The protective effect of crocin on the amyloid fibril formation of a[beta]42 peptide in vitro

A[beta] is the main constituent of the amyloid plaque found in the brains of patients with Alzheimer's disease. There are two common isoforms of A[beta]: the more common form, A[beta]^sub 40^, and the less common but more amyloidogenic form, A[beta]^sub 42^. Crocin is a carotenoid from the stigma of the saffron flower and it has many medicinal properties, including antioxidant effects. In this study, we examined the potential of crocin as a drug candidate against A[beta]^sub 42^ amyloid formation. The thioflavin T-binding assay and electron microscopy were used to examine the effects of crocin on the extension and disruption of A[beta]^sub 42^ amyloids. To further investigate the relationship between crocin and A[beta]^sub 42^ structure, we analyzed peptide conformation using the ANS-binding assay and circular dichroism (CD) spectroscopy. An increase in the thioflavin T fluorescence intensity upon incubation revealed amyloid formation in A[beta]^sub 42^. It was found that crocin has the ability to prevent amyloid formation by decreasing the fluorescence intensity. Electron microscopy data also indicated that crocin decreased the amyloid fibril content of A[beta]. The ANS-binding assay showed that crocin decreased the hydrophobic area in incubated A[beta]^sub 42^. CD spectroscopy results also showed that the peptide undergoes a structural change to [alpha]-helical and [beta]-turn. Our study shows that the anti-amyloidogenic effect of crocin may be exerted not only by the inhibition of A[beta] amyloid formation but also by the disruption of amyloid aggregates. Therefore, crocin could be essential in the search for therapies inhibiting aggregation or disrupting aggregation.[PUBLICATION ABSTRACT]