Aqueous extracts of two tropical ethnobotanicals (Tetrapleura tetraptera and Quassia undulata) improved spatial and non-spatial working memories in scopolamine-induced amnesic rats: Influence of neuronal cholinergic and antioxidant systems.

BACKGROUND: Tetrapleura tetraptera (TT) and Quassia undulata (QU) are two predominant tropical ethnobotanicals with various medicinal values but are commonly used in folklore for the treatment of mental illness without justifiable mechanisms of action. AIM OF THE STUDY: To investigate the effects of aqueous extracts from TT fruits and QU leaves on the spatial and non-spatial working memory, antioxidant status and activities of neuronal marker enzymes of scopolamine-induced amnesic rats and thus, understand the possible mechanism of action of these plants. MATERIALS AND METHODS: Fifty-five albino rats were divided into eleven groups. Group I (normal rats) received normal saline (p.o), Group II-V (normal rats) administered with 50 and 300 mg/kg of each extract group VI (induced rats) received 2 mg/kg of scopolamine (i.p.), groups VII-X (induced rats) pretreated with 50 and 300 mg/kg of TT and QU extracts (p.o) before scopolamine administration, group XI (induced rats) treated with 2.5 mg/kg of donepezil. The treatment lasted for 14 days and amnesia was induced by a single dose of 2 mg/kg of scopolamine on the last day. Spatial (Y-maze) and non-spatial (novel objectect recoginiton test) working memories of the rats were tested. Thereafter, the animals were sacrificed and homogenates of isolated brain samples were assayed for cholinesterase activity and malondialdehyde (MDA) content. The phenolic characterisation of the samples was also carried out using HPLC-DAD chromatography. RESULTS: Administration of 2 mg/kg of scopolamine brought about a decrease in spatial and non-spatial memory indeces, increase in acetylcholinesterase and butyrylcholinesterase activities, as well as increased MDA content compared to the control. However, pretreatment with both extracts improved both spatial and non-spatial working memories and ameliorated the increased enzyme activities and MDA contents. Furthermore, the HPLC-DAD characterization of the extracts revealed the presence of p-coumaric acid, rutin, catechin, ellagic acid, quercetin, caffeic acid, chlorogenic acid and galic acid. CONCLUSION: The ability of the extracts to improved cognitive function and ameliorate impairment in cholinergic enzyme activities and antioxidant status in scopolamine-induced amnesic rats could help justify the possible neuroprotective properties of TT and QU and also explain possible mechanism of action of these ethnobotanicals as obtained in folklore medical practices.

Aqueous extracts of avocado pear (Persea americana Mill.) leaves and seeds exhibit anti-cholinesterases and antioxidant activities in vitro.

BACKGROUND: Avocado pear (Persea americana Mill.) leaves and seeds are used in traditional medicine for the treatment/management of Alzheimer disease (AD); however, information on the mechanism of actions is limited. This study sought to investigate the effect of P. americana leaf and seed aqueous extracts on some enzymes linked with AD (acetylcholinesterase [AChE] and butyrylcholinesterase [BChE] activities) and their antioxidant potentials in vitro. METHODS: The inhibitory effects of extracts on AChE and BChE activities and antioxidant potentials (inhibition of Fe2+- and sodium nitroprusside-induced thiobarbiturate reactive species [TBARS] production in rat brain homogenates, radicals [1,1-diphenyl-2-picrylhydrazyl, hydroxyl, and nitric oxide] scavenging and iron [Fe] chelation abilities) were investigated. Phenolic content and phytochemical screening were carried out. Alkaloid profile was also determined using gas chromatography coupled with flame ionization detector (GC-FID). RESULTS: The extracts inhibited AChE and BChE activities and prooxidant-induced TBARS production in a dose-dependent manner, with the seed extract having the highest inhibitory effect and the leaf extract exhibiting higher phenolic content and radical scavenging abilities, but lower Fe chelation ability compared with that of the seed. The phytochemical screening revealed the presence of saponins, alkaloids, and terpenoids in both extracts, whereas the total alkaloid profile was higher in the seed extract than in the leaf extract, as revealed by GC-FID. CONCLUSIONS: The anti-cholinesterase and antioxidant activities of avocado leaf and seed could be linked to their phytoconstituents and might be the possible mechanisms underlying their use as a cheap and natural treatment/management of AD. However, these extracts should be further investigated in vivo.