Identification of haemanthamine as a phytotoxic alkaloid in Narcissus pseudonarcissus L. (Daffodil) emerging buds.

Emerging buds of Narcissus pseudonarcissus were found to accumulate the alkaloid haemanthamine (1) at high concentrations, exceeding that of narciclasine (2), the most abundant constituent in bulbs of the plant. A phytoactivity screening assay demonstrated the novel phytotoxicity of haemanthamine against Raphanus sativus (radish), Lactuca sativus (lettuce), Triticum aestivum (red wheat), Solanum lycopersicum (tomato), Cucumis sativus (cucumber), Ipomoea (Morning glory), and Lens culinaris (lentil). Haemanthamine (1) phytotoxicity was found to exceed that of the commercial herbicide glyphosate and less toxic than narciclasine (2).

Isolation, Synthesis, and Semisynthesis of Amaryllidaceae Constituents from Narcissus and Galanthus sp.: De Novo Total Synthesis of 2- epi-Narciclasine.

An efficient protocol for the isolation of narciclasine from common Amaryllidaceae bulbs, separation from haemanthamine, and the occurrence of a trace alkaloid, 2- epi-narciclasine, are reported. Attempts to convert natural narciclasine to its C-2 epimer by Mitsunobu inversion or oxidation/reduction sequences were compromised by rearrangement and aromatization processes, through which a synthesis of the alkaloid narciprimine was achieved. The methylation of the 7-hydroxy group of natural narciclasine followed by protection of the 3,4-diol function and oxidation/reduction sequence provided the target C-2 epimer. A de novo chemoenzymatic synthesis of 2- epi-narciclasine from m-dibromobenzene is also described. Haemanthamine and narciprimine were readily detected in the crude extracts of Narcissus and Galanthus bulbs containing narciclasine, and the occurrence of 2- epi-narciclasine as a trace natural product in Galanthus sp. is reported for the first time.