Monomeric Indole Alkaloids from Ervatamia hainanensis

New monoterpenoid indole alkaloids from the stems of Tabernaemontana bovina Lour (Apocynaceae)

Two new monoterpenoid indole alkaloids, named taberibogines E and F (1 and 2), together with three known ones (3-5) were isolated from the stems of Tabernaemontana bovina Lour (Apocynaceae). Their structures including absolute configurations were elucidated from a combination of NMR and HRESIMS data and NMR calculations as well as DP4+ probability analyses. Compounds 1 and 2 exhibited inhibitory effects on LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages.

Antiplasmodial activities of indole alkaloids from Tabernaemontana penduliflora K. Schum (Apocynaceae)

Five undescribed carboxy-indole alkaloids with corynanthe skeleton, penduflorines A-E (1-3) as well as a voacangine-N-oxide alkaloid, tabernaemontine (4), were isolated along with eight other known compounds (5-12) from the trunk bark of Tabernaemontana penduliflora K. Schum (Apocynaceae). Their structures were determined by means of spectroscopic and spectrometric methods such as UV, IR, NMR and HR-ESI-MS. Antiplasmodial activities of new isolates were evaluated against two strains of Plasmodium falciparum 3D7 and Dd2 by the Sybr green I-based fluorescence assay setup. Those compounds showed good in vitro activities. Among them, penduflorines A and B (1a and 1b) as well as tabernaemontine (4) showed significant inhibitory activities against the two strains with IC₅₀ values ranged between 1.85 and 7.88 μg/mL. This is the first report of quaternary-N-indole alkaloids (1a, 1b, 2, 3a, 3b and 4) occurring in the form of zwitterion from Tabernaemontana genus.

Molecular Networking Reveals Serpentinine-Related Bisindole Alkaloids from Picralima nitida, a Previously Well-Investigated Species

Five new monoterpene indole alkaloids (1-5), including four serpentinine-related bisindoles and one alstonine derivative monomer, have been isolated from the aerial parts of Picralima nitida. Their structures were elucidated by analysis of their HRMS and NMR spectroscopic data, and their absolute configurations were deduced from the comparison of experimental and simulated ECD spectra. In addition, two known compounds (6 and 7), previously undescribed from P. nitida, have also been purified. The compound isolation workflow was guided by a molecular networking-based dereplication strategy. Twenty-three compounds were dereplicated from the EtOH extract of P. nitida and fractions network and were assigned various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum as well as the cytotoxic activity against the MRC-5 cell line were determined for compounds 1-7.

Alkaloids isolated from Tabernaemontana bufalina display xanthine oxidase inhibitory activity

Continued interest in bioactive alkaloids led to the isolation of four undescribed alkaloids along with 74 known ones from the aerial parts of Tabernaemontana bufalina Lour. The structures of the yet undescribed alkaloids were elucidated based on NMR, IR, UV, MS and CD spectroscopic data and X-ray crystal diffraction and, according to the plant source, named as taberhaines A-D (1-4). The known compounds comprised of 66 monoterpenoid indole, three carboline and five isoquinoline alkaloids. Among them, the known apparicine inhibited significantly the activity of xanthine oxidase, which plays an important role for gout, with an IC₅₀ value of 0.65 μM, compared to the standard drug allopurinol (IC₅₀ = 0.60 μM).

The Iboga Alkaloids

Iboga alkaloids are a particular class of indolomonoterpenes most often characterized by an isoquinuclidine nucleus. Their first occurrence was detected in the roots of Tabernanthe iboga, a sacred plant to the people of Gabon, which made it cult object. Ibogaine is the main representative of this class of alkaloids and its psychoactive properties are well documented. It has been proposed as a drug cessation treatment and has a wide range of activities in targeting opioids, cocaine, and alcohol. The purpose of this chapter is to provide a background on this molecule and related compounds and to update knowledge on the most recent advances made. Difficulties linked to the status of ibogaine as a drug in several countries have hampered its development, but 18-methoxycoronaridine is currently under evaluation for the same purposes and for the treatment of leishmaniasis. The chapter is divided into six parts: an introduction aiming at defining what is called an iboga alkaloid, and this is followed by current knowledge on their biosynthesis, which unfortunately remains a "black box" as far as the key construction step is concerned. Many of these alkaloids are still being discovered and the third and fourth parts of the chapter discuss the analytical tools in use for this purpose and give lists of new monomeric and dimeric alkaloids belonging to this class. When necessary, the structures are discussed especially with regard to absolute configuration determinations, which remain a point of weakness in their assignments. Part V gives an account of progress made in the synthesis, partial and total, which the authors believe is key to providing solid solutions to the industrial development of the most promising molecules. The last part of the chapter is devoted to the biological properties of iboga alkaloids, with particular emphasis on ibogaine and 18-methoxycoronaridine.

New iboga-type alkaloids from Ervatamia hainanensis

The structures and absolute configurations of seven new iboga-type alkaloids 1–7 were determined by spectroscopic data, Mosher's method, single crystal X-ray diffraction and ECD analyses.

Indole alkaloids from Ervatamia hainanensis with potent acetylcholinesterase inhibition activities

Through bioassay-guided fractionation and chromatography technique, eight indole alkaloids were furnished from the stems of Ervatamia hainanensis. All isolates were evaluated for acetylcholinesterase (AChE) inhibition activities, in which compounds 1 and 3 exhibited the same level of activities as galantamine, a marketed cholinesterase inhibitor for the treatment of Alzheimer's disease. Discussion about the relationships between structure and activity of these alkaloids was also presented.

Ervahainanmine, a new indole alkaloid from the stems of Ervatamia hainanensis

A new sarpagine-type alkaloid with N-oxide group, called ervahainanmine, and three known ones including coronaridine, 19(S)-heyneanineguan, and coronaridine hydroxyindolenineguan were isolated from the stems of Evratamia hainanensis. The structure was established by spectroscopic methods, especially 2D NMR techniques.

Four tetracyclic oxindole alkaloids and a taberpsychine derivative from a Malayan Tabernaemontana

Four tetracyclic oxindole alkaloids, 7(R)- and 7(S)-geissoschizol oxindole (1 and 2), 7(R),16(R)- and 7(S),16(R)-19(E)-isositsirikine oxindole (3 and 4), in addition to a taberpsychine derivative, N(4)-demethyltaberpsychine (5), were isolated from the Malayan Tabernaemontana corymbosa and the structures were established using NMR and MS analysis.

Tabernaemontana L. (Apocynaceae): a review of its taxonomy, phytochemistry, ethnobotany and pharmacology

The taxonomy, phytochemistry, ethnobotany, and pharmacology of the genus Tabernaemontana L. (Apocynaceae) is reviewed. The genus is currently being revised taxonomically; most of the segregate genera are being reunited with it and the number of species that will ultimately be recognized will probably be about 100. All the names encountered in the chemical and ethnobotanical literature have been evaluated as far as possible, and a list is presented of the recognized species and their synonyms. The biogenesis and classification of the indole alkaloids found in Tabernaemontana species is set out and some problems in the determination of their stereochemistry are discussed. To facilitate access to the information, three lists have been compiled: the alkaloids in alphabetical order; the alkaloids in order of increasing molecular weight; and the alkaloids grouped according to their biogenetic classification, together with the species and plant part(s) in which they are known to occur. Biogenetic and chemotaxonomic aspects are briefly considered. A table of the non-alkaloidal constituents is also included. The ethnobotany of individual Tabernaemontana species is outlined and an overall assessment made. Likewise, information on the pharmacology of crude extracts and individual alkaloids from Tabernaemontana species has been assembled and appraised.