Yohimbe

Processes for the isolation and purification of yohimbine have been described by Thoms, Feldhoff, Chemnitius, Schwyzer, Raymond-Hamet and others. Some of these processes have been modified to provide for estimation of the yield of yohimbine, usually as the hydrochloride, from the bark, or to facilitate the identification of this alkaloid in commercial yohimbe bark, which is apt to vary both in quality and in botanical origin.According to Witkop (1943) modern technical yohimbine hydrochloride may contain a little isoyohimbine but no allo-yohimbine. 

When yohimbine is heated with potash solution it is eonverted into potassium yohimbate, from which yohimbic acid (the forms yohimboie and yohimboaic are also used and noryohimbine), C20H24O3N2. H2O, is liberated by acetie acid it crystallises from water in lustrous prisms, m.p. 269° or 299° (dry, dec.), [ajo 138-8° (pyridine), and, on esterification with methyl alcohol and its homologues, reproduces yohimbine and its homologues, analysis of which by Field confirmed the view that yohimbine is methyl yohimbate, and has the formula assigned to it by Fourneau and Page. ... 

The remaining yohimb alkaloids are described below ten of them are isomerides of yohimbine, and for convenience of comparison are dealt with in the table on p. 502. 

There is great similarity among the first three alkaloids in this table, and the suggestion has been made that they are identical, though a-yohimbine is laevorotatory and the other two are dextrorotatory. Also ethyl yohimbate has m.p. 190 , whilst ethyl woyohimbate is usually stated to melt at 243°, though Wibaut and van Gastel recorded 202° for the ester monohydrate. 

Constitution of Yohimbine and its Isomerides. The yohimb alkaloids are methyl esters of acids. Yohimbine, yohimbene, mesoyohimbine (isoyohimbine) and y-yohimbine (table, p. 502) are hydrolysed to four, distinct, monocarboxylic acids, C2,yH2402N2, each of which on decarboxylation by heating with soda-lime yields yohimbol, long supposed to be a secondary alcohol, Ci,yH240N2, but which Witkop has shown to be a ketone and has re-named yohimbone, C18H22ON2, m.p. 307° (dec.),... 

Other contributions to this discussion have been made by Harvey, Miller and Robson, and by Dewar and King, and important additional experimental evidence for the location of the. CHOH group at has been provided by Witkop, who explains the improvement in the yield of yohimbone, which occurs when the decarboxylation of yohimbic acid takes place under oxidising conditions, as due to the primary formation of a j8-ketocarboxylic acid, which is readily decarboxylated. This may be represented, using part of the yohimbine formula fXIV), as follows MeO. OC. CH. 1 CHOH. ->HO. OC. CH. CHOH. ... 

A variety of l,2,3,4-tetrahydro-j8-carbolines have been prepared from 3-piperidone phenylhydrazone derivatives. Used initially to obtain pentacyclic derivatives (35) related to the yohimbe alkaloids, this route was later extended to the synthesis of tetracyclic compounds (36). l-Methyl-5,6,7,8-tetrahydro-j8-carboline (37) was prepared in low yield by heating cyclohexanone 2-methyl-3-pyridylhydrazone with zinc chloride, a synthesis probably based on the similar preparation of the tetracyclic compound 38 starting from the corresponding quinolylhydrazine. Abramovitch and Adams extended this approach to the cyclization of cyclohexanone 3-pyri-dylhydrazone (39) itself. The main product was 6,7,8,9-tetrahydro-8-carboline (40), a smaller amount of the j8-isomer (41) also being obtained. This provides a convenient and readily reproducible route to the otherwise difficultly accessible 8-carboline ring system. The favored attack at carbon-2 over carbon-4 of the pyridine nucleus... 

Y-Legierung,/., Y-Metall, n. Y alloy, Y metal. Yohimboasaure, /, yohimboaic acid (yohimbic acid). 

Yohimbine is an indole alkaloid produced in the bark of yohimbe trees. It selectively inhibits a2-adrenergic receptors in the brain that are associated with libido and penile erection. Since there is only limited data supporting its efficacy, yohimbine is not a recommended treatment for any form of ED.22 Adverse effects of the drug include nausea, irritability, headaches, anxiety, tachycardia, and hypertension. 

Yohimbine (36) is a well-known and reasonably available alkaloid from Corynanthe yohimbe, inter alia. For this reason, and partly because of its intrinsic pharmacological activity (including reputed aphrodisiac activity), chemists have frequently studied its properties. Oppenauer oxidation is usually attended by saponification and decarboxylation in this series, and yohimbone (37) is the product. Wolf-Kischner reduction to yohimbane (38), followed by sodium hydride mediated alkylation, leads to the analgesic agent, mimbane (39). °... 

Yohimbe bark improves sexual performance in males... 

I Brand Name(s) Actibine, Aphrodyne, Dayto-Himbin, Yocon, Yohimbe, Yohimex, Yovi-tal... 

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