Investigation of anti–microbial ‎and anti-Alzheimer effects of ‎aqueous and hydro-alcoholic ‎extracts of Nigella sativa by ‎inhibiting the production of ‎amyloid fibrils

Nigella sativa is an annual herbaceous plantthat has various pharmacological effects. In this research study, anti–microbial and anti–Alzheimer effects of aqueous and hydro–alcoholic extracts of N. sativa were evaluated. After identification of hydro–alcoholic extract compounds by GC–MS, anti–microbial activity indices including well diffusion, MIC and MBC for E. coli and S. aureus, were carried out by tube and agar dilution methods. In Anti–Alzheimer's effects of hydro–alcoholic extract of N. sativa on bovine serum albumin were examined using Congo–red spectrophotometry and transmission electron microscopy. Oleic acid (52.18%) followed by palmitic (19.77%) and linoleic acid (14.96%) were the major fatty acids in the extract. The amounts of MIC and MBC for both E. coli and S. aureus were 30.6 and 61 mg.ml-1 respectively in hydro–alcoholic extract. Well diffusion method showed highest antimicrobial activity against S. aureus with inhibition zone diameter of 22.67±0.29 mm, but aqueous extract did not any effects on bacteria. Congo–red spectrophotometry results showed that the absorbance of the protein sample (as a measure of amyloid fibril presence) was reduced by increasing the concentration of N. sativa extract and the lowest percentage of adsorption, compared to the control (extract less), was observed at the highest concentration of extract (20 μL). These results were confirmed by transmission electron microscope. The present study shows that the N. sativa seed, as a natural and valuable source, can be used for controlling the microbial infections and reducing symptoms in patients with Alzheimer's disease.