Improved analytical techniques have shown that ethanolamine, long known to be a common constituent of higher plants (1,2), is virtually universal (3). However, this is the first report that the corresponding secondary amine is also a natural product. The relevant basic nitrogen fractions, recovered from extracts with carboxylic ion-exchange substrates (4), were always reacted with 5-(dimethylamino)-naphth-1-yl sulfonyl chloride (dansyl Cl) before further analysis. Dansyl-diethanolamine (dansyl-2,2'-iminobisethanol) was recognized as a fluorescent spot migrating comparatively slowly on tlc plates: Rfs were 0.05,0.06, 0.05, 0.08,0.43, and 0.54 in solvents A,B,C,D,E, and F, respectively. An isolate from Senecio dunedin (horticultural hybrid of Senecio compactus Kirk, Senecio greyi Hook f., and Senecio laxifolius Buchan) was initially characterized from its ¹H-nmr spectrum. Comparison with the spectra of synthetic standards showed that the dansyl group was represented by the singlet at δ 2.9 [N(Me)₂] and the signals in the δ 7.2-8.6 region (naphthalene ring protons). The absence of a signal for NH in the δ 4.2-5.0 range indicated that the amine originally dansylated was a secondary, not a primary amine. The chemical shift of the protons at δ 3.87 suggested an association with oxygen while the δ 3.87 and 3.48 signals were clearly coupled, suggesting the isolate was either dansyl-morpholine or dansyl-diethanolamine. The identification was confirmed to be the latter by comparison with synthetic dansyl-diethanolamine, which gave the same ¹H-nmr spectrum as the isolate and co-chromatographed with it in all six solvents (A-F) tested. Moreover, the mass spectrum of the isolate showed a molecular ion at the expected m/z value of 338. An isolate from Echinops exaltatus Rchb. et Auct. was far too small for ¹H-nmr analysis, but it co-chromatographed with dansyl-diethanolamine in all six solvents tested. Its eims gave a distinct molecular ion at the calculated precise mass of 338.218±0.005, which increased in relative intensity with increasing temperature, confirming that it was really derived from the sample rather than from solvent residues. Routine tlc analysis of the basic nitrogen fractions of 143 Compositae species showed that 24% of them gave a spot in the position of dansyl-diethanolamine on 2-D chromatograms. Such spots were found in members of the genera Aspilla (1 sp), Aster (1 sp), Baeria (1 sp), Carthamus (1 sp), Catanache (1 sp), Centaurea (1 sp), Chamaemelum (1 sp), Chrysanthemum (1 sp), Cramidendron (1 sp), Crepis (2 sp), Echinops (1 sp), Eupatorium (1 sp), Felicia (2 sp), Hieracium (2 sp), Kleinia (6 sp), Leontopodium (1 sp), Osteospermum (1 sp), Podolepis (1 sp), Pterocaulon (1 sp), Senecio (5 sp), and Vernonia (2 sp). The spot was sufficiently intense in seed extracts of Baeria coronaria Gray, Crepis capillaris (L.) Walk., and Crepis pulchra L., and in leaf extracts of a Kleinia sp. and Pterocaulon sphacelatum Labill. for it to be eluted from the 2-D plate and cochromatographed with the standard in solvents C and D. Fluorimetric comparisons with standards suggested that the detection limit in this survey was ca 50 ng diethanolamine/g fresh weight. This approximated the level of the free amine in E. exaltatus, whereas the level was ca 20 times greater in Senecio dunedin. These concentrations are fairly typical of the unknown amines now being revealed in plant extracts by the dansyl chloride technique. Diethanolamine is mildly toxic to vertebrates (5-8), invertebrates (9), bacteria (10), and fungi (11,12) as well as inducing a number of physiological changes (13-16). However, it is unlikely to be effective against potential pathogens at the concentrations found in these composites if uniformly distributed in the tissues. There has been only one previous example of the use of ¹H nmr to characterize a dansylated amine from a cell extract (17). The introduction of the fluorescent label obviously complicates the spectrum and often makes it necessary to use higher field instruments. However, this is offset by the advantages that dansylated amines can be detected at much lower levels than free amines, give much stronger molecular ions during eims, and are easier to purify, as they chromatograph cleanly and can be readily freed from salt by solvent extraction.