Ancistrocladus Abbreviatus Research Articles

Ancistrobrevinium A, the first N-methylated, cationic naphthylisoquinoline alkaloid, from the tropical liana Ancistrocladus abbreviatus (Ancistrocladaceae)

Ancistrobrevinium A (1) is the first N-methylated and non-hydrogenated, and thus cationic naphthylisoquinoline alkaloid. It was discovered in the root bark extract of the phytochemically productive West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Its constitution was elucidated by HR-ESI-MS and 1D and 2D NMR. Due to the steric hindrance in the proximity of the linkage between the naphthalene and isoquinoline parts, the biaryl axis is rotationally hindered. It thus constitutes a stable element of chirality – the only one in the new alkaloid since, different from most other naphthylisoquinoline alkaloids, it has no stereogenic centers. The axial configuration of 1 was assigned by electronic circular dichroism (ECD) investigations, which gave a positive couplet, indicating a ‘positive chirality’, here corresponding to a P-configuration. Ancistrobrevinium A (1) showed a weak cytotoxic activity against A549 lung cancer cells (IC50 = 50.6 μM).

Dioncophyllidine E: The first configurationally semi-stable, 7,3′-coupled naphthyldihydroisoquinoline alkaloid, from Ancistrocladus abbreviatus, with antiausterity activity against PANC-1 human pancreatic cancer cells

The discovery of a new naphthylisoquinoline alkaloid, dioncophyllidine E (4), from the tropical liana Ancistrocladus abbreviatus (Ancistrocladaceae) is described. Due to its rare 7,3′-coupling type, combined with the lack of an oxygen function at C-6, it is configurationally semi-stable at the biaryl axis, and thus occurs as a pair of slowly interconverting atropo-diastereomers, 4a and 4b. Its constitution was assigned mainly by 1D and 2D NMR. The absolute configuration at the stereocenter, C-3, was elucidated by oxidative degradation. The absolute axial configuration of the individual atropo-diastereomers was established by their HPLC resolution, combined with online electronic circular dichroism (ECD) investigations, providing nearly mirror-imaged LC-ECD spectra. These were assigned to the respective atropisomers by ECD comparison with a related, but configurationally stable alkaloid, ancistrocladidine (5). Dioncophyllidine E (4a/4b) exhibits a strong preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient-deprived conditions, with a PC50 value of 7.4 µM, suggesting its potential as an agent against pancreatic cancer.

Naphthylisoindolinone alkaloids: the first ring-contracted naphthylisoquinolines, from the tropical liana Ancistrocladus abbreviatus, with cytotoxic activity.

The West African liana Ancistrocladus abbreviatus is a rich source of structurally most diverse naphthylisoquinoline alkaloids. From its roots, a series of four novel representatives, named ancistrobrevolines A-D (14-17) have now been isolated, displaying an unprecedented heterocyclic ring system, where the usual isoquinoline entity is replaced by a ring-contracted isoindolinone part. Their constitutions were elucidated by 1D and 2D NMR and HR-ESI-MS. The absolute configurations at the chiral axis and at the stereogenic center were assigned by using experimental and computational electronic circular dichroism (ECD) investigations and a ruthenium-mediated oxidative degradation, respectively. For the biosynthetic origin of the isoindolinones from 'normal' naphthyltetrahydroisoquinolines, a hypothetic pathway is presented. It involves oxidative decarboxylation steps leading to a ring contraction by a benzilic acid rearrangement. Ancistrobrevolines A (14) and B (15) were found to display moderate cytotoxic effects (up to 72%) against MCF-7 breast and A549 lung cancer cells and to reduce the formation of spheroids (mammospheres) in the breast cancer cell line.

Ancistrobrevidines A-C and related naphthylisoquinoline alkaloids with cytotoxic activities against HeLa and pancreatic cancer cells, from the liana Ancistrocladus abbreviatus

From the leaves of Ancistrocladus abbreviatus (Ancistrocladaceae), six 5,1′-coupled naphthyldihydroisoquinoline alkaloids were isolated, ancistrobrevidines A-C (5–7), 5-epi-dioncophyllidine C2 (10), 6-O-methylhamatinine (8), and 6-O-methylancistectorine A3 (9); the two latter compounds were already known from related plants. Most strikingly, this series comprises alkaloids belonging to three different subclasses of naphthylisoquinolines. Ancistrobrevidine C (7) and the alkaloids 8 and 9, displaying the S-configuration at C-3 and an oxygen function at C-6, are three further representatives of the large subgroup of 5,1′-coupled Ancistrocladaceae-type compounds found in nature. 5-epi-Dioncophyllidine C2 (10), lacking an oxygen function at C-6 and having the R-configuration at C-3, is only the third representative of a 5,1′-linked Dioncophyllaceae-type naphthylisoquinoline. Likewise rare are 5,1′-coupled hybrid-type alkaloids, which are 6-oxygenated and 3R-configured. The ancistrobrevidines A (5) and B (6) are the only second and third examples of such 5,1′-linked naphthylisoquinolines in Ancistrocladus species showing the landmarks of both, Ancistrocladaceae- and Dioncophyllaceae-type naphthylisoquinolines. In the roots of A. abbreviatus, two further unprecedented 5,1′-coupled alkaloids were discovered, ancistrobreviquinones A (11) and B (12), consisting of a 3,4-naphthoquinone portion coupled to a tetrahydroisoquinoline subunit. They are the very first quinoid naphthylisoquinolines possessing an ortho-diketone entity. Ancistrobrevidine C (7) exerted pronounced antiproliferative activities against HeLa cervical cancer cells and preferential cytotoxicity towards PANC-1 human pancreatic cancer cells under nutrient-deprived conditions following the antiausterity approach. Moreover, 7 suppressed the migration of PANC-1 cells and significantly inhibited colony formation under nutrient-rich conditions in a concentration-dependent manner, and induced dramatic alteration in cell morphology, leading to cell death.

Naphthylisoquinoline alkaloids and their synthetic analogs as potent novel inhibitors against Babesia canis in vitro

Babesia canis is the predominant and clinically relevant canine Babesia species in Europe. Transmitted by vector ticks, the parasite enters red blood cells and induces a severe, potentially fatal hemolytic anemia. Here, we report on the antibabesial activities of three extracts of the West African tropical plant species Triphyophyllum peltatum (Dioncophyllaceae) and Ancistrocladus abbreviatus (Ancistrocladaceae) and of 13 genuine naphthylisoquinoline alkaloids isolated thereof. Two of the extracts and eight of the alkaloids were found to display strong activities against Babesia canis in vitro. Among the most potent compounds were the C,C-coupled dioncophyllines A (1a) and C (2) and the N,C-linked alkaloids ancistrocladium A (3) and B (4), with half-maximum inhibition concentration (IC50) values of 0.48 μM for 1a, 0.85 μM for 2, 1.90 μM for 3, and 1.23 μM for 4. Structure-activity relationship (SAR) studies on a small library of related genuine analogs and non-natural synthetic derivatives of 1a and 2 revealed the likewise naturally occurring alkaloid N-methyl-7-epi-dioncophylline A (6b) to be the most potent (IC50, 0.14 μM) among the investigated compounds. Although none of the tested naphthylisoquinolines showed 100 % inhibition of parasite infection – as displayed by imidocarb dipropionate (IC50, 0.07 μM), which was used as a positive control – the antibabesial potential of the dioncophyllines A (1a) and C (2) and related compounds such as 6b, its atropo-diastereomer 6a (IC50, 1.45 μM), and 8-O-(p-nitrobenzyl)dioncophylline A (14) (IC50, 0.82 μM) is to be considered as high. The SAR results showed that N-methylation and axial chirality exert a strong impact on the antibabasial activities of the naphthylisoquinolines presented here, whereas dimerization, as in jozimine A2 (5) (IC50, 140 μM), leads to a significant decrease of activity against B. canis. Alkaloids displaying good to high activities against B. canis like the dioncophyllines 1a, 2, 6a, and 6b were found to cause only a small degree of hemolysis (< 0.7 %), whereas compounds with moderate to weak antibabesial activities such as 6-O-methyl-4′-O-demethylancistrocladine (15a) (IC50, 14.0 μM) and its atropo-diastereomer 6-O-methyl-4′-O-demethylhamatine (15b) (IC50, 830 μM) caused a high degree of hemolysis (7.3 % for 15a and 11.2 % for 15b). In this respect, the most effective anti-Babesia naphthylisoquinolines are also the safest ones.

Ancistrosecolines A-F, Unprecedented seco-Naphthylisoquinoline Alkaloids from the Roots of Ancistrocladus abbreviatus, with Apoptosis-Inducing Potential against HeLa Cancer Cells.

Ancistrosecolines A-F (8-13) are the first seco-type naphthylisoquinoline alkaloids discovered in Nature. In all these novel compounds, the tetrahydroisoquinoline ring is cleaved, with loss of C-1. They were isolated from the root bark of Ancistrocladus abbreviatus (Ancistrocladaceae), along with 1-nor-8-O-demethylancistrobrevine H (14), which is the first naturally occurring naphthylisoquinoline lacking the otherwise generally present methyl group at C-1. The stereostructures of the new alkaloids were established by HRESIMS, 1D and 2D NMR, oxidative degradation, and experimental and quantum-chemical ECD investigations. Ancistrosecolines A-F (8-13) and 1-nor-8-O-demethylancistrobrevine H (14) are typical Ancistrocladaceae-type metabolites, i.e., oxygenated at C-6 and S-configured at C-3, belonging to the subclasses of 7,1'- and 7,8'-coupled alkaloids. The biaryl linkages of 8-14 are rotationally hindered due to bulky ortho-substituents next to the axes. Owing to the constitutionally unsymmetric substitution patterns on each side of the axis, this C-C single bond represents an element of chirality in 1-nor-8-O-demethylancistrobrevine H (14) and in ancistrosecolines A-D (8-11). In ancistrosecolines E (12) and F (13), however, the likewise rotationally hindered biaryl axes do not constitute chiral elements, due to a symmetric substitution pattern, with its identical two methoxy functions at C-6 and C-8 in the phenyl subunit. And these two methoxy groups are, for the first time, not constitutionally heterotopic, but diastereotopic to each other. Ancistrosecoline D (11) exhibits strong cytotoxicity against HeLa cervical cancer cells. As visualized by Hoechst nuclei staining and by real-time imaging experiments, 11 induced massive nuclei fragmentation in HeLa cells, leading to apoptotic cell death.

A Near-Complete Series of Four Atropisomeric Jozimine A2-Type Naphthylisoquinoline Dimers with Antiplasmodial and Cytotoxic Activities and Related Alkaloids from Ancistrocladus abbreviatus.

Three new naphthylisoquinoline dimers, jozibrevines A-C (1a-c), were isolated from the West African shrub Ancistrocladus abbreviatus, along with the known dimer jozimine A2 (1d). The two molecular moieties of 1a-d are coupled via the sterically constrained 3',3″-positions of their two naphthalene units, so that the central biaryl linkage is rotationally hindered. With the two outer axes also being chiral, 1a-d possess three consecutive stereogenic axes. The four isolated dimers all have the same constitutions and identical absolute configurations at the four stereogenic centers, but differ by their axial chirality. They belong to the extremely small class of Dioncophyllaceae-type naphthylisoquinoline dimers, i.e., being devoid of oxygen functions at C-6 and bearing the R-configuration at C-3 in their isoquinoline portions. Besides these dimers, the plant produces predominantly typical Ancistrocladaceae-type monomeric compounds, i.e., with the S-configuration at C-3 and an oxygen function at C-6, such as the new ancistrobrevines K (5) and L (6). Furthermore, a new hybrid-type (i.e., mixed Ancistrocladaceae/Dioncophyllaceae-type) alkaloid was identified, named ancistrobrevine M (7), which is 3R-configured and 6-oxygenated. Remarkable was the discovery of its "inverse hybrid-type" counterpart, dioncoline A (8). It is the as yet only known 3S-configured naphthylisoquinoline lacking an O-functionality at C-6. The new jozibrevines A-C (1a-c) exhibited pronounced antiplasmodial activities in the submicromolar range, with 1a being the most potent compound (IC50, 0.012 μM). Furthermore, jozimine A2 (1d) showed cytotoxicity against human colon carcinoma (HT-29), fibrosarcoma (HT1080), and multiple myeloma (MM.1S) cancer cells, displaying IC50 values of 12.0, 9.0, and 5.0 μM, respectively, whereas jozibrevines A (1a) and B (1b) were nontoxic in this concentration range.

Ancistrobreveines A-D and related dehydrogenated naphthylisoquinoline alkaloids with antiproliferative activities against leukemia cells, from the West African liana Ancistrocladus abbreviatus.

A unique series of six biaryl natural products displaying four different coupling types (5,1′, 7,1′, 7,8′, and 5,8′) were isolated from the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Although at first sight structurally diverse, these secondary metabolites all have in common that they belong to the rare group of naphthylisoquinoline alkaloids with a fully dehydrogenated isoquinoline portion. Among the African Ancistrocladus species, A. abbreviatus is so far only the second one that was found to produce compounds with such a molecular entity. Here, we report on four new representatives, named ancistrobreveines A–D (12–14, and 6). They were identified along with the two known alkaloids 6-O-methylhamateine (4) and ent-dioncophylleine A (10). The two latter naphthylisoquinolines had so far only been detected in Ancistrocladus species from Southeast Asia. All of these fully dehydrogenated alkaloids have in common being optically active despite the absence of stereogenic centers, due to the presence of the rotationally hindered biaryl axis as the only element of chirality. Except for ent-dioncophylleine A (10), which lacks an oxygen function at C-6, the ancistrobreveines A–D (12–14, and 6) and 6-O-methylhamateine (4) are 6-oxygenated alkaloids, and are, thus, typical ‘Ancistrocladaceae-type’ compounds. Ancistrobreveine C (14), is the first – and so far only – example of a 7,8′-linked fully dehydrogenated naphthylisoquinoline discovered in nature that is configurationally stable at the biaryl axis. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR) and chiroptical (electronic circular dichroism) methods. Ancistrobreveine C (14) and 6-O-methylhamateine (4) exhibited strong antiproliferative activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000.

Ancistrobrevines E-J and related naphthylisoquinoline alkaloids from the West African liana Ancistrocladus abbreviatus with inhibitory activities against Plasmodium falciparum and PANC-1 human pancreatic cancer cells

From the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae), ten new naphthylisoquinoline alkaloids (7a, 7b, 8a, 8b, and 9–14), displaying three different coupling types (5,1′, 5,8′, and 7,8′), were isolated, among them a series of five 5,1′-linked representatives and four metabolites belonging to the rare group of 7,8′-coupled alkaloids. Two of the alkaloids, the ancistrobrevines I (13) and J (14), are only the fourth and fifth examples of 7,8′-linked naphthyldihydroisoquinolines ever found in nature. The stereostructures of the new plant metabolites were determined by spectroscopic, chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. For the assignment of the axial configuration of 13 and 14 relative to the stereocenter at C-3, which is too far away for significant NOE long-range interactions, these 7,8′-coupled naphthyldihydroisoquinolines were stereoselectively converted into the respective cis-configured tetrahydroisoquinoline analogs. The newly generated ‘auxiliary’ stereocenter at C-1 permitted decisive NOE interactions between the isoquinoline and the naphthalene parts, and thus a reliable attribution of the axial configuration of 13 and 14. In addition, five known compounds (3, 5, 16, 17, and 20), previously discovered in related African and Asian Ancistrocladus species, have now for the first time been identified in A. abbreviatus. All of these alkaloids are S-configured at C-3 and bear an oxygen function at C-6, and are, thus, typical Ancistrocladaceae-type compounds. Some of the alkaloids of A. abbreviatus exhibited promising activities against the malaria parasite Plasmodium falciparum and PANC-1 human pancreatic cancer cells.

Antitumoral and antileishmanial dioncoquinones and ancistroquinones from cell cultures of Triphyophyllum peltatum (Dioncophyllaceae) and Ancistrocladus abbreviatus (Ancistrocladaceae)

From the methanolic extracts of solid callus cultures from two species of the closely related palaeotropical plant families Dioncophyllaceae and Ancistrocladaceae seven new natural naphthoquinones were isolated, dioncoquinones A ( 4) and B ( 5) from Triphyophyllum peltatum, and ancistroquinones B ( 6), C ( 7), D ( 9), E ( 10), and F ( 12) from Ancistrocladus abbreviatus. Their structures were elucidated by spectroscopic, chemical, and computational methods. Furthermore, the already known naphthoquinones plumbagin ( 2), droserone ( 3), malvone A ( 8), and nepenthone A ( 11) were found in the extract of A. abbreviatus. Dioncoquinones A ( 4) and B ( 5) showed good – and specific – activity against Leishmania major, while they were not active against other protozoic parasites. Moreover, treatment with 4 and 5 strongly induced apoptosis in human tumor cells derived from two different B cell malignancies, B cell lymphoma and multiple myeloma, without any significant toxicity towards normal peripheral mononuclear blood cells.

African medicinal plants in the search for new drugs based on ethnobotanical leads.

In the African world view the natural environment is a living entity whose components are intrinsically bound to mankind. Dietary plants, spices and common herbs dominate the materia medica, in contrast with modern orthodox medicine which uses many regulated poisons. Drug development based on ethnobotanical leads has followed two paths: the classical approach of identification of single plant species with biologically active compounds and the characterization and standardization of traditional recipes for reformulation as medicines. The first approach has led to the recognition of many African plants as medicines and the isolation of several biologically active molecules; examples range from the well physostigmine (from Physostigma venonosum) used for the treatment of glaucoma to the recently identified antiviral agents from Ancistrocladus abbreviatus. The second approach which aims at optimization of mixed remedies as formulated dosage forms is perhaps more relevant to the needs of the poor rural populations but has remained largely ignored. Drug development programmes based on ethnobotanical leads must provide for just and fair compensation for individual informants and local communities.

In vitro propagation of Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae)

Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae), a West African liana producing naphthylisoquinoline alkaloids, was successfully raised from seeds in vitro. Clonal propagation was best achieved growing nodal stem segments on 1/5 Linsmaier and Skoog medium with full strength organics and supplemented with 0.02 μM thidiazuron, 4.44 μM 6-benzylaminopurine and 0.05 μM 1-naphthaleneacetic acid. Detached axillary shoots were grown on Anderson's Rhododendron medium devoid of phytohormones and rooted within one month when dipped in 4.92 μM indole-3-butyric acid. Rooted plants became acclimatized to nonsterile greenhouse conditions.

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from dioncophyllaceae and ancistrocladaceae species

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from Dioncophyllaceae and Ancistrocladaceae species. International Journal for Parasitology 27: 29–32. Naphthylisoquinoline alkaloid-containing extracts (10 μg ml −1) of species belonging to the Dioncophyllaceae and the Ancistrocladaceae, 2 small tropical plant families, display pronounced in vitro activities against exoerythrocytic stages of Plasmodium berghei (Anka), developing in human hepatoma cells (Hep G2). The highest activities were obtained with CH 2Cl 2 root and bark extracts, and a CH 2Cl 2 NH 3 leaf extract from Triphyophyllum peltatum, a CH 2Cl 2 NH 3 root extract from Ancistrocladus abbreviatus, and a CH 2Cl 2 leaf extract from A. tectorius. The degrees of growth inhibition ranged within 27.7–70.0%. The commercially available drug primaquine diphosphate (25 μg ml −1) caused a comparable effect (62.1%) in the same test system.

Activities of extracts and naphthylisoquinoline alkaloids from Triphyophyllum peltatum, Ancistrocladus abbreviatus and Ancistrocladus barteri against Plasmodium berghei (Anka strain) in vitro

Extracts from three tropical medicinal plant species belonging to the Dioncophyllaceae ( Triphyophyllum peltatum) and the Ancistrocladaceae ( Ancistrocladus abbreviatus and Ancistrocladus barteri), and pure naphthylisoquinoline alkaloids derived from these species have been examined for the first time for their activity against asexual blood forms of Plasmodium berghei (Anka strain) in vitro. These activities were considerable and comparable with those earlier found against erythrocytic forms of Plasmodium falciparum. The extracts and constituents of species belonging to the Dioncophyllaceae (dioncophylline B, dioncopeltine A and dioncophylline A) appear to be more promising than those from the Ancistrocladaceae.

Activity of extracts and naphthylisoquinoline alkaloids from Triphyophyllum peltatum, Ancistrocladus abbreviatus and A. Barteri against Plasmodium falciparum in vitro

Five extracts from the tropical plant species Triphyophyllum peltatum, Ancistrocladus abbreviatus and A. barteri, and six pure naphthylisoquinoline alkaloids derived from these species have been examined for their antiplasmodial activity. These species are well-known in the traditional medicine of West Africa and are used for the treatment of fevers, malaria and other diseases. The extracts and alkaloids were tested against the asexual erythrocytic stages of two strains of Plasmodium falciparum in vitro (K1/chloroquine-resistant and NF 54/64, clone A1A9/ chloroquine-sensitive). Incorporation of 3H-hypoxanthine was measured in the presence of the test substances after 42 hr of incubation at 37°. All extracts and three alkaloids displayed activity. The two most potent compounds were dioncopeltine A and dioncophylline B. Structure-activity considerations indicate two possible criteria for antiplasmodial activity: an R-configuration at C-3 associated with the absence of an oxygen substituent at C-6 and the absence of N-methylation.

Determination of Michellamine B in Biological Fluids by High-Performance Liquid Chromatography with Fluorescence Detection

The National Cancer Institute is pursuing preclinical development of michellamine B (MB), a novel dimeric polyhydroxylated naphthalene-tetrahydroisoquinoline alkaloid isolated from Ancistrocladus abbreviatus, as an anti-human immunodeficiency virus (HIV) agent. MB protects human lymphoid cells from the cytopathic effects of both HIV-1 and HIV-2 in vitro. A specific, sensitive, and convenient method for assaying the compound in biological fluids has been developed. Samples were prepared for analysis by initial treatment with dilute trichloroacetic acid followed by thorough mixing with a solution of the internal standard (α-naphthoflavone) in acetonitrile to denature macromolecules. The supernatant afforded by centrifugation, upon dilution with the aqueous component of the liquid chromatographic eluent, was loaded onto a 4-μm Nova-Pak phenyl column (3.9mm × 15cm). Chromatography was performed at ambient temperature using an isocratic mobile phase composed of 10 mM octyl sodium sulfate and 15 μM tetrabutylammonium hydrogen sulfate in acetonitrile/0.05 M ammonium formate buffer, pH 4.0 (46/ 54, v/v), at a flow rate of 0.6 ml/min. The intense native fluorescence of MB, which exhibited excitation and emission maxima in the mobile phase at 232 and 393 am, respectively, provided a highly sensitive and selective means of detection. Mean values of the retention times for the drug and internal standard determined over 11 months were 10.71 ± 0.53 and 13.14 ± 0.52 mm, respectively (SD, n = 52). Employing a sample volume of 50 μl, the lowest concentration of MB included in the standard curves of mouse, dog, and human plasma, 10 ng/ml (11.4 nM), was quantified with coefficients of variation less than 10%. The assay has been extensively utilized to characterize drug stability in aqueous solutions and plasma pharmacokinetics in the mouse and dog. The use of widely available chromatographic instrumentation, commercially available reagents, the simplicity of sample preparation, minimal sample handling, and the ability to decontaminate specimens obtained from subjects infected with the acquired immune deficiency syndrome virus by heat treatment make the analytical method very well-suited for clinical drug level monitoring.

Ancistrobrevine C from Ancistrocladus abbreviatus: The first mixed ‘ancistrocladaceae/dioncophyllaceae-type’ naphthylisoquinoline alkaloid

The isolation of a new naphthylisoquinoline alkaloid, ancistrobrevine C, from the stem bark and the roots of Ancistrocladus abbreviatus is described. Its complete structure was established by spectroscopic, chiroptical and degradative methods. For additional structural confirmation, the new alkaloid was transformed into ent-ancistrocladisine, a stereochemically well known naphthylisoquinoline. Accordingly, ancistrobrevine C is neither a real Ancistrocladaceae- nor a true Dioncophyllaceae-type alkaloid, but the first mixed, hybrid-like naphthylisoquinoline alkaloid.

Ancistrobrevine B, the first naphthylisoquinoline alkaloid with A 5,8′-coupling site, and related compounds from Ancistrocladus abbreviatus

The isolation of ancistrobrevine B, a new naphthylisoquinoline alkaloid from Ancistrocladus abbreviatus, is described. Elucidation of the complete structure, including the absolute configuration at the two stereogenic centres and the axis, was achieved by chemical and spectroscopic methods. Ancistrobrevine B exhibits a hitherto unprecedented 5,8′-coupling type. The known alkaloids ancistrocladine, hamatine and dioncophylline A were also isolated for the first time from this species.

Novel alkaloids from the tropical plant Ancistrocladus abbreviatus inhibit cell killing by HIV-1 and HIV-2

Novel alkaloids from the tropical plant Ancistrocladus abbreviatus inhibit cell killing by HIV-1 and HIV-2

Atrop-diastereomer separation by racemate resolution techniques: N-methyl-dioncophylline A and its 7-epimer from Ancistrocladus abbreviatus

The isolation of N-methyl-dioncophylline A and N-methyl-7- epi-dioncophylline A from Ancistrocladus abbreviatus is described. Atrop-diastereomer resolution was achieved analytically on a chiral chromatographic phase, and preparatively after esterification with a chiral carboxylic acid. Structural elucidation assisted by partial synthesis is reported and chemotaxonomic implications of this first isolation of Dioncophyllaceae alkaloids from an Ancistrocladus species are discussed.