Monanchocidin (1), a guanidine alkaloid with an unprecedented skeleton system derived from a polyketide precursor, (ω-3)-hydroxy fatty acid, and containing a 2-aminoethyl- and 3-aminopropyl-substituted morpholine hemiketal ring, has been isolated from the sponge Monanhora pulchra. The structure of 1 was assigned on the basis of detailed analysis of 1D and 2D NMR spectra, mass spectrometry, and results of chemical transformations. Compound 1 shows pro-apoptotic and cytoxic activities.

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New unusual polycyclic guanidine alkaloids monanchocidins B-E (2-5) along with monanchocidin A (1), which we recently described, were isolated from the Far-Eastern marine sponge Monanchora pulchra. Their structures were established using spectroscopic data and chemical transformations. Compounds 1-5 show potent cytotoxic activities against HL-60 human leukemia cells with IC50 values of 540, 200, 110, 830, and 650 nM, respectively.

Aaptamine (8,9-dimethoxy-1H-benzo[de][1,6]naphthyridine) is a marine natural compound possessing antioxidative, antimicrobial, antifungal, and antiretroviral activity. Earlier, we have found that aaptamine and its derivatives demonstrate equal anticancer effects against the human germ cell cancer cell lines NT2 and NT2-R and cause some changes in the proteome of these cells. In order to explore further the mechanism of action of aaptamine and its derivatives, we studied the effects of aaptamine (1), demethyl(oxy)aaptamine (2), and isoaaptamine (3) on human cancer cell lines and on AP-1-, NF-κB-, and p53-dependent transcriptional activity in murine JB6 Cl41 cells. We showed that compounds 1–3 demonstrate anticancer activity in THP-1, HeLa, SNU-C4, SK-MEL-28, and MDA-MB-231 human cancer cell lines. Additionally, all compounds were found to prevent EGF-induced neoplastic transformation of murine JB6 Cl41 cells. Nuclear factors AP-1, NF-κB, and p53 are involved in the cellular response to high and nontoxic concentrations of aaptamine alkaloids 1–3. Furthermore, inhibition of EGF-induced JB6 cell transformation, which is exerted by the compounds 1–3 at low nontoxic concentrations of 0.7–2.1 μM, cannot be explained by activation of AP-1 and NF-κB.

Melonoside A (1), the first representative of a new class of ω-glycosylated fatty acid amides, was isolated from the Far Eastern marine sponge Melonanchora kobjakovae. The structure of 1, including absolute configuration, was established using detailed analysis of 1D and 2D NMR, CD, and mass spectra as well as chemical transformations. Compound 1 induces autophagy of human cisplatin-resistant germinal tumor cells NCCIT-R.

New pentacyclic guanidine alkaloids, normonanchocidins A, B and D (1-3) along with the earlier known monanchocidin A were isolated from the Far-Eastern marine sponge Monanchora pulchra. Structures of 1-3 were elucidated using 1D-and 2D-NMR spectroscopic and mass spectrometric data. Compound 1 and a mixture of 2 and 3 (1:1) exhibited cytotoxic activities against human leukemia THP-1 cells with IC 50 values of 2.1 µM and 3.7 µM, respectively, and against cervix epithelial carcinoma HeLa cells with IC 50 of 3.8 µM and 6.8 µM, respectively.

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Three new triterpene glycosides, pacificusosides A–C (1–3), and three previously known triterpene glycosides, cucumariosides C1 (4), C2 (5), and A10 (6), were isolated from the alcoholic extract of the Far Eastern starfish Solaster pacificus. The structures of 1–3 were elucidated by extensive NMR and ESIMS techniques and chemical transformations. Compound 1 has a novel, unique structure, containing an aldehyde group of side chains in its triterpene aglycon. This structural fragment has not previously been found in the sea cucumber triterpene glycosides or starfish steroidal glycosides. Probably, pacificusoside A (1) is a product of the metabolism of the glycoside obtained through dietary means from a sea cucumber in the starfish. Another two new triterpene glycosides (2, 3) have closely related characteristics to sea cucumber glycosides. The cytotoxicity of compounds 1–6 was tested against human embryonic kidney HEK 293 cells, colorectal carcinoma HT-29 cells, melanoma RPMI-7951 cells, and breast cancer MDA-MB-231 cells using MTS assay. Compounds 4–6 revealed the highest cytotoxic activity against the tested cell lines, while the other investigated compounds had moderate or slight cytotoxicity. The cytotoxic effects of 2–6 were reduced by cholesterol like the similar effects of the previously investigated individual triterpene glycosides. Compounds 3, 4, and 5 almost completely suppressed the colony formation of the HT-29, RPMI-7951, and MDA-MB-231 cells at a nontoxic concentration of 0.5 µM.