Rauwolfla alkaloids

The Rauwolfla alkaloid reserpine was originally used as a neuroleptic/antipsychotic agent. It was then discovered to be an effective antihypertensive agent. Reserpine causes depletion of the noradrenaline stores in peripheral postganglionic sympathetic neurons. In addition it causes depletion of noradrenalin in central nervous structures involved in the regulation of blood pressure. 

Sedative Atropine-like alkaloids Cardiac glycosides Hellebore (Veretrum viride) Rauwolfla alkaloids... 

Itoh, A., Kumashiro, T., Yamaguchi, M., Nagakura, N., Mizushina, Y., Nishi, T. and Tanahashi, T. 2005. Indole alkaloids and other constituents of Rauwolfla serpentina. Journal of Natural Products, 68 848-852. 

Carbocyclic variants related to ajmalicine such as yohimbine are likely to arise from dehy-drogeissoschizine by the mechanism indicated in Figure 6.77. Yohimbine is found in Yohimbe bark (Pausinystalia yohimbe, Rubiaceae) and Aspidosperma bark (Aspidosperma species Apocy-naceae) and has been used in folk medicine as an aphrodisiac. It does have some pharmacological activity and is known to dilate blood vessels. More important examples containing the same carbocyclic ring system are the alkaloids found in species of Rauwolfla, especially R. serpentina (Apocynaceae). Reserpine and deserpi-dine (Figure 6.78) are trimethoxybenzoyl esters of yohimbine-like alkaloids, whilst rescinnamine is... 

All terpenoid indole alkaloids are derived from tryptophan and the iridoid terpene secologanin (Fig. 2b). Tryptophan decarboxylase, a pyridoxal-dependent enzyme, converts tryptophan to tryptamine (62, 63). The enzyme strictosidine synthase catalyzes a stereoselective Pictet-Spengler condensation between tryptamine and secologanin to yield strictosidine. Strictosidine synthase (64) has been cloned from the plants C. roseus (65), Rauwolfla serpentine (66), and, recently, Ophiorrhiza pumila (67). A crystal structure of strictosidine synthase from R. serpentina has been reported (68, 69), and the substrate specificity of the enzyme can be modulated (70). 

In the next step of the ajmaline pathway, vinorine synthase transforms the sarpagan alkaloid epi-vellosamine to the ajmalan alkaloid vinorine (84). Vinorine synthase also has been purified from Rauwolfla cell culture, subjected to protein sequencing, and cloned from a cDNA library (85, 86). The enzyme, which seems to be an acetyl transferase homolog, has been expressed heterologously in E. coli. Crystallization and site-directed mutagenesis studies of this protein have led to a proposed mechanism (87). 

Yohimbine, (16a,I7a) 17-Hydroxyyohimban-I6-carboxylic acid methyl ester quebrachine corynine aphro-dine, C, HuNiOJ mol wt 354.43. C 71.16%, H 7,39%, N 7.90%, O 13.54%. Indole alkaloid with a,-adrenergic blocking activity. Found in Corynanthe johimbe K. Schum., Rubiaceae and related trees, also in Rauwolfla serpentina (L.) Benth., Apocynaceae Raymond -Hamet. J. Pharm. Chim. 

The roots of Rauwolfla serpentina, a climbing shrub indigenous to India, and named after the German botanist Rauwolf, contains an alkaloid Reserpine which was reported to possess both tranquilizing and hypotensive properties. 

Ronchetti F, Russo G, Bombardelli E, Bonati A (1971) A new alkaloid from Rauwolfla vomitoria. Phytoehemistry 10 1385-1388... 

---