Antioxidant and anti-cholinesterase activity of Sargassum wightii.

BACKGROUND

Sargassum has been used in traditional Chinese medicine since the eighth century AD to treat goiter. Sargassum wightii Greville (Sargassaceae) is a major source of alginic acid used widely in food and drug industries.

OBJECTIVE

To evaluate the anti-Alzheimer potential of S. wightii through evaluation of antioxidant and cholinesterase inhibitory activities.

METHODS

Successive extraction was done using solvents of varying polarity. Solvent extracts (100-500 µg/mL) were employed for all the antioxidant assays. Free radical scavenging activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl, OH•, H2O2 radical scavenging assay. The reducing power of the seaweed was evaluated by ferric reducing antioxidant power and reducing power assay. Cholinesterase (ChE) inhibitory activity was evaluated and the Km, Vmax and Ki were calculated. Further, compound characterization was done by GC-MS analysis.

RESULTS

The non-polar extracts were found to possess significant antioxidant activity. At 100 μg/mL, petroleum ether, hexane, benzene and dichloromethane extracts showed significant ChE inhibitory activity with IC50 values of 19.33 ± 0.56, 46.81 ± 1.62, 27.24 ± 0.90, 50.56 ± 0.90 µg/mL, respectively, for AChE, and 17.91 ± 0.65, 32.75 ± 1.00, 12.98 ± 0.31, 36.16 ± 0.64 µg/mL, respectively, for BuChE. GC-MS reveals that 1,2-benzenedicarboxylic acid, diisooctyl ester is the major compound present in dichloromethane extract of S. wightii. The mode of inhibition exhibited by dichloromethane extract against the cholinesterases was found to be competitive type.

CONCLUSIONS

The presence of high amount of terpenoids could be the possible reason for its potential antioxidant and ChE inhibitory activity.