Voacanga

The enzyme responsible for the stereospecific condensation of trypt-amine and secologanin 34) was called strictosidine synthase, and its presence was demonstrated by Treimer and Zenk 194) in a number of indole alkaloid-producing plants, including Amsonia salicifolia, Catharanthus roseus, Ochrosia elliptica, Rauwolfia vomitoria, Rhazya orientalis, Stem-madenia tomentosa. Vinca minor, and Voacanga africana. Enzyme activity as high as 1698 pkat/mg protein was observed for O. elliptica. No... 

The first reported preparation of a binary alkaloid of the vinblastine type came from the efforts of J. Harley-Mason and Atta-ur-Rahman 15,16). In accord with a proposal for the synthesis of vinblastine-type alkaloids (77), their synthetic strategy was based on a coupling reaction previously developed by G. Biichi et al. for the synthesis of Voacanga alkaloids (75), as shown in Scheme 1. There, acid-catalyzed ionization... 

Tabersonine Catharanthus ovalis Stemmademia tomentosum Voacanga africana... 

Creoceras, Rejoua, Schzozygia, Stemmadenia and Voacanga, have, with all their species, remained intact with their original names. 

Voacanga schweinfurthii var. puberula (known in the older literature as Voacanga puberula) contains some ten related alkaloids, the major one of which is found in the seeds, and is tabersonine present at a rather remarkable 3.5 %. Ibogaine is present in the root bark but, at a concentration of 200 mg/Kg (0.02%), it is truly a minor constituent. 

A new alkaloid of Voacanga chalotiana,115 3 -hydroxyvobtusine (195), is identical with hydratoamataine, earlier546 postulated to be an intermediate in the conversion of amataine (194) into vobtusine (196). In consonance with the structure (195), reduction (by NaBH4) gives vobtusine (196), and dehydration gives amataine (194), this last reaction being accompanied by inversion of C-14, as previously noted.546... 

Ehiabhi, O.S., Edet, U.U., Walker, T.M., Schmidt, J.M., Setzer, W.N., Ogunwande, I.A., Essien, E. and Ekundayo, O. (2003) Constituents of essential oils of Apium graveolens L., Allium cepa L., and Voacanga africana Staph, from Nigeria. Journal of Essential Oil Bearing Plants 9(2), 126-132. 

O-Acetyl-19,20-dihydrovoachalotine (156) is a new alkaloid, isolated from the root bark of Voacanga chalotiana 9lb the orientation at C-20 was deduced... 

In the Voacanga series, conodurine and voacamine are among the alkaloids of Peschiera laeta,62 and the symmetrical dimer 12,12 -bis-ll-hydroxycoronaridine (245) occurs in the leaves of Bonafousia tetrastachya.149... 

Under this heading are collected the alkaloids from the plants given in Table I, with the exception of the iboga bases already considered and those dealt with under Voacanga alkaloids. 

Gonopharyngia durissima has afforded iboga bases, two dimeric alkaloids discussed under Voacanga alkaloids, and a trace of a base, alkaloid E, mp 191°-193°, pif a 7.26, UV-maxima at 210 and 305 mp, which differed from the other isolates in having no carbonyl absorption in the IR-spectrum (14). Gonopharyngia pachysiphon, in contrast to C. durissima, has yielded only steroidal bases (45). 

From a pharmacological point of view, the Voacanga alkaloids are relatively nontoxic, rapidly eliminated, and of no great interest (68). The reported potent cardiotonic properties (9, 54, 69) of some of these alkaloids have apparently not withstood the test of time (52). 

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