The geographic isolation of Leucojum aestivum populations leads to divergation of alkaloid biosynthesis

Abstract

Leucojum aestivum, an industrial source of the acetylcholinesterase inhibitor galanthamine, shows a great chemodiversity in its alkaloid synthesis. Samples from various geographically distinct populations from Bulgaria and the Balearic Islands were studied by GC–MS. The alkaloid pattern of the plants of L. aestivum (subsp. pulchellum) from the Balearic Islands were dominated by crinine type compounds. Populations of homolycorine chemotype were distributed along the Danube river in the north part of Bulgaria, which is separated from the south part by the Balkan mountains. Populations with high accumulation of lycorine were found in East Bulgaria near the sea coast, while the south populations were dominated by galanthamine type synthesis. The average of the galanthamine content was found to vary from 0.003 to 0.08% (referred to dry weight) in the north, and up to 0.42% in the southern Bulgarian populations. Some individuals showed up to 0.65% galanthamine. The galanthamine content of the plants from the Balearic island was 0.1% of DW. The galanthamine percentage in the total alkaloid mixture ranged from 0.2 to 95% of the total alkaloids. Our study demonstrated that the geographic isolation of the populations of L. aestivum has led to divergation in the alkaloid biosynthesis and consequently to the occurrence of different chemotypes. This chemodiversity in both alkaloid patterns and galanthamine content provides an opportunity for further selection work toward a galanthamine-rich crop, on the one hand, and makes the species an excellent biological system for molecular studies leading to further improvement of the galanthamine production, which is a valuable alkaloid used in medicine for the treatment of Alzheimer's disease.