The Anti-amyloidogenic effect of natural product extracts on amyloid-like fibril formation of trypsin in aqueous organic solvents

The formation of amyloid fibrils has been associated with several human diseases. The appearance of amyloid aggregation is an indicator of different central nervous system neurological disorders and neurodevelopmental diseases, which affect the brain and peripheral tissues. The misfolding and aggregation of proteins cause a large number of different neurodegenerative diseases. Amyloid is a generic structural form of the polypeptide chain and most proteins can form amyloid-like fibrils under proper conditions. Natural product extracts contain important bioactive compounds without undesirable side effects, which are necessary for the prevention and cure of various diseases. 52 phenolic compounds were identified in culinary herbs and spices. The aromatic rings of polyphenols may competitively interact with aromatic residues in amyloidogenic proteins, prevent the π-π interaction and block the self-assembly process. The phenolic hydroxyls of polyphenols may inhibit amyloid fibril formation via binding the hydrophobic residues in amyloidogenic proteins. Here we report the inhibitory effect of some natural product extracts on the formation of amyloid fibrils using trypsin as a model protein in aqueous ethanol. Inhibition of aggregation and fibrillation of trypsin was determined based on turbidity measurement, aggregation kinetics assay, amyloid specific dye Congo red (CR), fouriertransformed infrared (FTIR) spectroscopy, electronic circular dicroism (ECD) and transmission electron microscopy (TEM). The experiments revealed that great anti-fibrillation activity was exerted by chili extract, P. ginseng extract, grapefruit seed extract, peppermint extract, Eduscho coffee extract, and Egri bikavér red wine. It was found that the amount of fibril formation was greatly reduced with increasing concentration of extracts and the inhibitory effect is dose-dependent

Inhibition of the formation of amyloid-like fibrils with spices, especially cloves

During the study of inhibition of amyloid fibril formation, α-chymotrypsin protein was developed in 55% ethanol at pH 7.0. We investigated the inhibitory effect of different spices on amyloid fibril formation using turbidity measurements and Congo red binding assays. We found that all spices except the black pepper and caraway seed prevented fibril formation. The highest inhibition was measured with the clove, which reduced the amount of aggregates by 90%. We studied the inhibitory effect of the cloves at different concentrations on aggregation, it was found that the inhibitory activity of clove is dependent on concentration. We have measured the total phenolic content of the spice extracts too. Based on all these findings we have come to the following conclusion: Our results indicate that spices can contain other compounds too – not only phenolic compounds – which influence the formation of amyloid fibrils, and the effectiveness of various phenolic compounds are different

Inhibition of the formation of amyloid-like fibrils using herbal extracts

We tested the amyloid fibril formation inhibitory effect of seven teas diluted in 55% ethanol at pH 7.0 at a protein concentration of 0.15 mg/ml α-chymotrypsin. In the experiments we investigated the formation and inhibition of amyloid fibrils by turbidity measurements, aggregation kinetics experiments and Congo red binding assay. The results suggest that the different teas effectively inhibit the formation of amyloidlike fibrils. The two most potent inhibitors were peppermint and melilot, extracts which almost completely inhibited the formation of aggregates in 5-fold dilution. The inhibitory effect on the aggregation formation of melilot and peppermint extracts was concentration dependant. The extent of inhibition was found to be proportional with the total concentration of phenolic compounds

Grapefruit Seed Extract Inhibits the Formation of Amyloid-like Fibrils by Trypsin in Aqueous Ethanol

Several natural compounds deriving from plants are known to be efficient anti-amyloid aggregation agents. In this study, anti-aggregation activity of grapefruit seed extract was investigated using trypsin as a model protein in aqueous ethanol at pH 7.0. Using turbidity measurement, Congo red (CR) binding assay, electronic circular dichroism (ECD) and transmission electron microscopy (TEM), we found that grapefruit seed extract has ability to inhibit trypsin amyloidlike fibril formation in vitro, and effectiveness increases with growing concentration of grapefruit seed extract. The total phenolic content of it was determined. The results showed that in addition to the polyphenolic compounds some other compounds are also responsible for the fibril formation inhibitory effect. We indicated it for the first time that limonin has anti-fibrillation effect