3β,5α,6β-Oxygenated sterols from the South China Sea gorgonian Muriceopsis flavida and their tumor cell growth inhibitory activity and apoptosis-inducing function

Antibacterial oxygenated ergostane-type steroids produced by the marine sponge-derived fungus Aspergillus sp

Two oxygenated ergostane-type steroids including one new compound, 3β-hydroxy-5α,6β-methoxyergosta-7,22-dien-15-one (1) along with a known analogue ergosta-6,22-dien-3β,5α,8α-triol (2) were isolated from the crude extracts of the marine sponge-derived fungus Aspergillus sp. Their structures were elucidated on the basis of combined NMR and MS spectroscopic methods. Compound 1 was a marine ergostane-type steroid with two methoxy groups at C-5 and C-6, respectively. These oxygenated ergostane-type steroids were evaluated for their antibacterial activities against human or aquatic pathogens. Among them, compound 1 exhibited antibacterial activity against Staphylococcus aureus.

Cholestane-3β,5α,6β-triol Induces Multiple Cell Death in A549 Cells via ER Stress and Autophagy Activation

Cholestane-3β,5α,6β-triol (CT) and its analogues are abundant in natural sources and are reported to demonstrate cytotoxicity toward different kinds of tumor cells without a deep probe into their mechanism of action. CT is also one of the major metabolic oxysterols of cholesterol in mammals and is found to accumulate in various diseases. An extensive exploration of the biological roles of CT over the past few decades has established its identity as an apoptosis inducer. In this study, the effects of CT on A549 cell death were investigated through cell viability assays. RNA-sequencing analysis and western blot of CT-treated A549 cells revealed the role of CT in inducing endoplasmic reticulum (ER) stress response and enhancing autophagy flux, suggesting a putative mechanism of CT-induced cell-death activation involving reactive oxygen species (ROS)-mediated ER stress and autophagy. It is reported for the first time that the upregulation of autophagy induced by CT can serve as a cellular cytotoxicity response in accelerating CT-induced cell death in A549 cells. This research provides evidence for the effect of CT as an oxysterol in cell response to oxidative damage and allows for a deep understanding of cholesterol in its response in an oxidative stress environment that commonly occurs in the progression of various diseases.

Sinulaspirolactam A, a novel aza-spirocyclic valerenane sesquiterpenoid from soft coral Sinularia sp

A novel valerenane sesquiterpenoid sinulaspirolactam A (1), together with five known compounds, was isolated from the soft coral Sinularia sp. Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by ECD calculation. Compound 1 was the first example of valerenane sesquiterpenoid bearing an aza-spiro[4.5] ring moiety, the plausible biogenetic pathway of which was proposed. Cytotoxic activities of these compounds were also evaluated.

Oxysterols from a Marine Sponge Inflatella sp. and Their Action in 6-Hydroxydopamine-Induced Cell Model of Parkinson's Disease

Four new oxysterols 1⁻4 along with previously known oxygenated sterols 5⁻14 were isolated from the sponge Inflatella sp., collected from the Sea of Okhotsk. Structures of 1⁻4 were elucidated by the detailed NMR spectroscopic and mass-spectrometric analyses as well as by comparison of the corresponding experimental data with those reported in literature. The influence of compounds 1⁻14 on the viability of neuronal Neuro2a cells treated by 6-hydroxydopamine and reactive oxygen species (ROS) formation in these cells was investigated.

Review of bioactive secondary metabolites from marine bryozoans in the progress of new drugs discovery

Marine bryozoans play an important role for the discovery of novel bioactive compounds among marine organisms. In this review, we summarize 164 new secondary metabolites including macrocyclic lactones, sterols, alkaloids, sphingolipids and so forth from 24 marine bryozoans in the last two decades. The structural features, bioactivity, structure-activity relationship, mechanism and strategies to address the resupply of these scarce secondary metabolites are discussed. The structural and bioactive diversity of the secondary metabolites from marine bryozoans indicated the possibility of using these compounds, especially bryostatin 1 (1), bryostatin analog (BA1), alkaloids (50, 53, 127-128 and 134-139), sphingolipids sulfates (148 and 149) and sulfur-containing aromatic compound (160), as the starting points for new drug discovery.

Antimicrobial Activities and Time-Kill Kinetics of Extracts of Selected Ghanaian Mushrooms

The rapid rise of antimicrobial resistance is a worldwide problem. This has necessitated the need to search for new antimicrobial agents. Mushrooms are rich sources of potential antimicrobial agents. This study investigated the antimicrobial properties of methanol extracts of Trametes gibbosa, Trametes elegans, Schizophyllum commune, and Volvariella volvacea. Agar well diffusion, broth microdilution, and time-kill kinetic assays were used to determine the antimicrobial activity of the extracts against selected test organisms. Preliminary mycochemical screening revealed the presence of tannins, flavonoids, triterpenoids, anthraquinones, and alkaloids in the extracts. Methanol extracts of T. gibbosa, T. elegans, S. commune, and V. volvacea showed mean zone of growth inhibition of 10.00 ± 0.0 to 21.50 ± 0.84, 10.00 ± 0.0 to 22.00 ± 1.10, 9.00 ± 0.63 to 21.83 ± 1.17, and 12.00 ± 0.0 to 21.17 ± 1.00 mm, respectively. The minimum inhibitory concentration of methanol extracts of T. gibbosa, T. elegans, S. commune, and V. volvacea ranged from 4.0 to 20, 6.0 to 30.0, 8.0 to 10.0, and 6.0 to 20.0 mg/mL, respectively. Time-kill kinetics studies showed that the extracts possess bacteriostatic action. Methanol extracts of T. gibbosa, T. elegans, S. commune, and V. volvacea exhibited antimicrobial activity and may contain bioactive compounds which may serve as potential antibacterial and antifungal agents.

Cytotoxic Steroids from the Vietnamese Soft Coral Sinularia conferta

Twelve steroids, including five new compounds 1-5, were isolated and structurally elucidated from a methanol extract of the Vietnamese soft coral Sinularia conferta. Their cytotoxic effects against three human cancer cell lines, lung carcinoma (A-549), cervical adenocarcinoma (HeLa), and pancreatic epithelioid carcinoma (PANC-1), were evaluated using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assays. Among isolated compounds, 10 exhibited potent cytotoxic effects on all three tested cell lines with IC₅₀ values of 3.64±0.18, 19.34±0.42, and 1.78±0.69 µM, respectively.

Obtusifoliol related steroids from Euphorbia sogdiana with cell growth inhibitory activity and apoptotic effects on breast cancer cells (MCF-7 and MDA-MB231)

From the aerial parts of Euphorbia sogdiana Popov, obtusifoliol (1) and two related steroids (2-3) have been isolated and characterized along with a known cycloartane derivative (4). The chemical structure of the obtusifoliol-related compounds, obtained by 1D and 2D NMR, and MS measurements, have been determined as: 3β,7α-dihydroxy-4α,14α-dimethyl-5α-ergosta-8,24(28)-diene-11-one (2) and 3β-hydroxy-4α,14α-dimethyl-5α-ergosta-8,24(28)-diene-1-one (3). Compound 2 has been previously isolated from Euphorbia chamaesyce while compound 3 was never reported before. The isolated compounds 1-4 were subjected to cytotoxic tests on the breast cancer cells, MCF-7 and MDA-MB231. Further pharmacological tests on the more active compounds 2 and 3 indicated their action to be related to cell growth inhibitory activity and apoptotic effects on the tested cells.

Oxysterols from an octocoral of the genus Gorgonia from the eastern Pacific of Panama

Eighteen new oxysterols were isolated from a previously undescribed octocoral of the genusGorgonia. Antimicrobial and antileishmanial properties of these compounds have been evaluated.

Marine natural products

This review covers the literature published in 2013 for marine natural products (MNPs), with 982 citations (644 for the period January to December 2013) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1163 for 2013), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

New polyhydroxylated sterols from Palythoa tuberculosa and their apoptotic activity in cancer cells

The chemical study on the total extract of the zoanthid Palythoa tuberculosa, collected from the Red Sea, resulted in the isolation of seven polyhydroxylated sterols (1-7), six of which, palysterols A-F (2-7), are new. Their chemical structures were elucidated on the basis of extensive analysis of their 1-, 2D NMR and MS spectroscopic data. This is the first chemical investigation on the species collected from Red Sea. We studied the cytotoxic effects of the total extract and some of the new polyhydroxylated sterols in three human cancer cell lines (MCF-7, HeLa, and HT-29) and one non-cancerous human cell line (KMST-6). Palysterol F (7), in particular, was able to selectively induce high levels of apoptosis (>75%) in breast adenocarcinoma (MCF-7) cells but not HeLa, HT-29 and KMST-6 cells.

Polyoxygenated steroids from the octocoral Leptogorgia punicea and in vitro evaluation of their cytotoxic activity

Five new polyoxygenated marine steroids-punicinols A-E (1-5)-were isolated from the gorgonian Leptogorgia punicea and characterized by spectroscopic methods (IR, MS, 1H, 13C and 2-D NMR). The five compounds induced in vitro cytotoxic effects against lung cancer A549 cells, while punicinols A and B were the most active, with IC50 values of 9.7 μM and 9.6 μM, respectively. The synergistic effects of these compounds with paclitaxel, as well as their effects on cell cycle distribution and their performance in the clonogenic assay, were also evaluated. Both compounds demonstrated significant synergistic effects with paclitaxel.

Polyoxygenated 24,28-epoxyergosterols inhibiting the proliferation of glioma cells from sea anemone Anthopleura midori

Eleven sterols (1-11) and one carotenoid (12) were isolated and identified from sea anemone Anthopleura midori. Compounds 1-6 are rare polyoxygenated ergosterols with a 24,28-epoxy moiety. The structures of these epoxyergosterols were determined by NMR and HRESIMS analyses as well as their chemical-physical properties. Epoxyergosterols 1 and 2 were found to be new natural products and 3-6 are new compounds. Bioactive assay showed that compounds 1, 2, 3, 5, 7, 8, 11, and 12 inhibited the proliferation of rat glioma C6 and human glioma U251 cells with IC50 in a range of 2.41-80.45 μM. Further investigation suggested that 1 and 3 induced apoptosis in glioma cells and 1 blocked U251 cells at the G0/G1 phase.

Cytotoxic steroids from the leaves of Dysoxylum binectariferum

Four new cholestane-type (1-4) and two new ergostane-type (5, 6) steroids were isolated from the leaves of Dysoxylum binectariferum. Their structures were elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR techniques. The absolute configurations were established by comparison with the literature and Mo2(OAc)4-induced electronic circular dichroism (ECD) data. All the isolates were evaluated for cytotoxicity against A549 (lung carcinoma), MCF-7 (breast adenocarcinoma), and HepG2 (hepatocellular carcinoma) human cancer cell lines. Three of the new cholestane-type steroids displayed potent antiproliferative effects on the tumor cells with IC50 values ranging from 1.5 to 9.6μM, whereas the two new ergostane-type (5, 6) steroids were deemed inactive.

Current status on development of steroids as anticancer agents

Steroids are important biodynamic agents. Their affinities for various nuclear receptors have been an interesting feature to utilize them for drug development particularly for receptor mediated diseases. Steroid biochemistry and its crucial role in human physiology, has attained importance among the researchers. Recent years have seen an extensive focus on modification of steroids. The rational modifications of perhydrocyclopentanophenanthrene nucleus of steroids have yielded several important anticancer lead molecules. Exemestane, SR16157, fulvestrant and 2-methoxyestradiol are some of the successful leads emerged on steroidal pharmacophores. The present review is an update on some of the steroidal leads obtained during past 25 years. Various steroid based enzyme inhibitors, antiestrogens, cytotoxic conjugates and steroidal cytotoxic molecules of natural as well as synthetic origin have been highlighted. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Tumor cell growth inhibitory activity and structure-activity relationship of polyoxygenated steroids from the gorgonian Menella kanisa

Fourteen new polyoxygenated steroids (6, 9, 14-18, 20-23, 25-27) having carbon skeletons of cholestane, ergostane, and 24-norcholestane, were isolated together with thirteen known analogues (1-5, 7, 8, 10-13, 19, 24) from the South China Sea gorgonian Menella kanisa. The structures of the new compounds were elucidated by detailed analysis of spectroscopic data and comparisons with reported data. This is the first report of chemical investigation on the title gorgonian. Compounds 12 and 13 were reported for the first time from natural sources. These compounds exhibited different levels of growth inhibition activity against A549 and MG-63 cell lines in bioassay in vitro. Preliminary structure-activity analysis revealed an important role of side chain in the activity. A substitution of a 5α-hydroxy or an oxidation of 6β-hydroxy to a ketone carbonyl group may decrease the activity whereas the contribution of the 1-ketone group remains uncertain.

Chemistry and tumor cell growth inhibitory activity of 11,20-epoxy-3Z,5(6)E-diene briaranes from the South China Sea gorgonian Dichotella gemmacea

Eighteen new 11,20-epoxy-3Z,5E-dien briaranes, gemmacolides AA-AR (1-18), were isolated together with three known analogs, dichotellides F (19) and I (20), and juncenolide C (21), from the South China Sea gorgonian Dichotella gemmacea. The structures of the compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configuration was determined based on the ECD experiment. In the in vitro bioassay, compounds 1-3, 5, 6, 8-12, and 14-19 exhibited different levels of growth inhibition activity against A549 and MG63 cell lines. Preliminary structure-activity analysis suggests that 12-O-isovalerate may increase the activity whereas 13- or 14-O-isovalerate may decrease the activity. Contribution of substitutions at C-2 and C-16 remains uncertain.