The Effect of Polyphenols in Spices on the Aggregation of the Amyloid-Beta Peptide 1-40

Overview

A primary characteristic of Alzheimer’s disease is the oligomerization of amyloid-beta (aβ) 1-40 random coil structures leading to the formation of amyloid plaques highly resistant to degradation. This study aimed to see the effect of the spices turmeric and chili pepper, with polyphenols curcumin and capsaicin respectively, on the aggregation of the aβ peptide. As pure turmeric is not often ingested alone, capsaicin was also studied, individually and in a mix alongside curcumin, to evaluate its effectiveness in inhibiting aggregation. Circular Dichroism (CD) was utilized to monitor the progress of aβ oligomerization daily, using CD sample holders (cells) at 50 mM per sample. A mixture of phosphate buffer and trifluoroacetic acid was added to maintain each CD cell’s contents at a pH of 7.4. Each cell was kept away from light, maintained at room temperature, and at a consistent pH and concentration in order to maintain as much control as practical. The CD passed light through each sample cell, and the results were plotted as a graph of wavelength (nm) vs. change in ellipticity (mdeg); the position of the minima of the curve at wavelengths of 220 and 210 nm signified how far a given sample was from aggregation. By day five, aggregation rates for curcumin, capsaicin and the mix were 6%, 7%, and 9% respectively, while the control aggregated at a rate of 25%. Further bioinformatics and biochemical data involving AD and aβ 1-42 indicated that anethole, tartaric acid and acetic acid had higher efficiency in inhibiting aβ oligomerization.