Marine pharmacology in 2009-2011: marine compounds with antibacterial, antidiabetic, antifungal, anti-inflammatory, antiprotozoal, antituberculosis, and antiviral activities; affecting the immune and nervous systems, and other miscellaneous mechanisms of action

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.

Novel antimycobacterial benzoxazole alkaloids, from the west Indian Sea whip Pseudopterogorgia elisabethae

[formula: see text] Our screening for marine natural products with anti-tuberculosis activity from the West Indian gorgonian coral Pseudopterogorgia elisabethae resulted in the isolation of two active diterpenoid alkaloids, pseudopteroxazole (1) and seco-pseudopteroxazole (2). Their structures were elucidated by NMR spectral analysis, including a variety of two-dimensional techniques. Compounds 1 and 2 are previously undescribed diterpenoids containing the uncommon benzoxazole moiety. Biological screening studies indicated that pseudopteroxazole (1) is a potent growth inhibitor of Mycobacterium tuberculosis H37Rv, while seco-pseudopteroxazole (2) shows moderate to strong inhibitorial activity.

Marine pharmacology in 2005-6: Marine compounds with anthelmintic, antibacterial, anticoagulant, antifungal, anti-inflammatory, antimalarial, antiprotozoal, antituberculosis, and antiviral activities; affecting the cardiovascular, immune and nervous systems, and other miscellaneous mechanisms of action

BACKGROUND

The review presents the 2005-2006 peer-reviewed marine pharmacology literature, and follows a similar format to the authors' 1998-2004 reviews. The preclinical pharmacology of chemically characterized marine compounds isolated from marine animals, algae, fungi and bacteria is systematically presented.

RESULTS

Anthelmintic, antibacterial, anticoagulant, antifungal, antimalarial, antiprotozoal, antituberculosis and antiviral activities were reported for 78 marine chemicals. Additionally 47 marine compounds were reported to affect the cardiovascular, immune and nervous system as well as possess anti-inflammatory effects. Finally, 58 marine compounds were shown to bind to a variety of molecular targets, and thus could potentially contribute to several pharmacological classes.

CONCLUSIONS

Marine pharmacology research during 2005-2006 was truly global in nature, involving investigators from 32 countries, and the United States, and contributed 183 marine chemical leads to the research pipeline aimed at the discovery of novel therapeutic agents.

GENERAL SIGNIFICANCE

Continued preclinical and clinical research with marine natural products demonstrating a broad spectrum of pharmacological activity will probably result in novel therapeutic agents for the treatment of multiple disease categories.

Marine pharmacology in 2007-8: Marine compounds with antibacterial, anticoagulant, antifungal, anti-inflammatory, antimalarial, antiprotozoal, antituberculosis, and antiviral activities; affecting the immune and nervous system, and other miscellaneous mechanisms of action

The peer-reviewed marine pharmacology literature in 2007-8 is covered in this review, which follows a similar format to the previous 1998-2006 reviews of this series. The preclinical pharmacology of structurally characterized marine compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, anticoagulant, antifungal, antimalarial, antiprotozoal, antituberculosis and antiviral activities were reported for 74 marine natural products. Additionally, 59 marine compounds were reported to affect the cardiovascular, immune and nervous systems as well as to possess anti-inflammatory effects. Finally, 65 marine metabolites were shown to bind to a variety of receptors and miscellaneous molecular targets, and thus upon further completion of mechanism of action studies, will contribute to several pharmacological classes. Marine pharmacology research during 2007-8 remained a global enterprise, with researchers from 26 countries, and the United States, contributing to the preclinical pharmacology of 197 marine compounds which are part of the preclinical marine pharmaceuticals pipeline. Sustained preclinical research with marine natural products demonstrating novel pharmacological activities, will probably result in the expansion of the current marine pharmaceutical clinical pipeline, which currently consists of 13 marine natural products, analogs or derivatives targeting a limited number of disease categories.

Resistance management strategies in malaria vector mosquito control. Baseline data for a large-scale field trial against Anopheles albimanus in Mexico

A high level of DDT resistance and low levels of resistance to organophosphorus, carbamate and pyrethroid insecticides were detected by discriminating dose assays in field populations of Anopheles albimanus in Chiapas, southern Mexico, prior to a large-scale resistance management project described by Hemingway et al. (1997). Biochemical assays showed that the DDT resistance was caused by elevated levels of glutathione S-transferase (GST) activity leading to increased rates of metabolism of DDT to DDE. The numbers of individuals with elevated GST and DDT resistance were well correlated, suggesting that this is the only major DDT resistance mechanism in this population. The carbamate resistance in this population is conferred by an altered acetylcholinesterase (AChE)-based resistance mechanism. The level of resistance observed in the bioassays correlates with the frequency of individuals homozygous for the altered AChE allele. This suggests that the level of resistance conferred by this mechanism in its heterozygous state is below the level of detection by the WHO carbamate discriminating dosage bioassay. The low levels of organophosphate (OP) and pyrethroid resistance could be conferred by either the elevated esterase or monooxygenase enzymes. The esterases were elevated only with the substrate pNPA, and are unlikely to be causing broad spectrum OP resistance. The altered AChE mechanism may also be contributing to the OP but not the pyrethroid resistance. Significant differences in resistance gene frequencies were obtained from the F1 mosquitoes resulting from adults obtained by different collection methods. This may be caused by different insecticide selection pressures on the insects immediately prior to collection, or may be an indication that the indoor- and outdoor-resting A. albimanus collections are not from a randomly mating single population. The underlying genetic variability of the populations is currently being investigated by molecular methods.

Bielschowskysin, a gorgonian-derived biologically active diterpene with an unprecedented carbon skeleton

Bielschowskysin is a naturally occurring diterpene isolated from the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly oxygenated hexacyclic structure is based on a previously undescribed tricyclo[9.3.0.0(2,10)]tetradecane ring system that was established through spectroscopic analysis and X-ray crystallographic analysis. Bielschowskysin was shown to exhibit antimalarial activity against Plasmodium falciparum as well as strong anticancer activity against two human cancer cell lines.

Marine pharmacology in 2003-4: marine compounds with anthelmintic antibacterial, anticoagulant, antifungal, anti-inflammatory, antimalarial, antiplatelet, antiprotozoal, antituberculosis, and antiviral activities; affecting the cardiovascular, immune and nervous systems, and other miscellaneous mechanisms of action

The current marine pharmacology review that covers the peer-reviewed literature during 2003 and 2004 is a sequel to the authors' 1998-2002 reviews, and highlights the preclinical pharmacology of 166 marine chemicals derived from a diverse group of marine animals, algae, fungi and bacteria. Anthelmintic, antibacterial, anticoagulant, antifungal, antimalarial, antiplatelet, antiprotozoal, antituberculosis or antiviral activities were reported for 67 marine chemicals. Additionally 45 marine compounds were shown to have significant effects on the cardiovascular, immune and nervous system as well as possessing anti-inflammatory effects. Finally, 54 marine compounds were reported to act on a variety of molecular targets and thus may potentially contribute to several pharmacological classes. Thus, during 2003-2004, research on the pharmacology of marine natural products which involved investigators from Argentina, Australia, Brazil, Belgium, Canada, China, France, Germany, India, Indonesia, Israel, Italy, Japan, Mexico, Morocco, the Netherlands, New Zealand, Norway, Panama, the Philippines, Portugal, Russia, Slovenia, South Korea, Spain, Thailand, Turkey, United Kingdom, and the United States, contributed numerous chemical leads for the continued global search for novel therapeutic agents with broad spectrum activity.

Novel terpenoids from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer). Elisapterosins A and B: rearranged diterpenes possessing an unprecedented cagelike framework

Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocyclic skeletons, were isolated from the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae. The structures and relative configurations of novel metabolites elisabethin D (2), elisabethin D acetate (3), 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyclic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C(20) rearranged diterpenes. Elisapterosin B displays strong in vitro anti-tuberculosis activity.

Serrulatane diterpenes with antimycobacterial activity isolated from the West Indian sea whip Pseudopterogorgia elisabethae

Two new antimycobacterial serrulatane diterpenes, erogorgiaene (3) and 7-hydroxyerogorgiaene (4), and a novel C(40) bisditerpene (5), have been isolated from the West Indian gorgonian octocoral Pseudopterogorgia elisabethae. The structures of compounds 3-5 were determined by spectral (1D and 2D NMR, IR, UV, and HREIMS) analysis.

Marine Pharmacology in 2012-2013: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The peer-reviewed marine pharmacology literature from 2012 to 2013 was systematically reviewed, consistent with the 1998–2011 reviews of this series. Marine pharmacology research from 2012 to 2013, conducted by scientists from 42 countries in addition to the United States, reported findings on the preclinical pharmacology of 257 marine compounds. The preclinical pharmacology of compounds isolated from marine organisms revealed antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral and anthelmitic pharmacological activities for 113 marine natural products. In addition, 75 marine compounds were reported to have antidiabetic and anti-inflammatory activities and affect the immune and nervous system. Finally, 69 marine compounds were shown to display miscellaneous mechanisms of action which could contribute to novel pharmacological classes. Thus, in 2012–2013, the preclinical marine natural product pharmacology pipeline provided novel pharmacology and lead compounds to the clinical marine pharmaceutical pipeline, and contributed significantly to potentially novel therapeutic approaches to several global disease categories.

Unusual Terpenes with Novel Carbon Skeletons from the West Indian Sea Whip Pseudopterogorgia elisabethae (Octocorallia)(1)

From the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae collected near San Andrés Island, Colombia, were isolated a marine diterpenoid, two nor-diterpenoids, and a bisnor-diterpenoid, all of which possess most unusual carbocyclic skeletons. The structures and relative configurations of novel metabolites elisabethins A-C (1-3) and elisabanolide (4) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods; IR, UV, and accurate mass measurements (HREIMS); chemical reactions; and X-ray diffraction analyses. One of these, elisabethin B (2), showed significant differential antitumor activity, and compounds 3 and 4 have weak in vitro antituberculosis activity.

New pseudopterosin and seco-pseudopterosin diterpene glycosides from two Colombian isolates of Pseudopterogorgia elisabethae and their diverse biological activities

As part of an ongoing program to explore the chemical constituents of Caribbean marine invertebrates, a family of 13 new diterpene glycosides, pseudopterosins P-Z (1-11) and seco-pseudopterosins H (12) and I (13), have been isolated from the organic extracts of two collections of the sea whip Pseudopterogorgia elisabethae procured near the Colombian Southwestern Caribbean Sea. The structures of compounds 1-13, including absolute stereochemistry, have been proposed on the basis of comprehensive spectral analyses, chemical transformations, specific rotation, and TLC chromatographic analyses. Pseudopterosin Q (2) inhibited thromboxane B2 (TXB2) (IC50 = 4.7 microM) and superoxide anion (O2-) (IC50 = 11.2 microM) generation from E. coli lipopolysaccharide (LPS) activated rat neonatal microglia in vitro. In contrast, pseudopterosins P (1), U (6), V (7), W (8), and X (9) as well as seco-pseudopterosins H (12) and I (13) demonstrated minimal effects on both TXB2 and O2- release. In addition, some of the new compounds displayed strong antituberculosis, antiviral, antimalarial, and anticancer activity.

A marine diterpene with a novel tetracyclic framework from the West Indian gorgonian octocoral Pseudopterogorgia elisabethae

[structure: see text] Colombiasin A (1) was isolated from an extract of the West Indian gorgonian octocoral Pseudopterogorgia elisabethae that showed strong inhibitorial activity against Mycobacterium tuberculosis H37Rv. Structure elucidation by interpretation of 2D-NMR spectroscopic data, IR, UV, and accurate mass measurements (HREI-MS) revealed that colombiasin A belongs to a previously undescribed class of C20 rearranged diterpenes possessing an intricate tetracyclic framework.

Monamphilectine A, a potent antimalarial β-lactam from marine sponge Hymeniacidon sp: isolation, structure, semisynthesis, and bioactivity

Monamphilectine A (1), a new diterpenoid β-lactam alkaloid showing potent antimalarial activity, was isolated in milligram quantities following bioassay-directed extraction of a Puerto Rican marine sponge Hymeniacidon sp. Its structure, established by interpretation of spectral data, was confirmed unequivocally by chemical interconversion and comparison of physical, chemical, and bioactivity data with the natural product. The one-step semisynthesis of monamphilectine A was based on a multicomponent Ugi reaction that also established its absolute stereostructure.

Isolation and structure of providencin: a highly oxygenated diterpene possessing a unique bicyclo[12.2.0]hexadecane ring system from the sea plume Pseudopterogorgia kallos

[structure: see text] Providencin (1) is a naturally occurring cytotoxin isolated from the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly oxygenated hexacyclic structure is based on a previously undescribed bicyclo[12.2.0]hexadecane ring system and was established through spectroscopic analysis and X-ray crystallographic analysis. Providencin (1) was shown to exhibit modest anticancer activity against human breast (MCF7), lung (NCI-H460), and CNS (SF-268) cancer cell lines.

Briarellins J-P and polyanthellin A: new eunicellin-based diterpenes from the gorgonian coral Briareum polyanthes and their antimalarial activity

A new chemical study of the hexane extract of the gorgonian Briareum polyanthes collected in Puerto Rico afforded 10 new diterpenes of the eunicellin class, briarellins 1-9 and polyanthellin A (10), along with the known diterpene briarellin D (11). The structures and relative stereochemistry of metabolites 1-10 were assigned on the basis of NMR studies, chemical methods, and comparisons to the spectral properties of 11. A reassessment of prior structural assignment for briarellin A and two known sclerophytin-type diterpenes, 13 and 14, is proposed. Antimalarial tests on 1-6 and 8-12 indicated that they were active against Plasmodium falciparum.

Intricarene, an Unprecedented Trispiropentacyclic Diterpene from the Caribbean Sea Plume Pseudopterogorgia kallos

[structure: see text] A novel trispiropentacyclic diterpene, intricarene (1), was isolated from the hexane extract of the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly entangled structure was established by interpretation of NMR, IR, UV, and HREIMS data and subsequently confirmed by X-ray diffraction analysis. The unprecedented carbon skeleton of 1 constitutes a new addition to the already impressive architectural diversity of the diterpene class of marine secondary metabolites.

Eupalmerin acetate, a novel anticancer agent from Caribbean gorgonian octocorals, induces apoptosis in malignant glioma cells via the c-Jun NH2-terminal kinase pathway

The marine ecosystem is a vast but largely untapped resource for potential naturally based medicines. We tested 15 compounds derived from organisms found in the Caribbean Sea (14 gorgonian octocoral-derived compounds and one sponge-derived compound) for their anticancer effects on human malignant glioma U87-MG and U373-MG cells. Eupalmerin acetate (EPA) was chosen as the lead compound based on its longer-term stability and greater cytotoxicity than those of the other compounds we tested in these cell types. EPA induced G(2)-M cell cycle arrest and apoptosis via the mitochondrial pathway; it translocated Bax from the cytoplasm to the mitochondria and dissipated the mitochondrial transmembrane potential in both cell types. EPA was found to increase phosphorylated c-Jun NH(2)-terminal kinase (JNK) by >50% in both U87-MG and U373-MG cells. A specific JNK inhibitor, SP600125, inhibited EPA-induced apoptosis, confirming the involvement of the JNK pathway in EPA-induced apoptotic cell death. Furthermore, 7 days of daily intratumoral injections of EPA significantly suppressed the growth of s.c. malignant glioma xenografts (P < 0.01, on day 19). These results indicate that EPA is therapeutically effective against malignant glioma cells in vitro and in vivo and that it, or a similar marine-based compound, may hold promise as a clinical anticancer agent.

Neopetrosiamine A, biologically active bis-piperidine alkaloid from the Caribbean sea sponge Neopetrosia proxima

A new tetracyclic bis-piperidine alkaloid, neopetrosiamine A (1), has been extracted from the marine sponge Neopetrosiaproxima collected off the west coast of Puerto Rico. The structure of compound 1 was elucidated by analysis of spectroscopic data coupled with careful comparisons of its (1)H and (13)C NMR data with those of a well-known 3-alkylbis-piperidine alkaloid model. The new alkaloid displayed strong in vitro cytotoxic activity against a panel of cancer cell lines as well as in vitro inhibitory activity against the pathogenic microbes Mycobacterium tuberculosis and Plasmodium falciparum.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Caribenols A and B, Sea Whip Derived Norditerpenes with Novel Tricarbocyclic Skeletons

The extraction of two specimens of Pseudopterogorgia elisabethae, each collected from a different location at the San Andrés Archipelago, afforded two new norditerpenes, caribenols A (1) and B (2). Metabolites 1 and 2 contain unusual carbon skeletons that are previously undescribed and therefore constitute new classes of C19 rearranged terpenes. Their molecular structures were established by a combination of single-crystal X-ray analysis and comprehensive 2D NMR measurements.

Anti-muscarinic activity of a family of C11N5 compounds isolated from Agelas sponges

In a search for potential target sites for C11N5 compounds obtained from marine sponges of the genus Agelas we evaluated their interaction with muscarinic acetylcholine receptors from rat brain membranes. In competition experiments with 3H-QNB these compounds displayed the following rank order of potency: sceptrin greater than oroidin greater than or equal to dibromosceptrin greater than or equal to clathrodin. Sceptrin (50 microM) was shown to be a competitive inhibitor of 3H-QNB binding as revealed by Scatchard analysis. The results demonstrate the ability of these compounds to interact with multiple target molecules in the micromolar range.