Sixteen alkaloids have been isolated from fresh bulbs of Ammocharis tinneana (Amaryllidaceae), seven of which contain a 1,2 beta-epoxide group. 6 alpha-Hydroxycrinamidine and 6 alpha-hydroxyundulatine are reported here for the first time from a natural source. The structures and stereochemistry of these new alkaloids have been determined by physical and spectroscopic methods. H-1 and C-13 NMR spectra of flexinine, 1,2 beta-epoxyambelline and 11-O-acetyl-1,2 beta-epoxyambelline were completely assigned by means of 2D NMR techniques. (C) 1999 Elsevier Science Ltd. All rights reserved.