Cytotoxic and antiplasmodial substances from marine-derived fungi, Nodulisporium sp. and CRI247-01

Mutagenetic analysis of the biosynthetic pathway of tetramate bripiodionen bearing 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione skeleton

BACKGROUND

Natural tetramates are a family of hybrid polyketides bearing tetramic acid (pyrrolidine-2,4-dione) moiety exhibiting a broad range of bioactivities. Biosynthesis of tetramates in microorganisms is normally directed by hybrid polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) machineries, which form the tetramic acid ring by recruiting trans- or cis-acting thioesterase-like Dieckmann cyclase in bacteria. There are a group of tetramates with unique skeleton of 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione, which remain to be investigated for their biosynthetic logics.

RESULTS

Herein, the tetramate type compounds bripiodionen (BPD) and its new analog, featuring the rare skeleton of 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione, were discovered from the sponge symbiotic bacterial Streptomyces reniochalinae LHW50302. Gene deletion and mutant complementation revealed the production of BPDs being correlated with a PKS-NRPS biosynthetic gene cluster (BGC), in which a Dieckmann cyclase gene bpdE was identified by sit-directed mutations. According to bioinformatic analysis, the tetramic acid moiety of BPDs should be formed on an atypical NRPS module constituted by two discrete proteins, including the C (condensation)-A (adenylation)-T (thiolation) domains of BpdC and the A-T domains of BpdD. Further site-directed mutagenetic analysis confirmed the natural silence of the A domain in BpdC and the functional necessities of the two T domains, therefore suggesting that an unusual aminoacyl transthiolation should occur between the T domains of two NRPS subunits. Additionally, characterization of a LuxR type regulator gene led to seven- to eight-fold increasement of BPDs production. The study presents the first biosynthesis case of the natural molecule with 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione skeleton. Genomic mining using BpdD as probe reveals that the aminoacyl transthiolation between separate NRPS subunits should occur in a certain population of NRPSs in nature.

Anti-Inflammatory Properties of Oxygenated Isocoumarins and Xanthone from Thai Mangrove-Associated Endophytic Fungus Setosphaeria rostrata

Chronic inflammation plays a crucial role in the development and progression of numerous chronic diseases. To search for anti-inflammatory metabolites from endophytic fungi isolated from plants growing in Thai mangrove areas, a chemical investigation of those fungi was performed. Five new oxygenated isocoumarins, setosphamarins A-E (1-5) were isolated from the EtOAc extract of an endophytic fungus Setosphaeria rostrata, along with four known isocoumarins and one xanthone. Their structures were determined by extensive spectroscopic analysis. The absolute configurations of the undescribed compounds were established by comparative analysis between experimental and calculated circular dichroism (ECD) spectroscopy. All the compounds were evaluated for their anti-inflammatory activity by monitoring nitric oxide inhibition in lipopolysaccharide-induced macrophage J774A.1 cells. Only a xanthone, ravenelin (9), showed potent activity, with an IC50 value of 6.27 μM, and detailed mechanistic study showed that it suppressed iNOS and COX-2 expression.

Cytotoxic tetronic acid derivatives from the mangrove endophytic fungus Hypomontagnella monticulosa YX702

Three new tetronic acid derivatives, nodulisporacid A ethyl ester (3), isosporothric acid methyl ester (4), and (R)-3-(methoxycarbonyl)-2-methyleneundecanoic acid (5) were isolated from mangrove endophytic fungus Hypomontagnella monticulosa YX702, together with three known analogues nodulisporacid A (1), nodulisporacid A methyl ester (2), and dihydrosporothriolide (6). The structures of these new compounds were elucidated by analysis of NMR and HR-ESI-MS spectroscopic data. In addition, the absolute configuration of nodulisporacid A (1) was confirmed by single-crystal X-ray diffraction for the first time. Subsequently, the absolute configuration of compounds 2 and 3 were determined by chemical derivatization of nodulisporacid A (1). The absolute configuration of compound 4 and 5 were established by TDDFT ECD calculations. Compounds 1 and 2 exhibited cytotoxic activities against A549 and Hela cancer cell lines with the IC50 values between 5.64 and 8.14 μM.

Seco-pimarane diterpenoids and androstane steroids from an endophytic Nodulisporium fungus derived from Cyclosorus parasiticus

Five previously undescribed specialized metabolites, including three 9,11-seco-pimarane diterpenoids, nodulisporenones A-C, and two androstane steroids, nodulisporisterones A and B, together with previously described ergosterol derivatives, dankasterone A and demethylincisterol A₃, were isolated from solid cultures of the endophytic fungus Nodulisporium sp. SC-J597. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis and theoretical calculations of electronic circular dichroism spectra. Among them, nodulisporenones A and B are the first examples of seco-pimarane diterpenoids that is cyclized to form an unprecedented diterpenoid lactone scaffold and nodulisporisterones A and B represent the first normal C₁₉ androstane steroids of fungal origin. Nodulisporisterone B exhibited potent inhibitory effect on the production of NO in LPS-stimulated RAW264.7 macrophages (IC₅₀ = 2.95 μM). This compound, together with the two known ergosterol derivatives, also displayed cytotoxicity against A549, HeLa, HepG2 and MCF-7 cancer cell lines with IC₅₀ values of 5.2-16.9 μM.

Marine organisms as potential sources of natural products for the prevention and treatment of malaria

Vector-borne diseases (VBDs) are a worldwide critical concern accounting for 17% of the estimated global burden of all infectious diseases in 2020. Despite the various medicines available for the management, the deadliest VBD malaria, caused by Plasmodium sp., has resulted in hundreds of thousands of deaths in sub-Saharan Africa only. This finding may be explained by the progressive loss of antimalarial medication efficacy, inherent toxicity, the rise of drug resistance, or a lack of treatment adherence. As a result, new drug discoveries from uncommon sources are desperately needed, especially against multi-drug resistant strains. Marine organisms have been investigated, including sponges, soft corals, algae, and cyanobacteria. They have been shown to produce many bioactive compounds that potentially affect the causative organism at different stages of its life cycle, including the chloroquine (CQ)-resistant strains of P. falciparum. These compounds also showed diverse chemical structures belonging to various phytochemical classes, including alkaloids, terpenoids, polyketides, macrolides, and others. The current article presents a comprehensive review of marine-derived natural products with antimalarial activity as potential candidates for targeting different stages and species of Plasmodium in both in vitro and in vivo and in comparison with the commercially available and terrestrial plant-derived products, i.e., quinine and artemisinin.

Structure and Antimicrobial Activity of Rare Lactone Lipids from the Sooty Mold (Scorias spongiosa)

Two new lactone lipids, scoriosin (1) and its methyl ester (2), with a rare furylidene ring joined to a tetrahydrofurandione ring, were isolated from Scorias spongiosa, commonly referred to as sooty mold. The planar structure of these compounds was assigned by 1D and 2D NMR. The conformational analysis of these molecules was undertaken to evaluate the relative and absolute configuration through GIAO NMR chemical shift analysis and ECD calculation. In addition to the potent antimicrobial activities, compound 2 strongly potentiated the activity of amphotericin B against Cryptococcus neoformans, suggesting the potential utility of this compound in combination therapies for treating cryptococcal infections.

Trends of antimalarial marine natural products: progresses, challenges and opportunities

This review provides an overview of the antimalarial marine natural products, focusing on their chemistry, malaria-related targets and mechanisms, and highlighting their potential for drug development.

Recent advances in the synthesis of naturally occurring tetronic acids

During the last decades the interest towards natural products containing the tetronic acid moiety augmented significantly, due to their challenging structures and to the wide range of biological activities they display. This increasing enthusiasm has led to noteworthy advances in the development of innovative methodologies for the construction of the butenolide nucleus. This review provides an overview of the progress in the synthesis of tetronic acid as a structural key motif of natural compounds, covering the last 15 years. Herein, the most representative synthetic pathways towards structurally diverse natural tetronic acids are grouped according to the strategy followed. The first part describes the functionalization of a preformed tetronic acid core by intermolecular reactions (cross-coupling reactions, nucleophilic substitution, multicomponent reactions) whereas the second part deals with intramolecular approaches (Dieckmann, cycloaddition or ring expansion reactions) to construct the heterocyclic core. This rational subcategorization allowed us to make some considerations about the best approaches for the synthesis of specific substrates, including modern intriguing methodologies such as microwave irradiation, solid phase anchoring, bio-transformations and continuous flow processes.

The grass root endophytic fungus Flavomyces fulophazii: An abundant source of tetramic acid and chlorinated azaphilone derivatives

Fungal endophytes are remarkable sources of biologically active metabolites of ecological and pharmacological significance. In this study, fungal isolates producing yellow pigments and originating from grass roots, were identified as the recently described grass root colonizing dark septate endophyte (DSE), Flavomyces fulophazii (Periconiaceae, Pleosporales). While analyzing the metabolite composition of 17 isolates of this fungus, 11 previously undescribed compounds, including four tetramic acids (dihydroxyvermelhotin, hydroxyvermelhotin, methoxyvermelhotin, oxovermelhotin), and seven chlorinated azaphilones (flavochlorines A-G), together with the known tetramic acid vermelhotin, were tentatively identified by high performance liquid chromatography (HPLC)-tandem mass spectrometry (MS/MS). Among them, flavochlorine A, flavochlorine G, hydroxyvermelhotin and vermelhotin could be isolated by preparative HPLC, thus their structures were also confirmed by nuclear magnetic resonance (NMR) spectroscopy. Vermelhotin was found to be the main compound, reaching its maximum level of 5.5 mg/g in the in vitro cultures of a selected F. fulophazii isolate. A significant amount of vermelhotin was isolated by preparative HPLC from these cultures (4.8 mg from 1.0 g lyophilized culture), confirming the practical utility of F. fulophazii in high-yield vermelhotin production. The main compounds of this endophyte expressed no activity in standardized plant bioassays (i.e., in the Lactuca sativa seed germination and Lemna minor growth tests). An antiproliferative study of the isolated compounds confirmed moderate activity of vermelhotin against a panel of twelve cancer cell lines, with IC₅₀ ranges of 10.1-37.0 μM, without inhibiting the non-cancer Vero cells, suggesting its selectivity towards cancers.

Recent Updates on Marine Cancer-Preventive Compounds

The natural compounds derived from marine organisms often exhibit unique chemical structures and potent biological activities. Cancer-preventive activity is one of the rather new activities that has emerged and been extensively studied over the last decades. This review summarizes the recent updates on the marine chemopreventive compounds covering the relevant literature published in 2013-2021 and following the previous comprehensive review by Stonik and Fedorov (Marine Drugs 2014, 12, 636-671). In the current article, only the molecules having an effect on malignant transformation (or related pathway and molecules), cancer stem cells, or carcinogen-induced in vivo tumor development were considered to be "true" cancer-preventive compounds and were, therefore, reviewed. Additionally, particular attention has been given to the molecular mechanisms of chemoprevention, executed by the reported marine compounds.

2-Oxaspiro[4.5]decane and α-pyrenocine derivatives from the endophytic fungus Roussoella sp. PSU-H51

One new 2-oxaspiro[4.5]decane, roussoellide, and one new α-pyrenocine, 2',3'-dihydropyrenocine A, together with nine known compounds including known arthropsolide A, and pyrenocines A and E, were obtained from the culture broth of the endophytic fungus Roussoella sp. Their structures were determined using spectroscopic data. The absolute configuration of known arthropsolide A was assigned on the basis of X-ray diffraction data using Cu Kα radiation. Known pyrenocine A displayed weak cytotoxic activity against breast cancer (MCF-7) cells with an IC₅₀ value of 27.1 µM and weak antifungal activity against Microsporum gypseum SH-MU-4 with an MIC value of 615.2 µM.

The Biological and Chemical Diversity of Tetramic Acid Compounds from Marine-Derived Microorganisms

Tetramic acid (pyrrolidine-2,4-dione) compounds, isolated from a variety of marine and terrestrial organisms, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities. In the past decade, marine-derived microorganisms have become great repositories of novel tetramic acids. Here, we discuss the biological activities of 277 tetramic acids of eight classifications (simple 3-acyl tetramic acids, 3-oligoenoyltetramic acids, 3-decalinoyltetramic acid, 3-spirotetramic acids, macrocyclic tetramic acids, N-acylated tetramic acids, α-cyclopiazonic acid-type tetramic acids, and other tetramic acids) from marine-derived microbes, including fungi, actinobacteria, bacteria, and cyanobacteria, as reported in 195 research studies up to 2019.

Medicinal Purposes: Bioactive Metabolites from Marine-derived Organisms

The environment of marine occupies about 95% biosphere of the world and it can be a critical source of bioactive compounds for humans to be explored. Special environment such as high salt, high pressure, low temperature, low nutrition and no light, etc. has made the production of bioactive substances different from terrestrial organisms. Natural ingredients secreted by marine-derived bacteria, fungi, actinomycetes, Cyanobacteria and other organisms have been separated as active pharmacophore. A number of evidences have demonstrated that bioactive ingredients isolated from marine organisms can be other means to discover novel medicines, since enormous natural compounds from marine environment were specified to be anticancer, antibacterial, antifungal, antitumor, cytotoxic, cytostatic, anti-inflammatory, antiviral agents, etc. Although considerable progress is being made within the field of chemical synthesis and engineering biosynthesis of bioactive compounds, marine environment still remains the richest and the most diverse sources for new drugs. This paper reviewed the natural compounds discovered recently from metabolites of marine organisms, which possess distinct chemical structures that may form the basis for the synthesis of new drugs to combat resistant pathogens of human life. With developing sciences and technologies, marine-derived bioactive compounds are still being found, showing the hope of solving the problems of human survival and sustainable development of resources and environment.

Bioactive Secondary Metabolites from Octocoral-Associated Microbes-New Chances for Blue Growth

Octocorals (Cnidaria, Anthozoa Octocorallia) are magnificent repositories of natural products with fascinating and unusual chemical structures and bioactivities of interest to medicine and biotechnology. However, mechanistic understanding of the contribution of microbial symbionts to the chemical diversity of octocorals is yet to be achieved. This review inventories the natural products so-far described for octocoral-derived bacteria and fungi, uncovering a true chemical arsenal of terpenes, steroids, alkaloids, and polyketides with antibacterial, antifungal, antiviral, antifouling, anticancer, anti-inflammatory, and antimalarial activities of enormous potential for blue growth. Genome mining of 15 bacterial associates (spanning 12 genera) cultivated from Eunicella spp. resulted in the identification of 440 putative and classifiable secondary metabolite biosynthetic gene clusters (BGCs), encompassing varied terpene-, polyketide-, bacteriocin-, and nonribosomal peptide-synthase BGCs. This points towards a widespread yet uncharted capacity of octocoral-associated bacteria to synthetize a broad range of natural products. However, to extend our knowledge and foster the near-future laboratory production of bioactive compounds from (cultivatable and currently uncultivatable) octocoral symbionts, optimal blending between targeted metagenomics, DNA recombinant technologies, improved symbiont cultivation, functional genomics, and analytical chemistry are required. Such a multidisciplinary undertaking is key to achieving a sustainable response to the urgent industrial demand for novel drugs and enzyme varieties.

Unstable Tetramic Acid Derivatives from the Deep-Sea-Derived Fungus Cladosporium sphaerospermum EIODSF 008

Seven new unstable tetramic acid derivatives, cladosporiumins I-O (1–7), together with the known analogue cladodionen (8) were isolated from the extract of the deep-sea-derived fungus Cladosporium sphaerospermum EIODSF 008. Their structures were elucidated by spectroscopic analysis, quantum chemical calculations and ECD spectra. Compound 4 was a Mg complex of tetramic acid derivative. In acidic solvent, 4 could change to 1 and 6, and 7 could change to 5. In addition, 1, 5 and 8 existed as two exchangeable isomers, respectively. The structures of cladosporiumins E-H were reassigned as their Na complexes. The antibacterial and cytotoxic activities of 1–8 were also evaluated. However, because of their instability, all of the isolated compounds did not show significant antibacterial activity as the preliminary EtOAc extracts of the fungal strain.

Synthesis, Characterization, and Antifungal Activity of Phenylpyrrole-Substituted Tetramic Acids Bearing Carbonates

For the aim of discovering new fungicide, a series of phenylpyrrole-substituted tetramic acid derivatives bearing carbonates 6a-q were designed and synthesized via 4-(2,4-dioxopyrrolidin-3-ylidene)-4-(phenylamino)butanoic acids 4a-k and the cyclized products 1',3,4,5'-tetrahydro-[2,3'-bipyrrolylidene]-2',4',5(1H)-triones 5a-k. The compounds were characterized using IR, ¹H- and (13)C-NMR spectroscopy, mass spectrometry (EI-MS), and elemental analysis. The structure of 6b was confirmed by X-ray diffraction crystallography. The title compounds 6a-q were bioassayed in vitro against the phytopathogenic fungi Fusarium graminearum, Botrytis cinerea and Rhizoctonia solani at a concentration of 100 μg/mL, respectively. Most compounds displayed good inhibitory activity.

Lindgomycin, an Unusual Antibiotic Polyketide from a Marine Fungus of the Lindgomycetaceae

An unusual polyketide with a new carbon skeleton, lindgomycin (1), and the recently described ascosetin (2) were extracted from mycelia and culture broth of different Lindgomycetaceae strains, which were isolated from a sponge of the Kiel Fjord in the Baltic Sea (Germany) and from the Antarctic. Their structures were established by spectroscopic means. In the new polyketide, two distinct domains, a bicyclic hydrocarbon and a tetramic acid, are connected by a bridging carbonyl. The tetramic acid substructure of compound 1 was proved to possess a unique 5-benzylpyrrolidine-2,4-dione unit. The combination of 5-benzylpyrrolidine-2,4-dione of compound 1 in its tetramic acid half and 3-methylbut-3-enoic acid pendant in its decalin half allow the assignment of a new carbon skeleton. The new compound 1 and ascosetin showed antibiotic activities with IC50 value of 5.1 (±0.2) µM and 3.2 (±0.4) μM, respectively, against methicillin-resistant Staphylococcus aureus.

New PKS-NRPS tetramic acids and pyridinone from an Australian marine-derived fungus, Chaunopycnis sp

Marine-derived fungus Chaunopycnis sp. yielded the tetramic acid F-14329 (1) and new analogues, chaunolidines A–C (2–4), together with the new pyridinone chaunolidone A (5), and pyridoxatin (6).

Naturally occurring tetramic acid products: isolation, structure elucidation and biological activity

Natural products containing the tetramic acid core scaffold have been isolated from an assortment of terrestrial and marine species and often display wide ranging and potent biological activities including antibacterial, antiviral and antitumoral activities.

Vermelhotin, an anti-inflammatory agent, suppresses nitric oxide production in RAW 264.7 cells via p38 inhibition

Vermelhotin exhibited potential anti-inflammatory activity through inhibition of nitric oxide production (IC₅₀ = 5.35 ± 0.59 μM) in LPS-stimulated RAW 264.7 macrophage cells. Vermelhotin suppressed expression of inducible nitric oxide synthase (iNOS) at mRNA and protein levels, in a dose-dependent manner. Mechanistic studies revealed that vermelhotin abrogated upstream signaling of iNOS expression by selectively inhibiting p38 phosphorylation, while ERK and JNK activations were not affected.

Nodulisporisteriods A and B, the first 3,4-seco-4-methyl-progesteroids from Nodulisporium sp

Two new 4-methyl-progesteroids, nodulisporisteriod A (1) and nodulisporisteriod B (2), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (No. 65-17-2-1), along with two related metabolites, demethoxyviridin (3) and inoterpene B (4). Their structures were determined by detailed spectroscopic analyses, X-ray crystallographic analysis and comparison of the NMR data with those of the closely related compounds previously reported. Nodulisporisteriod A (1) and nodulisporisteriod B (2) possess new carbon skeletons, which are the first cases of fission at C-3,4 in 4-methyl-progesteroids. A hypothetical biosynthetic pathway for 1 and 2 was proposed. Moreover, the Aβ42 aggregation inhibitory activities of 1-4 were evaluated using standard thioflavin T (ThT) fluorescence assay with epigallocatechin gallate (EGCG) as positive control. Demethoxyviridin (3) displayed anti-Aβ42 aggregation activity with IC50 value of 13.4μM.

Pharmacologically prospective antibiotic agents and their sources: a marine microbial perspective

Marine microbes have been a storehouse of bioactive metabolites with tremendous potential as drug candidates. Marine microorganism derived secondary metabolites (chemical compounds/peptides) are considered to be a burning area of research since recent past. Many of such compounds have been proven to be anti-bacterial, anti-fungal, anti-algal, anti-HIV, anti-helminthic, anti-protozoan, anti-tumor and anti-allergic agents. Marine bacteria and fungi have been reported to be the producers of such compounds owing to their defense mechanisms and metabolic by products. Although the number of natural products isolated from these classes of marine microbial flora is large, a limited number of such compounds reach the clinical trial and even less number of them get approved as a drug. Here we discuss the recent studies on the isolation, characterization and the pharmacological significances of anti-bacterial, anti-fungal and anti-infective agents of marine microbial origin. Further, the clinical status of such compounds has also been discussed in comparison with those derived from their terrestrial counterparts.

(+)-Ascosalitoxin and vermelhotin, a calmodulin inhibitor, from an endophytic fungus isolated from Hintonia latiflora

Chemical investigation of the endophytic MEXU 26343, isolated from the medicinal plant Hintonia latiflora, yielded the known polyketide vermelhotin (1) and a new salicylic aldehyde derivative, namely, 9S,11R-(+)-ascosalitoxin (2). The structure and absolute configuration of the new compound were established through extensive NMR spectroscopy and molecular modeling calculations at the DFT B3LYP/DGDZVP level, which included the comparison between theoretical and experimental optical rotation values. In addition, chemical transformations of 2 yielded suitable derivatives for NOESY and (1)H-(1)H NMR coupling constant analyses, which reinforce the stereochemical assignment. The potential affinity of 1 and 2 with (Ca(2+))(4)-hCaM in solution was measured using the fluorescent biosensor hCaM M124C-mBBr. The results showed that 1 bound to the protein with a dissociation constant (K(d)) of 0.25 ± 0.04 μM, close to that of chlorpromazine (K(d) = 0.64 ± 0.03 μM), a classical CaM inhibitor. The stoichiometry ratio of 1 to (Ca(2+))(4)-hCaM was 1:4, similar to other well-known CaM ligands.

Bioactive secondary metabolites from marine microbes for drug discovery

The isolation and extraction of novel bioactive secondary metabolites from marine microorganisms have a biomedical potential for future drug discovery as the oceans cover 70% of the planet's surface and life on earth originates from sea. Wide range of novel bioactive secondary metabolites exhibiting pharmacodynamic properties has been isolated from marine microorganisms and many to be discovered. The compounds isolated from marine organisms (macro and micro) are important in their natural form and also as templates for synthetic modifications for the treatments for variety of deadly to minor diseases. Many technical issues are yet to overcome before wide-scale bioprospecting of marine microorganisms becomes a reality. This chapter focuses on some novel secondary metabolites having antitumor, antivirus, enzyme inhibitor, and other bioactive properties identified and isolated from marine microorganisms including bacteria, actinomycetes, fungi, and cyanobacteria, which could serve as potentials for drug discovery after their clinical trials.

Itaconic acid derivatives and diketopiperazine from the marine-derived fungus Aspergillus aculeatus CRI322-03

Three metabolites, pre-aurantiamine (1), (-)-9-hydroxyhexylitaconic acid (4) and (-)-9-hydroxyhexylitaconic acid-4-methyl ester (5), together with two known compounds, paraherquamide E (6) and secalonic acid D (7), were isolated from the marine-derived fungus, Aspergillus aculeatus.

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.

The structural diversity and promise of antiparasitic marine invertebrate-derived small molecules

This review focuses on six important parasitic diseases that adversely affect the health and lives of over one billion people worldwide. In light of the global human impact of these neglected tropical diseases (NTDs), several initiatives and campaigns have been mounted to eradicate these infections once and for all. Currently available therapeutics summarized herein are either ineffective and/or have severe and deleterious side effects. Resistant strains continue to emerge and there is an overall unmet and urgent need for new antiparasitic drugs. Marine-derived small molecules (MDSMs) from invertebrates comprise an extremely diverse and promising source of compounds from a wide variety of structural classes. New discoveries of marine natural product privileged structures and compound classes that are being made via natural product library screening using whole cell in vitro assays are highlighted. It is striking to note that for the first time in history the entire genomes of all six parasites have been sequenced and additional transcriptome and proteomic analyses are available. Furthermore, open and shared, publicly available databases of the genome sequences, compounds, screening assays, and druggable molecular targets are being used by the worldwide research community. A combined assessment of all of the above factors, especially of current discoveries in marine natural products, implies a brighter future with more effective, affordable, and benign antiparasitic therapeutics.