High-performance countercurrent chromatography for the efficient isolation of alkaloid acetylcholinesterase inhibitors from Nerine species (Amaryllidaceae)

In a general screening of South African Amaryllidaceae for inhibitors of the enzyme acetylcholinesterase, the genus Nerine was found to be a good source of novel alkaloids which exhibit this bioactivity [1]. In view of material losses when performing separations of these alkaloids by multiple chromatographic steps on silica gel, an all-liquid strategy was investigated. Bulbs of the plants were extracted with 90% ethanol and the resulting extracts were partitioned between chloroform and 1% ammonia solution. Chloroform fractions were chromatographed on a Dynamic Extractions Spectrum instrument with suitable 2-phase solvent systems, chosen by a TLC screening approach [2]. The high rotation speed (1500 rpm) of the high-performance countercurrent chromatography (HPCCC) instrument allowed separations to be completed within 2–3 hours. This procedure led to the one-step purification of numerous alkaloids, on injection of sample charges up to 2g. Certain alkaloids, such as lycorine, could be isolated by direct crystallisation of the relevant HPCCC fractions. Other alkaloids required a Sephadex LH-20 gel filtration clean-up step. The interest in inhibitors of acetylcholinesterase lies in their possible contribution to the management of Alzheimer's disease by modifying levels of acetylcholine in the brain [3].

References: 1. Marston, A. et al. (2009) Planta Med. 75: 944.

2. Marston, A. and Hostettmann, K. (2006)J. Chromatogr. A 1112: 181–194.

3. Houghton, P. et al. (2006) Nat. Prod. Rep. 23: 181–199.