Isolation, characterisation and anti-cholinesterase activities of Physostigma venenosum (Calabar bean)

Abstract

Chemical investigation of the anticholenestrases activity of the seeds of physostigma venenosum (ordeal or calabar bean, esere bean or calabar bohme) resulted in the isolation of sangainarine N-diglycoside. The structure of the compound was established using NMR spectroscopy of ( 1 H, 13 C, COSY, DEPT and HSQC) in combination with IR and MS spectral data. The seed of the plant was extracted by percolation using ethanol. The extract was partitioned to obtain chloroform, water, methanol, and pet-ether fractions. The chloroform fraction was discovered as the most active fraction in anticholinesterase activity. The compound displayed a very high anticholinesterase activity (99.5%) in an in vitro test. The result did not support the use of physostigma venenosum as an ordeal poison by the Calabar people of Nigeria to justify person accused of witch craft.