Alkaloids of Uncaria attenuata from Thailand

The major alkaloids of a sample of leaves of Uncaria attenuata obtained from Thailand have been identified as the pentacyclic heteroyohimbine alkaloids tetrahydroalstonine, rauniticine and the novel 14-β-hydroxy-3-iso-rauniticine. Evidence for the structure of the new alkaloid was obtained from a study of UV, IR, MS, ¹H NMR and ¹C NMR spectra.     

Partial purification and characterization of geissoschizine dehydrogenase from suspension cultures of Catharanthus roseus

The characterization and partial purification of geissoschizine dehydrogenase from Catharanthus roseus cell suspension cultures are described. The 35-fold purified enzyme removes the 21α-hydrogen of geissoschizine in a NADP⁺-dependent reaction. NAD⁺, FAD or FMN cannot act as cofactors for the dehydrogenation. Structurally related indole alkaloids are not dehydrogenated. In comparison to enzymes of the ajmalicine pathway, geissoschizine dehydrogenase shows an extremely low specific activity.     

Leaf alkaloids of Rauwolfia vomitoria

Nineteen indole alkaloids were isolated from Ghanaian Rauwolfia vomitoria leaves. The alkaloids comprised E-seco indole, sarpagan, picrinine, akuammiline, heteroyohimbine, oxindole, yohimbine and indolenine types. The biosynthetic relationship of the alkaloids is discussed.     

Stem alkaloids of Rauwolfia vomitoria

22 indole alkaloids were isolated from the stem bark of Nigerian Rauwolfia vomitoria and 20 characterized. The alkaloids comprised E-seco heteroyohimbine, sarpagan, dihydroindole, yohimbine and heteroyohimbine types. The biosynthetic relationship of the alkaloids is discussed.     

Alkaloids of Rauwolfia cumminsii stem

24 indole alkaloids were isolated from the stem bark of Rauwolfia cumminsii and 21 identified. The alkaloids comprised E-seco, sarpagan, dihydroindole, yohimbine, heteroyohimbine, 18-hydroxyyohimbine ester and anhydronium types together with peraksine and deacetylpicraline. The probable biosynthesis of the alkaloids is discussed.     

Leaf alkaloids of Rauwolfia oreogiton

Twenty-one indole alkaloids were isolated from the leaves of Rauwolfia oreogiton and identified. The alkaloids comprised E-seco heteroyohimbine, heteroyohimbine, akuammiline, akuammicine, pleiocarpamine, picraline, picrinine, dihydroindole and sarpagan types. No chemical differentiation between the leaves of R. oreogiton and R. volkensii could be established.     

Alkaloids of Uncaria attenuata,U. orientalis and U. Canescens

3-Iso-19-epi-ajmalicine, epiallo-corynantheine and dihydrocorynantheine pseudoindoxyl, not previously known as natural products, have been isolated from samples of U. attenuata. Akuammigine, dihydrocorynantheine, hirsutine, hirsuteine, mitraphylline, speciophylline, uncarines A and B, isorhynchophylline rhynchophylline, isocorynoxeine, corynoxeine, corynoxine B, rotundifoline, speciofoline, two yohimbine isomers, a yohimbine oxindole and an unidentified indole alkaloid (M⁺, m/e 347) have been obtained from samples of the same species. 3-Iso-ajmalicine, harmane, isopteropodine, pteropodine, uncarine F, speciophylline, isomitraphylline, mitraphylline and N-oxides of these six oxindole alkaloids have been isolated from samples of U. orientalis. Several samples of U. canescens have yielded harmane while one sample contained the four pteropodine isomers. The variation in the alkaloid content of these three species is discussed.     

Alkaloids of Rauwolfia nitida root bark

Thirty-three indole alkaloids were isolated from the root bark of Rauwolfia nitida. Sarpagan, dihydroindole, indolenine, yohimbine, 18-hydroxy-yohimbine ester, heteroyohimbine and anhydronium base types were isolated. The principal alkaloids were reserpine (0.034%), serpentinine (0.033%), pseudoreserpine (0.013%) and reserpiline (0.012%).