Polyphenol-enriched Desmodium elegans DC. ameliorate scopolamine-induced amnesia in animal model of Alzheimer's disease: In Vitro, In Vivo and In Silico approaches.

The current study aims to quantify HPLC-DAD polyphenolics in the crude extracts of Desmodium elegans, evaluating its cholinesterase inhibitory, antioxidant, molecular docking and protective effects against scopolamine-induced amnesia in mice. A total of 16 compounds were identified which include gallic acid (239 mg g), p-hydroxybenzoic acid (11.2 mg g), coumaric acid (10.0 mg g), chlorogenic acid (10.88 mg g), caffeic acid (13.9 mg g), p-coumaroylhexose (41.2 mg g), 3-O-caffeoylquinic acid (22.4 mg g), 4-O-caffeoylquinic acid (6.16 mg g), (+)-catechin (71.34 mg g), (-)-catechin (211.79 mg g), quercetin-3-O-glucuronide (17.9 mg g), kaempferol-7-O-glucuronide (13.2 mg g), kaempferol-7-O-rutinoside (53.67 mg g), quercetin-3-rutinoside (12.4 mg g), isorhamnetin-7-O-glucuronide (17.6 mg g) and isorhamnetin-3-O-rutinoside (15.0 mg g). In a DPPH free radical scavenging assay, the chloroform fraction showed the highest antioxidant activity, with an IC value of 31.43 µg mL. In an AChE inhibitory assay, the methanolic and chloroform fractions showed high inhibitory activities causing 89% and 86.5% inhibitions with IC values of 62.34 and 47.32 µg mL respectively. In a BChE inhibition assay, the chloroform fraction exhibited 84.36% inhibition with IC values of 45.98 µg mL. Furthermore, molecular docking studies revealed that quercetin-3-rutinoside and quercetin-3-O-glucuronide fit perfectly in the active sites of AChE and BChE respectively. Overall, the polyphenols identified exhibited good efficacy, which is likely as a result of the compounds' electron-donating hydroxyl groups (-OH) and electron cloud density. The administration of methanolic extract improved cognitive performance and demonstrated anxiolytic behavior among tested animals.