Introduction: Diagnosing and treating diseases associated with amyloid fibers remain a great
challenge despite of intensive research carried out. One important approach in the development
of therapeutics is the use of herbal extracts which are rich in aromatic small molecules.
Cinnamomum verum extract (CE) contains proanthocyanidin and cinnamaldehyde, which have
been suggested to be capable of directly inhibiting amyloid fibril formation in vitro. This study
is aimed at characterizing the inhibitory activity of CE against the fibrillation of hen egg white
lysozyme (HEWL).
Methods: Acidic pH and high temperatures were used to drive the protein towards amyloid
formation. Lysozyme was dissolved at 2 mg/mL in 50mM glycine buffer (pH 2.5), and then
incubated at 57 °C for the specified durations while stirred gently by Teflon magnetic bars.
Various techniques including thioflavin T, fluorescence, Congo red absorbance assay and AFM
micrography were used to characterize the HEWL fibrillation processes.
Results: In the absence of CE typical amyloid fibrils (like amyloids formed in Alzheimer disease)
became evident after 48 h of incubation. Upon incubation with various extract concentrations in
the range of 0.1-1 mg/ml, formation of fibrillar assemblies were significantly inhibited (p<0.05).
AFM analysis and MTT assay also confirmed the role of the extract in amyloid inhibition. Our
studies showed that the presence of CE did not have any effect on protein stabilization and thus
directly interact with amyloid structure and inhibit formation of these structures. Furthermore, a
docking experiment showed that a pi-pi interaction may occur between the aromatic component
of cinnamaldehyde and W62. Interestingly, W62 is one of the principal aromatic residues that
interact with glycine amide, which is an aggregation suppressor of HEWL.
Discussion: These observations suggest that aromatic small molecules of CE may directly insert
into amyloidogenic core of early aggregates and inhibit amyloid fibril formation by disrupting
the pi-pi interactions.
Type of Study:
Original |
Subject:
Clinical Neuroscience Received: 2014/02/8 | Accepted: 2014/11/25 | Published: 2015/01/1