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Orfanoudaki M, Smith EA, Hill NT, Garman KA, Brownell I, Copp BR, Grkovic T, Henrich CJ. An Investigation of Structure-Activity Relationships and Cell Death Mechanisms of the Marine Alkaloids Discorhabdins in Merkel Cell Carcinoma Cells. Mar Drugs 2023; 21:474. [PMID: 37755087 PMCID: PMC10532587 DOI: 10.3390/md21090474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/23/2023] [Accepted: 08/25/2023] [Indexed: 09/28/2023] Open
Abstract
A library of naturally occurring and semi-synthetic discorhabdins was assessed for their effects on Merkel cell carcinoma (MCC) cell viability. The set included five new natural products and semi-synthetic compounds whose structures were elucidated with NMR, HRMS, and ECD techniques. Several discorhabdins averaged sub-micromolar potency against the MCC cell lines tested and most of the active compounds showed selectivity towards virus-positive MCC cell lines. An investigation of structure-activity relationships resulted in an expanded understanding of the crucial structural features of the discorhabdin scaffold. Mechanistic cell death assays suggested that discorhabdins, unlike many other MCC-active small molecules, do not induce apoptosis, as shown by the lack of caspase activation, annexin V staining, and response to caspase inhibition. Similarly, discorhabdin treatment failed to increase MCC intracellular calcium and ROS levels. In contrast, the rapid loss of cellular reducing potential and mitochondrial membrane potential suggested that discorhabdins induce mitochondrial dysfunction leading to non-apoptotic cell death.
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Affiliation(s)
- Maria Orfanoudaki
- Molecular Targets Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; (M.O.); (E.A.S.)
| | - Emily A. Smith
- Molecular Targets Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; (M.O.); (E.A.S.)
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Natasha T. Hill
- Dermatology Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20891, USA; (N.T.H.); (K.A.G.); (I.B.)
| | - Khalid A. Garman
- Dermatology Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20891, USA; (N.T.H.); (K.A.G.); (I.B.)
| | - Isaac Brownell
- Dermatology Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20891, USA; (N.T.H.); (K.A.G.); (I.B.)
| | - Brent R. Copp
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand;
| | - Tanja Grkovic
- Molecular Targets Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; (M.O.); (E.A.S.)
- Natural Products Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Frederick, MD 21702, USA
| | - Curtis J. Henrich
- Molecular Targets Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; (M.O.); (E.A.S.)
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
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Current Perspectives on Pyrroloiminoquinones: Distribution, Biosynthesis and Drug Discovery Potential. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27248724. [PMID: 36557854 PMCID: PMC9787360 DOI: 10.3390/molecules27248724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/04/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022]
Abstract
Pyrroloiminoquinones are a group of cytotoxic alkaloids most commonly isolated from marine sponges. Structurally, they are based on a tricyclic pyrrolo[4,3,2-de]quinoline core and encompass marine natural products such as makaluvamines, tsitsikammamines and discorhabdins. These diverse compounds are known to exhibit a broad spectrum of biological activities including anticancer, antiplasmodial, antimicrobial, antifungal and antiviral activities as well as the inhibition of several key cellular enzymes. The resurgence of interest in pyrroloiminoquinones and the convoluted understanding regarding their biological activities have prompted this review. Herein, we provided a concise summary of key findings and recent developments pertaining to their structural diversity, distribution, biogenesis, and their potential as chemical probes for drug development, including a discussion of promising synthetic analogs.
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Hamama WS, Hassanien AE, Zoorob HH. Regiochemistry in Cycloaddition Reaction to Synthesize of Some Novel Lawsone-Spiro Compounds. Polycycl Aromat Compd 2021. [DOI: 10.1080/10406638.2021.2005639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Wafaa S. Hamama
- Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt
| | - Alaa E. Hassanien
- Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt
| | - Hanafi H. Zoorob
- Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt
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Noro T, Sakata J, Tokuyama H. Synthetic studies on discorhabdin V: Construction of the A–F hexacyclic framework. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Exploration of the Electrophilic Reactivity of the Cytotoxic Marine Alkaloid Discorhabdin C and Subsequent Discovery of a New Dimeric C-1/N-13-Linked Discorhabdin Natural Product. Mar Drugs 2020; 18:md18080404. [PMID: 32752009 PMCID: PMC7460216 DOI: 10.3390/md18080404] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 07/24/2020] [Accepted: 07/28/2020] [Indexed: 12/20/2022] Open
Abstract
The cytotoxic marine natural product discorhabdin C contains a 2,6-dibromo-cyclohexa-2,5-diene moiety, previously proposed to be a critical feature required for biological activity. We have determined that the dienone-ring of discorhabdin C is indeed electrophilic, reacting with thiol and amine nucleophiles, affording debrominated adducts. In the case of reaction with 1-aminopentane the product contains an unusual C-2/N-18 ring closed, double-hydrate moiety. This electrophilic reactivity also extends to proteins, with lysozyme-discorhabdin C adducts being detected by ESI mass spectrometry. These results prompted further examination of an extract of discorhabdin C-producing sponge, Latrunculia (Latrunculia) trivetricillata, leading to the isolation and characterisation of a new example of a C-1/N-13 linked discorhabdin dimer that shared structural similarities with the 1-aminopentane-discorhabdin C adduct. To definitively assess the influence of the dienone moiety of discorhabdin C on cytotoxicity, a semi-synthetic hydrogenation derivative was prepared, affording a didebrominated ring-closed carbinolamine that was essentially devoid of tumour cell line cytotoxicity. Antiparasitic activity was assessed for a set of 14 discorhabdin alkaloids composed of natural products and semi-synthetic derivatives. Three compounds, (-)-discorhabdin L, a dimer of discorhabdin B and the discorhabdin C hydrogenation carbinolamine, exhibited pronounced activity towards Plasmodium falciparum K1 (IC50 30–90 nM) with acceptable to excellent selectivity (selectivity index 19–510) versus a non-malignant cell line.
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Kruschel RD, Buzid A, Khandavilli UBR, Lawrence SE, Glennon JD, McCarthy FO. Isoquinolinequinone N-oxides as anticancer agents effective against drug resistant cell lines. Org Biomol Chem 2020; 18:557-568. [PMID: 31894828 DOI: 10.1039/c9ob02441g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The isoquinolinequinone (IQQ) pharmacophore is a privileged framework in known cytotoxic natural product families, caulibugulones and mansouramycins. Exploiting both families as a chemical starting point, we report on the structured development of an IQQ N-oxide anticancer framework which exhibits growth inhibition in the nM range across melanoma, ovarian and leukaemia cancer cell lines. A new lead compound (16, R6 = benzyl, R7 = H) exhibits nM GI50 values against 31/57 human tumour cell lines screened as part of the NCI60 panel and shows activity against doxorubicin resistant tumour cell lines. An electrochemical study highlights a correlation between electropositivity of the IQQ N-oxide framework and cytotoxicity. Adduct binding to sulfur based biological nucleophiles glutathione and cysteine was observed in vitro. This new framework possesses significant anticancer potential.
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Affiliation(s)
- Ryan D Kruschel
- School of Chemistry, Analytical and Biological Chemistry Research Facility, University College Cork, Cork T12 K8AF, Ireland.
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McCauley EP, Smith GC, Crews P. Unraveling Structures Containing Highly Conjugated Pyrrolo[4,3,2- de]quinoline Cores That Are Deficient in Diagnostic Proton NMR Signals. JOURNAL OF NATURAL PRODUCTS 2020; 83:174-178. [PMID: 31904956 DOI: 10.1021/acs.jnatprod.9b01111] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This study began with the goal of identifying additional constituents from Zyzzya fuliginosa extracts obtained from an Indo-Pacific sponge (coll. no. 06132). The previous work identified several red and green pyrroloiminiquinones (aka pyrrolo[4,3,2-de]quinolines), and this reinvestigation provided two additional analogues, a blue compound named zyzzamine A (1) and a green compound named zyzzamine B (2). The relatively low ratio of H/[sum(CNO)] = 0.71 or 0.76 of this pair greatly complicated the final steps of compound characterization and required the use of five 2D NMR strategies and MS2 data sets.
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Affiliation(s)
- Erin P McCauley
- Department of Chemistry and Biochemistry , University of California Santa Cruz , Santa Cruz , California 95064 , United States
| | - Gavin C Smith
- Department of Chemistry and Biochemistry , University of California Santa Cruz , Santa Cruz , California 95064 , United States
| | - Phillip Crews
- Department of Chemistry and Biochemistry , University of California Santa Cruz , Santa Cruz , California 95064 , United States
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Kalinski JCJ, Waterworth SC, Noundou XS, Jiwaji M, Parker-Nance S, Krause RWM, McPhail KL, Dorrington RA. Molecular Networking Reveals Two Distinct Chemotypes in Pyrroloiminoquinone-Producing Tsitsikamma favus Sponges. Mar Drugs 2019; 17:E60. [PMID: 30654589 PMCID: PMC6356464 DOI: 10.3390/md17010060] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/09/2019] [Accepted: 01/11/2019] [Indexed: 12/11/2022] Open
Abstract
The temperate marine sponge, Tsitsikamma favus, produces pyrroloiminoquinone alkaloids with potential as anticancer drug leads. We profiled the secondary metabolite reservoir of T. favus sponges using HR-ESI-LC-MS/MS-based molecular networking analysis followed by preparative purification efforts to map the diversity of new and known pyrroloiminoquinones and related compounds in extracts of seven specimens. Molecular taxonomic identification confirmed all sponges as T. favus and five specimens (chemotype I) were found to produce mainly discorhabdins and tsitsikammamines. Remarkably, however, two specimens (chemotype II) exhibited distinct morphological and chemical characteristics: the absence of discorhabdins, only trace levels of tsitsikammamines and, instead, an abundance of unbranched and halogenated makaluvamines. Targeted chromatographic isolation provided the new makaluvamine Q, the known makaluvamines A and I, tsitsikammamine B, 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C, and the related pyrrolo-ortho-quinones makaluvamine O and makaluvone. Purified compounds displayed different activity profiles in assays for topoisomerase I inhibition, DNA intercalation and antimetabolic activity against human cell lines. This is the first report of makaluvamines from a Tsitsikamma sponge species, and the first description of distinct chemotypes within a species of the Latrunculiidae family. This study sheds new light on the putative pyrroloiminoquinone biosynthetic pathway of latrunculid sponges.
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Affiliation(s)
- Jarmo-Charles J Kalinski
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
| | - Samantha C Waterworth
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI, USA.
| | - Xavier Siwe Noundou
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
| | - Meesbah Jiwaji
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
| | - Shirley Parker-Nance
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
- South African Environmental Observation Network, Elwandle Node, Nelson Mandela University Ocean Sciences Campus, Summerstrand, Port Elizabeth 6001, South Africa.
| | - Rui W M Krause
- Department of Chemistry, Rhodes University PO Box 94, Grahamstown 6140, South Africa.
| | - Kerry L McPhail
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis 97331, OR, USA.
| | - Rosemary A Dorrington
- Department of Biochemistry and Microbiology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
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