Cognitive-enhancing and antioxidant activities of the aqueous extract from Markhamia tomentosa (Benth.) K. Schum. stem bark in a rat model of scopolamine

Abstract

Background: Plants of the genus Markhamia have been traditionally used by different tribes in various parts of West African countries, including Cameroun. Markhamia tomentosa (Benth.) K. Schum. (Bignoniaceae) is used as an antimalarial, anti-inflammatory, analgesic, antioxidant and anti-Alzheimer agent. The current study was undertaken in order to investigate its anti-amnesic and antioxidant potential on scopolamine-induced cognitive impairment and to determine its possible mechanism of action.

Methods: Rats were pretreated with the aqueous extract (50 and 200 mg/kg, p.o.), for 10 days, and received a single injection of scopolamine (0.7 mg/kg, i.p.) before training in Y-maze and radial arm-maze tests. The biochemical parameters in the rat hippocampus were also assessed to explore oxidative status. Statistical analyses were performed using two-way ANOVA followed by Tukey's post hoc test. F values for which p < 0.05 were regarded as statistically significant.

Results: In the scopolamine-treated rats, the aqueous extract improved memory in behavioral tests and decreased the oxidative stress in the rat hippocampus. Also, the aqueous extract exhibited anti-acetylcholinesterase activity.

Conclusions: These results suggest that the aqueous extract ameliorates scopolamine-induced spatial memory impairment by attenuation of the oxidative stress in the rat hippocampus.

Keywords: Acetylcholinesterase; Alzheimer’s disease; Markhamia tomentosa stem bark extract; Oxidative stress; Scopolamine; Spatial memory.

Fig. 1

HPLC chromatogram the aqueous extract from Markhamia tomentosa stem bark. The major identified compounds were rozmarinic acid, (+)-catechin, procyanidin dimer, (−)-epicatechin and cyanidin trimmers

Fig. 2

Effects of the aqueous extract from Markhamia tomentosa stem bark (50 and 200 mg/kg) in the Y-maze on spontaneous alternation  % (a) and on the working memory errors (b) and the reference memory errors (c) during 7 days training in radial arm-maze task in the scopolamine-treated rats. Values are mean ± SEM (n = 5 animals per group). For Tukey’s post hoc analysis—^##Control vs. Sco: p < 0.001, ^#Sco vs. Sco+ME (50 mg/kg): p < 0.01 and ^##Sco vs. Sco+ME (200 mg/kg): p < 0.001 (a), ^##Control vs. Sco: p < 0.0001, ^#Sco vs. Sco+ME (50 mg/kg): p < 0.001 and ^##Sco vs. Sco+ME (200 mg/kg): p < 0.0001 (b) and ^#Control vs. Sco+ME (50 mg/kg): p < 0.001, ^##Control vs. Sco+ME (50 mg/kg): p < 0.001, ^##Sco vs. Sco+ME (50 mg/kg): p < 0.0001 and ^###Sco vs. Sco+ME (200 mg/kg): p < 0.0001 (c)

Fig. 3

Effects of the aqueous extract from Markhamia tomentosa stem bark (50 and 200 mg/kg) on AChE (a), SOD (b) and GPX (c) specific activities, on reduced GSH (d), protein carbonyl (e) and MDA (f) levels in the scopolamine-treated rats. Values are mean ± SEM. (n = 5 animals per group). For Tukey’s post hoc analysis—^#Control vs. Sco: p < 0.01, ^#Sco vs. Sco+ME (50 mg/kg): p < 0.01 and ^##Sco vs. Sco+ME (200 mg/kg: p < 0.001 (a), ^###Control vs. Sco: p < 0.0001, ^##Sco vs. Sco+ME (50 mg/kg): p < 0.001 and ^###Sco vs. Sco+ME (200 mg/kg): p < 0.0001 (b), ^###Control vs. Sco: p < 0.0001, ^###Control vs. Sco+ME (50 mg/kg): p < 0.0001, ^###Control vs. Sco+ME (200 mg/kg): p < 0.0001, ^#Sco vs. Sco+ME (50 mg/kg): p < 0.01 and ^##Sco vs. Sco+ME (200 mg/kg): p < 0.001 (c), ^#Control vs. Sco: p < 0.01, ^#Sco vs. Sco+ME (50 mg/kg): p < 0.01 and ^##Sco vs. Sco+ME (200 mg/kg): p < 0.001 (d), ^##Control vs. Sco: p < 0.0001, ^##Sco vs. Sco+ME (50 mg/kg): p < 0.0001 and ^###Sco vs. Sco+ME (200 mg/kg): p < 0.00001 (e) and ^##Control vs. Sco: p < 0.0001, ^##Sco vs. Sco+ME (50 mg/kg): p < 0.0001 and ^###Sco vs. Sco+ME (200 mg/kg): p < 0.00001 (f)

Fig. 4

Pearson’s correlation between the spontaneous alternation percentage vs. AChE (a), spontaneous alternation percentage vs. MDA (b), working memory errors vs. AChE (c), working memory errors vs. MDA (d), reference memory errors vs. AChE (e) and reference memory errors vs. MDA (f) in control group (filled circle), scopolamine alone treated-group (filled square), Sco+ME (50 mg/kg) group (filled diamond) and Sco+ME (200 mg/kg) group (filled triangle)

Fig. 5

Pearson’s correlation between SOD vs. MDA (a), GSH vs. MDA (b), protein carbonyl vs. MDA (c) and AChE vs. MDA (d) in control group (filled circle), scopolamine alone treated-group (filled square), Sco+ME (50 mg/kg) group (filled diamond) and Sco+ME (200 mg/kg) group (filled triangle)