Assessment of anti-amyloidogenic activity of marine red alga G. acerosa against Alzheimer's beta-amyloid peptide 25-35

Objective: The amyloid hypothesis stimulates the discovery of compounds, which promotes beta-amyloid peptide (A beta) clearance, thereby altering the underlying pathophysiology of Alzheimer's disease (AD). Hence, the present study aims at the evaluation of anti-amyloidogenic potential of Gelidiella acerosa. Methods: Prevention of A beta 25-35 aggregate formation and disaggregation of pre-formed fibrils by G. acerosa was evaluated in three phases by thioflavin T spectrophotometric assay. The results were further validated by confocal microscopic analysis. The conformational changes in the aggregated and non-aggregated A beta in the presence of G. acerosa were analyzed by Fourier transform infrared (FTIR) spectroscopic analysis. Results: Phase-I study shows that G. acerosa reverts (4.56 +/- 0.35 AU at 96 hours) the increase in fluorescence intensity of aggregated A beta (18.76 +/- 0.99 AU) significantly (P < 0.05) as that of non-aggregated peptides, which suggests that G. acerosa prevents the formation of oligomers from monomers. The seaweed also prevents the fibril formation even after the aggregation process was initiated at 20 hours, which was verified by the significant (P < 0.05) decrease in the fluorescence intensity (2.94 +/- 0.0721 AU) at 36 hours (Phase II). In addition, G. acerosa promotes fibrillar destabilization (Phase III), which was further substantiated by confocal microscopic analysis. Fourier transform infrared spectroscopy reveals that alteration in amide I and amide II band spectrum, which occurs due to A beta 25-35 aggregation was restored upon co-treatment with G. acerosa benzene extract. Conclusion: Overall, the results suggest that G. acerosa might have direct interaction with the aggregated peptide, thereby preventing oligomerization and fibrillation of A beta 25-35.