Cladieunicellins A-E, new eunicellins from an Indonesian soft coral Cladiella sp

The application and sustainable development of coral in traditional medicine and its chemical composition, pharmacology, toxicology, and clinical research

This review discusses the variety, chemical composition, pharmacological effects, toxicology, and clinical research of corals used in traditional medicine in the past two decades. At present, several types of medicinal coral resources are identified, which are used in 56 formulas such as traditional Chinese medicine, Tibetan medicine, Mongolian medicine, and Uyghur medicine. A total of 34 families and 99 genera of corals are involved in medical research, with the Alcyoniidae family and Sarcophyton genus being the main research objects. Based on the structural types of compounds and the families and genera of corals, this review summarizes the compounds primarily reported during the period, including terpenoids, steroids, nitrogen-containing compounds, and other terpenoids dominated by sesquiterpene and diterpenes. The biological activities of coral include cytotoxicity (antitumor and anticancer), anti-inflammatory, analgesic, antibacterial, antiviral, immunosuppressive, antioxidant, and neurological properties, and a detailed summary of the mechanisms underlying these activities or related targets is provided. Coral toxicity mostly occurs in the marine ornamental soft coral Zoanthidae family, with palytoxin as the main toxic compound. In addition, nonpeptide neurotoxins are extracted from aquatic corals. The compatibility of coral-related preparations did not show significant acute toxicity, but if used for a long time, it will still cause toxicity to the liver, kidneys, lungs, and other internal organs in a dose-dependent manner. In clinical applications, individual application of coral is often used as a substitute for orthopedic materials to treat diseases such as bone defects and bone hyperplasia. Second, coral is primarily available in the form of compound preparations, such as Ershiwuwei Shanhu pills and Shanhu Qishiwei pills, which are widely used in the treatment of neurological diseases such as migraine, primary headache, epilepsy, cerebral infarction, hypertension, and other cardiovascular and cerebrovascular diseases. It is undeniable that the effectiveness of coral research has exacerbated the endangered status of corals. Therefore, there should be no distinction between the advantages and disadvantages of listed endangered species, and it is imperative to completely prohibit their use and provide equal protection to help them recover to their normal numbers. This article can provide some reference for research on coral chemical composition, biological activity, chemical ecology, and the discovery of marine drug lead compounds. At the same time, it calls for people to protect endangered corals from the perspectives of prohibition, substitution, and synthesis.

Cladiella Octocorals: Enormous Sources of Secondary Metabolites with Diverse Structural and Biological Properties

Marine octocorals belonging to the genus Cladiella, usually encountered on reefs in the Indo-Pacific region, have been proven to be rich sources of diverse secondary metabolites with intriguing structural features and promising bioactivities. In this review, 155 compounds from six unambiguously identified C. krempfi, C. australis, C. pachyclados, C. hirsuta, C. tuberculosa, C. conifera, together with several unidentified Cladiella spp. are summarized covering the literatures from 2006 to August 2022. It is noteworthy that diterpenoids dominated the secondary metabolite profile of this genus counting for 78 %. Structurally, the majority of these diterpenes belonged to eunicellan family characterized by different patterns of ether linkage. The impacts of these chemical compositions on an array of potential pharmacological activities were also reviewed, giving an overview of the potential application of Cladiella secondary metabolites.

Cytotoxic Compounds from Alcyoniidae: An Overview of the Last 30 Years

The octocoral family Alcyoniidae represents a rich source of bioactive substances with intriguing and unique structural features. This review aims to provide an updated overview of the compounds isolated from Alcyoniidae and displaying potential cytotoxic activity. In order to allow a better comparison among the bioactive compounds, we focused on molecules evaluated in vitro by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, by far the most widely used method to analyze cell proliferation and viability. Specifically, we surveyed the last thirty years of research, finding 153 papers reporting on 344 compounds with proven cytotoxicity. The data were organized in tables to provide a ranking of the most active compounds, to be exploited for the selection of the most promising candidates for further screening and pre-clinical evaluation as anti-cancer agents. Specifically, we found that (22S,24S)-24-methyl-22,25-epoxyfurost-5-ene-3β,20β-diol (16), 3β,11-dihydroxy-24-methylene-9,11-secocholestan-5-en-9-one (23), (24S)-ergostane-3β,5α,6β,25 tetraol (146), sinulerectadione (227), sinulerectol C (229), and cladieunicellin I (277) exhibited stronger cytotoxicity than their respective positive control and that their mechanism of action has not yet been further investigated.

Diving into the world of marine 2,11-cyclized cembranoids: a summary of new compounds and their biological activities

This review summarises new marine 2,11-cyclized cembranoids from the past decade in a structured presentation according to their hypothetical biosynthesis.

Construction of a 6/5/9-membered tricyclic structure of cladiellins via radical-polar crossover reaction

A three-component coupling reaction of structurally simple 6-8 was successfully applied for expeditious synthesis of the 6/5/9-membered tricyclic structure 3 of cladieunicellin D (1) and klysimplexin U (2). Upon treatment with the Et₃B/O₂ reagent system, α-alkoxyacyl telluride 6, six-membered enone 7, and (Z)-4-hexenal (8) were linked in one pot to provide the densely functionalized 5 via sequential decarbonylative radical generation, radical addition, boron enolate formation, and intermolecular aldol reaction. Subsequent Lewis acid-promoted reductive etherification and SiO₂-induced C10-epimerization gave rise to the cis-fused five-membered ether of 4. Finally, cyclization of the nine-membered ring was achieved by the ring-closing metathesis reaction, giving rise to 3. Compound 3 possesses the six stereocenters of 1 and 2, and would thus serve as an advanced intermediate for their total syntheses.

Marine Natural Product Inhibitors of Neutrophil-Associated Inflammation

Neutrophils are widely recognized to play an important role in acute inflammatory responses, and recent evidence has expanded their role to modulating chronic inflammatory and autoimmune diseases. Reactive oxygen species (ROS) and microbicidal compounds released from neutrophils that are recruited to the site of inflammation contribute to the pathogenesis of multiple inflammation-associated diseases such as chronic obstructive pulmonary disease, atherosclerosis, and hepatitis. Marine organisms are a valuable source of bioactive compounds with potential for industrial and pharmaceutical application. Marine natural products that inhibit neutrophil activation could be used as drugs for the treatment of inflammatory diseases. Numerous studies investigating marine natural products have reported novel anti-inflammatory agents. Nevertheless, the detailed mechanisms underlying their actions, which could facilitate our understanding of the molecular events occurring in neutrophils, have not been reported in most of the associated research studies. Therefore, in this review, we will present marine products that inhibit neutrophil-associated inflammation. Furthermore, we will be limiting the detailed discussion to agents with well-investigated molecular targets.

Marine Diterpenoids as Potential Anti-Inflammatory Agents

The inflammatory response is a highly regulated process, and its dysregulation can lead to the establishment of chronic inflammation and, in some cases, to death. Inflammation is the cause of several diseases, including rheumatoid arthritis, inflammatory bowel diseases, multiple sclerosis, and asthma. The search for agents inhibiting inflammation is a great challenge as the inflammatory response plays an important role in the defense of the host to infections. Marine invertebrates are exceptional sources of new natural products, and among those diterpenoids secondary metabolites exhibit notable anti-inflammatory properties. Novel anti-inflammatory diterpenoids, exclusively produced by marine organisms, have been identified and synthetic molecules based on those structures have been obtained. The anti-inflammatory activity of marine diterpenoids has been attributed to the inhibition of Nuclear Factor-κB activation and to the modulation of arachidonic acid metabolism. However, more research is necessary to describe the mechanisms of action of these secondary metabolites. This review is a compilation of marine diterpenoids, mainly isolated from corals, which have been described as potential anti-inflammatory molecules.

Eunicellin-Based Diterpenoids, Hirsutalins S-V, from the Formosan Soft Coral Cladiella hirsuta

Four new eunicellin-type hirsutalins S–V (1–4), along with a known compound (–)-6α-hydroxy polyanthellin A (5), were isolated from the soft coral Cladiella hirsuta. The structures of the metabolites were determined by extensive spectroscopic analysis. Cytotoxity of compounds 1–5 against the proliferation of a limited panel of cancer cell lines was measured. Anti-inflammatory activity of compounds 1–5 was evaluated by measuring their ability in suppressing superoxide anion generation and elastase release in fMLP/CB-induced human neutrophils.

New anti-inflammatory tocopherol-derived metabolites from the Taiwanese soft coral Cladiella hirsuta

Two new tocopherol-derived metabolites, hirsutocospiro A (1) and hirsutocoquinone A (2), were isolated from the soft coral Cladiella hirsuta. The structures of 1 and 2 were determined by extensive spectroscopic analysis. The in vitro anti-inflammatory activity of compounds 1 and 2 was evaluated by measuring their ability in suppressing superoxide anion generation and elastase release in fMLP/CB-induced human neutrophils. Compound 1 was shown to exhibit significant anti-inflammatory activity.

Cladieunicellin J, a New Hydroperoxyeunicellin from Cladiella sp

A new 6-hydroperoxyeunicellin diterpenoid, designated as cladieunicellin J (1), was isolated from an octocoral Cladiella sp., and its structure elucidated by spectroscopic methods. Compound 1 was found to exhibit cytotoxicity toward CCRF-CEM human T-cell acute lymphoblastic leukemia.

Eunicellin-based diterpenoids, hirsutalins N-R, from the formosan soft coral Cladiella hirsuta

New eunicellin-type hirsutalins N–R (1–5), along with two known eunicellins, (6 and 7) were isolated from the soft coral Cladiellahirsuta. The structures of the metabolites were determined by extensive spectroscopic analysis. Cytotoxic activity of compounds 1–7 against the proliferation of a limited panel of cancer cell lines was measured. The invitro anti-inflammatory activity of compounds 1–7 was evaluated by measuring their ability in suppressing superoxide anion generation and elastase release in fMLP/CB-induced human neutrophils.

Discovery of new eunicellin-based diterpenoids from a Formosan soft coral Cladiella sp

A new eunicellin diterpenoid, cladieunicellin I (1), and a new natural eunicellin, litophynin I diacetate (2), were isolated from a Formosan soft coral identified as Cladiella sp. The structures of eunicellins 1 and 2 were elucidated by spectroscopic methods and by comparison of the spectral data with those of related analogues. Eunicellin 1 exhibited significant cytotoxicity toward the DLD-1 human colorectal adenocarcinoma cells.

Cladieunicellins K and L, new eunicellin-based diterpenoids from an octocoral Cladiella sp

Two new eunicellin-based diterpenoids, cladieunicellins K (1) and L (2), were isolated from an octocoral Cladiella sp. The structures of 1 and 2 were elucidated by spectroscopic methods and 2 exhibited moderate cytotoxicity towards the MOLT-4 human leukemia.

Anti-inflammatory activities of natural products isolated from soft corals of Taiwan between 2008 and 2012

This review reports details on the natural products isolated from Taiwan soft corals during the period 2008–2012 focusing on their in vitro and/or in vivo anti-inflammatory activities. Chemical structures, names, and literature references are also reported. This review provides useful and specific information on potent anti-inflammatory marine metabolites for future development of immune-modulatory therapeutics.

Eunicellin-based diterpenoids from the Formosan soft coral Klyxum molle with inhibitory activity on superoxide generation and elastase release by neutrophils

Eleven new eunicellin-based diterpenoids possessing a cladiellane skeleton with a C-2, C-9 ether bridge, klymollins I-S (1-11), have been isolated from the EtOAc extract of the soft coral Klyxum molle from Taiwan waters. The structures of compounds 1-11 were elucidated by extensive spectroscopic analysis, including 2D NMR spectroscopy (COSY, HSQC, HMBC, and NOESY). Compound 5 exhibited cytotoxicity toward several cancer cell lines. Compound 5 is the first eunicellin-based metabolite bearing a phenyl group and displays significant inhibition of both superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced human neutrophils.

Marine natural products

This review covers the literature published in 2011 for marine natural products, with 870 citations (558 for the period January to December 2011) 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 (1152 for 2011), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Simplexins P-S, eunicellin-based diterpenes from the soft coral Klyxum simplex

Four new eunicellin-based diterpenes, simplexins P–S (1–4), and the known compound simplexin A (5), have been isolated from the soft coral Klyxum simplex. The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis, particularly 1D and 2D NMR experiments. Compounds 1 and 3–5 were shown to exhibit cytotoxicity against a limited panel of cancer cell lines, 3 being the most cytotoxic.

New 6-hydroxyeunicellins from a soft coral Cladiella sp

Two new 6-hydroxyeunicellin diterpenoids, cladieunicellin G (1) and 6-epi-cladieunicellin F (2), were isolated from an Indonesian octocoral Cladiella sp. The structures of eunicellins 1 and 2 were established by spectroscopic methods and 2 was found to be an epimer of the known eunicellin cladieunicellin F (3). Eunicellin 2 displayed inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

Cladieunicellin H, a New Hemiketal Eunicellin-Based Diterpenoid from the Octocoral Cladiella sp

A new hemiketal eunicellin-based diterpenoid, cladieunicellin H (1), was isolated from an Indonesian octocoral identified as Cladiella sp. The structure of 1 was determined by spectroscopic methods. This compound was found to display moderate inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

Klymollins A-H, bioactive eunicellin-based diterpenoids from the formosan soft coral Klyxum molle

Eight new eunicellin-based diterpenoids, klymollins A-H (1-8), were isolated during the chemical investigation of the soft coral Klyxum molle from Taiwan waters. Their structures were elucidated by extensive spectroscopic analysis. The absolute configuration of 4 was determined by Mosher's method. Bioassays of the new metabolites showed that compounds 3-8 displayed significant in vitro anti-inflammatory activity by inhibiting the expression of the iNOS protein, and compounds 3, 4, and 6-8 also could effectively reduce the accumulation of COX-2 protein in LPS-stimulated RAW264.7 macrophage cells.

Discovery of new eunicellins from an Indonesian octocoral Cladiella sp

Two new 11-hydroxyeunicellin diterpenoids, cladieunicellin F (1) and (–)-solenopodin C (2), were isolated from an Indonesian octocoral Cladiella sp. The structures of eunicellins 1 and 2 were established by spectroscopic methods, and eunicellin 2 was found to be an enantiomer of the known eunicellin solenopodin C (3). Eunicellin 2 displayed inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils. The previously reported structures of two eunicellin-based compounds, cladielloides A and B, are corrected in this study.