Bioassays guided isolation of berberine from Berberis lycium and its neuroprotective role in aluminium chloride induced rat model of Alzheimer’s disease combined with insilico molecular docking

OBJECTIVE: Berberis lycium is an indigenous plant of Pakistan that is known for its medicinal properties. In the current study, we investigated the anti-Alzheimer’s effect of berberine isolated from Berberis lycium. METHODS: Root extract of B. lycium was subjected to acetylcholinesterase inhibition assay and column chromatography for bioassays guided isolation of a compound. The neuroprotective and memory improving effects of isolated compound were evaluated by aluminium chloride induced Alzheimer’s disease rat model, elevated plus maze (EPM) and Morris water maze (MWM) tests., Levels of dopamine and serotonin in rats brains were determined using HPLC. Moreover, western blot and docking were performed to determine interaction between berberine and β-secretase. RESULTS: During fractionation, ethyl acetate and methanol (3:7) fraction was collected from solvent mixture of ethyl acetate and methanol. This fraction showed the highest anti-acetylcholinesterase activity and was alkaloid positive. The results of TLC and HPLC analysis indicated the presence of the isolated compound as berberine. Additionally, the confirmation of isolated compound as berberine was carried out using FTIR and NMR analysis. In vivo EPM and MWM tests showed improved memory patterns after berberine treatment in Alzheimer’s disease model. The levels of dopamine, serotonin and activity of antioxidant enzymes were significantly (p<0.05) enhanced in brain tissue homogenates of berberine treated group. This was supported by decreased expression of β-secretase in berberine treated rat brain homogenates and good binding affinity of berberine with β-secretase in docking studies. Binding energies for interaction of β-secretase with berberine and drug Rivastigmine is -7.0 kcal/mol and -5.8 kcal/mol respectively representing the strong interactions. The results of docked complex of secretase with berberine and Rivastigmine was carried out using Gromacs which showed significant stability of complex in terms of RMSD and radius of gyration. Overall, the study presents berberine as a potential drug against Alzheimer’s disease by providing evidence of its effects in improving memory, neurotransmitter levels and reducing β-secretase expression in the Alzheimer’s disease model.