Structural variety and pharmacological potential of naphthylisoquinoline alkaloids.

Naphthylisoquinoline alkaloids are a fascinating class of natural biaryl compounds. They show characteristic mono- and dimeric scaffolds, with chiral axes and stereogenic centers. Since the appearance of the last comprehensive overview on these secondary plant metabolites in this series in 1995, the number of discovered representatives has tremendously increased to more than 280 examples known today. Many novel-type compounds have meanwhile been discovered, among them naphthylisoquinoline-related follow-up products like e.g., the first seco-type (i.e., ring-opened) and ring-contracted analogues. As highlighted in this review, the knowledge on the broad structural chemodiversity of naphthylisoquinoline alkaloids has been decisively driven forward by extensive phytochemical studies on the metabolite pattern of Ancistrocladus abbreviatus from Coastal West Africa, which is a particularly "creative" plant. These investigations furnished a considerable number of more than 80-mostly new-natural products from this single species, with promising antiplasmodial activities and with pronounced cytotoxic effects against human leukemia, pancreatic, cervical, and breast cancer cells. Another unique feature of naphthylisoquinoline alkaloids is their unprecedented biosynthetic origin from polyketidic precursors and not, as usual for isoquinoline alkaloids, from aromatic amino acids-a striking example of biosynthetic convergence in nature. Furthermore, remarkable botanical results are presented on the natural producers of naphthylisoquinoline alkaloids, the paleotropical Dioncophyllaceae and Ancistrocladaceae lianas, including first investigations on the chemoecological role of these plant metabolites and their storage and accumulation in particular plant organs.

Naphthylisoquinoline alkaloids: novel agents against the causative pathogens of eumycetoma and actinomycetoma-en route to broad-spectrum antimycetomal drugs.

Mycetoma is a devastating neglected tropical infection of the subcutaneous tissues. It is caused by fungal and bacterial pathogens recognized as eumycetoma and actinomycetoma, respectively. Mycetoma treatment involves diagnosing the causative microorganism as a prerequisite to prescribing a proper medication. Current therapy of fungal eumycetoma causative agents, such as Madurella mycetomatis, consists of long-term antifungal medication with itraconazole followed by surgery, yet with usually unsatisfactory clinical outcomes. Actinomycetoma, on the contrary, usually responds to treatment with co-trimoxazole and amikacin. Therefore, there is a pressing need to discover novel broad-spectrum antimicrobial agents to circumvent the time-consuming and costly diagnosis. Using the resazurin assay, a series of 23 naphthylisoquinoline (NIQ) alkaloids and related naphthoquinones were subjected to in vitro screening against two fungal strains of M. mycetomatis and three bacterial strains of Actinomadura madurae and A. syzygii. Seven NIQs, mostly dimers, showed promising in vitro activities against at least one strain of the mycetoma-causative pathogens, while the naphthoquinones did not show any activity. A synthetic NIQ dimer, 8,8'''-O,O-dimethylmichellamine A (18), inhibited all tested fungal and bacterial strains (IC50 = 2.81-12.07 µg/mL). One of the dimeric NIQs, michellamine B (14), inhibited a strain of M. mycetomatis and significantly enhanced the survival rate of Galleria mellonella larvae infected with M. mycetomatis at concentrations of 1 and 4 µg/mL, without being toxic to the uninfected larvae. As a result, broad-spectrum dimeric NIQs like 14 and 18 with antimicrobial activity are considered hit compounds that could be worth further optimization to develop novel lead antimycetomal agents.

Ancistrocladinium A Induces Apoptosis in Proteasome Inhibitor-Resistant Multiple Myeloma Cells: A Promising Therapeutic Agent Candidate.

The N,C-coupled naphthylisoquinoline alkaloid ancistrocladinium A belongs to a novel class of natural products with potent antiprotozoal activity. Its effects on tumor cells, however, have not yet been explored. We demonstrate the antitumor activity of ancistrocladinium A in multiple myeloma (MM), a yet incurable blood cancer that represents a model disease for adaptation to proteotoxic stress. Viability assays showed a potent apoptosis-inducing effect of ancistrocladinium A in MM cell lines, including those with proteasome inhibitor (PI) resistance, and in primary MM cells, but not in non-malignant blood cells. Concomitant treatment with the PI carfilzomib or the histone deacetylase inhibitor panobinostat strongly enhanced the ancistrocladinium A-induced apoptosis. Mass spectrometry with biotinylated ancistrocladinium A revealed significant enrichment of RNA-splicing-associated proteins. Affected RNA-splicing-associated pathways included genes involved in proteotoxic stress response, such as PSMB5-associated genes and the heat shock proteins HSP90 and HSP70. Furthermore, we found strong induction of ATF4 and the ATM/H2AX pathway, both of which are critically involved in the integrated cellular response following proteotoxic and oxidative stress. Taken together, our data indicate that ancistrocladinium A targets cellular stress regulation in MM and improves the therapeutic response to PIs or overcomes PI resistance, and thus may represent a promising potential therapeutic agent.

Unprecedented Direct Asymmetric Total Syntheses of 5,8'-Naphthylisoquinoline Alkaloids from their Fully Substituted Precursors Employing a Novel Nickel/N,N-ligand-Catalyzed Atroposelective Cross-Coupling Reaction.

A general and concise synthetic pathway for the preparation of four different 5,8'-coupled naphthylisoquinoline alkaloids, employing a specially developed nickel/N,N-ligand-catalyzed atroposelective Negishi coupling is reported. In the first reported direct atroposelective coupling of the fully substituted precursors, the naturally occurring cross-coupled products were generally obtained directly in reasonable yields and high enantiomeric purities. For the synthesis of the cross-coupling precursors, we employed a modification of Bringmann's known approach to the dihydroisoquinoline compounds and a newly developed route for the naphthalene building blocks. For the latter 1,8-dioxynaphthalene precursors, our strategy utilized Hartwig's borylation/methylation approach and included the efficient installation of orthogonal protecting groups.

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.

Asian Ancistrocladus Lianas as Creative Producers of Naphthylisoquinoline Alkaloids.

This book describes a unique class of secondary metabolites, the mono- and dimeric naphthylisoquinoline alkaloids. They occur in lianas of the paleotropical Ancistrocladaceae and Dioncophyllaceae families, exclusively. Their unprecedented structures include stereogenic centers and rotationally hindered, and thus likewise stereogenic, axes. Extended recent investigations on six Ancistrocladus species from Asia, as reported in this review, shed light on their fascinating phytochemical productivity, with over 100 such intriguing natural products. This high chemodiversity arises from a likewise unique biosynthesis from acetate-malonate units, following a novel polyketidic pathway to plant-derived isoquinoline alkaloids. Some of the compounds show most promising antiparasitic activities. Likewise presented are strategies for the regio- and stereoselective total synthesis of the alkaloids, including the directed construction of the chiral axis.

A Modular Approach for Diversity-Oriented Synthesis of 1,3-trans-Disubstituted Tetrahydroisoquinolines: Seven-Step Asymmetric Synthesis of Michellamines†B and C.

1,3-trans-Disubstituted tetrahydroisoquinoline (THIQ) is a common heterocyclic structural unit of naphthylisoquinoline alkaloids. The assembly of this structural unit is not trivial, which constitutes a substantial challenge in the total synthesis of naphthylisoquinoline alkaloids and related pharmaceuticals. Herein, we report a modular and convergent method for the rapid assembly of 1,3-trans-disubstituted THIQ frameworks through a three-component Catellani reaction and a AuI -catalyzed cyclization/reduction cascade. With widely available simple aryl iodides, aziridines and (triisopropylsilyl)acetylene as the building blocks, this method paves a practical way for the diversity-oriented synthesis of 1,3-trans-disubstituted THIQs. Based on this new method, concise syntheses of an analogue of the new drug mevidalen and four naphthylisoquinoline alkaloids have been accomplished, demonstrating the broad synthetic utility of this approach.

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.

Induction of apoptosis in breast cancer cells by naphthylisoquinoline alkaloids.

Breast cancer is one of the most common types of cancer in the world and a major cause of mortality. Present therapeutic strategies against breast cancer have severe drawbacks such as allergies, damage to healthy tissues, reoccurrence of cancer, and emergence of drug resistance. Naphthylisoquinoline alkaloids are a group of structurally unique natural products produced by tropical lianas belonging to the plant families Dioncophyllaceae and Ancistrocladaceae indigenous to Asia and Africa. These secondary metabolites have been reported to show anti-infective activity, but they also act against leukemic and pancreatic cancer cells. In the present study we have tested the potential of eleven mono- and dimeric naphthylisoquinoline compounds against two breast cancer cell lines, MCF-7 and MDA-MB-231. Three out of the compounds (agents 1, 4, and 11) showed significant activities against both tested cancer cell lines. Further mechanistic investigations revealed that all of the three substances induce apoptotic cell death via its intrinsic pathway by causing deformation of the nuclear membrane, disruption of the mitochondrial membrane potential (MMP), and elevated reactive oxygen species (ROS) production in both cell lines. Flow cytometric analysis using Annexin V - FITC/PI double staining showed an increased number of apoptotic cells in both, the early and the late phases.

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.

Naphthylisoquinoline alkaloids, validated as hit multistage antiplasmodial natural products.

The discovery and development of multistage antimalarial drugs targeting intra-erythrocytic asexual and sexual Plasmodium falciparum parasites is of utmost importance to achieve the ambitious goal of malaria elimination. Here, we report the validation of naphthylisoquinoline (NIQ) alkaloids and their synthetic analogues as multistage active antimalarial drug candidates. A total of 30 compounds were tested, of which 17 exhibited IC50 values <1 µM against drug-sensitive P. falciparum parasites (NF54 strain); 15 of these retained activity against a panel of drug-resistant strains. These compounds showed low in vitro cytotoxicity against HepG2 cells, with selectivity indices of >10. The tested compounds showed activity in vitro against both early- and late-stage P. falciparum gametocytes while blocking male gamete formation (>70% inhibition of exflagellation at 2 µM). Additionally, five selected compounds were found to have good solubility (≥170 µM in PBS at pH 6.5), while metabolic stability towards human, mouse, and rat microsomes ranged from >90% to >7% after 30 min. Dioncophylline C (2a) emerged as a front runner from the study, displaying activity against both asexual parasites and gametocytes, a lack of cross-resistance to chloroquine, good solubility, and microsomal stability. Overall, this is the first report on the multistage activity of NIQs and their synthetic analogues including gametocytocidal and gametocidal effects induced by this class of compounds.

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.

Ancistroyafungines A-D, 5,8'- and 5,1'-coupled naphthylisoquinoline alkaloids from a Congolese Ancistrocladus species, with antiausterity activities against human PANC-1 pancreatic cancer cells.

Four new naphthylisoquinoline alkaloids, the 5,8'-coupled ancistroyafungines A-C (1-3) and the 5,1'-linked ancistroyafungine D (4), have been isolated from the stem bark of an as yet unidentified Ancistrocladus (Ancistrocladaceae) liana recently discovered near the village Yafunga, in the North-Central region of the Democratic Republic of the Congo. Likewise obtained were eleven analogs previously identified in related African and Asian Ancistrocladus species, exhibiting five different coupling types, viz., 5,8', 5,1', 7,1', N,6', and N,8'. All of the alkaloids are S-configured at C-3 and possess an oxygen function at C-6 in the isoquinoline portion, and, thus, belong to the subclass of "Ancistrocladaceae-type" alkaloids. This finding is geo- and chemotaxonomically remarkable, since - apart from one other Ancistrocladus species from the Central Congo Basin - only Southeast Asian and East African Ancistrocladaceae are known to exclusively produce naphthylisoquinolines with these structural features. Moreover, the alkaloid pattern of this Congolese liana clearly demarcates this plant from all other Ancistrocladus taxa that have so far been botanically described, which suggests that it might represent a new species or subspecies. The new ancistroyafungines display strong preferential cytotoxic activities towards human PANC-1 pancreatic cancer cells in nutrient-deprived medium, without showing toxicity in normal, nutrient-rich conditions.

Ancistrolikokine I and further 5,8'-coupled naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus likoko and their cytotoxic activities against drug-sensitive and multidrug resistant human leukemia cells.

The Congolese liana Ancistrocladus likoko (Ancistrocladaceae) produces naphthylisoquinoline alkaloids that are, chemotaxonomically remarkable, all based on the same coupling type, with the biaryl axis located between C-5 and C-8'. About 20 alkaloids, belonging to the subclass of 5,8'-linked naphthylisoquinolines, have so far been discovered in this plant species. Here, we report on the isolation and structure elucidation of six further such 5,8'-coupled monomeric alkaloids, named ancistrolikokines I (9), C3 (10), F2 (11), J (12), J2 (13), and J3 (14). They were identified in the twigs of A. likoko, along with the two new atropo-diastereomeric dimers michellamines A8 (15a) and B8 (15b) and the naphthalene-devoid dihydroisoquinoline ent-ealaine D (19). The latter had previously only been known from total synthesis and has now been identified for the first time as an authentic natural product. Three of the new alkaloids, 12-14, are the only fully dehydrogenated naphthylisoquinolines with a 5,8'-biaryl linkage, apart from one single known other example previously likewise found in A. likoko. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR), chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. The new ancistrolikokines exhibited moderate to strong cytotoxic activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and against cells of their multidrug-resistant subline, CEM/ADR5000. A first structure-activity relationship (SAR) study on a small library of 5,8'-coupled naphthylisoquinolines from the twigs of A. likoko suggests that the oxygenation patterns in the isoquinoline portion at C-6 and C-8 play a crucial role for the antileukemic activities within this group of alkaloids.

Antileukemic ancistrobenomine B and related 5,1'-coupled naphthylisoquinoline alkaloids from the Chinese liana Ancistrocladus tectorius.

A striking feature of the metabolite pattern of the Southeast Asian liana Ancistrocladus tectorius (Ancistrocladaceae) is the predominance of 5,1'-coupled naphthylisoquinoline alkaloids. About 20 alkaloids of this coupling type have so far been discovered in this plant species. Here, we report on the isolation of four new 5,1'-linked naphthylisoquinolines from the twigs and stems of A. tectorius. Two of them, the ancistrobenomines B (5) and C (6), belong to the very rare group of alkaloids with a fully dehydrogenated isoquinoline portion. Likewise unusual for naphthylisoquinoline alkaloids is the presence of a hydroxymethylene group at C-3. Within the large class of meanwhile ca. 180 such natural products, this structural peculiarity had so far been known only from two other representatives isolated from the Malaysian species A. benomensis, and from one single naphthalene-devoid 3-hydroxymethyleneisoquinoline from A. tectorius. Seven further 5,1'-linked alkaloids, previously isolated from related Asian and African Ancistrocladus species, have now been identified for the first time in A. tectorius. Their structural elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (electronic circular dichroism) methods. Ancistrobenomine B (5) exhibited moderate effects against Plasmodium falciparum and Trypanosoma brucei rhodesiense in vitro, and it was found to display strong cytotoxic activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000.

Ancistectorine D, a naphthylisoquinoline alkaloid with antiprotozoal and antileukemic activities, and further 5,8'- and 7,1'-linked metabolites from the Chinese liana Ancistrocladus tectorius.

From the twigs and stems of the Chinese liana Ancistrocladus tectorius (Ancistrocladaceae), two new 5,8'-coupled naphthylisoquinolines, ancistectorine D (5) and its 6-O-demethyl derivative 6, were isolated, along with two new 7,1'-linked alkaloids, 6-O-methylancistectorine B1 (7) and ancistectorine B2 (8). Two further compounds, ancistroealaine A (4) and 6-O-demethyl-8-O-methyl-7-epi-ancistrobrevine D (10), already known from related Asian and African Ancistrocladus species, were discovered for the first time in A. tectorius. The structure elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (circular dichroism) methods. Chemotaxonomically remarkable, 5,8'-coupled naphthylisoquinolines have as yet been found quite rarely in Asian Ancistrocladus species, where only two examples have so far been detected, while alkaloids with this coupling type represent the by far the largest group of constituents in African taxa. Ancistectorine D (5) shows promising activities against the protozoan parasites Trypanosoma cruzi and Leishmania donovani, and it was likewise found to display strong cytotoxic activities against human leukemia (CCRF-CEM) and multidrug-resistant tumor cells (CEM/ADR5000).

HIV-inhibitory michellamine-type dimeric naphthylisoquinoline alkaloids from the Central African liana Ancistrocladus congolensis.

Five michellamine-type dimeric naphthylisoquinoline alkaloids (NIQs), named michellamines A2, A3, A4, B2, and B3, have been isolated from the root bark of the Central African liana Ancistrocladus congolensisJ. Léonard (Ancistrocladaceae), along with their two known parent compounds, the michellamines A and B, which had so far only been detected in the Cameroonian species Ancistrocladus korupensis. Five monomeric representatives, viz., korupensamine D, ancistrobrevine B, hamatine, 5'-O-demethylhamatine, and 6-O-methylhamatine, already known from related Ancistrocladus species, have likewise been identified. The structure elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical and chiroptical methods. The michellamines A2, A3, B3, and A4 were evaluated for their cytotoxic and anti-HIV activities at a concentration range of 0-100 µM against the HIV reference strain IIIB/LAI in A3.01 T lymphoblast cell cultures, and their effects were compared to the ones displayed by the known michellamines A and B. Inhibitory activities for HIV replication were monitored for the michellamines A2 (IC50 = 29.6 µM), A3 (IC50 = 15.2 µM), A4 (IC50 = 35.9 µM), and B (IC50 = 20.4 µM). The michellamines A and B3, by contrast, did not inhibit HIV replication. No cytotoxicity was observed. Furthermore, the chemotaxonomic significance of the previously undescribed michellamines is discussed.