In vitro screening for acetylcholinesterase inhibition and antioxidant activity of medicinal plants from southern Africa

Objective:To determine the acetylcholinesterase inhibitory(AChE1) and antioxidant activity of the ethyl acetate and methanol extracts of 12 traditional medicinal plants used in the treatment of neurological disorders.Methods:AChEI activity was determined spectrophotometrically using the Ellman’s colorimetric method.Antioxidant activity was carried out by determining the ability of the extracts to scavenge 2,2-diphenyl-1-picryl hydrazyl(DPPH) and 2,2’-azinobis- 3-ethylbenzothiazoline-6-sulfonic acid(ABTS) radicals.The levels of total phenols,flavonoids and flavonols were determined quantitatively using spectrophotometric methods.Results:AChEI was observed to be dose-dependent.Lannea schweinfurthii(L.schweinfurthii)(Engl.) Engl.and Scadoxus puniceus(S.puniceus)(L.) Friis & I.Nordal.root extracts showed the lowest ICvalue of 0.000 3 mg/mL for the ethyl acetate extracts while Zanthoxylum davyi(Z.davyi)(I.Verd.) P.G. Watermann had the lowest ICvalue of 0.01 mg/mL for the methanol extracts in the AChEI assay. The roots of Piper capense(P.capense) L.f.,L.schweinfurthii,Ziziphus mucronata(Z.mucronata) Willd.,Z.davyi and Crinum bulbispermum(C.bulbispermum)(Burm.f.) Milne-Redh.& Schweick.showed noteworthy radical scavenging activity and good AChEI activity.Conclusions: Five plants show good antioxidant and AChEI activity.These findings support the traditional use of the plants for treating neurological disorders especially where a cholinesterase mechanism and reactive oxygen species(ROS) are involved.