2.4. Thioflavine T assay (ThT)

Aβ₄₂ aggregation was evaluated by the (ThT) assay as previously described with some modifications [21]. Aβ₄₂ (25 μM) samples, incubated alone or with different concentrations of A. roseum extract, were diluted to 15 μM (monomeric peptide concentration) in 20 mM phosphate buffer, pH 7.4, at 25°C and supplemented with a small volume of a 1.0 mM Thioflavin T (ThT) solution adjusted to 20 μM final concentration. Then, each sample was transferred into multiple wells of a 96-well plate (200 μL/well) and ThT fluorescence was read at 485 nm, the maximum intensity of fluorescence, using a Biotek Synergy 1H plate reader; excitation wavelength was 440 nm. Buffer fluorescence was subtracted from fluorescence values of all samples. The percent inhibition of Aß₄₂ aggregation was calculated using the following formula: I (%) = [(F0-F1)/F0]*100, where F0 and F1 are the florescence of Aß₄₂ and Aß₄₂ + Sample at 485 nm, respectively.