Cytotoxicity and acetylcholinesterase inhibitory activity of an isolated crinine alkaloid from Boophane disticha (Amaryllidaceae)

Ethnopharmacological relevance

Boophane disticha of the family Amaryllidaceae is used traditionally in southern Africa in the treatment of several neurological disorders.

Aim of the study

Although acetylcholinesterase (AChE) inhibitory activity has been reported for this plant, the aim of the study was to identify and characterise the compound responsible for this activity using bioassay guided fractionation. Toxicity of the isolated compound was also assessed.

Materials and methods

Bioassay guided isolation of the active compound from the methanol extract was carried out using column chromatography, TLC and preparative thin layer chromatography. Structural elucidation was carried out using high field 1D and 2D NMR and mass spectroscopy. AChE inhibitory activity was determined using the Ellman’s colorimetric method. Cytotoxicity assessment was determined in human neuroblastoma (SH-SY5Y) cells using the MTT and neutral red uptake assays.

Results

The data obtained from the integration of the ¹H spectra confirmed the compound to be a 3:1 mixture of two epimers, with epimer A, 6α-hydroxycrinamine as the major epimer. The IC₅₀ value for AChE inhibitory activity of the compound was 445 μM. The compound was observed to be cytotoxic in both the MTT and neutral red assays with IC₅₀ values of 54.5 and 61.7 μM, respectively.

Conclusion

The present study describes for the first time, the isolation of 6-hydroxycrinamine, a crinine alkaloid, from the methanol extract of the bulbs of B. disticha. Although this compound possessed AChE inhibitory activity, it was found to be toxic to the neuroblastoma cells. Quantitative structure–activity relationship studies could be carried out to modify the structure in order to make it less toxic and improve its activity.