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.

The peer-reviewed articles were retrieved from searches of several databases, including MarinLit, PubMed, Chemical Abstracts ® , ISI Web of Knowledge and Google Scholar. The review only includes bioactivity and/or pharmacology of structurally characterized marine chemicals, which we have classified using a modification of Schmitz's chemical classification [9] into six major chemical classes; namely, polyketides, terpenes, peptides, alkaloids, shikimates, and sugars. The preclinical antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral and anthelmintic pharmacology of marine chemicals is reported in Table 1, with the structures shown in Figure 1. Marine compounds that affect the immune and nervous systems, as well as those with antidiabetic and anti-inflammatory effects, are exhibited in Table 2, with their structures presented in Figure 2. Finally, marine compounds that affected a variety of cellular and molecular targets are noted in Table 3, and their structures presented in Figure 3. A number of publications during 2012-2013 reported extracts or structurally uncharacterized marine compounds, with novel and interesting preclinical and/or clinical pharmacology: in vitro antimalarial activity in crude extracts from Fiji marine organisms using a semi-automated RNA fluorescence-based high-content live cell-imaging assay [10]; the first report of in vitro liver stage antiplasmodial activity and dual stage inhibitory potential of British seaweeds [11]; anti-hepatitis C virus activity affecting the viral helicase NS3 and replication, in crude extracts from the marine feather star Alloeocomatella polycladia [12]; anti-herpes simplex virus HSV-1 and HSV-2 activity in a purified sulfoglycolipid fraction from the Brazilian marine alga Osmundaria obtusiloba [13]; in vivo anti-inflammatory activity of a heterofucan from the Brazilian seaweed Dictyota menstrualis that inhibited leukocyte migration to sites of tissue injury by binding to the cell membrane [14]; in vivo antinociceptive and anti-inflammatory activity in a crude methanolic extract of the red alga Bryothamnion triquetrum [15]; in vivo anti-inflammatory activity in a sulfate polysaccharide fraction from the red alga Gracilaria caudata resulting in significant inhibition of neutrophil migration and cytokine release [16]; in vitro anti-inflammatory effect of a hexane-soluble fraction of the brown alga Laminaria japonica that inhibited nitric oxide, prostaglandin E 2 , interleukin (IL)-1β and IL-6 release from lipopolysaccharide-stimulated macrophages via inactivation of nuclear factor-κB transcription factor [17]; in vivo anti-inflammatory of a polysaccharide-rich fraction from the marine red alga Lithothamnion muelleri that reduced organ injury and lethality, as well as pro-inflammatory cytokines and chemokines, associated with graft-versus-host disease in mice [18]; in vivo clinical effectiveness in an osteoarthritis trial by PCSO-524 TM , a nonpolar lipid extract from the New Zealand marine green lipped mussel Perna canaliculus, which may offer "potential alternative complementary therapy with no side effects for osteoarthritis patients" [19]; enhanced antioxidant activity of chitosan nanoparticles as compared to chitosan on hydrogen peroxide-induced stress injury in mouse macrophages in vitro [20]; induction of concentration-dependent vasoconstrictive activity on isolated rat aorta by a tentacle extract from the jellyfish Cyanea capillata [21]; significant antioxidant effect of a sulfated-polysaccharide fraction of the marine red alga Gracilaria birdiae which prevented naproxen-induced gastrointestinal damage in rats by reversing glutathione depletion [22]; in vitro antioxidant properties of a polysaccharide from the brown seaweed Sargassum graminifolium (Turn.) that was also observed to inhibit calcium oxalate crystallization, a constituent of urinary kidney stones [23]; antioxidant activity in organic extracts from 30 species of Hawaiian marine algae, with the carotenoid fucoxanthin identified as the major bioactive antioxidant compound in the brown alga T. ornata [24]; screening of antioxidant activity in 18 cyanobacteria and 23 microalgae cell extracts identified Scenedesmus obliquus strain M2-1, which protected against DNA oxidative damage induced by copper (II)-ascorbic acid [25]; anxiolytic-like effect of a salmon phospholipopeptidic complex composed of polyunsaturated fatty acids and bioactive peptides associated with strong free radical scavenging properties [26]; antinociceptive activity in extracts of the skin of the Brazilian planehead filefish Stephanolepis hispidus with partial activation of opioid receptors in the nervous system [27]; strong in vitro acetylcholinesterase inhibition, an enzyme targeted by drugs used to treat Alzheimer's disease, myasthenia gravis and glaucoma, by an extract from the polar marine sponge Latrunculia sp. [28]; central nervous system activity of a phlorotannin-rich extract from the edible brown seaweed Ecklonia cava targeting gamma-aminobutyric acid type A benzodiazepine receptors [29]; and novel protease inhibitors from Norwegian spring spawning herring determined by screening of marine extracts with assays combining fluorescence resonance energy transfer activity and surface plasmon resonance spectroscopy-based binding [30].  Table 1 presents 2012-2013 preclinical pharmacological research on the antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral and anthelmintic activities of marine natural products  shown in Figure 1.

Antibacterial Activity
During 2012-2013, 31 studies reported antibacterial marine natural products (1-50) isolated from bacteria, fungi, tunicates, sponges, and algae, a global effort that may contribute to the search for novel leads for developing newer drugs to treat drug-resistant bacterial infections.
As shown in Table 1 and Figure 1, three papers reported molecular mechanism of action studies with marine antibacterial compounds. Jang and colleagues reported a potent antianthrax antibiotic, anthracimycin (1), derived from a marine actinomycete with significant activity against Bacillus anthracis, by a mechanism that " . . . remains to be fully defined . . . " but that appears to involve DNA/RNA synthesis inhibition [31]. Keffer and colleagues extended the mechanism of action of bis-diarylbutene macrocycle chrysophaentins (2,3), isolated from the chrysophyte alga Chrysophaeum taylori, by determining that they competitively inhibited the biochemical activity of the Gram-positive and Gram-negative cell division protein FtsZ by binding to its GTP-binding site [32]. Sakoulas and colleagues reported the antibacterial activity of merochlorin A (4), a meroterpenoid isolated from a marine-derived actinomycete strain CNH189, which demonstrated activity against Gram-positive bacteria including Clostridium difficile, but not against Gram-negative bacteria, by a mechanism that appeared to involve " . . . global inhibition of DNA, RNA, protein, and cell wall synthesis . . . " [33].
As shown in Table 1 and Figure 1, two reports described antifungal marine chemicals with novel mechanisms of action. Rubiolo and colleagues investigated the guanidine antifungal alkaloid crambescidin-816 (51), previously isolated from the Mediterranean sponge Crambe crambe [62]. Detailed cell cycle studies in the yeast Saccharomyces cerevisiae demonstrated that this compound induced G2/M cell cycle arrest followed by apoptosis and mitochondrial disfunction, suggesting that although cytotoxic crambescidin-816 " . . . .could serve as a lead compound to fight fungal infections". Yibmantasiri and colleagues investigated the molecular basis for the fungicidal action of the triterpene glycoside neothyonidioside (52) isolated from the sea cucumber Australostichopus mollis [63], demonstrating that neothyonidioside binds directly to fungal ergosterol affecting membrane curvature and fusion capability essential for membrane recycling and lysosomal degradation.
As shown in Table 1 and Figure 1, nine marine compounds (79-86) isolated from bacteria, ascidians, sponges, soft corals and algae were reported to possess bioactivity towards so-called neglected protozoal diseases, namely leishmaniasis, caused by the genus Leishmania (L.), amebiasis, trichomoniasis, and both African sleeping sickness (caused by Trypanosoma (T.) brucei rhodesiense and T. brucei gambiense) and American sleeping sickness or Chagas disease (caused by T. cruzi).
As shown in Table 1, three reports described four antitrypanosomal marine chemicals (79)(80)(81)(82) as well as their mechanisms of action. Sanchez and colleagues examined the mode of action of almiramides (79,80), originally isolated from the cyanobacterium Lyngbya majuscula, and demonstrated for the first time that these compounds inhibited T. brucei by disrupting the parasite's glycosomal function by targeting two membrane proteins, and were thus considered "encouraging candidates for further lead development" [85]. Abdelmohsen and colleagues reported that the dibenzodiazepine alkaloid diazepinomicin (81) isolated from a strain of Micromonospora sp. RV115 associated with the Croatian marine sponge Aplysina aerophoba showed activity against T. brucei trypmastigote forms and inhibited the parasite protease rhodesain [86]. Desoti and colleagues extended the pharmacology of (−)-elatol (82), a sesquiterpene isolated from the Brazilian red alga Laurencia dendroidea shown to affect trypomastigotes of T. cruzi, demonstrating that it induced initial depolarization of the parasite's mitochondrial membrane, followed by an increase in superoxide generation, as well as loss of cell membrane and DNA integrity [87].
As shown in Table 1 and Figure 1, five marine natural products (63,(83)(84)(85)(86) were characterized to exhibit antileishmanial and antiprotozoal activity, although the mechanism of action remained undetermined. Lam and colleagues reported that the known dioxothiazino-quinoline-quinone metabolite ascidiathiazone A (63), isolated from a New Zealand ascidian, moderately inhibited the growth of T. brucei rhodesiense, but was ineffective against T. cruzi and L. donovani [72]. Balunas and colleagues isolated the polyketide coibacin A (83) from a Panamanian marine cyanobacterium Oscillatoria sp., and observed potent activity against L. donovani axenic amastigotes [88]. Ishigami and colleagues isolated a new xenicane diterpenoid cristaxenicin A (84) from the deep-sea gorgonian Acanthoprimnoa cristata, which showed potent activity against L. amazonensis and T. congolense [89]. Chianese and colleagues completed structure-activity relationship studies with several natural and semisynthetic manadoperoxide B analogues (85,86), isolated from the Indonesian sponge Plakortis sfr. lita, and determined that both were highly active towards the parasite T. brucei rhodesiense, highlighting the 1,2-dioxane ring to be a key pharmacophore [90].
Because of the surge in drug-resistant strains of the intracellular pathogen Mycobacterium tuberculosis (Mtb), there is a global need for the development of novel drugs with novel mechanisms of action. As shown in Table 1 and Figure 1, seven novel marine natural products (78,(87)(88)(89)(90)(91)(92), isolated from bacteria, sponges and fungi, contributed to the ongoing global search for novel antituberculosis agents. Although these marine natural products were characterized to exhibit antituberculosis activity, unfortunately the mechanism of action of these compounds remained undetermined.
Huang and colleagues reported a novel sesterterpenoid asperterpenoid A (87) from a mangrove endophytic fungus Aspergillus sp. that demonstrated strong inhibitory activity against M. tuberculosis protein tyrosine phosphatase B, an enzyme that is " . . . considered a promissory target for pulmonary tuberculosis cure" [91]. Song and colleagues isolated a new dimeric diketopiperazine, brevianamide S (88), from Aspergillus versicolor collected in the Bohai Sea, China, which demonstrated selective antibacterial activity against Bacille Calmette-Guérin (BCG), "suggestive of a new mechanism of action that could inform the development of next generation antitubercular drugs . . . if translated to M. tuberculosis . . . " [92]. Chen and colleagues reported a new spirotetronate, lobophorin G (89), from a marine-derived Streptomyces sp. MS100061 which exhibited strong anti-M. bovis BCG activity, providing relevant pharmacological information as this screen is thought to "serve as a useful screening surrogate for M. tuberculosis" [93]. Yamano and colleagues discovered a new cyclic depsipeptide neamphamide B (90) in a Japanese marine sponge Neamphius sp., which showed activity against M. bovis BCG in "both actively growing and dormant states" [94]. Avilés and colleagues isolated two new tricyclic diterpenes (91,92) from the Bahamian marine sponge Svenzea flava that displayed moderate antimycobacterial activity against M. tuberculosis H37Rv, the data suggesting that "the isoneoamphilectane backbone" may be "responsible for the observed activity" [95]. In addition to the antimalarial activity described earlier, Supong and colleagues reported that the novel C-glycosylated benz[a]anthraquinone derivative, urdamycinone E (78), inhibited M. tuberculosis strain H37Rv [84].

Antiviral Activity
As shown in Table 1 and Figure 1, thirteen reports were published during 2012-2013 on the antiviral pharmacology of marine natural products (93-102) against hepatitis C, human immunodeficiency virus type-1 (HIV-1), influenza virus, human rhinovirus (HRV) and herpes simplex virus (HSV).
As shown in Table 1, only six reports described antiviral marine chemicals and their mechanisms of action. Da Rosa Guimarães and colleagues extended the pharmacology of the known steroids halistanol sulfate (93) and halistanol sulfate C (94), isolated from the Brazilian marine sponge Petromica citrina, by demonstrating that the compounds inhibited attachment and penetration of the "early events of HSV-1 infection" [96]. Ellithey and colleagues investigated several known metabolites (95-97) from the Red Sea soft coral Litophyton arboreum and demonstrated selective inhibition of the HIV-1 protease by a mechanism that "confirms the contribution of the hydrophobicity of inhibitors of HIV protease" [97]. Salam and colleagues reported a novel pharmacological activity for the sesterterpene manoalide (98), which was observed to affect the hepatitis C virus NS3 helicase by inhibiting RNA binding and ATPase activity [98]. Park and colleagues reported that two polybromocatechol compounds (99,100), isolated from the red alga Neorhodomela aculeate, inhibited infection and cytopathic effects on a HeLa cell line by HRV2 and HRV3, causal agents of viral respiratory infections and common colds [99]. Ma and colleagues determined that the novel phenylspirodrimane stachybotrin D (101), isolated from the fungus Stachybotrys chartarum MXH-X73 derived from the Chinese marine sponge Xestospongia testudinaria, inhibited HIV-1 replication of wild-type and five non-nucleoside reverse transcriptase inhibitor (NNRTI)-resistant HIV-1 strains by inhibiting the reverse transcriptase, and thus "provides a new class of chemotype for the search of NNRT inhibitors" [100]. Jiao and colleagues reported that streptoseolactone (102), derived from the actinomycete Streptomyces seoulensis strain isolated from the shrimp Penasus orientalis, inhibited neuraminidase by a noncompetitive mechanism, a finding "of value in terms of drug discovery for the treatment of influenza" [101].

Anthelmintic Activity
As shown in Table 1, only one report was published during 2012-2013 on the anthelmintic pharmacology of marine natural products. Melek and colleagues isolated triterpene glycosides echinosides A and B (112,113) from the sea cucumbers Actinopyga echinites and Holothuria polii that displayed "potential in vitro schisotomicidal activity against worms of Schistosoma mansoni", suggesting that these compounds may be "promising lead compounds for the development of new schistosomicidal agents" [109]. Table 2 presents the 2012-2013 preclinical pharmacology of marine chemicals , which demonstrated either antidiabetic or anti-inflammatory activity, as well as those affecting the immune or nervous system; their structures are depicted in Figure 2.      , which demonstrated either antidiabetic or anti-inflammatory activity, as well as those affecting the immune or nervous system; their structures are depicted in Figure 2.

Antidiabetic Activity
Lee and colleagues reported the pharmacology of octaphlorethol A (114), a novel phenolic compound isolated from the marine brown alga Ishige foliacea, by showing that octaphlorethol A enhanced glucose uptake in L6 rat myoblast cells by increasing glucose transporter 4 translocation to the plasma membrane and protein kinase B and AMP-activated protein kinase activity [120].
Chae and colleagues evaluated the anti-inflammatory properties of apo-9 -fucoxanthinone (115), isolated from the marine edible brown alga Sargassum muticum [121] in unmethylated CpG DNA-stimulated bone marrow-derived macrophages and dendritic cells. Inhibition of interleukin-12 p40, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) production, as well as concomitant attenuation of the mitogen-activated protein kinase pathways, was observed, leading the authors to conclude that apo-9 -fucoxanthinone may have "potential therapeutic use . . . for inflammatory disease". In a detailed mechanistic study, Speranza and colleagues investigated the antioxidant marine carotenoid astaxanthin (116), showing that it inhibited hydrogen peroxide-stimulated production of pro-inflammatory cytokines IL-1, IL-6 and TNF-α in a human U937 monocytic cell line by selectively restoring physiological levels and function of the tyrosine phosphatase SHP-1, thus proposing that astaxanthin might become a novel agent for the therapy of inflammatory diseases [122]. Johnson and colleagues identified the alkaloids bengamide A and B (117,118) as potent inhibitors of NFκB and LPS-induced expression of cytokines IL-6, TNF-α and chemokine monocyte chemoattractant protein-1 (MCP-1) release from murine RAW 264.7 macrophages, concluding that these compounds may "serve as therapeutic leads for immune disorders involving inflammation" [123]. Song and colleagues determined that bis-N-norgliovictin (119) derived from a marine fungus S3-1-c inhibited TNF-α, IL-6, interferon-β, and MCP-1 production by LPS-stimulated RAW 264.7 macrophages and affecting Toll-like receptor 4 (TLR-4) signal transduction pathways, as well as LPS-induced septic shock in mice, thus suggesting bis-N-norgliovictin might result in a useful therapeutic candidate for "sepsis and other inflammatory diseases" [124]. Investigations by Yang and colleagues with phlorotannin 6,6'-bieckol (120), isolated from the marine brown alga Ecklonia cava, showed that the compound inhibited expression and release of nitric oxide, prostaglandin E 2 , TNF-α and IL-6 in LPS-stimulated macrophages, with concomitant inhibition of NFκB activation, suggesting that compound 120 is potentially useful for the treatment of inflammatory diseases [125]. Balunas and colleagues determined that the polyketide coibacin B (121), isolated from the Panamanian marine cyanobacterium, cf. Oscillatoria sp. possessed not only antileishmanial activity, but also significant anti-inflammatory activity, as it significantly decreased LPS-induced nitric oxide, TNF-α and IL-6 release from RAW 264.7 macrophages [88]. Hsu and colleages reported that the soft coral S. flexibilis-derived 11-epi-sinulariolide acetate (122) inhibited cyclooxygenase-2 and interleukin-8 expression in human epidermoid carcinoma A431 cells in vitro by inhibition of Ca 2+ signaling, suggesting that it might become a lead compound to target "store-operated calcium signaling-dependent inflammatory diseases" [126]. Choi and colleagues demonstrated that the novel honaucin A (123) from the Hawaiian cyanobacterium Leptolyngbya crossbyana, which inhibited LPS-induced nitric oxide production, and TNF-α, IL-1β, IL-6 and iNOS gene transcription in RAW 264.7 macrophages, had functional groups "critical for anti-inflammatory... activity" [127]. Rat brain microglia, a macrophage type involved in neuroinflammation and neurodegeneration [180] was used by Mayer and colleagues to investigate several known diterpene isocyanide amphilectane metabolites (124,125) from the Caribbean marine sponge Hymeniacidon sp., which potently inhibited thromboxane B 2 generation from LPS activated rat neonatal microglia in vitro, with concomitant low lactate dehydrogenase release and minimal mitochondrial dehydrogenase inhibition. The authors concluded that the potency of these compounds warranted "further investigation . . . as lead compounds to modulate . . . activated microglia in neuroinflammatory disorders" [128]. Ahmed and colleagues extended the pharmacology of largazole (126), originally isolated from a marine cyanobacterium Symploca sp., by reporting that largazole inhibited class I histone deacetylase 6 in vitro in human rheumatoid arthritis. Furthermore, largazole-enhanced expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 was observed to be mediated by activation of the p38 and Akt signal transduction pathways in synovial fibroblasts [129]. Lee and colleagues reported that the sesquiterpenoid lemnalol (127), isolated from the Japanese soft coral Lemnalia tenuis, attenuated monosodium urate-induced gouty rat arthritis, by a mechanism that involved inhibition of inducible nitric oxide synthase and cyclooxygenase-2, thus becoming a potential new candidate for "development of a new treatment for gout" [130]. Kim and colleagues reported that the diketopiperazine-type indole alkaloid neoechinulin A (128), isolated from an Antarctic marine fungus Eurotium sp. SF-5989, inhibited LPS-stimulated RAW264.7 macrophages expression, release of nitric oxide and prostaglandin E 2 , with concomitant inhibition of NFκB activation, and reduced inhibitor NFκB and p38 mitogen-activated protein kinase (MAPK) phosphorylation [131]. In a detailed study, Lee and colleagues investigated penstyrylpyrone (129), isolated from a marine-derived fungus Penicillium sp. JF-55, and determined that the inhibition of LPS-treated murine peritoneal macrophage production of NO, PGE 2 , TNF-α, IL-1β, was correlated with suppression of iκB-α and NF-κB and concomitant expression of heme oxygenase-1 [132]. Vilasi and colleagues extended the molecular pharmacology of the novel cyclic octapepetide perthamide C (130), isolated from the marine sponge Theonella swinhoei, by investigating its effect on the proteome of murine macrophages J774.A1 using two-dimensional proteomics, and determining differential effect on several cytosolic and ER-associated proteins, mainly involved in cellular folding processes, thus "shed(ding) more light on the . . . mechanisms of action" of this natural product [133]. Reina and colleagues reported that R-prostaglandins (131,132) isolated from the Caribbean Colombian soft coral Plexaura homomalla inhibited 12-O-tetradecanoylphorbol-13-acetate-induced mouse ear inflammation in vivo and decreased human polymorphonuclear leukocytes degranulation, as well as myeloperoxidase and elastase levels in vitro, thus concluding that prostaglandins from " . . . P. homomalla are promising molecules with an interesting anti-inflammatory activity profile" [134]. Huang and colleagues extended the pharmacology of the known compound sinularin (133), demonstrating that it modulates nociceptive responses and spinal neuroinflammation by a mechanism that may involve inhibition of leukocyte iNOS and cyclooxygenase-2 (COX-2) and the upregulation of the anti-inflammatory cytokine transforming growth factor-β [135]. Marino and colleagues reported the molecular pharmacology of the novel polyhydroxylated steroid swinhosterol B (134) isolated from the Solomon Islands marine sponge T. swinhoei [136]. Swinhosterol B was shown to be a highly specific agonist for the human pregnane-X-receptor (PXR), and in transgenic PXR murine monocytes, it attenuated pro-inflammatory cytokine production in vitro, thus supporting "the exploitation of this compound in rodent model(s) of liver inflammation and cholestasis".

Marine Compounds with Activity on the Immune System
In 2012-2013 preclinical pharmacology of marine compounds that affected the immune system showed a decline as previously reported in this series.
Lin and colleagues reported that the cembrane-type diterpenoid lobocrassin B (158), isolated from the marine soft coral Lobophytum crissum, demonstrated immunomodulatory effects on bone marrow-derived dendritic cells (DC), a cell type known to be an important link between the innate and adaptive immune response [157]. Lobocrassin B was shown to attenuate DC maturation and activation with concomitant inhibition of toll-like receptor-stimulated translocation of NF-κB and TNF-α production, data that suggested that lobocrassin B might have "therapeutic applications in certain immune disfunctions". Chen and colleagues reported that a novel mycophenolic acid derivative, penicacid B (159), isolated from a South China sea fungus Penicillium sp. SOF07, inhibited splenocyte lymphocyte proliferation by a mechanism that involved inhibition of inosine 5 -monophosphate dehydrogenase, an essential rate-limiting enzyme in purine metabolic pathway and an "important drug target for immunosuppressive" activity [158].

Marine Compounds Affecting the Nervous System
In 2012-2013, the preclinical marine nervous system pharmacology with compounds , which is consolidated in Table 2 and Figure 2, was focused on sodium and potassium channels, nicotinic acetylcholine receptors, as well as, analgesia, antinociception, and neuroprotection.
Four marine compounds (160)(161)(162)(163) were shown to bind to sodium (Na + ) and potassium (K + ) channels. Jensen and colleagues determined the effect of cyclisation on the stability of the sea anemone peptide APETx2 (160). Cyclization with either a six-, seven-or eight-residue linker appeared to be a "promising strategy" to increase protease resistance of APETx2, but it decreased its potency against non-voltage gated, pH-sensitive Na + channel ASIC3 (IC 50 = 61 nM). Furthermore, truncation at either Nand C-terminus significantly affected APETx2 binding to ASIC3, demonstrating their critical role in this process [159]. Li and colleagues reported the discovery of a cysteine-crosslinked peptide asteropsin A (161), isolated from a Korean marine sponge Asteropus sp., that affected neuronal Ca 2+ influx by a mechanism that involved murine cerebrocortical neurons agonist-induced Na + channel activation, and may thus represent " . . . a valuable contribution to the cysteine knot peptide-based drug development as a model scaffold" [160]. Orts and colleagues published the biochemical and electrophysiological characterization of two novel sea anemone type 1 potassium toxins, namely Bcs Tx1 (162) and Bcs Tx2 (163) isolated from the Atlantic sea anemone Bunodosoma caissarum, and demonstrated by electrophysiological screening of 12 subtypes of voltage-gated Kv K + channels, that BcsTx1 showed highest affinity for rKv1.2 (IC 50 = 0.03 ± 0.006 nM) while Bcs Tx2 potently inhibited rKv1.6 (IC 50 = 7.76 ± 1.90 nM) [161].
Four studies extended the pharmacology of conopeptides (164)(165)(166)(167). Favreau and colleagues reported that a novel µ-conopeptide CnIIIIC (164) isolated from the venom of the marine snail C. consors strongly decreased mouse hemidiaphragm contraction by a mechanism that involved potently blocking muscle Na v 1.4 (IC 50 = 1.3 nM) and rat brain Na v 1.2 (IC 50 < 1 µM) voltage-gated Na + channels in a "virtually irreversible" manner, which will probably result in potential development of 164 " . . . as a myorelaxing drug candidate" [162]. Vetter and colleagues reported the isolation and characterization of a novel hydrophobic 32-residue µO-conotoxin MfVIA (165), isolated from the venom of marine snail C. magnificus, and by using a variety of electrophysiological techniques demonstrated that it preferentially inhibited Nav1.8 (IC 50 = 96 nM) and Nav1.4 (IC 50 < 81 nM) voltage-gated Na + channels, leading the authors to propose it as a "drug lead for development of improved analgesic molecules . . . to improve pain management" [163]. Franco and colleagues isolated an α4/7-conotoxin RegIIA (166) from the venom of the marine cone snail C. regius, and demonstrated that it potently inhibited α3β4 neuronal nicotinic acetylcholine receptors (IC 50 = 33 nM) by a mechanism that will require continuous investigation to determine "the precise binding mode of this peptide" [164]. Bernáldez and colleagues described the isolation and biochemical characterization of the first Conus regularis conotoxin designated RsXXIVA (167) with an eight-cysteine framework, which "diverges from other known conotoxins" and that inhibited Ca v 2.2 channels (IC 50 = 2.8 µM) in rat superior cervical ganglion neurons, and also displayed both analgesic and anti-nociceptive activity in the hot-plate and formalin murine in vivo assays, which may contribute to the "design of analgesic peptides" [165].
Two studies reported marine compounds (168,169) that contributed to nociceptive pharmacology. Figuereido and colleagues extended the pharmacology of convolutamydine A (168), isolated from the Floridian marine bryozoan Amantia convoluta, demonstrating that it caused peripheral anti-nociceptive and anti-inflammatory effects in several acute pain models, an effect probably mediated by the cholinergic, opioid and nitric oxide systems and "comparable to morphine's effects" [166]. Andreev and colleagues contributed an extensive in vitro and in vivo pharmacological study of two polypeptides APHC1 and PAHC3 (169), isolated from the sea anemone Heteractis crispa, shown to have significant anti-nociceptive and analgesic activity in a number of in vivo murine models with associated hypothermia. Furthermore, the two compounds were proposed as a new class of vanilloid 1 receptors modulators based on detailed in vitro biochemical studies [167].
Neuroprotective activity of marine compounds (170,171) was reported in two studies. Feng and colleagues observed that the novel octopamine derivative ianthellamide A (170), isolated from the Australian marine sponge Ianthella quadrangulate, increased endogenous kynurenic acid in rat brain, as well as selectively inhibited the kynurenine 3-hydroxylase in vitro, thus revealing that modulation of the kynurenine pathway of tryptophan metabolism by this compound suggested "potential as a neuroprotective agent" [168]. Burgy and colleagues completed an extensive pharmacological study on the selectivity, co-crystal structures and neuroprotective properties of the leucettines, analogues of the marine sponge alkaloid leucettamine B (171), originally isolated from the calcareous sponge Leucetta microraphis. An optimized product, leucettine L41, with multi-target selectivity that resulted in neuroprotective effects was proposed for "further optimization as potential therapeutics against neurodegenerative diseases such as Alzheimer's disease" [169].
As shown in Table 2, additional marine compounds (172)(173)(174) were shown to modulate other molecular targets, i.e., TRPV1 and cannabinoid receptors, and the acetylcholinesterase enzyme. Guzii and colleagues reported that a novel guanidine-containing compound pulchranin A (172), isolated from the marine sponge Monanchora pulchra inhibited TRPV1 receptor, an ionic channel involved in the regulation of pain and body temperature. Pulchranin A, "the first marine non-peptide inhibitor of TRPV1 channels", led to a decrease of Ca 2+ response in a CHO cell line expressing the rat TRPV1 channel by a mechanism the authors propose may result from "direct action on the channel pore" [170]. Montaser and colleagues reported a new fatty acid amide, serinolamide B (173), isolated from the Guam cyanobacterium Lyngbya majuscula that bound with higher selectivity to cannabinoid receptor CB2 and inhibited forskolin-stimulated cAMP accumulation in Chinese hamster ovary cells expressing the CB1 and CB2 receptors, a finding that "introduces a new structural lead to the cannabimimetic" field of research [171]. Huang and colleagues reported the isolation of a new α-pyrone meroterpene arigsugacin I (174), isolated from an endophytic fungus Penicillium sp. Sk5GW1L [172] that was observed to potently inhibit acetylcholinesterase, thus contributing to the "best-established treatment target for the design of anti-Alzheimer's drugs".

Reviews on Marine Pharmacology
In 2012-2013, several reviews were published covering general and/or specific areas of marine preclinical pharmacology: (a) marine pharmacology and marine pharmaceuticals: new marine natural products and relevant biological activities published in 2010 and 2011 [243,244]; natural products drug discovery as a continuing source of novel drug leads [245]; guiding principles for natural product drug discovery [246]; challenges and triumphs to genomic-based natural product discovery and pharmacology [247]; future of marine natural products drug discovery [248]; bioactive marine natural products from Antarctic and Arctic organisms [249]; biological activities of terpenes from the soft coral genus Sarcophyton [250]; pharmacologically active marine peptides from fish and shellfish [251]; preclinical pharmacology of marine diterpene glycosides [252]; bioactivity of fucoidan, a complex algal sulfated polysaccharide [253]; therapeutic application of marine fucanomics and galactanomics in drug development [254]; marine pharmacology of cosmopolitan brown alga Cystoseira genus secondary metabolites [255]; pharmacological activity of sulfated polysaccharides from marine algae [256]; biological activities and functions of halogenated organic molecules of red algae Rhodomelaceae [257]; pharmacological potential of marine cyanobacterial secondary metabolites [258]; pharmaceutical agents from filamentous marine cyanobacteria [259]; chemistry and preclinical pharmacology of sponge glycosides [260]; sea cucumbers as drug candidates [261]; bioactives from microalgal dinoflagellates [262]; the global marine pharmaceutical pipeline in 2017: U.S. Food and Drug Administration-approved compounds and those in Phase I, II and III of clinical

Reviews on Marine Pharmacology
In 2012-2013, several reviews were published covering general and/or specific areas of marine preclinical pharmacology: (a) marine pharmacology and marine pharmaceuticals: new marine natural products and relevant biological activities published in 2010 and 2011 [243,244]; natural products drug discovery as a continuing source of novel drug leads [245]; guiding principles for natural product drug discovery [246]; challenges and triumphs to genomic-based natural product discovery and pharmacology [247]; future of marine natural products drug discovery [248]; bioactive marine natural products from Antarctic and Arctic organisms [249]; biological activities of terpenes from the soft coral genus Sarcophyton [250]; pharmacologically active marine peptides from fish and shellfish [251]; preclinical pharmacology of marine diterpene glycosides [252]; bioactivity of fucoidan, a complex algal sulfated polysaccharide [253]; therapeutic application of marine fucanomics and galactanomics in drug development [254]; marine pharmacology of cosmopolitan brown alga Cystoseira genus secondary metabolites [255]; pharmacological activity of sulfated polysaccharides from marine algae [256]; biological activities and functions of halogenated organic molecules of red algae Rhodomelaceae [257]; pharmacological potential of marine cyanobacterial secondary metabolites [258]; pharmaceutical agents from filamentous marine cyanobacteria [259]; chemistry and preclinical pharmacology of sponge glycosides [260]; sea cucumbers as drug candidates [261]; bioactives from microalgal dinoflagellates [262]; the global marine pharmaceutical pipeline in 2017: U.S. Food and Drug Administration-approved compounds and those in Phase I, II and III of clinical development http://marinepharmacology.midwestern.edu/clinPipeline.htm; (b) antimicrobial marine pharmacology: antimicrobial non-ribosomal peptides from abundant α-, γand δ-marine Proteobacteria classes [263]; marine bacteria as potential sources for compounds to overcome methicillin-resistant Staphylococcus aureus [264]; marine coral alkaloids and antibacterial activities [265]; marine fish and invertebrates as sources of antimicrobial peptides [266]; marine actinomycetes as an emerging resource for drug development [267]; chemistry and biological activity of marine Bacillus sp. secondary metabolites [268]; marine compounds with therapeutic potential in Gram-negative sepsis [269]; antimicrobial properties of tunichromes [270]; drug discovery from marine microbes [271]; (c) antiviral marine pharmacology: marine natural products with anti-HIV activities in the last decade [272]; fucoidans as potential inhibitors of human immunodeficiency virus type 1 (HIV-1) [273]; discovery of potent broad spectrum antivirals derived from marine Actinobacteria [274]; algal lectins for prevention of HIV transmission [275]; (d) antiprotozoal, antimalarial, antituberculosis and antifungal marine pharmacology: trypanocidal activity of marine natural products [276]; natural sesquiterpenes as lead compounds for the design of trypanocidal drugs [277]; antifungal compounds from marine fungi [278]; (e) immuno-and anti-inflammatory marine pharmacology: immunoregulatory properties of bryostatin [279]; bioactive marine peptides as potential anti-inflammatory therapeutics [280]; anti-inflammatory soft coral marine natural products from Taiwan [281]; marine natural products with potential for the therapeutics of inflammatory diseases [282]; antioxidant properties of crude extracts and compounds from brown marine algae [283]; (f) cardiovascular and antidiabetic marine pharmacology: oxidation of marine omega-3 supplements and human health [284]; marine peptides for prevention of metabolic syndrome [285]; antidiabetic effect of marine brown algae-derived phlorotannins [286]; marine bioactive peptides as potential antioxidants [287]; cardioprotective peptides from marine sources [288]; antioxidant and antidiabetic pharmacology of fucoxantin [289]; marine-derived bioactive peptides as new anticoagulants [290]; (g) nervous system marine pharmacology: marine neurotoxins, structures, molecular targets and pharmacology [291]; the phosphatase inhibitor okadaic acid as a tool to identify phosphoepitopes relevant to neurodegeneration [292]; marine toxins and drug discovery targeting nicotinic acetylcholine receptors [293]; marine-derived marine secondary metabolites and neuroprotection [294]; cone snail polyketides active in neurological assays [295]; and (h) miscellaneous molecular targets and uses: small-molecule inhibitors of clinically validated protein and lipid kinases of marine origin [296]; natural products as kinase inhibitors [297]; marine natural products with protein tyrosine phosphatase 1B activity [298]; current development strategies for marine conotoxins and their mimetics as therapeutic leads [299]; therapeutic potential of novel conotoxins reported in 2007-2011 [300]; computational studies of marine toxins targeting ion channels [301]; marine invertebrates as sources of skeletal proteins for bone regeneration [302]; marine algal compounds in cosmeceuticals [303]; and marine sponge steroids as nuclear receptor ligands [304].

Conclusions
The purpose of the current marine pharmacology review was to continue the marine preclinical pharmacology pipeline review series that was initiated in 1998 [1][2][3][4][5][6][7][8]  pharmaceutical pipeline continued to provide novel pharmacological lead compounds that enriched the marine clinical pharmaceutical pipeline. Currently, the clinical pharmaceutical pipeline consists of 6 pharmaceuticals approved by the U.S. Food and Drug Administration, and 29 compounds in Phase I, II and III of clinical pharmaceutical development, as shown at a dedicated website: http://marinepharmacology.midwestern.edu/clinPipeline.htm.