Protective Effect of Curcumin on Thermally Aggregated Bovine Serum Albumin

Curcumin is a polyphenol with medicinal properties, including antioxidant properties. It scavenges free radicals by increasing glutathione transferase activity. It is shown to inhibit the aggregation of proteins such as α-synuclein and amyloid β-peptide. In our study, BSA samples were incubated at 65 °C and then analyzed for aggregate formation. Furthermore, curcumin was examined for its anti-aggregatory potential. The inspection of aggregates was done using various spectrophotometric assays like UV-absorbance, congo red, turbidity, and CD spectra, as well as spectrofluorometric measurements such as intrinsic and ThT fluorescence. Visualisation of aggregates was done by transmission electron microscopy. BSA was incubated at 65 °C for 124 h. Intrinsic fluorescence and UV-absorbance showed increased spectra, suggesting unfolding of BSA. Aggregate formation was confirmed by increased ThT intensity, 15 nm red shift in CR absorbance, and appearance of a peak at 218 nm in CD spectra. Addition of 60 µM curcumin was found to be an effective concentration that inhibits the BSA aggregation as validated by decreased ThT fluorescence and CR absorbance. The UV-absorbance, intrinsic fluorescence, and reappearance of peaks at 208 and 222 nm in CD spectra confirmed that curcumin helps to maintain the native contacts of BSA and protects it from unfolding as well as aggregation. Protein aggregates are associated with various pathological conditions. In this study, curcumin was found to be a potential therapeutic molecule to clear aggregates in vitro. These results suggest developing a clinically used imitative of curcumin and related compounds.