Acetylcholinesterase (AChE) inhibitory activity, antioxidant properties and phenolic composition of two Aframomum species.

BACKGROUND

Aframomum species are widely used as a food supplement and remedy in folklore medicine for the management of several diseases. This study was designed to investigate the acetylcholinesterase inhibitory activity and antioxidant properties of phenolic-rich extracts from two Aframomum species: Aframomum danielli (Hook F.) K. Schum (Zingiberaceae) and Aframomum melegueta (Roscoe) K. Schum (Zingiberaceae) seeds.

METHODS

Acetylcholinesterase inhibitory activity and antioxidant properties [inhibition of quinolinic acid (QA)-induced lipid peroxidation in rat brain, reducing properties, 2,2-azinobis (3-ethylbenzo-thiazoline-6-sulfonate) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging abilities] using in vitro models were evaluated. Phenolic composition of the seed extracts using reversed phase high performance chromatography (RP-HPLC) and gas chromatography coupled with flame ionization detector (GC-FID) were also assessed.

RESULTS

Both extracts exhibited acetylcholinesterase inhibitory activity in a dose-dependent manner (125-1000 μg/mL); however, A. melegueta extract (IC50=373.33 μg/mL) had a significantly higher (p<0.05) acetylcholinesterase inhibitory activity than A. danielli extract (IC50=417.10 μg/mL). Furthermore, both extracts significantly decreased QA-elevated brain malondialdehyde (MDA) contents, reduced Fe3+ to Fe2+ and scavenged DPPH and ABTS radicals. Phenolic characterization of the seeds by RP-HPLC at 280 nm showed abundance of quercetin and kaempferol in A. melegueta and chlorogenic acid in A. danielli, whereas GC-FID revealed that p-hydroxybenzoic acid was abundant in both seeds.

CONCLUSIONS

Inhibitory effect of these extracts on acetylcholinesterase activity and their antioxidant property could be attributed to the combined effect of phenolic and non-phenolic constituents of the seeds. These effects could be part of the possible biochemical mechanism by which these seeds elicit their protection against oxidative stress in brain; however, A. melegueta showed the more promising potential.