Probing the Antiplasmodial Properties of Plakortinic Acids C and D: An Uncommon Pair of Marine Peroxide-Polyketides Isolated from a Two-Sponge Association of Plakortis symbiotica and Xetospongia deweerdtae Collected near Puerto Rico.

Plakortinic acids C (1) and D (2), an unseparable pair of endoperoxide polyketides isolated and purified from the symbiotic association of Caribbean Sea sponges Plakortis symbiotica-Xestospongia deweerdtae, underwent in vitro evaluation for antiplasmodial activity against the malaria parasite Plasmodium berghei using a drug luminescence assay. Initial screening at 10 µM revealed 50% in vitro parasite growth inhibition. The title compounds displayed antiplasmodial activity with an EC50 of 5.3 µM toward P. berghei parasites. The lytic activity against erythrocytes was assessed through an erythrocyte cell lysis assay, which showed non-lytic activity at lower concentrations ranging from 1.95 to 3.91 µM. The antiplasmodial activity and the absence of hemolytic activity support the potential of plakortinic acids C (1) and D (2) as promising lead compounds. Moreover, drug-likeness (ADMET) properties assessed through the pkCSM server predicted high intestinal absorption, hepatic metabolism, and volume of distribution, indicating favorable pharmacokinetic profiles for oral administration. These findings suggest the potential suitability of these metabolites for further investigations of antiplasmodial activity in multiple parasitic stages in the mosquito and Plasmodium falciparum. Notably, this study represents the first report of a marine natural product exhibiting the unique 7,8-dioxatricyclo[4.2.2.02,5]dec-9-ene motif being evaluated against malaria.

Exploring the Sponge Consortium Plakortis symbiotica-Xestospongia deweerdtae as a Potential Source of Antimicrobial Compounds and Probing the Pharmacophore for Antituberculosis Activity of Smenothiazole A by Diverted Total Synthesis.

Fractionation of the bioactive CHCl3-MeOH (1:1) extracts obtained from two collections of the sponge consortium Plakortis symbiotica-Xestospongia deweerdtae from Puerto Rico provided two new plakinidone analogues, designated as plakinidone B (2) and plakinidone C (3), as well as the known plakinidone (1), plakortolide F (4), and smenothiazole A (5). The structures of 1-5 were characterized on the basis of 1D and 2D NMR spectroscopic, IR, UV, and HRMS analysis. The absolute configurations of plakinidones 2 and 3 were established through chemical correlation methods, VCD/ECD experiments, and spectroscopic data comparisons. When assayed in vitro against Mycobacterium tuberculosis H37Rv, none of the plakinidones 1-3 displayed significant activity, whereas smenothiazole A (5) was the most active compound, exhibiting an MIC value of 4.1 µg/mL. Synthesis and subsequent biological screening of 8, a dechlorinated version of smenothiazole A, revealed that the chlorine atom in 5 is indispensable for anti-TB activity.

Plakortinic Acids A and B: Cytotoxic Cycloperoxides with a Bicyclo[4.2.0]octene Unit from Sponges of the Genera Plakortis and Xestospongia.

Plakortinic acids A (2) and B (3), two polyketide endoperoxides with a bicyclo[4.2.0]octene unit, were isolated as minor constituents from the sponge-sponge symbiotic association Plakortis halichondrioides-Xestospongia deweerdtae, along with known epiplakinic acid F (1). The structures of the mixture of two inseparable compounds were determined by spectroscopic analysis. Screening for cytotoxic activity of the mixture against two human tumor cell lines revealed that these compounds are very active at sub-micromolar concentration.

Kallolide A acetate pyrazoline.

IN THE CRYSTAL STRUCTURE OF KALLOLIDE A ACETATE PYRAZOLINE [SYSTEMATIC NAME: 7-methyl-16-oxo-4,10-bis-(prop-1-en-2-yl)-17,18-dioxa-14,15-diaza-tetra-cyclo-[9.4.2.1(6,9).0(1,12)]octa-deca-6,8,14-trien-5-yl acetate], C(23)H(28)N(2)O(5), there is a 12-member-ed carbon macrocyclic structure. In addition, there is a tris-ubstituted furan ring, an approximately planar γ-lactone ring [maximum deviation of 0.057 (3) Å] and a pyraz-oline ring, the latter in an envelope conformation. The pyrazoline and the γ-lactone rings are fused in a cis configuration. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions, forming a two-dimensional network parallel to (001). An intra-molecular C-H⋯O hydrogen bond is also present.

3ß-Chloro-N-methoxy-N-methyl-cholest-5-ene-24-carboxamide.

The title compound, C26H42ClNO2, is a 3ß-chloro steroid with a Weinreb amide at the C-24 position. The two cyclo-hexane and the cyclo-hexene rings adopt chair and boat conformations, respectively. The cyclo-pentane ring has an envelope conformation.

Bioactive Cycloperoxides Isolated from the Puerto Rican Sponge Plakortis halichondrioides.

Two new five-membered-ring polyketide endoperoxides, epiplakinic acid F methyl ester (1) and epiplakinidioic acid (3), and a peroxide-lactone, plakortolide J (2), were isolated from the Puerto Rican sponge Plakortis halichondrioides, along with two previously reported cyclic peroxides, 4 and 5. The structures of the new metabolites were determined by spectroscopic and chemical analyses. The absolute stereostructures of 1, 2, and 5 were determined by degradation reactions followed by application of Kishi's method for the assignment of absolute configuration of alcohols. Biological screening of cycloperoxides 1-5 and semisynthetic analogues 7-12 for cytotoxic activity against various human tumor cell lines revealed that compounds 3, 4, and 11 are very active. Upon assaying for antimalarial and antitubercular activity, some of the compounds tested showed strong activity against the pathogenic microbes Plasmodium falciparum and Mycobacterium tuberculosis.

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.

Synthesis and in vitro biological evaluation of ring B abeo-sterols as novel inhibitors of Mycobacterium tuberculosis.

A series of 3beta-hydroxy steroid analogues possessing a contracted cyclopentane B-ring were prepared based on the initial activity screening of a recently reported naturally occurring marine 5(6-->7)abeo-sterol against Mycobacterium tuberculosis. All of the novel ring B abeo-sterols synthesized showed good inhibitory activity, whereas none of the starting steroids based on the common 3beta-hydroxy-Delta(5)-cholestane nucleus, proved to be active. Therefore, the 5(6-->7)abeo-sterol nucleus present in compounds 3, 5, 7, 9, and 11 represents a novel scaffold for the development of new antitubercular agents.

Bioactive compounds from the gorgonian Briareum polyanthes. Correction of the structures of four asbestinane-type diterpenes.

Our extended chemical investigation of the crude MeOH-CHCl3 extract of the gorgonian octocoral Briareum polyanthes from Puerto Rico has led to the isolation of three eunicellin-type diterpenoids, 1-3, along with five (4-8) diterpenoids of the asbestinane-type and one (9) of the briarane-type of polycyclized diterpenes. The structures and relative stereochemistry of the new compounds 1-9 were established on the basis of spectroscopic analysis (1H NMR, 13C NMR, HMQC, HMBC, NOESY). The biological activity of these compounds against pathogenic microbes responsible for various human infectious diseases was investigated. In addition, new data recorded for four known asbestinin diterpenes also isolated during this investigation and further analysis through chemical reactions have prompted us to revise our original structural assignments for these compounds.

Caucanolides A-F, unusual antiplasmodial constituents from a colombian collection of the gorgonian coral Pseudopterogorgia bipinnata.

Six new diterpenoids, caucanolides A-F (1-6), have been isolated from extracts of the gorgonian octocoral Pseudopterogorgia bipinnata collected near the Colombian Southwestern Caribbean Sea. The structures of 1-6 were elucidated by comprehensive analysis of spectroscopic data. The caucanolides showed in vitro antiplasmodial activity against the malaria parasite, Plasmodium falciparum. In addition to possessing structures based on novel carbon skeletons, one of these metabolites, caucanolide B (2), constitutes the only example from nature of a secondary metabolite possessing the N(1),N(1)-dimethyl-N(2)-acylformamidine functionality.

Tobacco cembranoids protect the function of acute hippocampal slices against NMDA by a mechanism mediated by alpha4beta2 nicotinic receptors.

Nicotine has been reported to be neuroprotective in experimental and epidemiological studies. In addition to nicotine, tobacco and cigarette smoke contain cembranoids, which are antagonists of neuronal nicotinic receptors (nAChR). Exposure of hippocampal slices to N-methyl-D-aspartate (NMDA) decreases the population spikes (PS). This parameter has been used as a measure of excitotoxicity. Surprisingly, both nicotine and tobacco cembranoids protected against NMDA and this neuroprotection was not blocked by methyllycaconitine (MLA), an antagonist of alpha7 nAChR. On the contrary, MLA had a neuroprotective effect of its own. We examined the effect of the tobacco cembranoid (1S,2E,4R,6R,7E,11E)-cembra-2,7,11-triene-4,6-diol (4R) on the neuroprotection against NMDA. DHbetaE, a selective antagonist of alpha4beta2 nAChR, inhibited the neuroprotection by nicotine, 4R, and MLA, suggesting the involvement of alpha4beta2 nAChRs in the neuroprotection. The cell-signaling pathways underlying the neuroprotection by 4R and by nicotine are different. The activity of phosphatidylinositol-3 kinase (PI3K) was required in both cases; however, 4R required the activity of L-type calcium channels and CAM kinase, whereas nicotine required the extracellular signal regulated kinase-1,2 (ERK) and protein kinase C (PKC). In addition, 4R did not enhance total phospho-ERK-1/2 but increased the amount of total Akt/PKB phosphorylated on the activation site and of glycogen synthase kinase 3-beta phosphorylated on the inhibitory site. Total levels of phosphoenzymes are presented instead of the ratio of phospho- over total enzyme because in preliminary experiments total ERK-1/2 levels were slightly increased by 4R. In conclusion, these findings demonstrate that there are two different nicotinic neuroprotective mechanisms mediated by alpha4beta2.

Sesquiterpenoid metabolites with antiplasmodial activity from a Caribbean gorgonian coral, Eunicea sp.

A chemical investigation of the Caribbean gorgonian octocoral Eunicea sp. collected along the northwest coast of Puerto Rico has afforded seven new secondary metabolites, 1-7, belonging to several types of sesquiterpenes, including elemane, eudesmane, and germacrane types, along with the known steroidal glycoside 8. Some of the new metabolites, 4-7, carry an unusual ester side chain at the C-6 position. The structures of all compounds, including their relative stereochemistry, were determined by combined spectroscopic methods. The present compounds exhibited a significant inhibitory effect upon the growth of the malarial parasite Plasmodium falciparum.

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.

Differential inhibition of nicotine- and acetylcholine-evoked currents through alpha4beta2 neuronal nicotinic receptors by tobacco cembranoids in Xenopus oocytes.

In tobacco, there are two types of compounds that interact with neuronal nicotinic acetylcholine receptors (nnAChRs) in the brain. The first is the addictive component of tobacco and an agonist of these receptors, nicotine. The second are cyclic diterpenoids called cembranoids that non-competitively inhibit many types of nnAChRs. Nictotinic receptors composed of alpha4beta2 subunits are the predominant type of nicotinic receptors in the brain. These alpha4beta2 receptors are up-regulated upon chronic exposure to nicotine and have been implicated in nicotine addiction. The present study was designed to determine whether the inhibitory effects of two cembranoids from tobacco [(1S, 2E, 4R, 6R, 7E, 11E)-2,7,11-cembratriene-4,6-diol (4R) and its diastereoisomer (1S, 2E, 4S, 6R, 7E, 11E)-2,7,11-cembratriene-4,6-diol (4S)] were comparable on acetylcholine (ACh) and nicotine-evoked currents through alpha4beta2 nnAChRs. alpha4beta2 nnAChRs from rat brain were expressed in Xenopus oocytes and studied using the two-electrode voltage-clamp technique. The dose-response curves for acetylcholine and nicotine were hyperbolic and bell-shaped, respectively. Although there was no difference in the potency between cembranoids 4R and 4S, both of these cembranoids more potently inhibited nicotine-induced currents than acetylcholine-induced currents. Furthermore, both cembranoids were more potent inhibitors of this receptor when they were preincubated for 1 min prior to application of agonist. The finding that cembranoids preferentially inhibit nicotine-induced currents over those elicited by the natural neurotransmitter acetylcholine may have important implications when developing strategies to prevent nicotine addiction and tobacco use.

Homopseudopteroxazole, a new antimycobacterial diterpene alkaloid from Pseudopterogorgia elisabethae.

In the course of our study to find novel antimycobacterial secondary metabolites from Caribbean gorgonian octocorals, we have isolated a new diterpene alkaloid, namely, homopseudopteroxazole (1), as a minor constituent of the hexane extract from the sea plume Pseudopterogorgia elisabethae. Its structure was deduced by interpretation of combined spectroscopic data, including extensive 1D and 2D NMR measurements, and NMR spectral comparisons with known amphilectane models. Biological screening studies indicate that homopseudopteroxazole (1) is a strong growth inhibitor of Mycobacterium tuberculosis H(37)Rv.

Plakortides M and N, bioactive polyketide endoperoxides from the Caribbean marine sponge Plakortis halichondrioides.

From a small specimen of the marine sponge Plakortis halichondrioides collected in Puerto Rico we have isolated the known unsaturated ester methyl (2Z,6R,8R,9E)-3,6-epoxy-4,6,8-triethyl-2,4,9-dodecatrienoate (1) along with the known cyclic peroxide plakortide F (2). In addition, the structures of two new polyketide endoperoxides, namely, plakortide O (3) and plakortide P (4), were fully characterized by spectroscopic and chemical methods. The absolute stereochemistry of plakortide O methyl ester (3a) has been determined by analysis of the (R)- and (S)-MTPA esters of the acyclic derivative 5 obtained by hydrogenolysis. Plakortide O (3) and plakortide P (4) exhibited potent cytotoxicity in the NCI human cancer screening program, whereas plakortide O methyl ester, 3a, displayed strong antimalarial activity against Plasmodium falciparum [corrected].

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.

New terpenoid constituents from Eunicea pinta.

The secondary metabolite composition of the gorgonian octocoral Eunicea pinta from San Andrés Island, Colombia, is described for the first time. This investigation has resulted in the isolation of eight new gamma-cembranolide-type diterpenes, namely, compounds 3-10, and a new saponin, 13, possessing a pregnene-derived aglycon. In addition, two previously known alpha-methylene-gamma-lactone cembranolides, euniolide (1) and succinolide (2), were also isolated. Their structures were determined on the basis of the results of spectroscopic analysis, X-ray diffraction analysis, and chemical conversions. The discovery of cembranolides 3-10 has prompted us to conclude that the structures proposed earlier for several uprolide-type cembranolides need revision and that a minor stereochemical correction is also in order for succinolide. Cytotoxicity of compounds 3, 4, and 13 toward various cancer cell lines and results of an antimycobacterial screening for 2, 4, and 13 also are described.

Phospholipid fatty acid composition of Gorgonia mariae and Gorgonia ventalina.

The phospholipid fatty acid composition of the Caribbean gorgonians Gorgonia mariae (Bayer) and Gorgonia ventalina (Linnaeus) is described for the first time. The main phospholipids identified were phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine. The main fatty acids were 14:0, 16:0, 18:3(n-6), 18:4(n-3), 18:2(n-6), 20:4(n-6), 22:6(n-3), and 24:5(n-6). In both G. mariae and G. ventalina n-6 polyunsaturated fatty acids predominated over the n-3 family. In addition, the 7-methyl-6(E)-hexadecenoic acid was identified in both gorgonians. The occurrence of tetracosapolyenoic fatty acids in the genus Gorgonia is also reported for the first time.

The Calyculaglycosides: Dilophol-Type Diterpene Glycosides Exhibiting Antiinflammatory Activity from the Caribbean Gorgonian Eunicea sp.(1)(,)(2).

Three new diterpenoid hexose-glycosides, calyculaglycosides A-C (1-3) were isolated from the Caribbean gorgonian Eunicea sp. Calyculaglycosides A-C are rare diterpene glycosides possessing dilophol (4) aglycones related in biosynthetic origin to the elemene-type glycoside class of potent antiinflammatory agents known as fuscosides. The structures of the new compounds, which were assigned on the basis of spectral studies, were further corroborated by molecular modeling studies. Calyculaglycoside B (2) is an effective topical antiinflammatory agent stronger in potency than the industrial standard indomethacin. Calyculaglycoside B inhibits the synthesis of both prostaglandin PGE(2) and leukotriene LTB(4), suggesting it is a nonselective inhibitor of the 5-lipoxygenase and cyclooxygenase pathways. At concentrations of 10(-4)-10(-5)M, calyculaglycoside B produced LC(50)-level differential responses against a majority of the NCI ovarian cancer lines and several of the renal, prostate, and colon tumor lines.