Qualitative determination of indole alkaloids of Tabernaemontana fuchsiaefolia (Apocynaceae)

Abstract

Este trabalho descreve um procedimento rápido e eficiente para a separação e identificação de alcalóides indólicos do extrato etanólico de Tabernaemontana fuchsiaefolia (Apocynaceae). As frações alcaloídicas obtidas dos extratos etanólicos (das folhas, das cascas do caule e das cascas das raízes) foram fracionadas e analisadas por cromatografia em camada delgada (CCD) e por cromatografia gasosa acoplada a espectrometria de massa (CG-EM). Foram identificados os alcalóides indólicos ibogamina, coronaridina, pseudoindoxil ibogaina, hidroxiindolenina voacangina, pseudoindoxil voacangina, tabernantina, catarantina, voacangina, 19-oxovoacangina, 10-hidroxicoronaridina, afinisina, 16-epi-afinina, voachalotina, ibogalina e conofaringina. This paper describes a fast and efficient procedure to separate and identify indole alkaloids from the ethanolic extract of Tabernaemontana fuchsiaefolia (Apocynaceae). The alkaloidal fractions obtained from ethanolic extracts of leaves and stem barks and root barks were fractioned and analyzed by Thin-Layer Chromatography (TLC) and by Gas Chromatography coupled to Mass Spectrometry (GC-MS). The following indole alkaloids were identified: ibogamine, coronaridine, ibogaine pseudoindoxyl, voacangine hydroxyindolenine, voacangine pseudoindoxyl, tabernanthine, catharanthine, voacangine, 19-oxovoacangine, 10-hydroxycoronaridine, affinisine, 16-epi-affinine, voachalotine, ibogaline, and conopharyngine.

Chemical constituents from Tabernaemontana catharinensis root bark: a brief NMR review of indole alkaloids and in vitro cytotoxicity

“…The carbonyl and the methoxy group of compound 11 resonate at downfield of 2,7 and 1,8 ppm, respectively due to the proximity of those groups indicating the S configuration for C-16. 13 C NMR spectra data of those a-acylindole alkaloids also denote the typical anisotropic effect of indole on the carbonyl of the ester group 16 .…”

“…Of the 12 alkaloids isolated 10 are of the ibogan class and the other 2 of the corynanthean class. They were identified by comparison with published data (UV, IR, 1 H NMR, 13 C NMR and MS) 3,5,[9][10][11][12][13][14] .…”

“…Structures of compounds 1-10, were elucidated on the basis of the 13 C NMR chemical shifts (Table 1) and comparison with the signals attributed to ibogamine (5).…”

“…The shifts of the carbons C-15, C-20 and C-21, very close to those reported by Perera et al 9 , clearly confirm the configuration of 19S for compounds 6, 7 and 8. In the isolated alkaloids 13 C NMR resonance signals near at 88 ppm and 187 ppm are indicative of the presence of a hydroxy group at C-7 of structures 2, 4, 8 and 10, shielding C-7 and deshielding C-2, respectively. Moreover, comparing the nearly identical shift pattern of structures 10 and 2, the presence of a hydroxy group attached to the C-3 of compound 10 is denoted by the downfield shift of C-3 by 12 ppm and the interactions of this group causing downfield shifts of C-14, C-15, C-17 and C-20.…”

“…On the basis of chemical shifts from the 13 C NMR spectra, isolated triterpenes of the oleanane, ursane and lupane type were identified 17 .…”