Phytochemical evaluation and antioxidant and inhibitory effects of Citrullus colocynthis L. extract on the production of amyloid nano–biofibrils from bovine serum albumin as a model protein

Colocynth with the scientific name of Citrullus colocynthis L. is one of the plants that it's anti–oxidant and anti–diabetic effects has been shown in previous research. In this study, in addition to the phytochemical study of hydro–alcoholic extract of Colocynth, its anti–oxidant and inhibitory effects on the production of amyloid nanobiofibrils from bovine serum albumin as a model protein have been investigated. The fruit of the plant was collected from the desert areas around Qom in the fall of 2017, dried and then extracted by maaceration method. Analysis of secondary compounds of the extract was performed by gas chromatography-mass spectrometry and the amount of its most important compounds including citrulline and citronellol was obtained by HPLC. The antioxidant activity of the extract was evaluated using DPPH method and then the amyloid fibrils were prepared in the test tube at high temperature and low pH and electron microscope imaging was used to confirm the presence of the fibrils. Congored spectroscopy was used to investigate the inhibitory effects on the production of amyloid fibrils. The results showed that methyl beta-galactopyranoside and beta-diglucopyranoside with 29.51% and 6.31% respectively, were the most abundant chemical compounds and tetradcanoic acid with 16.31% and then octa and hexadecanoic acid with respectively 14.11% and 10.94% were the most compounds found in the extract. The levels of citrulline and citronellol in the extract were 0.0041 and 0.013 mg, respectively. The highest anti–oxidant activity was in the concentration of 10 mg/ml of the extract with 71.5% and the highest inhibition of production of amyloid fibers in the concentration of 1 mg/ml and 99% were seen. Colocynth extract with the presence of potent anti–oxidant compounds and its inhibitory effects on the production of amyloid fibrils, will be very useful in preventing and reducing the incidence of Alzheimer's disease.