Tropane alkaloids from Schizanthus hookeri

Tropine, a pair of diastereoisomeric hygrolines and two new tropane alkaloids; 3α-senecioyloxytropan-6β-ol and 6β-angeloyloxytropan-3α-ol, were isolated from roots of Schizanthus hookeri.     

Biosynthesis of meteloidine

Tropine-3β-³H, N-methyl-¹⁴C was fed to Datura meteloides plants. After 7 days radioactive meteloidine, scopolamine, hyoscyamine, and 7β-hydroxy-3α,6β-ditigloyloxytropane were isolated from the plants and found to have essentially the same ³H/¹⁴C ratio as in the administered tropine. Degradation of the meteloidine established that all its tritium was located at C-3 and all the ¹⁴C was on the N-methyl group, indicating that tropine is a direct precursor of teloidine.     

Tropane alkaloid metabolism by Pseudomonas AT3 cell cultures: Interchange between the nortropine and norpseudotropine catabolic pathways

Selected strains of Pseudomonas bacteria can degrade tropane alkaloids to obtain both nitrogen and carbon for growth. In order to probe the mechanisms of the catabolic enzymes involved, the metabolic process responsible for the opening of the 8-azabicyclo[3.2.1]octan-3-ol ring of nortropane alkaloids has been explored. It is found that the bacteria contain considerable flexibility in their enzyme complement and can convert (3-endo)-8-azabicyclo[3.2.1]octan-3-ol) (nortropine (2) to (3-exo)-8-azabicyclo[3.2.1]octan-3-ol) (norpseudotropine). Both of these compounds can serve as substrates for the catalytic cascade. In order to establish the proportionation between direct and indirect pathways, metabolism has been probed by competitive substrate availability and by incorporation of stable heavy labels into substrate pools. The results indicate that, while norpseudotropine is almost entirely metabolized directly, nortropine is partitioned c. 4:1 between direct and indirect catabolism.     

Formation of acetyltropine in Datura callus cultures

The production of tropoylesters in suspension cultures of Datura innoxia stem callus was significantly stimulated by dl-tropic acid, phenylpyruvate or tropine, but was little affected by l-phenylalanine or l-ornithine. Analyses have shown that acetyltropine is synthesized in large quantities by cultured cells when tropine has been supplied to various cultures of D. innoxia and D. tatula. Acetyltropine has been isolated from either the culture medium or cells supplied with tropine. These results indicate that tropine absorbed by the cultured cells of Datura is esterified predominantly by acetic acid to form acetyltropine, instead of other tropane alkaloids.     

Esterification reactions in the biosynthesis of tropane alkaloids in transformed root cultures

Transformed root cultures of Datura stramonium and of related species contain both aliphatic and aromatic tropane esters. It has been shown that these esters are produced by the action of several acyl transferases that transfer the acidic moiety to tropan-3-ol (tropine) or tropan-3-ol (pseudotropine) from various acyl-coenzyme A thioesters. The presence of these enzymes has been examined in a range of tropane-alkaloid-producing and non-tropane-alkaloid-producing species. Activities that esterify tropine appear to be confined to species that accumulate tropane alkaloids, whereas a number of species that do not accumulate tropane alkaloids possess some ability to esterify pseudotropine.The present state of knowledge of these enzymes is reviewed. One of these activities, tigloyl-Coenzyme A:pseudotropine acyl transferase, has been purified to near homogeneity and the properties of this enzyme are summarized.Abbreviations CoA coenzyme A - gc gas chromatography - ms mass spectrometry     

Influence of the ion-composition of the medium on alkaloid production by “hairy roots” ofDatura stramonium

The influence of culture age on biomass production and alkaloid yield of “hairy roots” obtained after infection ofDatura stramonium L. withAgrobacterium ATCC 15834 was investigated. Maximal hyoscyamine yield was obtained with roots harvested after six weeks. Fluctuations were found for tropine yield, the precursor of the ring moiety of hyoscyamine. These indicate a continuous conversion to hyoscyamine during the exponential growth phase. The effect of the ion-balance was investigated by preparing five different media that only differed in their ionic composition. The ionic interactions between macroelements, differently influenced biomass production and alkaloid yield. As a result, highest biomass yield was found with NO₃ ⁻ - and K⁺-dominance, whereas hyoscyamine yield was highest with the culture medium in which SO₄ ²⁻ and K⁺ were dominant. Shifting the intercationic balance to strongly towards Ca²⁺ caused an overall reduced metabolism, since as well biomass yield as hyoscyamine yield was lowest with the NO₃ ⁻Ca²⁺-medium. Also tropine yield was affected by the ion-balance, indicating that this culture parameter also influences alkaloid synthesis.[/p]