Rauvolfia plant

Synthesis of the anti-arrhythmic drug ajmaline from Rauvolfia plants, an efficient source of several alkaloid types used in therapy, represents an even more advanced study of the total enzymatic synthesis of terpenoid indole alkaloids. Ajmaline is a class I anti-arrhythmic alkaloid because of its activity as heart muscle sodium channels antagonist [35],... 

Lengd. Chem. Pharm. In. SU-587-939. 20.05076-SU-364546 (17-01-1978). Ajmaline pharmaceutical preparation by extraction of Rauvolfia plant tissue culture with isopropanol, methanol, and benzene, using tartaric acid. 

Sekisui-Plastics. J6 0259-1% 07-10-1983 JP-187111 21-12-1985. A process for preparing Rauvolfia alkaloids, e.g., reserpine, by tissue culture of Rauvolfia plants, using a culture medium containing 2,4-D and kinetin for callus proliferation and a culture medium containing naphthaleneacetic acid and cytokinins for callus growth deterioration. Chem. Abstr. 104, 147155d. 

But that was only one half of the logic behind the chemical-imbalance theory. The other half came from studies of reserpine, a drug that was extracted from Rauvolfia serpentina or the Indian snakeroot plant, which had historically been used to treat snakebite, hypertension, insomnia and insanity. In studies of animals, reserpine was reported to induce sedation and to decrease brain levels of norepinephrine, serotonin and dopamine. Clinical reports indicated that some people became severely depressed when taking reserpine.14 Putting these two findings together, it seemed likely that reserpine made people depressed because it decreased neurotransmitter levels. 

KUTCHAN, T.M., Expression of enzymatically active cloned strictosidine synthase from the higher plant Rauvolfia serpentina in Escherichia coli, FEBS Lett., 1989, 257, 127-130. 

Ruppert, M., Woll, J., Giritch, A., Genady, E., Ma, X. Y. and Stockigt, J. 2005. Functional expression of an ajmaline pathway-specific esterase from Rauvolfia in a novel plant-virus expression system. Planta, 222(5) 888-898. 

Ruppert, M., Panjikar, S., Barleben, L. and Stockigt, J. 2006. Heterologous expression, purification, crystallization and primary X-ray analysis of raucaffricine glu-cosidase, a plant enzyme specifically involved in Rauvolfia alkaloid biosynthesis. Acta Crystallographica Section F-Structural Biology and Crystallization Communications, 62 257-260. 

Bracher, D. and Kutchan, T. M. 1992. Polymerase chain reaction comparison of the gene for strictoside synthase from ten Rauvolfia species. Plant Cell Reports, 11 179-182. 

Within the natural products field, the investigation of complete biosynthetic pathways at the enzyme level has been especially successful for plant alkaloids of the monoterpenoid indole alkaloid family generated from the monoterpene gluco-side secologanin and decarboxylation product of tryptophan, tryptamine [3-5]. The most comprehensive enzymatic data are now available for the alkaloids ajmalicine (raubasine) from Catharanthus roseus, and for ajmaline from Indian Rauvolfia serpentina [6] the latter alkaloid with a six-membered ring system bearing nine chiral carbon atoms. Entymatic data exsist also for vindoline, the vincaleucoblastin (VLB) precursor for which some studies on enzymatic coupling of vindoline and catharanthine exist in order to get the so-called dimeric Catharanthus indole-alkaloids VLB or vincristine [7-9] with pronounced anti-cancer activity [10, 11]. 

Thirty-six plant species tested in cell suspension culture could be elicited by exogenously supplied methyl jasmonate to accumulate secondary metabolites by a factor of 9 to 30 over the control values. Induction by MJ was not specific to any one type of secondary metabolite but rather general to a wide spectrum of low molecular weight substances ranging from flavonoids, guaianolides and anthraquinones to various classes of alkaloids [96]. Endogenous jasmonic acid and its methyl ester (MJ) accumulate rapidly and transiently after treatment of plant cell suspension cultures of Rauvolfia canescens and Eschscholtzia califor-nica with a yeast elicitor [97]. 

Isolation of the stereospecific strictosidine s)mthase (STS) and formation of strictosidine with the 3a-(S) configuration proved conclusively that this was the natural precursor of the terpenoid indole alkaloids. Strictosidine occurs naturally in Rhazya stricta and the synthase has been isolated from a number of other species Amsonia salicifolia, A. tabemaemontam, Catharanthus pusillus, C. roseus, Rauvolfia verticillata, R. vomitoria, R. serpentina, Rhazya orientalis and Voacanga africana. The enzyme has been purified to homogeneity from R. serpentina (Hampp and Zenk, 1988). A comparison of the activity of STS from C. roseus roots, the only portion of the plant to contain ajmalicine, with that present in plant cell cultures producing the same alkaloid demonstrated that the plant cell cultures are far more metabolically active (Ziegler and Facchini, 2008). 

Ma X, Panjikar S, Koepke J, Loris E, Stockigt J. The structure of 86. Rauvolfia serpentina strictosidine synthase is a novel six-bladed beta-propeller fold in plant proteins. Plant Cell 2006 18 907-920. 

Functional expression of an ajmaline pathway-specific esterase from Rauvolfia in a novel plant-virus expression system. Planta 2005 222 888-898. 109. 

In their studies on the biosynthesis of terpenoid indole alkaloids, De Silva and co-workers have carried out a screening of some indole alkaloid producing plants of Sri Lanka for the occurrence of the first nitrogenous monoterpenoid precursor (70,71). In this survey, Rauvolfia serpentina, Strychnos nux-vomica, Cinchona ledgeriana, and a number of Mitragyna and Vinca species were tested for the presence of vincoside and 5a-carboxyvincoside. Although these two proposed bio-intermediates (at the time) were not detected, macroisolation techniques revealed the occurrence of 5a-carboxystrictosidine (78), an isomer of 5a-carboxyvincoside, in all plants tested, and strictosidine (79), an isomer of vincoside, only in... 

Based on knowledge of a biosynthetic pathway one can select certain steps which could be of interest for bioconversion of (a) readily available precursor(s). This could, for example, be stereospecific reactions, like the reduction of quinidinone in quinine or quinidine and the epoxidation of atropine to scopolamine. For the bioconversion one can consider using plant cells [e.g., the production of L-dopa from tyrosine by immobilized cells of Mucuna pruriens (10)] or isolated enzymes from the plant itself. An interesting example of the latter is the (5)-tetrahydroprotoberberine oxidase (STOX) enzyme, which oxidizes (5)-reticuline but not its stereoisomer (11). This feature can be used in the production of (i )-reticuline from a racemic mixture (see below). Immobilized strictosidine synthase has been successfully used to couple secologanin and tryptamine. The gene for this enzyme has been isolated from Rauvolfia (6) and cloned in Escherichia coli, in which it is expressed, resulting in the biosynthesis of active enzyme (7). The cultured bacteria produced 20 times more enzyme... 

Rauvolfia serpentina roots are the source used in industrial extraction of the alkaloids. The plant is propagated by root cuttings as it has low seed viability (697). The use of micropropagation is thus of interest, and several authors reported successful procedures for micropropagation (698-701). Mathur et al. (697) reported the micropropagation of colchicine-induced tetraploids. Multiple shoot formation was obtained, as reported by Roja et al. (688), on MS medium containing 1 ppm BAP and 0.1 ppm NAA. 

American Cyanamid Co. Dl-108-769. 26-07-72-Dl-164695 (05-10-1974). Cell culture production of plant metabolites by inducing redifferentiation of undifferentiated plant cell cultures (among others Rauvolfia for reserpine production). 

Sumitomo Chemical. Jpn. Kokai Tokkyo Koho. JP 55096096, 21-07-1980. JP 79-4275 16-01-1979. Enhancement of protoplast fusion in plant cell cultures (Rauvolfia serpentina). Chem. Abstr. 93, 218142q. 

Biosynthesis The biosynthesis of these alkaloids begins with the key reaction, the condensation of tryptamine with secologanin to give strictosidine catalyzed by the enzyme strictosidine synthase. The biosynthesis was elucidated mainly by the use of plant cell suspension cultures. Cell cultures of Catharanthus and Rauvolfia species have been the subject of intense phytochemical studies. 

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