In vitro antioxidant assessment and a rapid HPTLC bioautographic method for the detection of anticholinesterase inhibitory activity of Geophila repens.

OBJECTIVE: Geophila repens (L.) I. M. Johnst. (Rubiaceae), a small, creeping, perennial herb, is claimed to have memory-enhancing property. The goal of this study was to assess its antioxidant and anticholinesterase activity and conduct a rapid bioautographic enzyme assay for screening acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition of G. repens extracts.

METHODS: Antioxidant activity of G. repens extracts was assessed by performing 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO), superoxide (SOD), hydroxyl (OH) and total antioxidant capacity (TAC) assays. Anticholinesterase activity was investigated by quantifying the AChE and BChE inhibitory activities of chloroform (CGR), ethyl acetate (EGR) and methanol (MGR) extract fractions from G. repens leaves. A rapid high-performance thin-layer chromatography (HPTLC) bioautographic method for the detection of AChE and BChE inhibition was performed.

RESULTS: Among all extract fractions, EGR exhibited the highest half maximal inhibitory concentration (IC50) in DPPH, SOD, NO, OH and TAC assays, with IC50 of (38.33 ± 3.21), (45.14 ± 1.78), (59.81 ± 1.32), (39.45 ± 0.79) and (43.76 ± 0.81) μg/mL respectively. EGR displayed competitive, reversible inhibition of AChE and BChE activities with IC50 of (68.63 ± 0.45) and (59.45 ± 0.45) μg/mL, respectively. Total phenolic and flavonoids contents of EGR were found to be 360.42 mg gallic acid equivalents and 257.31 mg quercetin equivalents per gram of extract. Phytoconstituents of the EGR extract that were inhibitors of cholinesterase produced white spots on the yellow background of HPTLC plates in the bioautographic test.

CONCLUSION: The results of this study revealed that phenols and flavonoids could be responsible for the antioxidant, anticholinesterase activities of G. repens.