Briaexcavatolides K-N, new briarane diterpenes from the gorgonian Briareum excavatum

Marine diterpenoid targets STING palmitoylation in mammalian cells

Natural products are important sources of therapeutic agents and useful drug discovery tools. The fused macrocycles and multiple stereocenters of briarane-type diterpenoids pose a major challenge to total synthesis and efforts to characterize their biological activities. Harnessing a scalable source of excavatolide B (excB) from cultured soft coral Briareum stechei, we generated analogs by late-stage diversification and performed structure-activity analysis, which was critical for the development of functional excB probes. We further used these probes in a chemoproteomic strategy to identify Stimulator of Interferon Genes (STING) as a direct target of excB in mammalian cells. We showed that the epoxylactone warhead of excB is required to covalently engage STING at its membrane-proximal Cys91, inhibiting STING palmitoylation and signaling. This study reveals a possible mechanism-of-action of excB, and expands the repertoire of covalent STING inhibitors.

Briarenones A‒C, New Briarellin Diterpenoids from the Gorgonian Briareum violaceum

Three new eunicellin-derived diterpenoids of briarellin type, briarenones A‒C (1‒3), were isolated from a Formosan gorgonian Briareum violaceum. The chemical structures of the compounds were elucidated on the basis of extensive spectroscopic analyses, including two-dimensional (2D) NMR. The absolute configuration of 1 was further confirmed by a single crystal X-ray diffraction analysis. The in vitro cytotoxic and anti-inflammatory potentialities of the isolated metabolites were tested against the growth of a limited panel of cancer cell lines and against the production of superoxide anions and elastase release in N-formyl-methionyl-leucyl-phenyl-alanine and cytochalasin B (fMLF/CB)-stimulated human neutrophils, respectively.

Briaviolides K-N, New Briarane-Type Diterpenoids from Cultured Octocoral Briareum violaceum

Four new briarane diterpenoids, briaviolides K-N (1-4), have been obtained from the cultured-type octocoral Briareum violaceum. Using a spectroscopic approach, the structures of briaranes 1-4 were identified. This study employed an in vitro model of lipopolysaccharide (LPS)-induced inflammation in the murine macrophage RAW 264.7 cell line, and found that among the four briaranes, briarane 2 possessed anti-inflammatory activity against inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expressions in cells. In addition, principal component analysis using the chemical global positioning system (ChemGPS) for natural products (ChemGPS-NP) was employed in order to analyze the structure-activity relationship (SAR), and the results indicated that the ring conformation of the compound has a leading role in suppressing the expressions of pro-inflammatory iNOS and COX-2 proteins in macrophages.

Terpenoids from Octocorals of the Genus Pachyclavularia

In this paper, we reviewed natural compounds isolated from octocorals belonging to the genus Pachyclavularia, including 20 cembrane-, 39 briarane-, and eight briarellin-related diterpenoids, and one secosterol. The chemical constituents of these 68 secondary metabolites, and their names, structures, and bioactivities, along with studies of their biological activities, are summarized in this review. Based on the literature, many of these compounds possess bioactivities, including anti-inflammation properties, cytotoxicity, and ichthyotoxicity, suggesting that they may have the potential to be developed into biomedical agents for treatment.

Briarenolides U-Y, New Anti-Inflammatory Briarane Diterpenoids from an Octocoral Briareum sp. (Briareidae)

Five new 13,14-epoxybriarane diterpenoids, briarenolides U–Y (1–5), were isolated from the octocoral Briareum sp. The structures of briaranes 1–5 were elucidated by spectroscopic methods. Briarenolides U–Y (1–5) were found to significantly inhibit the expression of the pro-inflammatory inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein of the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells.

Briarenolides K and L, new anti-inflammatory briarane diterpenoids from an octocoral Briareum sp. (Briareidae)

Two new briarane-type diterpenoids, briarenolides K (1) and L (2), were isolated from an octocoral identified as Briareum sp. The structures of new briaranes 1 and 2 were elucidated by spectroscopic methods. In the in vitro anti-inflammatory effects test, briaranes 1 and 2 were found to significantly inhibit the accumulation of the pro-inflammatory iNOS protein of the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells.

2-Acetoxyverecynarmin C, a New Briarane COX Inhibitory Diterpenoid from Pennatula aculeata

A new briarane-type diterpenoid, named 2-acetoxyverecynarmin C, was isolated from the methanolic extract of an octocoral, Pennatula aculeata, that exhibited cyclooxygenase (COX) inhibitory activity. The structure of the compound was elucidated by ESI-HRMS, 1D and 2D NMR spectroscopy and comparison of the measured spectral data with those reported in the literature. The relative stereochemistry at chiral carbons was established from 2D NOESY experiments. 2-Acetoxyverecynarmin C is a tricyclic compound containing a furan ring at C-7,8 of a briarane skeleton. 2-Acetoxyverecynarmin C showed moderate inhibitory activity in in vitro COX-1 and COX-2 assays.

Cytotoxic and cytolytic cnidarian venoms. A review on health implications and possible therapeutic applications

The toxicity of Cnidaria is a subject of concern for its influence on human activities and public health. During the last decades, the mechanisms of cell injury caused by cnidarian venoms have been studied utilizing extracts from several Cnidaria that have been tested in order to evaluate some fundamental parameters, such as the activity on cell survival, functioning and metabolism, and to improve the knowledge about the mechanisms of action of these compounds. In agreement with the modern tendency aimed to avoid the utilization of living animals in the experiments and to substitute them with in vitro systems, established cell lines or primary cultures have been employed to test cnidarian extracts or derivatives. Several cnidarian venoms have been found to have cytotoxic properties and have been also shown to cause hemolytic effects. Some studied substances have been shown to affect tumour cells and microorganisms, so making cnidarian extracts particularly interesting for their possible therapeutic employment. The review aims to emphasize the up-to-date knowledge about this subject taking in consideration the importance of such venoms in human pathology, the health implications and the possible therapeutic application of these natural compounds.

Four new briarane diterpenoids from Taiwanese gorgonian Junceella fragilis

Four new 8-hydroxybriarane diterpenoids, frajunolides P–S (1–4), together with umbraculolide A, juncenolide C, junceellonoid A and juncin R, were isolated from the acetone extract of the gorgonian Junceella fragilis, collected from the southeast coast of Taiwan. Compound 1 contains an unusual pivaloyloxy group at C-2, while 3 is a rare compound having a chlorine atom on the olefinic carbon (C-6). The structures of the isolated compounds were established by extensive spectroscopic analysis, including 1D- and 2D-NMR, as well as HRMS data. Compound 1 was further confirmed by X-ray crystallographic analysis. In the anti-inflammatory test, compounds 1 and 2 exhibited moderate inhibition on superoxide anion generation and elastase release by human neutrophils in response to formylmethionylleucyl-phenylalanine/dihydrocytochalasin B (fMLP/CB).

Briarenolides F and G, new briarane diterpenoids from a Briareum sp. octocoral

Two new briarane diterpenoids, briarenolides, F (1) and G (2), were isolated from an octocoral identified as Briareum sp. The structures of briaranes 1 and 2 were established by spectroscopic methods and by comparison of the spectroscopic data with those of known briarane analogues. Briarenolide F was proven to be the first 6-hydroperoxybriarane derivative and this compound displayed a significant inhibitory effect on the generation of superoxide anion by human neutrophils.

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.

Excavatoids E and F: discovery of two new briaranes from the cultured octocoral Briareum excavatum

Two new briarane-related diterpenoids, designated as excavatoids E (1) and F (2), were isolated from the cultured octocoral Briareum excavatum. The structures of compounds 1 and 2 were established on the basis of extensive spectral data analysis. Briaranes 1 and 2 were found to exhibit moderate inhibitory effects on elastase release by human neutrophils.

Diterpenes from gorgonian corals

Covering: 1995 to April 2008. Gorgonian corals continue to provide a wealth of novel structures, many of which exhibit potentially useful biological activity. Notably, the families Briareidae, Gorgoniidae and Plexauridae have been demonstrated to contain a wide variety of natural products including steroids, acetogenins, sesquiterpenes and diterpenes. The most common of the gorgonian natural products are the diterpenes, and the intent of this review is to describe such compounds isolated from gorgonian corals, with a focus on the structures of new compounds as well as their biological activity. There have been developments improving our understanding of the biosynthetic origin of selected diterpenes, and these will also be discussed. This review describes 602 new compounds from 177 articles.

Marine pharmacology in 2001-2: antitumour and cytotoxic compounds

During 2001 and 2002, marine antitumour pharmacology research aimed at the discovery of novel antitumour agents was published in 175 peer-reviewed articles. The purpose of this paper is to present a structured Review of the antitumour and cytotoxic properties of 97 marine natural products, many of them novel compounds that belong to diverse structural classes, including polyketides, terpenes, steroids, and peptides. The organisms yielding these bioactive compounds comprise a taxonomically diverse group of marine invertebrate animals, algae, fungi and bacteria. Antitumour pharmacological studies were conducted with 30 structurally characterised natural marine products in a number of experimental and clinical models which further defined their mechanisms of action. Particularly potent in vitro cytotoxicity data generated with murine and human tumour cell lines was reported for 67 novel marine chemicals with as yet undetermined mechanisms of action. Noteworthy, is the fact that marine anticancer research was sustained by a collaborative effort, involving researchers from Australia, Brazil, Canada, Denmark, Egypt, France, Germany, Italy, Japan, Netherlands, New Zealand, The Philippines, Russia, Singapore, South Korea, Thailand, Taiwan, Turkey, Spain, Switzerland, Taiwan, Thailand, Turkey, and the United States. Finally, this 2001-2 overview of the marine pharmacology literature highlights the fact that the discovery of novel marine antitumour agents has continued at the same pace as during 1998, 1999 and 2000.