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New observations on the secondary chemistry of world Ephedra (Ephedraceae)¹

²Department of Zoology, University of Western Ontario, London, Ontario, Canada N6A 5B7 ³Department of Biological Sciences S2B, Community College of Southern Nevada, 3200 East Cheyenne Avenue, North Las Vegas, NV 89030 ⁴Department of Morphology and Systematics of Plants, University of Kassel, D-34132 Kassel, Germany ⁵Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada N6V 4T3

For several millennia, stem extracts of Ephedra (Ephedraceae, Gnetales) have been used as folk medicines in both the Old and New World. Some species were used in treatments of questionable efficacy for venereal disease in North America during the last century. Many Eurasian species produce phenylethylamine alkaloids, mostly ephedrine and pseudoephedrine, that interact with adrenergic receptors in the mammalian sympathetic nervous system. Asian Ephedra have been used recently in the clandestine manufacture of a street drug, methamphetamine. Although ephedrine alkaloids are not detectable in New World species of Ephedra, together with Asian species they contain other nitrogen-containing secondary metabolites with known neuropharmacological activity. Many mesic and particularly xeric species worldwide accumulate substantial amounts of quinoline-2-carboxylic acids, or kynurenates, in their aerial parts. Many species of Ephedra accumulate cyclopropyl amino acid analogues of glutamate and proline in their stems and roots, and particularly in the seed endosperm. Mesic species synthesize substantial amounts of three L-2-(carboxycyclopropyl)glycine stereomers rarely seen in nature. A cyclopropyl analogue of proline with known antimicrobial activity, cis-3,4-methanoproline, is found in large amounts in the stems and seeds of many Ephedra species. The ability to synthesize cyclopropyl amino acids may be an ancestral feature in the taxon. The natural function in the taxon of these three groups of secondary compounds remains to be established.

Key Words: cis-3,4-methanoproline • Ephedra • ephedrine alkaloids • 6-hydroxykynurenic acid • L-2-(carboxycyclopropyl)glycine • kynurenic acid • 6-methoxykynurenic acid

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