In vitro and in silico approach to determine neuroprotective properties of iridoid glycosides from aerial parts of Scrophularia amplexicaulis by investigating their cholinesterase inhibition and anti-oxidant activities

Three iridoid glycosides included 6-O-methyl, 1-glucopyranosyl catalpol (Compound 1), 6-O-α-L (3"-O-trans, 4"-O-trans cinnamoyl)-rhamnopyranosyl catalpol (Compound 2) and scropolioside D (Compound 3) were isolated from aerial parts of S. amplexicaulis using chromatographic methods. The structures were determined by different spectroscopic data. The inhibitory effects (IC50 values) of the compounds on cholinesterase (AChE and BChE) was determined by in-vitro assays. Docking studied were performed to investigate receptor-ligands interactions. The antioxidant capacity was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, 2, 2'-azino-bis[3-ethylbenzothiazoline]-6-sulphonic acid (ABTS) radical cation, cupric ion reducing activity (CUPRAC), ferric reducing antioxidant power (FRAP), phosphomolybdenum and metal chelating assays. AChE and BChE were moderately inhibited by all of the investigated iridoid glycosides (compared to galantamine). Compound 2 and compound 3 showed comparable anti-oxidant effects with the Trolox as the control in phosphomolybdenum assay. Also, compound 1, showed acceptable activities in ABTS radical scavenging and Phosphomolybdenum assays compared to the control.