Cyclotheonellazoles D-I, Potent Elastase Inhibitory Thiazole-Containing Cyclic Peptides from Theonella sp. (2131)

Six new thiazole-containing cyclic peptides, the cyclotheonellazoles D-I (1-6), were isolated from the Australian marine sponge Theonella sp. (2131) with their structures assigned by comprehensive 1D and 2D NMR spectroscopic and MS spectrometric analyses, Marfey's derivatization studies, and comparison with time-dependent density functional theory (TDDFT) calculated ECD data. The Type 2 azole-homologated peptides herein comprise up to five nonproteinogenic amino acids, including the protease transition state mimic α-keto-β-amino acid residue 3-amino-4-methyl-2-oxohexanoic acid (Amoha), while 1-3 also contain a terminal hydantoin residue not previously found in cyclotheonellazoles. The keramamides A (7) and L (8) were reisolated affording expanded exploration of their biological activities. The peptides were examined for protease inhibitory activities against two mammalian serine proteases (elastase and chymotrypsin) and SARS-CoV-2 3-chymotrypsin-like protease (3CLpro), a validated antiviral therapeutic target for COVID-19. Peptides 1-6 and keramamide A (7) displayed potent nanomolar inhibition of elastase (IC50 16.0 to 61.8 nM), while 7 also contained modest inhibition of chymotrypsin and SARS-CoV-2 3CLpro (IC50 0.73 and 1.1 μM, respectively). The cyclotheonellazoles D-E (1-3) do not affect the viability of human breast, ovarian, and colon cancer cells (>100 μM), with the cytotoxicity previously reported for keramamide L (8) not replicated (inactive >20 μM).

Two Onnamide Analogs from the Marine Sponge Theonella conica: Evaluation of Geometric Effects in the Polyene Systems on Biological Activity

Two previously unreported onnamide analogs, 2Z- and 6Z-onnamides A (1 and 2), were isolated from the marine sponge Theonella conica collected at Amami-Oshima Is., Kagoshima Prefecture, Japan. Structures of compounds 1 and 2 were elucidated by spectral analysis. Structure–activity relationships (SARs) for effects on histone modifications and cytotoxicity against HeLa and P388 cells were characterized. The geometry in the polyene systems of onnamides affected the histone modification levels and cytotoxicity.

New Theonellapeptolides from Indonesian Marine Sponge Theonella swinhoei as Anti-austerity Agents

We reported three new members of the theonellapeptolide family from theonellapeptolide II series, namely theonellapeptolides IIb (1), IIa (2), IIc (3), and three known members—IId (4), IIe (5), and Id (6)—from Kodingarengan marine sponge Theonella swinhoei collected in Makassar, Indonesia. The structures of tridecadepsipeptides 1–3, including the absolute configurations of their amino acids, were determined by the integrated NMR and tandem MS analyses followed by Marfey’s analysis. To the best of our knowledge, 1 and 2 are the first theonellapeptolide-type compounds to have a valine residue with _D configuration at residue position 6. The isolated theonellapeptolide-type compounds 1–6 showed selective cytotoxic activity against human pancreatic MIA PaCa-2 cancer cells in a nutrient-deprived medium. Among them, the most potent preferential cytotoxicity was observed in new theonellapeptolide IIc (3) and known IId (4), IIe (5), and Id (6).

Swinhopeptolides A and B: Cyclic Depsipeptides from the Sponge Theonella swinhoei That Inhibit Ras/Raf Interaction

Two new cyclic depsipeptides named swinhopeptolides A (1) and B (2) have been isolated from the marine sponge Theonella swinhoei cf. verrucosa, collected from Papua New Guinea. They each contain 11 diverse amino acid residues and 13-carbon polyketide moieties attached at the N-terminus. Compounds 1 and 2 each exist as two conformers in DMSO-d₆ due to cis/trans isomerism of the proline residue, and their structures were successfully assigned by extensive NMR analyses complemented by chemical degradation and derivatization studies. Swinhopeptolide B (2) contains a previously undescribed 2,6,8-trimethyldeca-(2E,4E,6E)-trienoic acid moiety N-linked to a terminal serine residue. Swinhopeptolides A (1) and B (2) showed significant inhibition of the Ras/Raf signaling pathway with IC₅₀ values of 5.8 and 8.5 μM, respectively.

Colony-wise Analysis of a Theonella swinhoei Marine Sponge with a Yellow Interior Permitted the Isolation of Theonellamide I

There are several examples of marine organisms whose metabolic profiles differ among conspecifics inhabiting the same region. We have analyzed the metabolic profile of each colony of a Theonella swinhoei marine sponge with a yellow interior and noticed the patchy distribution of one metabolite. This compound was isolated and its structure was studied by a combination of spectrometric analyses and chemical degradation, showing it to be a congener in the theonellamide class of bicyclic peptides. Theonellamides had previously been isolated by us only from T. swinhoei with a white interior and not from those with a yellow interior.

Swinhoeisterols from the South China Sea Sponge Theonella swinhoei

Swinhoeisterols C-F (1-4), four new steroids having a rearranged 6/6/5/7 ring system, were isolated from the Xisha sponge Theonella swinhoei, together with the known analogue swinhoeisterol A (5). Their structures were determined based on spectroscopic analysis, TDDFT-ECD and optical rotation calculations, and biogenetic correlations. In an in vitro assay, compound 1 showed an inhibitory effect on (h)p300 with an IC₅₀ value of 8.8 μM, whereas compounds 2-4 were not active.

Cyclotheonellazoles A-C, Potent Protease Inhibitors from the Marine Sponge Theonella aff. swinhoei

The extract of a sample of the sponge Theonella aff. swinhoei collected in Madagascar exhibited promising in vitro antiplasmodial activity. The antiplasmodial activity was ascribed in part to the known metabolite swinholide A. Further investigation of the extract afforded three unusual cyclic peptides, cyclotheonellazoles A-C (1-3), which contain six nonproteinogenic amino acids out of the eight acid units that compose these natural products. Among these acids the most novel were 4-propenoyl-2-tyrosylthiazole and 3-amino-4-methyl-2-oxohexanoic acid. The structure of the compounds was elucidated by interpretation of the 1D and 2D NMR data, HRESIMS, and advanced Merfay's techniques. The new compounds were found to be nanomolar inhibitors of chymotrypsin and sub-nanomolar inhibitors of elastase, but did not present antiplasmodial activity.

Jamaicensamide A, a Peptide Containing β-Amino-α-keto and Thiazole-Homologated η-Amino Acid Residues from the Sponge Plakina jamaicensis

A new cyclic peptide, jamaicensamide A, composed of six amino acids, including a thiazole-homologated amino acid, was isolated from the Bahamian sponge Plakina jamaicensis, along with known compounds bitungolide A and franklinolide A. The structure of the title peptide was solved by integrated analysis of MS, 1D and 2D NMR data, oxidation-hydrolyses to α-amino acids, and their stereodetermination by Marfey's method. The close structural resemblance of Western Atlantic-derived jamaicensamide A to known Western Pacific-derived peptides of lithistid sponges in the genus Theonella and Discodermia suggests a common origin: the symbiotic bacterium Entotheonella sp., a so-called "talented producer" responsible for biosynthesis of most Theonella-associated peptides. Similar natural products from sponges of disparate genera evince the likelihood that these invertebrates harbor the same or a very similar symbiont.

Yakushinamides, Polyoxygenated Fatty Acid Amides That Inhibit HDACs and SIRTs, from the Marine Sponge Theonella swinhoei

Yakushinamides A (1) and B (2), prolyl amides of polyoxygenated fatty acids, have been isolated from the marine sponge Theonella swinhoei as inhibitors of HDACs and SIRTs. Their planar structures were determined by interpretation of the NMR data of the intact molecules and tandem FABMS data of the methanolysis products. For the assignment of the relative configurations of the three contiguous oxymethine carbons in 1 and 2, Kishi's universal NMR database was applied to the methanolysis products. During the assignments of relative configurations of the isolated 1-hydroxy-3-methyl moiety in 1 and the isolated 1-hydroxy-2-methyl moiety in 2, we found diagnostic NMR features to distinguish each pair of diastereomers. The absolute configurations of 1 and 2 were determined by a combination of the modified Mosher's method and Marfey's method. Although the modified Mosher's method was successfully applied to the methanolysis product of 1, this method gave an ambiguous result at C-20 when applied to the methanolysis product of 2, even after oxidative cleavage of the C-14 and C-15 bond.

Mirabolides A and B; New Cytotoxic Glycerides from the Red Sea Sponge Theonella mirabilis

As a part of our continuing work to find out bioactive lead molecules from marine invertebrates, the CHCl₃ fraction of the organic extract of the Red Sea sponge Theonella mirabilis showed cytotoxic activity in our primary screen. Bioassay-guided purification of the active fractions of the sponge’s extract resulted in the isolation of two new glycerides, mirabolides A and B (1 and 2), together with the reported 4-methylene sterols, conicasterol (3) and swinhosterol B (4). The structures of the compounds were assigned by interpretation of their 1D (¹H, ¹³C), 2D (COSY, HSQC, HMBC, ROESY) NMR spectral data and high-resolution mass determinations. Compounds 1–4 displayed marked cytotoxic activity against human breast adenocarcinoma cell line (MCF-7) with IC₅₀ values of 16.4, 5.18, 6.23 and 3.0 μg/mL, respectively, compared to 5.4 μg/mL observed by doxorubicin as reference drug.

Nazumazoles D-F, Cyclic Pentapeptides That Inhibit Chymotrypsin, from the Marine Sponge Theonella swinhoei

Nazumazoles D-F (1-3) were isolated from the marine sponge Theonella swinhoei. The compounds gave extremely broad peaks by reversed-phase HPLC using an ODS column. HPLC using a gel permeation column was instrumental for the separation of the three compounds. Their planar structures were determined by interpretation of NMR data to be cyclic pentapeptides. Nazumazoles D-F contained one residue each of α-keto-l-norvaline (l-Knv) {or α-keto-d-leucine (l-Kle)}, l-alanyloxazole (l-Aox), d-Abu (or d-Ser), N-α-CHO-β-l-Dpr, and cis-4-methyl-l-proline. The absolute configuration of each amino acid residue was determined by Marfey's method in combination with conversion of the α-keto-β-amino acid to the α-amino acid by oxidation. Nazumazoles D-F are not cytotoxic against P388 cells at 50 μM, but inhibit chymotrypsin.

Increasing the Richness of Culturable Arsenic-Tolerant Bacteria from Theonella swinhoei by Addition of Sponge Skeleton to the Growth Medium

Theonella swinhoei is an arsenic hyper-accumulator sponge, harboring a multitude of associated bacteria. These bacteria reside in the mesohyl, the dense extracellular matrix of the sponge. Previous elemental analysis of separated cell fractions from the sponge had determined that arsenic is localized to the associated bacteria. Subsequently, sponge-associated arsenic-tolerant bacteria were isolated here and grouped into 15 operational taxonomic units (OTUs, 97% similarity). Both culture-dependent and culture-independent work had revealed that T. swinhoei harbors a highly diverse bacterial community. It was thus hypothesized the acclimation of bacteria in the presence of a sponge skeleton, better mimicking its natural environment, would increase the yield of isolation of sponge-associated bacteria. Using seven modularly designed media, 380 bacteria isolates were grown and grouped into 22 OTUs. Inclusion of sponge skeleton in the growth medium promoted bacterial growth in all seven media, accounting for 20 of the 22 identified OTUs (the other two in a medium without skeleton). Diversity and richness indices were calculated for each treatment or combination of treatments with shared growth parameters. Integrating data inherent in the modularly designed media with the ecological indices led to the formation of new hypotheses regarding the aeration conditions and expected arsenic form in situ. Both aerobic and anoxic conditions are expected to occur in the sponge (temporally and/or spatially). Arsenate is expected to be the dominant (or even the only) arsenic form in the sponge.

Amitorines A and B, Nitrogenous Diterpene Metabolites of Theonella swinhoei: Isolation, Structure Elucidation, and Asymmetric Synthesis

Two new nitrogenous prenylbisabolanes never before found in Lithistid sponges have been isolated from Theonella swinhoei. These new diterpenes, named amitorine A (1) and amitorine B (2), containing a prenylbisabolane skeleton have been characterized by spectroscopic analyses, and the relative and absolute configurations of 1 and 2 were determined by asymmetric synthesis of both diastereomers via the common bicyclic lactone 6 intermediate.

Theonellamide G, a potent antifungal and cytotoxic bicyclic glycopeptide from the Red Sea marine sponge Theonella swinhoei

In our search for bioactive metabolites from marine organisms, we have investigated the polar fraction of the organic extract of the Red Sea sponge Theonella swinhoei. Successive chromatographic separations and final HPLC purification of the potent antifungal fraction afforded a new bicyclic glycopeptide, theonellamide G (1). The structure of the peptide was determined using extensive 1D and 2D NMR and high-resolution mass spectral determinations. The absolute configuration of theonellamide G was determined by chemical degradation and 2D NMR spectroscopy. Theonellamide G showed potent antifungal activity towards wild and amphotericin B-resistant strains of Candida albicans with IC₅₀ of 4.49 and 2.0 μM, respectively. Additionally, it displayed cytotoxic activity against the human colon adenocarcinoma cell line (HCT-16) with IC₅₀ of 6.0 μM. These findings provide further insight into the chemical diversity and biological activities of this class of compounds.

Structural insights into Estrogen Related Receptor-β modulation: 4-methylenesterols from Theonella swinhoei sponge as the first example of marine natural antagonists

In this paper, we report the first evidence of 4-methylenesterols, isolated from the marine sponge Theonella swinhoei, as antagonists of Estrogen Related Receptors (ERRs). The interactions of 4-methylenesterols with ERRs were investigated through a multi-parametric approach involving biological assays and molecular modelling. Here the first homology model of active and inactive conformations of the Estrogen Related Receptor β (ERRβ) is also reported, benchmarked with the well known agonists gsk4716 and genistein, and the antagonists 4-hydroxytamoxifen and diethylstilbestrol. Our proposed model could contribute to the clarification of small molecule interaction mode in the ERRβ and, notably, to the rational design of new potential and selective modulators of this emerging therapeutic target.

4-Methylenesterols from a sponge Theonella swinhoei

Three new 4-methylenesterols, theonellasterol K (1), acetyltheonellasterol (2) and acetyldehydroconicasterol (3), along with two known sterols, theonellasterol (4) and theonellasterone (5), were isolated from the sponge Theonella swinhoei. The structures of these compounds were elucidated on the basis of their spectroscopic data and comparison of the NMR data with those of known analogues. Compound 1 exhibited significant cytotoxic activity against HCT-116, K562 and Molt 4 cancer cell lines.

4-Methylenesterols from Theonella swinhoei sponge are natural pregnane-X-receptor agonists and farnesoid-X-receptor antagonists that modulate innate immunity

We report the isolation and the structural elucidation of a family of polyhydroxylated steroids from the marine sponge Theonella swinhoei. Decodification of interactions of these family with nuclear receptors shows that these steroids are potent agonists of human pregnane-X-receptor (PXR) and antagonists of human farnesoid-X-receptor (FXR) with the putative binding mode to nuclear receptors (NRs) obtained through docking experiments. By using monocytes isolated from transgenic mice harboring hPXR, we demonstrated that swinhosterol B counter-regulates induction of pro-inflammatory cytokines in a PXR-dependent manner. Exposure of CD4(+) T cells to swinhosterol B upregulates the expression of IL-10 causing a shift toward a T cells regulatory phenotype in a PXR dependent manner. These results pave the way to development of a dual PXR agonist/FXR antagonist with a robust immunomodulatory activity and endowed with the ability to modulate the expression of bile acid-regulated genes in the liver.

Calyxamides A and B, cytotoxic cyclic peptides from the marine sponge Discodermia calyx

Cyclic peptides containing 5-hydroxytryptophan and thiazole moieties were isolated from the marine sponge Discodermia calyx collected near Shikine-jima Island, Japan. The structures of calyxamides A (1) and B (2), including the absolute configurations of all amino acids, were elucidated by spectroscopic analyses and degradation experiments. The structures are similar to keramamides F and G, previously isolated from Theonella sp. The analysis of the 16S rDNA sequences obtained from the metagenomic DNA of D. calyx revealed the presence of Candidatus Entotheonella sp., an unculturable δ-proteobacterium inhabiting the Theonella genus and implicated in the biosynthesis of bioactive peptides.

A cytotoxic peptide from a marine sponge exhibits ion channel activity through vectorial-insertion into the membrane

A cytotoxic peptide, polytheonamide B (pTB), from marine sponge was examined for cytotoxic spectrum and specific activity to mammalian cells was demonstrated. pTB is composed of alternative D- and L-amino acid residues throughout the 48-mer peptide. This suggests the formation of a β-helix similar to gramicidin channels. Planar bilayer experiments revealed that pTB forms monovalent cation-selective channels, being compatible with the inner pore diameter of ∼4Å for a β-helical structure. pTB penetrated vectorially into the membrane, formed a channel by means of a single molecule, and remained in the membrane. These functional properties may account for specific cytotoxic activity.

Mutremdamide A and koshikamides C-H, peptide inhibitors of HIV-1 entry from different Theonella species

A new sulfated cyclic depsipeptide, termed mutremdamide A, and six new highly N-methylated peptides, termed koshikamides C-H, were isolated from different deep-water specimens of Theonella swinhoei and Theonella cupola. Their structures were determined using extensive 2D NMR, ESI, or CDESI and QTOF-MS/MS experiments and absolute configurations established by quantum mechanical calculations, advanced Marfey's method, and chiral HPLC. Mutremdamide A displays a rare 2-amino-3-(2-hydroxyphenyl)propanoic acid and a new N(delta)-carbamoyl-beta-sulfated asparagine. Koshikamides C-E are linear undecapeptides, and koshikamides F-H are 17-residue depsipeptides containing a 10-residue macrolactone. Koshikamides F and G differ from B and H in part by the presence of the conjugated unit 2-(3-amino-5-oxopyrrolidin-2-ylidene)propanoic acid. Cyclic koshikamides F and H inhibited HIV-1 entry at low micromolar concentrations while their linear counterparts were inactive. The Theonella collections studied here are distinguished by co-occurrence of mutremdamide A, koshikamides, and theonellamides, the combination of which appears to define a new Theonella chemotype that can be found in deeper waters.

Paltolides A--C, anabaenopeptin-type peptides from the palau sponge Theonella swinhoei

Three new anabaenopeptin-like peptides, named paltolides A-C, were isolated from a deep-water specimen of the marine sponge Theonella swinhoei from Palau. Paltolides belong to a rare subgroup of sponge-derived anabaenopeptins that have in common a C-terminal tryptophan residue linked to the epsilon-amine of a lysine bearing a d configuration. The structures of paltolides A-C were determined by NMR and tandem MS techniques. Paltolide A is the first anabaenopeptin structure where a non-N-methylated amino acid precedes the C-terminal residue.

Dehydroconicasterol and aurantoic acid, a chlorinated polyene derivative, from the Indonesian sponge Theonella swinhoei

The chlorinated polyene aurantoic acid (1) and the 4-methylene sterol dehydroconicasterol (2) were isolated from the Indonesian sponge Theonella swinhoei, and their structures were elucidated by interpretation of spectroscopic data. Aurantoic acid is a unique member in the class of naturally occurring conjugated polyene derivatives, while dehydroconicasterol is the likely biogenetic precursor of the major Theonella 4-methylene sterols.

Total synthesis of theopederin D

The total synthesis of the potent cytotoxin theopederin D has been achieved through the use of an oxidative carbon–carbon bond cleavage reaction to form an acyliminium ion in the presence of acid labile acetal groups Other key transformations include an acid mediated functionalization of a tetrahydrofuranyl alcohol in the presence of a tetrahydropyranyl alcohol, a syn -selective glycal epoxide opening, and a catalytic asymmetric aldehyde-acid chloride condensation.

A serendipitous discovery of isomotuporin-containing sponge populations of Theonella swinhoei

An in-depth LCMS examination of 14 different collections of Indo-Pacific Theonella swinhoei sponges resulted in the discovery of four diastereomeric analogues of the cyclic pentapeptide motuporin. These motuporin analogues all contain a novel 2R configuration for the Adda amino acid. Additionally, one analogue has a unique nonoxygenated Adda amino acid. In all, 15 different compounds were observed by LCMS or isolated. The stereochemistries of the constituent amino acids were determined through a combination of the advanced Marfey technique and 1H NMR data.

Theopapuamide, a cyclic depsipeptide from a Papua New Guinea lithistid sponge Theonella swinhoei

Theopapuamide (1), a new cytotoxic peptide, has been isolated from the lithistid sponge Theonella swinhoei from Papua New Guinea. The structure was established by analysis of NMR, mass spectrometry, and chemical methods. The undecapeptide (1) contains several unusual amino acid residues, of which the occurrence of beta-methoxyasparagine and 4-amino-5-methyl-2,3,5-trihydroxyhexanoic acid (Amtha) is unprecedented in natural peptides. Compound 1 also contains an amide-linked fatty acid moiety, 3-hydroxy-2,4,6-trimethyloctanoic acid (Htoa). Theopapuamide (1) was cytotoxic against CEM-TART and HCT-116 cell lines, with EC50 values of 0.5 and 0.9 microM, respectively.

Brunsvicamides A−C: Sponge-Related Cyanobacterial Peptides with Mycobacterium tuberculosis Protein Tyrosine Phosphatase Inhibitory Activity

The cyanobacterium Tychonema sp. produces the new cyclic hexapeptides brunsvicamide A-C (1-3). Brunsvicamide B (2) and C (3) selectively inhibit the Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB), a potential drug target for tuberculosis therapy for which no inhibitors are known to date. Brunsvicamide C contains an N-methylated N'-formylkynurenine moiety, a unique structural motif in cyclic peptides. The new peptides are related to the sponge-derived mozamides, supporting the suggestion that secondary metabolites of certain marine invertebrates are produced by associated microorganisms. Thus, microorganisms phylogenetically related to symbionts of marine invertebrates can be judged as a means to supply "marine-like" compounds for drug development.

Koshikamide A2, a cytotoxic linear undecapeptide isolated from a marine sponge of Theonella sp

Koshikamide A2 (2) was isolated as a cytotoxic metabolite from a marine sponge of Theonella sp. Its structure was elucidated to be a linear undecapeptide by spectroscopic and chemical methods, together with enzymatic conversion to known koshikamide A1 (1). The new peptide moderately inhibited the growth of P388 murine leukemia cells.

Polytheonamides A and B, Highly Cytotoxic, Linear Polypeptides with Unprecedented Structural Features, from the Marine Sponge,Theonellaswinhoei

Polytheonamides A and B are highly cytotoxic polypeptides with 48 amino acid residues isolated from the marine sponge, Theonella swinhoei. The structure of polytheonamide B was determined by spectral and chemical methods, especially extensive 2D NMR experiments, which resulted in the unprecedented polypeptide structure; the N-terminal glycine blocked with a 5,5-dimethyl-2-oxo-hexanoyl group, the presence of eight tert-leucine, three beta-hydroxyvaline, six gamma-N-methylasparagine, two gamma-N-methyl-beta-hydroxyasparagine, and beta,beta-dimethymethionine sulfoxide residues. More significantly, it has the sequence of alternating D- and L-amino acids. Polytheonamide A is an epimer of polytheonamide B differing only in the stereochemistry of the sulfoxide of the 44(th) residue.