properties that include neuroprotective effects. In a previous study, we found that the ethanol extracts of U. pinnatifida (UPE) and S. japonica (SJE) had neurite promoting activities on developing hippocampal neurons. In the present study, we studied and compared the effects of UPE and SJE on neuronal maturation. Both UPE and SJE promoted neurite outgrowth in a dose-dependent manner with optimal concentrations of 5 and 15 μg/mL, respectively. Initial neuronal differentiation was significantly promoted by UPE and SJE. Subsequently, treatment with both increased indices of axonal and dendritic cytoarchitecture, such as, the numbers and lengths of primary processes, although only UPE had a significant effect on branching frequencies. In addition, UPE and SJE showed no evidence of cytotoxicity, rather they protected neurons from naturally occurring death in vitro. These results indicate that UPE and SJE promote axodendritic maturation and neuronal survival and suggest that these algal extracts, especially UPE, have beneficial effects on the nervous system.