Rauwolfia alkaloids yohimbine

The arbitrary classification of Rauwolfia alkaloids (91) is simplified here, and it is slightly different from a recent arrangement (92). The Rauwolfia alkaloids can all be regarded as yohimbinoid derivatives as shown in Chart I, viz. the yohimbines (all yohimbine isomers) 18-hydroxyyohimbines (reserpine-type alkaloids) ring E heterocycles and their anhydronium analogs (ajmalicine, serpentine) ajmaline-type (which includes sarpagine) and compounds of unknown constitution. 

Rauwolfia alkaloids a group of about 50 structurally related indole alkaloids firom the roots and rhizomes of various species of Rauwolfa, Aspidosperma and Corynanihe. All R. a. contain a -carbolene skeleton they are classified into 3 types 1. yohimbine (cory-nanthine), 2. ajmaline, 3. serpentine. The large number of R. a. is due to the existence of stereoisomers. Thus Rauwolfia contains seven stereoisomers of yohimbine. 

Reserpine therapeutically the most important Rauwolfia alkaloid. M, 608.9, m.p. 265 C, (oj -123° (CHQj). Hydrolysis of R. with alcoholic KOH produces reserpinic add (structurally similar to yohimbine), trihydroxybenzoic add and methanol. R. is found widely in Ae genus Rauwolfia and is responsible for the sedative properties of these plants. After a latent period, R. causes long lasting sedation, with decrease of blood pressure and decreased pulse rate. It is used as a powerful neuroleptic drug in psychiatry. 

Yohimbine a Rauwolfia alkaloid (see), M, 354.45, ra.p. 235-236 °C, [a]D + 106° (pyridine). Y. has five chiral centers and therefore many stereoisomers seven of these occur naturally, the most important being CorynoHthine, m.p. 225-226°C (d),... 

One of the earliest reports on the combinatorial modification of natural products described the derivatization of the Rauwolfia indole alkaloids yohimbine and rauwolscine (Figure 11.58). The... 

Bark may contain up to 6 % total alkaloids, of which 10-15 % is yohimbine [120]. Concentrations of yohimbine in commercial products ranged from less than 0.1 to 489 parts per million (ppm) compared with 7,089 ppm in the authentic material. The alkaloid yohimbine also is obtained from Aspidosperma quebracho-bianco and Rauwolfia serpentina [121]. Its interest outside the African continent was first recorded in Germany, where yohimbine, the main alkaloid of the drug and also known as aphrodine, quebrachine, or corynine, was isolated for the first time by Spiegel in 1896 [130]. Recent advancements in the development of yohimbe-based... 

Members of the yohimbine alkaloid family possess a characteristic penta-cyclic indole skeleton 1. Representative compounds in this family include the Rauwolfia alkaloids, such as reserpine (2) and deserpidine (3), and the yohimbines (4-9). These compounds exhibit a wide range of medicinal properties (1,2). Reserpine, for example, has been used extensively in the treatment... 

Material Yohimbine is one of several indole-based alkaloids found in Corynanthe yohimbe, Rauwolfia serpentina, and several other plants. 

For laboratory purposes, methanol is the usual solvent, and procedures based on its use have been described in detail (21, 39, 81). Of great practical usefulness for the separation of the weakly basic fraction is the solubility of certain alkaloidal acetates in chloroform, e.g., reserpine, ajmalicine, and aricine, whereas other acetates are insoluble in this solvent, e.g., ajmaline, yohimbine, and a-yohimbine. Since the anhyd-ronium alkaloids are extremely strong bases, they can only be extracted into an organic solvent in their tertiary base form at pH 11. For industrial purposes, the best process extracts water-moistened Rauwolfia root with hydrocarbons such as benzene, toluene, or xylene. In this procedure, only the weak bases are extracted. No complicated separation processes are involved, and reserpine is obtained in high yields (122). 

Yohimbine is a major carboline alkaloid in the bark of Pausinystalia species, such as Pausinystalia yohimbe (Corynanthe yohimbe), Pausinystalia macrocerus, Pausinystalia paniculata, and Pausinystalia trillesi. It is also found in Pseudocinchona africana and Rauwolfia canescens. 

Yohimbine alkaloids possess a characteristic pentacyclic indole skeleton. Representative members of the family include the rauwolfia (reserpine and deserpidine) and the yohimbines. A wide range of medicinal properties has been associated with these compounds and extensive studies have been carried out on the synthesis of the yohimbine alkaloids, including enantioselective syntheses [13,14]. In our approach, we view the acetylenic sulfoxide as a two-carbon synthon for the C3-C14 segment of the pentacyclic system (see 27). The chirali-... 

Rauwolfia serpentina. Rauwoifla serpentina (L.) Benth. (Ophioxylon serpentinum L.) Apocynaceae. A small shrub native to the Orient from India to Sumatra, The crude botanical drug is usually the root. Contains many indole alkaloids, e.g., reserpine, reserpinine, yohimbine, ajmaline, serpentine, serpetinine. Review and bibliography with botanical information Monachino. Eton. Bot. 8, 349. 365 (1954). The genus Rauwolfia is large and has a wide distribution in the tropics. 

Yohimbine (yocon), a competitive a2 antagonist, is an indolealkylamine alkaloid found in the bark of the tree Pausinystalia yohimbe and in Rauwolfia root structurally, yohimbine resembles reserpine. 

Yohimbine, an indole alkaloid isolated from PausinystUa yohimbe bark and Rauwolfia roots is an a2-antagonist with greater selectivity for q2- than for... 

Up to the 1960s, the treatment of atherosclerosis was only symptomatic. [363] Thus, for example for lowering blood pressure, there was used an extract from the snake-shaped roots of Rauwolfia serpentina, which was already known to the ancient Hindus (Fig. 5.149). [364] In 1952, EmU Schlittler (1906-1979) of the Ciba company isolated reserpine as its hypotensive principle, and determined its constitution. In particular, he also recognised the relationship to the large class of yohimbine alkaloids. The first constitutional total synthesis was achieved in 1956 by R. B. Woodward. [365-367] It counts as one of his most notable contributions to modern synthetic chemistry and formed the basis of industrial processes for the synthesis of this drug. In 1989, Gilbert Stork published a stereospecific total synthesis. [368]... 

It is a common knowledge that plants are useful sources of many valuable medicines. Among these medicines several indole alkaloids can be found, e.g. reserpine and deserpidine from Rauwolfia serpentina ajmalicine and yohimbine from Corynanthe yohimhe vinblastine and vincristine from Catharanthus roseus just to mention a few of them. 

Some R. a. have valuable pharmacological properties. They may act centrally (e.g. see Reserpine) or peripherally (e g. see Yohimbine, Ajmaline). In addition to the pure alkaloids or their synthetic analogs, extracts of the drug Radix Rauwolfiae and combination preparations are also used. The drug has been known since early times in Indian folk medicine, and its systematic investigation began in 1930. 

Yohimbine, which is described in Sect. 5.2.2.6.S on Yohimbe alkaloids, has also been isolated from the roots of Rauwolfia serpentina (67). 

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