Calystegines nortropane alkaloids

Goldmann, A., B. Message, D. Tepfer, R. J. Molyneux, O. Duclos, F. D. Boyer, and A. D. Elbein. Biological activities of the nortropane alkaloid, calystegine B2, and analogs structure-function relationships. J. Nat. Prod. 59 1137-1142. 

Molyneux RJ, Nash RJ and Asano N (1996) Chemistry and biological activity of the calystegines and related nortropane alkaloids. Alkaloids, Chemical and Biological Perspectives (ed Pelletier SW) Vol 11. Elsevier, Amsterdam, pp 303-343. 

The next step from the biosynthetic pathway is a branch point of the tropane alkaloid pathway [1,2]. Tropinone 24 is the first intermediate with a tropane ring, and it is converted into intermediates that lead to hyoscyamine 1 or calystegines production depending on the stereochemistry of the reduction [37], Two stereospecific tropinone reductases (TR EC 1.1.1.236) - tropinone reductase I (TR-I) reduces the 3-carbonyl group of tropinone 24 to the 3a-hydroxy group of tropine 27 and tropinone reductase II (TR-II) to the 3p-hydroxy group of pseudotropine 25. TR-I leads to hyoscyamine 1 and scopolamine 6 formation via tropine 27, whereas pseudotropine 25 produced by TR-II is converted into calystegines and other nortropane alkaloids [1, 7, 36]. 

Ducrot PH, Lallemand JY (1990) Stmcture of the calystegines new alkaloids of the nortropane family. Tetrahedron Lett 31 3879-3882... 

Molyneux RJ, Nash RJ, Asano N (1996) The chemistry and biological activity of calystegines and related nortropane alkaloids. In PeUetier SW (ed) Alkaloids chemical and biological perspectives, vol 11. Pergamon/Elsevier Science, London, pp 303-343 Morris CE (1983) Uptake and metabolism of nicotine by the CNS of a nicotine-resistant insect, the tobacco hornworm Manduca sexto). J Insect Physiol 29 807-817 Mortimer PI (1957) A note on Duboisia myoporoides from the Acacia Plateau, near Killarney, Queensland. Austral J Sci 20 87-88... 

Nortropane alkaloids Putrescine Potatoes, tomatoes Calystegines... 

R. J. Molyneux, R. J. Nash, N. Asano, The chemistry and biological activity of calystegines and related nortropane alkaloids. 

Tropane alkaloids (TAs), a class of specialized metabolites with a bicyclic tropane ring in their structures, include clinically important hyoscyamine and scopolamine, the stimulant and narcotic cocaine, and the nortropane alkaloids calystegines. Plants producing TAs are distributed, sometime sporadically, across separate angiosperm families (e.g., Proteaceae, Convolvulaceae, Brassicaceae, Euphorbiaceae, Rhizophoraceae, Solanaceae, and Erythroxylaceae) (Griffin and Lin 2000). Studies of TA biosynthesis have been performed predominantly in Solanaceae plants, and thus little is known regarding TA pathways in other families. 

Both alkaloids have (+) and (-) forms but only the (-) hyoscyamine and (-) scopolamine are active. The biosynthetic pathway of tropane alkaloids, Fig. (1) is not totally understood, especially at the enzymatic level. Edward Leete has pioneered the biosynthetic studies of tropane alkaloid since 1950"s using whole plants and isotope labels [85-86]. The tropane alkaloid hyoscyamine is bioconverted by the enzyme H6H (hyoscyamine 6p-hydroxylase, EC 1.14.11.11) to scopolamine via 6p-hydroxyhyoscyamine. Hyoscyamine is the ester of tropine and (S)-tropic acid. The (S)-tropic acid moiety derives from the amino acid L-phenylalanine, while the bicyclic tropane ring derives from L-omithine primarily or L-arginine via tropinone. Tropinone is stereospecifically reduced to form either, tropine which is incorporated into hyoscyamine, or on the other hand into pseudotropine which proceeds to calystegines, a group of nortropane derivates that were first found in the Convolvulaceae family [87]. 

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