Abstract:
This study investigated a nutraceutical approach to the management of neurological disorders
(ND). Aqueous extracts of aidan (Tetrapleura tetraptera) and bitter ash (Quassia undulata) were
prepared, lyophilised and then pulverized. The total phenol and total flavonoid contents were
determined. Also determined was the antioxidant activities in both cell free [2,2-diphenyl-1-
picrylhydrazyl radical (DPPH*), 2,2- azinobis (3-ethylbenzothiazoline-6-sulfonate radical
(ABTS*), Fe- chelation and ferric reducing antioxidant property (FRAP)] and cell based systems
[glutathione peroxidase (GPx), glutathione reductase (GR)]. The effects of the aqueous extracts
of aidan and bitter ash on acetylcholinesterase (AChE), butyrylcholinesterase (BuChE),
monoamine oxidase (MAO) and beta secretase activities were determined in vitro. The tolerance/
effective safe dose of the extracts was determined. The effect of the extracts on behavioural
status and key enzymes linked to neurodegeneration in scopolamine- induced brain damage in
Wistar rat was investigated. Also, the effect of the extracts on amyloid peptide aggregation was
determined. Phenolic constituents of the plants were characterized using high performance liquid
chromatography coupled with a diode array detector (HPLC-DAD). Total phenol and flavonoid
contents of aidan plant (27.14 mg/g; 18.28 mg/g) were significantly (p < 0.05) higher than bitter
ash (24.76mg/g; 12.22 mg/g) plant. The aqueous extracts had antioxidant activities in vitro and
in the neuronal and endothelial cells as typified by the cellular antioxidant activity; and also
increased the activities of intracellular GPx and GR in both cell lines. The extracts also reduced
malondialdehyde (MDA) production in both cell lines. Furthermore, the extracts inhibited AChE,
BuChE, MAO and beta secretase activities in vitro. The tolerance/effective safe dose of the
extracts ranged from 50- 2000 mg/kg body weight. Both extracts increased the memory index of
the scopolamine induced rats. Similarly, the aqueous extracts inhibited TDP-43 amyloid aggregation in humanized yeast cells. P- coumeric acid, rutin and quercetin were revealed by
HPLC-DAD as the most predominant phenolic compounds in both plant extracts. The
antioxidant ability of the extracts and their inhibitory effect on some key enzymes and
biomolecules linked to ND pathology is an indication of their potential as
nutraceuticals/functional food in the management of ND.
