A Study on the Inhibitory Effects of Silymarin on Amyloid Fibrillation of Hen Egg White Lysozyme

An increasing number of studies have demonstrated that polyphenols, compounds frequently occurring in many herbs with antioxidant properties, prevent amyloid fibril formation. However, the mechanisms by which these natural molecules modulate the protein aggregation process are poorly understood. Silybum Marianum is one of the medicinal plants with a wide range of health benefits. Silymarin, extract of the seeds of Silybum Marianum, contains a mixture of flavonolignans and a flavonoid. In the present study, using a range of techniques including Thioflavin T and Nile red fluorescence assays, Congo red binding assay, Circular Dichroism spectroscopy, and Atomic Force Microscopy the efficacy of Silymarin on the inhibition of Hen Egg White Lysozyme (HEWL) fibril formation was investigated. Obtained results demonstrated that Silymarin effectively inhibits fibrillogenesis of HEWL in a concentration-dependent manner. AFM images indicated typical fibrillation in the control solutions, while in samples incubated in the presence of Silymarin extensive inhibition of HEWL fibrillation and amorphous aggregates formation was observed. Based on obtained results, we suggest that preventing of hydrophobic interactions between HEWL amyloidogenic prefibrillar species is the mechanism by which Silymarin inhibits amyloid fibril formation by HEWL. However, additional studies are needed to elucidate the detailed mechanisms involved.