BackgroundE. coccinae (SIMS) G. (Asteraceae) is an annual plant commonly found throughout the plain of the Central Africa and widely used in Cameroonian folk medicine for the treatment of fever and convulsions in children. We previously reported that the methanolic extract of this plant improved spatial memory. However no underlying mechanism was explored. The present study was undertaken to investigate the effects of the hydroalcoholic extract of Emilia coccinae on memory in scopolamine treated rats and to propose possible mechanisms of action.MethodsNovel object recognition and Y-maze paradigm were used to test memory while oxidative profile, AChE and ACh level of the whole brain were assessed to outline the mechanism of nootropic activity of the extract. 200 and 400 mg/kg of the extract were chronically administrated during 14 consecutive days in separate groups of scopolamine intraperitoneal treated rats (1.5 mg/kg).ResultsThe hydroalcoholic extract of Emilia coccinae (HEEC) at the dose of 200 mg/kg significantly improved the memory of rats and reversed the amnesia induced by scopolamine. In addition, we showed that this extract is decreasing the acetyl cholinesterase activity while also increasing the acetylcholine levels in the brain. HEEC (200 and 400 mg/kg) significantly increased antioxidant enzyme activities (SOD, GSH and CAT) and reduced lipid peroxidation (MDA level) in the rat whole brain homogenates.ConclusionsTaken together, our results suggested that the hydroalcoholic extract of Emilia coccinae ameliorated the cognitive dysfunction in scopolamine treated rats through the blockage of the oxidative effect of scopolamine and inhibition of AChE activity.

Ziziphus mucronata Willd, also known as “buffalo thorn,” belongs to the family Rhamnaceae. Its bark and leaves are used in folk medicine for the treatment of various deficiencies related to nociception, inflammation, mood, and depression. Still, there is a lack of scientific data regarding its potential effect on learning and memory process. The present study was designed to investigate the neuroprotective potential of Ziziphus mucronata (ZM) on learning and memory impairment in a scopolamine-induced model of dementia in mice. The phytochemical analysis revealed five cyclopeptide alkaloids (sanjoinines) in the extract from Ziziphus Mucronata leaves using LC-HRMS, and the structural characterization of these compounds was determined via MS/MS. Alzheimer-type amnesia was induced by an intraperitoneal injection of scopolamine (1 mg/kg) to mice for 7 consecutive days. ZM (150 mg/kg, 300 mg/kg, and 600 mg/kg) and piracetam (150 mg/kg) were orally administrated to mice daily for a period of 14 days. Memory-related behavioural parameters were evaluated using the radial arm maze task for 7 days, Y-maze, and novel object recognition task. At the end of protocol schedule, animals were sacrificed, and the levels of acetylcholinesterase, malondialdehyde, catalase, and superoxide dismutase were determined in brain homogenates. Histological studies of the hippocampus were subsequently performed. The long-term scopolamine-injected group decreased the spontaneous alternation (Y-maze), the discrimination index, and the time taken to explore the new object (novel object recognition task). These effects were significantly reversed by ZM at all the doses tested. In the radial arm maze task, ZM (300 and 600 mg/kg) significantly decreased the working and reference memory errors when compared with the demented group. Scopolamine-mediated changes in AChE activity were also attenuated by ZM in mice. In addition, extract-treated groups showed a significant increase in the level of CAT and SOD activity and decreased levels of MDA in the mice brains, as compared with the control group. The present study suggests that ZM could have an important role in neuroprotection on this scopolamine-induced model of Alzheimer-type dementia.

Daniellia oliveri (DO) is a traditional medicinal plant used for the treatment of diseases such as inflammation, schizophrenia, and epilepsy in Nigeria, Kenya, Congo, and Cameroon. This study was carried out to evaluate the potential neuroprotection effect of the aqueous root bark extract of Daniellia oliveri against diazepam-induced amnesia in mice. Thirty-six adult male mice were distributed into six groups: the three test groups received Daniellia oliveri root bark extract (100, 200, and 300 mg/kg), the normal control group received distilled water (10 ml/kg), a positive control group received piracetam (150 mg/kg), and the negative control received diazepam (2.5 mg/kg). Learning and memory were evaluated using the radial arm maze and the T-maze. Biomarkers of oxidative stress were also quantified in mice brains. Statistical analyses were performed using two-way ANOVA followed by Tukey’s post hoc test. Daniellia oliveri root bark aqueous extract decreased the number of working memory errors and number of reference memory errors in amnesic mice evaluated in the radial arm maze. Also, an increase in glutathione activity and a decrease in malondialdehyde levels were noted in the hippocampi homogenate of the extract-treated mice as compared to the diazepam-demented but untreated group. Moreover, pretreatment with Daniellia oliveri aqueous root bark extract reversed the decrease in hippocampal cell density observed in the nontreated diazepam group. Taken together, these results suggest that the aqueous extract of DO leaves possesses antioxidant potential and might provide an opportunity for the management of neurological abnormalities in amnesic conditions.

The present study was conducted to investigate protective effects of the aqueous extract of V. subterranea seeds landrace on amnesia induced by scopolamine in mice. V. subterranea aqueous extract (100, 200 and 400 mg/kg BW) was administered by gavage for nine consecutive days and memory impairment was induced by repeated intraperitoneal injection of scopolamine (1.5 mg/kg). The Y-maze (YM), Morris water maze (MWM), novel object recognition paradigm (NOR) and the T maze (TM) were used to assess learning, memory and retention. Superoxide dismutase (SOD), Catalase (CAT), Malondialdehyde (MDA) levels and Acetylcholine esterase activity was also evaluated in the mice hippocampi homogenates. V. subterranea aqueous extract (400 mg/kg) significantly increased the percentage of spontaneous alternation in the YM task and decreased escape latency in the MWM. Moreover, this dose brought about a significantly improvement in the time spent in the preferred TM arm and discrimination index in the NOR tasks despite repeated scopolamine injection. Additionally, low acetylcholine esterase levels, reduced lipid peroxidation (malondialdehyde) but increased antioxidant enzymes (catalase and superoxide dismutase) activity was observed in hippocampi homogenate of mice pre-treated with the extract. A protective action against hippocampal cell damage was also evident. This finding suggests that the aqueous extract of V. subterranea seed landrace may improve learning and memory.

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