Calystegines plant activity

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]. 

A. Structure-Effect Relations between Calystegines and Glycosidases Mechanism of Inhibition Toxicology of Calystegines Possible Medicinal Applications Activity of Calystegines in Plants A. Plant Rhizosphere Allelopathic Activity Insect Feeding Repellent Activity Anti-Nematode Activity Plant-Fungi Interactions... 

Tropinone (32) hardly accumulates in plant tissues, thus the two TRs were assumed to compete for the substrate (Figure 6). Metabolite flux into both arms of the tropane alkaloid pathway appears to be determined by the activity of the TRs. First evidence for this view was given by the inhibition of tropinone reduction to tropine in cultures of D. stramonium (246). More pseudotropine (12) was observed and decreased levels of tropine (33) and tropine products, e.g., acetyltropine and hyoscyamine (35) (247). In those studies, calystegine measurements were not included, but in A. belladonna root cultures, both hyoscyamine (35) and... 

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