Ingenines A and B, Two New Alkaloids from the Indonesian Sponge Acanthostrongylophora ingens

Genus Smenospongia: Untapped Treasure of Biometabolites—Biosynthesis, Synthesis, and Bioactivities

Marine sponges continue to attract remarkable attention as one of the richest pools of bioactive metabolites in the marine environment. The genus Smenospongia (order Dictyoceratida, family Thorectidae) sponges can produce diverse classes of metabolites with unique and unusual chemical skeletons, including terpenoids (sesqui-, di-, and sesterterpenoids), indole alkaloids, aplysinopsins, bisspiroimidazolidinones, chromenes, γ-pyrones, phenyl alkenes, naphthoquinones, and polyketides that possessed diversified bioactivities. This review provided an overview of the reported metabolites from Smenospongia sponges, including their biosynthesis, synthesis, and bioactivities in the period from 1980 to June 2022. The structural characteristics and diverse bioactivities of these metabolites could attract a great deal of attention from natural-product chemists and pharmaceuticals seeking to develop these metabolites into medicine for the treatment and prevention of certain health concerns.

Total Syntheses of the Structures Assigned to the Marine Natural Products Orthoscuticellines A-E

The readily prepared and vinylated β-carboline 11 has been converted over one or two steps into compounds 1-5, the structures assigned to the recently reported marine natural products orthoscuticellines A-E. The spectral data recorded on the synthetically derived compounds are fully consistent with the assigned structures and, on making allowances for variations in the pH of the medium in which the spectra of the natural products were recorded, it is concluded that the structures assigned to orthoscuticellines A-E are most likely correct. Certainly, the calculated ¹³C NMR spectra of the α-, γ-, and δ-carboline isomers of compounds 1-5 suggest that orthoscuticellines A-E do incorporate the assigned β-carboline core.

Visible-Light-Irradiated Cascade Reaction of Indole-Tethered Alkenes to Access Tetracyclic Tetrahydro-γ-carbolines

A series of indole-derived alkenes have been designed and applied in a photocatalytic cascade reaction with bromodifluoroacetate esters, affording an unknown type of tetracyclic tetrahydro-γ-carboline derivative in up to 90% yields. Mechanistic studies suggest that the reaction proceeds with tetrahydro-γ-carboline as a key intermediate. The reaction tolerates a diverse pool of substrates, which provides an efficient method for the construction of tetracyclic tetrahydro-γ-carboline compounds.

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

1,5-Disubstituted indole-2-carboxaldehyde derivatives 1a-h and glycine alkyl esters 2a-c are shown to undergo a novel cascade imination-heterocylization in the presence of the organic base DIPEA to provide 1-indolyl-3,5,8-substituted γ-carbolines 3aa-ea in good yields. The γ-carbolines are fluorescent and exhibit anticancer activities against cervical, lung, breast, skin, and kidney cancer cells.

Orthogonal Syntheses of γ-Carbolinone and Spiro[pyrrolidinone-3,3']indole Derivatives in One Pot through Reaction Telescoping

Herein we report a series of telescoping methodologies for one pot synthesis of biologically relevant γ-carboline derivatives 6 and spiro[pyrrolidinone-3,3']indole 7. Initially the three consecutive steps of cyclopropanation, phthalimide deprotection, and Boc-deprotection have been congregated in a single reaction vessel to afford a ∼1:1 mixture of 6 and 7. Next, careful optimization of the reaction sequence and the conditions generated an orthogonal approach to access compounds 6 and 7 exclusively. Air oxidation of the γ-carbolinones 6 afforded aromatic γ-carbolines 8.

Synthesis and Investigation of Tetrahydro-β-carboline Derivatives as Inhibitors of Plant Pathogenic Fungi

A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B.

Naturally Inspired Pyrimidines Analogues for Alzheimer's Disease

Alzheimer's disease (AD) is a multifarious and developing neurodegenerative disorder. The treatment of AD is still a challenge and availability of drug therapy on the basis of symptoms is not up to the mark. In the context of existence, which is getting worse for the human brain, it is necessary to take care of all critical measures. The disease is caused due to multidirectional pathology of the body, which demands the multi-target-directed ligand (MTDL) approach. This gives hope for new drugs for AD, summarized here in with the pyrimidine based natural product inspired molecule as a lead. The review is sufficient in providing a list of chemical ingredients of the plant to cure AD and screen them against various potential targets of AD. The synthesis of a highly functionalized scaffold in one step in a single pot without isolating the intermediate is a challenging task. In few examples, we have highlighted the importance of this kind of reaction, generally known as multi-component reaction. Multi-component is a widely accepted technique by the drug discovery people due to its high atom economy. It reduces multi-step process to a one-step process, therefore the compounds library can be made in minimum time and cost. This review has highlighted the importance of multicomponent reactions by giving the example of active scaffolds of pyrimidine/fused pyrimidines. This would bring importance to the fast as well as smart synthesis of bio-relevant molecules.

Review of Natural Compounds for the Management and Prevention of Lymphoma

Lymphoma is a type of blood cancer that can be categorized into two types-Hodgkin lymphoma (HL) and Non-Hodgkin lymphoma (NHL). A total of 509,590 and 79,990 cases of NHL and HL were newly diagnosed in 2018, respectively. Although conventional therapy has stridden forward over recent decades, its adverse effects are still a hurdle to be solved. Thus, to help researchers develop better lymphoma treatment, this study aims to review the systematic anticancer data for natural products and their compounds. A variety of natural products showed anticancerous effects on lymphoma by regulation of intracellular mechanisms including apoptosis as well as cell cycle arrest. As these results shed light on the potential to substitute conventional therapy with natural products, it may become a promising strategy for lymphoma treatment in the near future.

Anti-Infective and Anti-Cancer Properties of the Annona Species: Their Ethnomedicinal Uses, Alkaloid Diversity, and Pharmacological Activities

Annona species have been a valuable source of anti-infective and anticancer agents. However, only limited evaluations of their alkaloids have been carried out. This review collates and evaluates the biological data from extracts and purified isolates for their anti-infective and anti-cancer activities. An isoquinoline backbone is a major structural alkaloid moiety of the Annona genus, and more than 83 alkaloids have been isolated from this genus alone. Crude extracts of Annona genus are reported with moderate activities against Plasmodium falciparum showing larvicidal activities. However, no pure compounds from the Annona genus were tested against the parasite. The methanol extract of Annona muricata showed apparent antimicrobial activities. The isolated alkaloids from this genus including liriodenine, anonaine, asimilobine showed sensitivity against Staphylococcus epidermidis. Other alkaloids such as (+)-Xylopine and isocoreximine indicated significant anti-cancer activity against A549 and K-562 cell lines, respectively. This review revealed that the alkaloids from Annona genus are rich in structural diversity and pharmacological activities. Further exploration of this genus and their alkaloids has potential for developing novel anti-infective and anticancer drugs.

Marine Natural Products from Indonesian Waters

Natural products are primal and have been a driver in the evolution of organic chemistry and ultimately in science. The chemical structures obtained from marine organisms are diverse, reflecting biodiversity of genes, species and ecosystems. Biodiversity is an extraordinary feature of life and provides benefits to humanity while promoting the importance of environment conservation. This review covers the literature on marine natural products (MNPs) discovered in Indonesian waters published from January 1970 to December 2017, and includes 732 original MNPs, 4 structures isolated for the first time but known to be synthetic entities, 34 structural revisions, 9 artifacts, and 4 proposed MNPs. Indonesian MNPs were found in 270 papers from 94 species, 106 genera, 64 families, 32 orders, 14 classes, 10 phyla, and 5 kingdoms. The emphasis is placed on the structures of organic molecules (original and revised), relevant biological activities, structure elucidation, chemical ecology aspects, biosynthesis, and bioorganic studies. Through the synthesis of past and future data, huge and partly undescribed biodiversity of marine tropical invertebrates and their importance for crucial societal benefits should greatly be appreciated.

Spatio-Temporal Variation of Alkaloids in Annona purpurea and the Associated Influence on Their Antifungal Activity

Annona purpurea grows in the areas of low elevation in deciduous forests of Mexico, those areas have marked rainy and dry seasons. This species produces more than 30 bioactive alkaloids that could have potential in the control of phytopathogens. This research provides data on the variation of the content and number of alkaloids during an annual cycle and the associated inhibitory potential of the compounds against three phytopathogenic fungi. For one year, alkaloidal extracts of stems and leaves were obtained every two months. The extract profiles were determined by gas chromatography with tandem mass spectrometry and their antifungal activity was examined in vitro. The alkaloids, annomontine and oxopurpureine, obtained from the roots and leaves, respectively, were also evaluated individually. The yields, profiles and activities of the extracts, as well as the abundance of annomontine and oxopurpureine in the extracts, were contrasted with the seasonality and phenological phases of the plant. The data indicate that the alkaloid content was higher at the height of the dry season. High yields also occurred during flowering. The strongest inhibitory effect was obtained from the root extracts during the last month of dry season. This finding seems to be explained by the higher chemodiversity of alkaloids in extracts from this season. Annomontine and oxopurpureine inhibited all three phytopathogens; however, they were not solely responsible for the activity of A. purpurea.

γ-Carboline Synthesis by Heterocyclization of TosMIC Derivatives

A new method for the synthesis of γ-carbolines by a heterocyclization that involves α-indol-2-ylmethyl TosMIC derivatives and different electrophiles has been developed. This methodology has been successfully applied to the synthesis of several highly substituted γ-carbolines.

Ingenine F: A New Cytotoxic Tetrahydro Carboline Alkaloid from the Indonesian Marine Sponge Acanthostrongylophora ingens

Background

Marine organisms are established to be a wealthy source of bioactive compounds with diverse chemical structures and bioactivities. Acanthostrongylophora ingens is known to be rich with pyrimidine b-carboline and manzamine-type alkaloids. The goal of the present work is to isolate and identify new alkaloids from A. ingens as well as to assess the cytotoxic potential of these metabolites towards various cancer cell lines.

Methods

The crude MeOH extract of the sponge was separated by vacuum liquid chromatography (VLC), using n-hexane, EtOAc, and MeOH. The EtOAc fraction was chromatographed on VLC, SiO2, sephadex LH-20, and RP₁₈ columns, affording four metabolites. Their structures were identified using infrared, ultraviolet, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopic techniques, as well as comparison with the published data.

Results

A new 1,2,3,4-tetrahydro-β-carboline (THβCs) alkaloid, ingenine F (4) and three known compounds: Annomontine (1), acanthomine A (2), and 1-oxo-1,2,3,4-THβCs (3) were isolated and identified. Ingenine F (4) exhibited cytotoxic activity toward hormone-dependent breast carcinoma (MCF7), colon carcinoma (HCT116), and lung carcinoma (A549) cell lines with IC50 values of 2.82, 1.00, and 2.37 μM, respectively, compared to doxorubicin (IC50 0.012, 0.036, and 0.102 μM, respectively).

Conclusion

It is the first report for the isolation of THβCs alkaloids from A. ingens. The THβCs alkaloid with N-methylbutyramide unit as found in ingenine F is very rarely encountered in nature. Ingenine F may provide new promising candidates for potential cytotoxic agent.

SUMMARY

Ingenine F, a new 1,2,3,4-THβCs derivative (4) and three known alkaloids (1-3) were isolated from A. ingens. Their structures were verified by various spectroscopic analyses. Compound 4 had potent cytotoxic effect toward MCF7, HCT116, and A549 cancer cell lines. Abbreviations used: 1D: One-dimensional; 2D: Two-dimensional; CC: Column chromatography; COSY: Correlations spectroscopy; DMSO: Dimethyl sulfoxide; HMBC: Heteronuclear multiple bond correlation experiment; HRESIMS: High resolution electrospray ionization mass spectrometry; HSQC: Heteronuclear single quantum correlation; IR: Infrared; LCQ: Liquid chromatography quadrupole; LTQ: Linear trap quadropole; NMR: Nuclear magnetic resonance; RP: Reversed phase; SiO2: Silica gel; TLC: Thin-layer chromatography; UV: Ultraviolet; VLC: Vacuum liquid chromatography.

Alkenyl Isocyanide Conjugate Additions: A Rapid Route to γ-Carbolines

Isocyanides are exceptional building blocks, the wide deployment of which in multicomponent and metal-insertion reactions belies their limited availability. The first conjugate addition/alkylation to alkenyl isocyanides is described, which addresses this deficiency. An array of organolithiums, magnesiates, enolates, and metalated nitriles add conjugately to β- and β,β-disubstituted arylsulfonyl alkenyl isocyanides to rapidly assemble diverse isocyanide scaffolds. The intermediate metalated isocyanides are efficiently trapped with electrophiles to generate substituted isocyanides incorporating contiguous tri- and tetra-substituted centers. The substituted isocyanides are ideally functionalized for elaboration into synthetic targets as illustrated by the three-step synthesis of γ-carboline N-methyl ingenine B.