Targeted Isolation of Monoterpene Indole Alkaloids from Palicourea sessilis.

Phytochemical investigation of the alkaloid extract of Palicourea sessilis by LC-HRMS/MS using molecular networking and an in silico MS/MS fragmentation approach suggested the presence of several new monoterpene indole alkaloids. These compounds were isolated by semipreparative HPLC, and their structures confirmed by means of HRMS, NMR, and ECD measurements as 4-N-methyllyaloside (3), 4-N-methyl-3,4-dehydrostrictosidine (4), 4ß-hydroxyisodolichantoside (6), and 4α-hydroxyisodolichantoside (7), as well as the known alkaloids alline (1), N-methyltryptamine (2), isodolichantoside (5), and 5-oxodolichantoside (8). In addition, the acetylcholinesterase inhibitory activity of the compounds was evaluated up to 50 µM.

Revisiting Previously Investigated Plants: A Molecular Networking-Based Study of Geissospermum laeve.

Three new monoterpene indole alkaloids (1-3) have been isolated from the bark of Geissospermum laeve, together with the known alkaloids (-)-leuconolam (4), geissolosimine (5), and geissospermine (6). The structures of 1-3 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of geissolaevine (1) was deduced from the comparison of experimental and theoretically calculated ECD spectra. The isolation workflow was guided by a molecular networking-based dereplication strategy using an in-house database of monoterpene indole alkaloids. In addition, five known compounds previously undescribed in the Geissospermum genus were dereplicated from the G. laeve alkaloid extract network and were assigned with various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum and Leishmania donovani as well as the cytotoxic activity against the MRC-5 cell line were determined for compounds 1-5.

Loganin and secologanin derived tryptamine-iridoid alkaloids from Palicourea crocea and Palicourea padifolia (Rubiaceae).

During comparative analysis on Palicourea species from Costa Rica, two unusual loganin derived tryptamine-iridoid alkaloids were isolated from an accession of Palicourea crocea. Besides the already known brachycerine (2), palicroceaine (1) features a novel hexacyclic backbone. A second provenance, however, yielded strictosidinic acid (3), belonging to the more common secologanin derived tryptamine-iridoid alkaloids, such as those found in Palicourea padifolia. From this species, strictosidine (4), lyaloside (5) and its derivative (E)-O-(6')-(4″-hydroxy-3″,5″-dimethoxy)-cinnamoyl lyaloside (6) could be isolated. A herbarium specimen-based screening was performed, indicating some degree of regional differentiation in alkaloid content and biosynthetic pathways within the widespread and variable Pal. crocea. It further shows its differentiation from the related strictosidine containing Palicourea croceoides. The occurrence of loganin derived tryptamine-iridoid alkaloids in Pal. crocea, Psychotria brachyceras and Psychotria brachypoda, all putatively unrelated members of the Palicourea s.l. clade, is a noteworthy exception within the genus, otherwise largely characterized by secologanin-derived tryptamine-iridoid alkaloids.

Antiparasitic indole alkaloids from Aspidosperma desmanthum and A. spruceanum from the Peruvian Amazonia.

Twenty-three indole alkaloids were isolated from Aspidosperma desmanthum and A. spruceanum. Alkaloids 1-4 were isolated from the leaves, 5-8 from the stem bark and 9-15 from the root bark of A. desmanthum. Alkaloids 5, 11, 16, 17 and 19 were isolated from the stem bark, 18 and 20-22 from the root bark and 23 from the flowers of A. spruceanum. Compounds 4, 14, and 15 have not been previously reported as natural products while 16 and 20 have been isolated for the first time from the genus Aspidosperma. Their structures were determined by spectroscopic techniques including 1D and 2D NMR experiments (COSY, NOESY, HSQC, HMBC). The antiparasitic activity of these compounds was tested against Trypanosoma cruzi and Leishmania infantum and their non-specific cytotoxicity on mammalian cells. The most active compounds were 10, 12, 13, and 14 from A. desmanthum, and 19, 21 and 22 from A. spruceanum. Aspidolimine (10) aspidocarpine (12) and tubotaiwine (21) showed selective activity against L. infantum.

Anti-leishmanial activity of alkaloidal extracts obtained from different organs of Aspidosperma ramiflorum.

The present study was designated to evaluate semi-quantitative antileishmanial activity of alkaloidal extracts that were obtained from 1g of different parts of Aspidosperma ramiflorum (leaves, roots, seeds, and stem barks). Alkaloidal extracts of barks and leaves presented a good activity against the extracellular form (promastigotes) of Leishmania (L.) amazonensis. It is known that compounds responsible for the antileishmanial activity in the alkaloidal extracts from A. ramiflorum are the monoterpenoid indole alkaloids ramiflorine A and ramiflorine B, therefore extracts obtained from different plant parts were analyzed by electrospray ionization mass spectrometry (ESI-MS) in order to evidence the presence of these bioactive alkaloids. Based on these findings, alkaloidal extract from leaves was fractionated on preparative thin-layer chromatography in a bioassay-guided fractionation affording individual purified ramiflorines A and B. Both ramiflorines A and B showed significant activity against Leishmania (L.) amazonensis (LD(50) values of 18.5±6.5µg/ml and 12.63±5.52µg/ml, respectively). Our results are showing that alkaloidal extract from leaves is a promising alternative to the use of stem barks from A. ramiflorum.

Application of preparative high-speed counter-current chromatography for the separation of two alkaloids from the roots of Tabernaemontana catharinensis (Apocynaceae).

The methanolic extract of Tabernaemontana catharinensis (Apocynaceae) roots, which contains alkaloids with several biological activities, was separated on a preparative scale using high-speed counter-current chromatography. The optimum solvent system was found to be a mixture of CHCl(3)-MeOH-H(2)O [5:10:6 (v/v/v)] and led to a successful separation of two monoterpenic indole alkaloids, voachalotine (1) and 12-methoxy-N(b)-methylvoachalotine (2) in approximately 4.0 hours. The alkaloids were all isolated at purities over 95%, and their structures were established on the basis of spectroscopic methods, including 1D and 2D NMR and EI/MS.

Bases débiles minoritarias de la raiz de Rauvolfia Viridis Roem. Et Schult / Weak minor bases of the root of Rauwolfia viridis Roem. et Schult

Se realizó un estudio químico de la raíz de la especie Rauvolfia viridis Roem. et Schult que crece en Cuba, con el objetivo de profundizar en este tema. Se aislaron, purificaron y caracterizaron diferentes alcaloides correspondientes a las bases débiles, entre los que se encuentran la ajmalidina, la -yohimbina, la quebrachidina, la reserpinina y la yohimbina. Se descarta la presencia de reserpina

Alcaloides de rauwolfia: VII; alcaloides de la corteza del tallo de rauwolfia virides roem et Schult / Alkaloids of rauwolfia: VII; alkaloids of the bark of the stem of rauwolfia viridis roem et Schult

Se le realiza un estudio a la fracción alcaloidal obtenida a partir de la corteza del tallo de la Rauwolfia viridis Roem. et Schult. El fraccionamiento en gradiente ácido y por distribución en contracorriente ha permitido aislar y purificar 7 alcaloides que se identifican como las bases (-) tabernaemontanina, (-) vobasina, (+) ajmalina, (+) quebrachidina y (+) serpentina. Otros 2 componentes novedosos purificados pertenecen al grupo de las bases 2-acilindólicas, los que se denominan rauviridina y epi-rauviridina. Se incluyen las constantes de distribución de los alcaloides aislados en varias combinaciones de fases inmiscibles

Estructura de las bases rauviridina y epi-rauviridina / Structures of rauviridine and epi-rauviridine

El análisis espectroscópico (UV, IR, 1H, 13C-RMN y MS) de las bases rauviridina y epi-rauviridina ha permitido establecer una constitución correspondiente a la Nb-metil-4,5-seco-5,6-deshidro vobasina para ambos productos aislados de la corteza del tallo de Rauwolfia viridis Roem. et Schult. Se incluyen ensayos preliminares encaminados a determinar el posible origen de estas bases

Alcaloides de rauwolfia cubana A. DC. (I): estudio preliminar de la corteza del tallo / Alkaloids of rauwolfia cubana A. DC. (I): preliminary study of the bark of the stem

Se le realiza un estudio fitoquímico preliminar a la corteza del tallo de la Rauwolfia cubana A. dC. que crece en Cuba. El fraccionamiento cromatográfico, asociado con una distribución en gradiente de acidez, permite purificar el alcaloide más abundante en esta parte del vegetal, que se identifica como 16-epi affinina, atendiendo a sus propiedades físicas y espectroscópicas. Se incluyen los espectros de 1H y 13C-RMN