Three new chlorinated marine steroids, yonarasterols G, H and I, isolated from the okinawan soft coral, Clavularia viridis

Synthesis and Investigation of Antibacterial Properties of Thymol, Carvacrol, Eugenol, and Perillyl Alcohol Based β-Halo Alcohol and β-Halo Thiol Compounds

A total of 12 new β-halo alcohols and 12 new β-halo thiol derivatives were synthesized. Natural alcohol compounds with known pharmacological properties were selected as starting substrates, aiming to synthesize compounds that have the potential to exhibit biological activity. The synthesis of β-halo alcohol derivatives involved a two-step process, while β-halo thiol derivatives were carried out in three steps. Effective and inexpensive methods were used for all transformations. Yields for β-halo alcohol derivatives ranged from 79% to 82%, and for β-halo thiol derivatives from 66% to 71%. Their antibacterial properties against some gram (+) (Staphylococcus aureus, Enterococcus faecalis) and gram (-) (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) strains were investigated. The antibacterial effects of 24 newly synthesized compounds were compared to commercially available antibiotics Chloramphenicol and Streptomycin.

Biological Activity and Structural Diversity of Steroids Containing Aromatic Rings, Phosphate Groups, or Halogen Atoms

This review delves into the investigation of the biological activity and structural diversity of steroids and related isoprenoid lipids. The study encompasses various natural compounds, such as steroids with aromatic ring(s), steroid phosphate esters derived from marine invertebrates, and steroids incorporating halogen atoms (I, Br, or Cl). These compounds are either produced by fungi or fungal endophytes or found in extracts of plants, algae, or marine invertebrates. To assess the biological activity of these natural compounds, an extensive examination of referenced literature sources was conducted. The evaluation encompassed in vivo and in vitro studies, as well as the utilization of the QSAR method. Numerous compounds exhibited notable properties such as strong anti-inflammatory, anti-neoplastic, anti-proliferative, anti-hypercholesterolemic, anti-Parkinsonian, diuretic, anti-eczematic, anti-psoriatic, and various other activities. Throughout the review, 3D graphs illustrating the activity of individual steroids are presented alongside images of selected terrestrial or marine organisms. Additionally, the review provides explanations for specific types of biological activity associated with these compounds. The data presented in this review hold scientific interest for academic science as well as practical implications in the fields of pharmacology and practical medicine. The analysis of the biological activity and structural diversity of steroids and related isoprenoid lipids provides valuable insights that can contribute to advancements in both theoretical understanding and applied research.

Two-Stage Syntheses of Clionastatins A and B

A concise and divergent synthesis of the polychlorinated marine steroids clionastatin A and B from inexpensive testosterone has been achieved through a unique two-stage chlorination-oxidation strategy. Key features of the two-stage synthesis include (1) conformationally controlled, highly stereoselective dichlorination at C1 and C2 and C4-OH-directed C19 oxygenation followed by a challenging neopentyl chlorination to install three chlorine atoms; (2) desaturation through one-pot photochemical dibromination-reductive debromination and anti-Markovnikov olefin oxidation by photoredox-metal dual catalysis to enhance the oxidation level of the backbone; and (3) Wharton transposition to furnish the D-ring enone. This synthesis proved that the introduction of the C19 chloride in the early stage of the synthesis secured the stability of the backbone against susceptibility to aromatization during the oxidation stage.

Chemical Review of Gorgostane-Type Steroids Isolated from Marine Organisms and Their 13C-NMR Spectroscopic Data Characteristics

Gorgostane steroids are isolated from marine organisms and consist of 30 carbon atoms with a characteristic cyclopropane moiety. From the pioneering results to the end of 2021, isolation, biosynthesis, and structural elucidation using 13C-NMR will be used. Overall, 75 compounds are categorized into five major groups: gorgost-5-ene, 5,6-epoxygorgostane, 5,6-dihydroxygorgostane, 9,11-secogorgostane, and 23-demethylgorgostane, in addition to miscellaneous gorgostane. The structural diversity, selectivity for marine organisms, and biological effects of gorgostane steroids have generated considerable interest in the field of drug discovery research.

A Temperature-Controlled Switch between Fürst-Plattner Rule and Anti-Fürst-Plattner Rule Ring Opening of 2,3-Epoxy-steroids with Various Halide Sources in the Presence of Imidazolium Ionic Liquids

The ring opening of 2α,3α- and 2β,3β-epoxy-5α-androstan-17-one with halide reagents (AlCl₃, TMSCl, LiCl, and LiBr) was investigated using imidazolium ionic liquids in the dual role of solvent and catalyst. The application of the ionic liquid was shown to result in an increase in the amount of the unusual diequatorial halohydrins especially at temperatures above 100 °C. With a careful choice of reaction conditions, the latter derivatives could be produced with 43-96% selectivity depending on the nature of the halide ion. Moreover, the usual diaxial products could also be isolated in 70-85% yields by a proper change in the reaction conditions. The reusability of the ionic liquid was demonstrated in both types of reactions. The structures of the products were proved unequivocally by nuclear magnetic resonance (NMR) measurements including two-dimensional (2D) techniques as well as high-resolution mass spectrometry (HRMS). Based on quantum chemical calculations, the effect of the ionic liquid could be explained by the stabilization of the transition state leading to the diequatorial product.

Chemical Diversity of Soft Coral Steroids and Their Pharmacological Activities

The review is devoted to the chemical diversity of steroids produced by soft corals and their determined and potential activities. There are about 200 steroids that belong to different types of steroids such as secosteroids, spirosteroids, epoxy- and peroxy-steroids, steroid glycosides, halogenated steroids, polyoxygenated steroids and steroids containing sulfur or nitrogen heteroatoms. Of greatest interest is the pharmacological activity of these steroids. More than 40 steroids exhibit antitumor and related activity with a confidence level of over 90 percent. A group of 32 steroids shows anti-hypercholesterolemic activity with over 90 percent confidence. Ten steroids exhibit anti-inflammatory activity and 20 steroids can be classified as respiratory analeptic drugs. Several steroids exhibit rather rare and very specific activities. Steroids exhibit anti-osteoporotic properties and can be used to treat osteoporosis, as well as have strong anti-eczemic and anti-psoriatic properties and antispasmodic properties. Thus, this review is probably the first and exclusive to present the known as well as the potential pharmacological activities of 200 marine steroids.

Bioactive compounds from marine invertebrates as potent anticancer drugs: the possible pharmacophores modulating cell death pathways

Marine invertebrates are extremely diverse, largely productive, untapped oceanic resources with chemically unique bioactive lead compound contributing a wide range of screening for the discovery of anticancer compounds. The lead compounds have unfurled an extensive array of pharmacological properties owing to the presence of polyphenols, alkaloids, terpenoids and other secondary metabolites. The antioxidant, immunomodulatory and anti-tumor activities exhibited, are possibly regulated by the apoptosis induction, scavenging of ROS and modulation of cellular signaling pathways to defy the cellular deafness during carcinogenesis. Despite the enriched bioactive compounds, the marine invertebrates are largely unexplored as identification, screening, pre-clinical and clinical assessment of lead compounds and their synthetic analogs remain a major task to be solved. In the current review, we focus on the principle strategy and underlying mechanisms deployed by the bioactive anticancer compounds derived from marine invertebrates to combat cancer with special insight into the cell death mechanism.

Halogenated Compounds from Corals: Chemical Diversity and Biological Activities

As important marine biological resources, corals produce a large amount of active organic compounds in their secondary metabolic processes, including numerous brominated, chlorinated, and iodinated compounds. These compounds, with novel structures and unique activities, guide the discovery and research of important lead compounds and novel biological mechanisms. Through a large number of literature surveys, this paper summarized a total of 145 halogenated secondary metabolites which were roughly divided into four major classes of terpenes, prostaglandins, steroids and alkaloids, and they were mainly isolated from ten coral families, Ellisellidae, Gorgoniidae, Briareidae, Plexauridae, Anthothelidae, Alcyoniidae, Clavularidae, Tubiporidae, Nephtheidae and Dendrophyllidae to the best of our knowledge. In addition, their organism species, structure composition and biological activity were also discussed in the form of a chart in this essay.

Cnidarians as a source of new marine bioactive compounds--an overview of the last decade and future steps for bioprospecting

Marine invertebrates are rich sources of bioactive compounds and their biotechnological potential attracts scientific and economic interest worldwide. Although sponges are the foremost providers of marine bioactive compounds, cnidarians are also being studied with promising results. This diverse group of marine invertebrates includes over 11,000 species, 7500 of them belonging to the class Anthozoa. We present an overview of some of the most promising marine bioactive compounds from a therapeutic point of view isolated from cnidarians in the first decade of the 21st century. Anthozoan orders Alcyonacea and Gorgonacea exhibit by far the highest number of species yielding promising compounds. Antitumor activity has been the major area of interest in the screening of cnidarian compounds, the most promising ones being terpenoids (monoterpenoids, diterpenoids, sesquiterpenoids). We also discuss the future of bioprospecting for new marine bioactive compounds produced by cnidarians.

Bioactive marine prostanoids from octocoral Clavularia viridis

Chemical investigation of the nonpolar extract of soft coral Clavularia viridis resulted in isolation of five new prostanoids, designated as claviridic acids A-E (1-5, resp.), in addition to the known clavulones I-III. Their structures were determined on the basis of spectroscopic techniques, especially HR-ESI-MS, CD, and 2D-NMR experiments. The isolated marine prostanoids exhibited potent inhibitory effect on PHA-induced proliferation of peripheral blood mononuclear cells (PBMC), as well as significant cytotoxic activity against human gastric cancer cells (AGS).

Proteomic identification, cDNA cloning and enzymatic activity of glutathione S-transferases from the generalist marine gastropod, Cyphoma gibbosum

Glutathione S-transferases (GST) were characterized from the digestive gland of Cyphoma gibbosum (Mollusca; Gastropoda), to investigate the possible role of these detoxification enzymes in conferring resistance to allelochemicals present in its gorgonian coral diet. We identified the collection of expressed cytosolic Cyphoma GST classes using a proteomic approach involving affinity chromatography, HPLC and nano-spray liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two major GST subunits were identified as putative mu-class GSTs; while one minor GST subunit was identified as a putative theta-class GST, apparently the first theta-class GST identified from a mollusc. Two Cyphoma GST cDNAs (CgGSTM1 and CgGSTM2) were isolated by RT-PCR using primers derived from peptide sequences. Phylogenetic analyses established both cDNAs as mu-class GSTs and revealed a mollusc-specific subclass of the GST-mu clade. These results provide new insights into metazoan GST diversity and the biochemical mechanisms used by marine organisms to cope with their chemically defended prey.

6β-Chloro-5α-hydr-oxy-20-oxopregnan-3β-yl acetate

The title steroid, C₂₃H₃₅ClO₄, is a pregnane derivative prepared by ring opening of the corresponding 5α,6α-ep­oxy steroid with BiCl₃. There are two symmetry-independent mol­ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. The conformation of the six-membered rings in both mol­ecules is close to a chair form, while the five-membered ring adopts an envelope conformation. All rings in both mol­ecules are trans-fused. The mol­ecules are held together by an extensive O—H⋯O hydrogen-bonding network.

Stolonilactone, a novel terpenoid-related compound, isolated from the Okinawan soft coral Clavularia koellikeri

A novel terpenoid-related compound, stolonilactone (1), was isolated from the Okinawan soft coral Clavularia koellikeri. The structure of 1 was elucidated on the basis of spectroscopic analysis. A possible biogenesis of 1 through the [4 + 2]-cycloaddition of a trisnorsesquiterpenoid-type diene and a cembranolide-type dienophile is proposed.

New biologically active marine sesquiterpenoid and steroid from the okinawan sponge of the genus Axinyssa

A new bisabolane-type sesquiterpenoid, (E)-3-isocyanobisabolane-7,10-diene (1), and a new epidioxyergostane-type steroid, 9(11)-dehydroaxinysterol (2), were isolated from the Okinawan sponge of the genus Axinyssa. Their structures were elucidated based on the results of spectroscopic analysis and chemical conversion. Epidioxysterol 2 was found to show significant growth inhibitory effects against human cancer cell lines.

New halogenated marine prostanoids with cytotoxic activity from the Okinawan soft coral Clavularia viridis

Five new halogenated prostanoids 1-4 and 6 were isolated from the Okinawan soft coral Clavularia viridis. The gross structure of 1 was elucidated mainly on the basis of NMR spectral data. The relative and absolute configurations were determined by analysis of NOESY and CD data, chemical conversion, and the modified Mosher's method. The structures of 2-4 and 6 were deduced by comparison of their spectral data with those of 1. Compound 1 demonstrated cytotoxic activity.