Stereochemical analysis of natural products: alkaloids from the root bark of Strychnos panganensis
Abstract
The present communication deals with the stereochemical analysis of natural bisindole alkaloids, 1,2 more precisely, a detailed structural analysis of four alkaloids 1-4 extracted from the root bark of Strychnos panganensis known as panganensines R, S, X and Y (Figure 1) is performed. Historically, panganensines 1-4 were identified as novel alkaloids in addition to known representatives of this series like matopensine. These alkaloids are characterized by their unique dimeric structure composed of two smaller alkaloid almost similar units linked together. In this pioneering communication, we have performed state-of-the-art stereochemical study of four most interesting classical representatives of this series by means of the original high-level DFT calculations of their 1 H and 13 C NMR chemical shifts, as compared to experiment.
Plant Strychnos panganensis Gilg is a scrambling shrub or liana, 3-20 m climbing in trees (see Online Supplementary Materials). Panganensines S, X and Y evaluated against chloroquine-resistant and sensitive lines of Plasmodium falciparum exhibited moderate to weak activity with antiplasmodial IC 50 values of 5-20 mm against Plasmodium lines. 3 The amount of isolated panganensine R was not sufficient for the pharmacological testing. The leaves of two East African specimens were screened for alkaloids but only traces have been found for of the two. 4 On the other hand, the alkaloids of root bark of Strychnos panganensis collected in Tanzania were extracted and deeply studied at the University of Reims. 5 From 6.6 g fraction of crude alkaloids, twelve alkaloids were isolated. Among them six were new, among which dimeric indolinic alkaloids were named as panganensines R, S, X and Y. These alkaloids were made up of N-deacetylated retuline, isoretuline and spermostrychnine and it was soon realized that they were pairs of diastereoisomers. The first pair was named panganensines R and S, without knowing which was C-21' R and C-21' S. For the second pair, the letters X and Y were chosen and supposed to possess R-or S-configurations at C-19, respectively. With the tools available at that time, it was not possible to determine the missing configurations.
Thus, at the first stage of the present study, a preliminary conformational search was carried out to establish the spatial three-dimensional structures of 1-4. It is worth noting that the entries for panganensines S and X in the PubChem database were deposited with incorrect designations of their three-
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BibTeX
@article{grigoriev2026stereochemical,
title = {{Stereochemical analysis of natural products: alkaloids from the root bark of Strychnos panganensis}},
author = {Dmitry A Grigoriev and Valentin Alexandrovich Semenov and Luc Angenot and Georges Massiot and Leonid Borisovich Krivdin},
journal = {Mendeleev Communications},
year = {2026},
month = sep,
doi = {10.71267/mencom.7827},
url = {https://univ-reims.hal.science/hal-05743505v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Stereochemical analysis of natural products: alkaloids from the root bark of Strychnos panganensis
AU - Dmitry A Grigoriev
AU - Valentin Alexandrovich Semenov
AU - Luc Angenot
AU - Georges Massiot
AU - Leonid Borisovich Krivdin
PY - 2026
DA - 2026/09/09
JO - Mendeleev Communications
DO - 10.71267/mencom.7827
UR - https://univ-reims.hal.science/hal-05743505v1
AB - The present communication deals with the stereochemical analysis of natural bisindole alkaloids, 1,2 more precisely, a detailed structural analysis of four alkaloids 1-4 extracted from the root bark of Strychnos panganensis known as panganensines R, S, X and Y (Figure 1) is performed. Historically, panganensines 1-4 were identified as novel alkaloids in addition to known representatives of this series like matopensine. These alkaloids are characterized by their unique dimeric structure composed of two smaller alkaloid almost similar units linked together. In this pioneering communication, we have performed state-of-the-art stereochemical study of four most interesting classical representatives of this series by means of the original high-level DFT calculations of their 1 H and 13 C NMR chemical shifts, as compared to experiment. Plant Strychnos panganensis Gilg is a scrambling shrub or liana, 3-20 m climbing in trees (see Online Supplementary Materials). Panganensines S, X and Y evaluated against chloroquine-resistant and sensitive lines of Plasmodium falciparum exhibited moderate to weak activity with antiplasmodial IC 50 values of 5-20 mm against Plasmodium lines. 3 The amount of isolated panganensine R was not sufficient for the pharmacological testing. The leaves of two East African specimens were screened for alkaloids but only traces have been found for of the two. 4 On the other hand, the alkaloids of root bark of Strychnos panganensis collected in Tanzania were extracted and deeply studied at the University of Reims. 5 From 6.6 g fraction of crude alkaloids, twelve alkaloids were isolated. Among them six were new, among which dimeric indolinic alkaloids were named as panganensines R, S, X and Y. These alkaloids were made up of N-deacetylated retuline, isoretuline and spermostrychnine and it was soon realized that they were pairs of diastereoisomers. The first pair was named panganensines R and S, without knowing which was C-21' R and C-21' S. For the second pair, the letters X and Y were chosen and supposed to possess R-or S-configurations at C-19, respectively. With the tools available at that time, it was not possible to determine the missing configurations. Thus, at the first stage of the present study, a preliminary conformational search was carried out to establish the spatial three-dimensional structures of 1-4. It is worth noting that the entries for panganensines S and X in the PubChem database were deposited with incorrect designations of their three-
SN - 0959-9436
SN - 1364-551X
ER -