Formamido-diterpenes from the South China Sea sponge Acanthella cavernosa

Genus Acanthella-A Wealthy Treasure: Secondary Metabolites, Synthesis, Biosynthesis, and Bioactivities

Marine sponges are multicellular and primitive animals that potentially represent a wealthy source of novel drugs. The genus Acanthella (family Axinellidae) is renowned to produce various metabolites with various structural characteristics and bioactivities, including nitrogen-containing terpenoids, alkaloids, and sterols. The current work provides an up-to-date literature survey and comprehensive insight into the reported metabolites from the members of this genus, as well as their sources, biosynthesis, syntheses, and biological activities whenever available. In the current work, 226 metabolites have been discussed based on published data from the period from 1974 to the beginning of 2023 with 90 references.

Kalihiacyloxyamides A-H, α-acyloxy amide substituted kalihinane diterpenes isolated from the sponge Acanthella cavernosa collected in the South China Sea

Eight unreported α-acyloxy amide substituted kalihinane diterpenes, named kalihiacyloxyamides A-H were isolated from the South China Sea sponge Acanthella cavernosa. The planar structures and absolute configurations were elucidated by detailed 1D and 2D NMR experiments along with HRESIMS analysis, single crystal X-ray diffraction and CD spectroscopic analysis. Two compounds showed significant cytotoxicity against K562 cell line with IC₅₀ values of 6.4 and 6.3 μM, while two other compounds displayed moderate cytotoxicity against MDA-MB-231 with IC₅₀ values of 7.3 and 7.9 μM.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Medicinal Chemistry of Isocyanides

In eons of evolution, isocyanides carved out a niche in the ecological systems probably thanks to their metal coordinating properties. In 1859 the first isocyanide was synthesized by humans and in 1950 the first natural isocyanide was discovered. Now, at the beginning of XXI century, hundreds of isocyanides have been isolated both in prokaryotes and eukaryotes and thousands have been synthesized in the laboratory. For some of them their ecological role is known, and their potent biological activity as antibacterial, antifungal, antimalarial, antifouling, and antitumoral compounds has been described. Notwithstanding, the isocyanides have not gained a good reputation among medicinal chemists who have erroneously considered them either too reactive or metabolically unstable, and this has restricted their main use to technical applications as ligands in coordination chemistry. The aim of this review is therefore to show the richness in biological activity of the isocyanide-containing molecules, to support the idea of using the isocyanide functional group as an unconventional pharmacophore especially useful as a metal coordinating warhead. The unhidden hope is to convince the skeptical medicinal chemists of the isocyanide potential in many areas of drug discovery and considering them in the design of future drugs.

Marine-Derived Compounds and Prospects for Their Antifungal Application

The introduction of antifungals in clinical practice has an enormous impact on the provision of medical care, increasing the expectancy and quality of life mainly of immunocompromised patients. However, the emergence of pathogenic fungi that are resistant and multi-resistant to the existing antifungal therapy has culminated in fungal infections that are almost impossible to treat. Therefore, there is an urgent need to discover new strategies. The marine environment has proven to be a promising rich resource for the discovery and development of new antifungal compounds. Thus, this review summarizes more than one hundred marine natural products, or their derivatives, which are categorized according to their sources—sponges, bacteria, fungi, and sea cucumbers—as potential candidates as antifungal agents. In addition, this review focus on recent developments using marine antifungal compounds as new and effective approaches for the treatment of infections caused by resistant and multi-resistant pathogenic fungi and/or biofilm formation; other perspectives on antifungal marine products highlight new mechanisms of action, the combination of antifungal and non-antifungal agents, and the use of nanoparticles and anti-virulence therapy.

Cytotoxic Nitrogenous Terpenoids from Two South China Sea Nudibranchs Phyllidiella pustulosa, Phyllidia coelestis, and Their Sponge-Prey Acanthella cavernosa

A detailed chemical investigation of two South China Sea nudibranchs Phyllidiella pustulosa and Phyllidia coelestis, as well as their possible sponge-prey Acanthella cavernosa, led to the isolation of one new nitrogenous cadinane-type sesquiterpenoid xidaoisocyanate A (1), one new naturally occurring nitrogen-containing kalihinane-type diterpenoid bisformamidokalihinol A (16), along with 17 known nitrogenous terpenoids (2⁻15, 17⁻19). The structures of all the isolates were elucidated by detailed spectroscopic analysis and by the comparison of their spectroscopic data with those reported in the literature. In addition, the absolute stereochemistry of the previously reported axiriabiline A (5) was determined by X-ray diffraction (XRD) analysis. In a bioassay, the bisabolane-type sesquiterpenoids 8, 10, and 11 exhibited cytotoxicity against several human cancer cell lines.

Preussins with Inhibition of IL-6 Expression from Aspergillus flocculosus 16D-1, a Fungus Isolated from the Marine Sponge Phakellia fusca

New pyrrolidine alkaloids, preussins C-I (1-7) and (11 R)/(11 S)-preussins J and K (8 and 9), were isolated from the sponge-derived fungus Aspergillus flocculosus 16D-1. The structures and configurations of these preussins were elucidated by detailed spectroscopic analysis, modified Mosher's method, and comparisons with literature data. These compounds showed strong to moderate inhibitory activity toward IL-6 production in lipopolysaccharide-induced THP-1 cells with IC₅₀ values ranging from 0.11 to 22 μM, but were inactive against normal tumor cell lines and fungi.

Diterpenes and Their Derivatives as Potential Anticancer Agents

As therapeutic tools, diterpenes and their derivatives have gained much attention of the medicinal scientists nowadays. It is due to their pledging and important biological activities. This review congregates the anticancer diterpenes. For this, a search was made with selected keywords in PubMed, Science Direct, Web of Science, Scopus, The American Chemical Society and miscellaneous databases from January 2012 to January 2017 for the published articles. A total 28, 789 published articles were seen. Among them, 240 were included in this study. More than 250 important anticancer diterpenes and their derivatives were seen in the databases, acting in the different pathways. Some of them are already under clinical trials, while others are in the nonclinical and/or pre-clinical trials. In conclusion, diterpenes may be one of the lead molecules in the treatment of cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Structure-activity of antifungal compounds inspired by aminobisabolenes from the sponge Halichondria sp

Structure-activity relationships of the antifungal aminobisabolene natural product, 1 isolated from Halichondria sp., and synthetic analogs were explored, in parallel with the antidermatophytic allylamine, Terbinafine®, against a panel of pathogenic fungi: Candida spp., Cryptococcus spp. and Trichophyton rubrum. Interpretation of the results suggest different modes of action in antifungal activity for the two classes of compounds.

Marine Isonitriles and Their Related Compounds

Marine isonitriles represent the largest group of natural products carrying the remarkable isocyanide moiety. Together with marine isothiocyanates and formamides, which originate from the same biosynthetic pathways, they offer diverse biological activities and in spite of their exotic nature they may constitute potential lead structures for pharmaceutical development. Among other biological activities, several marine isonitriles show antimalarial, antitubercular, antifouling and antiplasmodial effects. In contrast to terrestrial isonitriles, which are mostly derived from α-amino acids, the vast majority of marine representatives are of terpenoid origin. An overview of all known marine isonitriles and their congeners will be given and their biological and chemical aspects will be discussed.

Syntheses and biological studies of marine terpenoids derived from inorganic cyanide

Isocyanoterpenes (ICTs) are marine natural products biosynthesized through an unusual pathway that adorns terpene scaffolds with nitrogenous functionality derived from cyanide. The appendage of nitrogen functional groups - isonitriles in particular - onto stereochemically-rich carbocyclic ring systems provides enigmatic, bioactive molecules that have required innovative chemical syntheses. This review discusses the challenges inherent to the synthesis of this diverse family and details the development of the field. We also present recent progress in isolation and discuss key aspects of the remarkable biological activity of these compounds.

Biological Activity of Recently Discovered Halogenated Marine Natural Products

This review presents the biological activity-antibacterial, antifungal, anti-parasitic, antiviral, antitumor, antiinflammatory, antioxidant, and enzymatic activity-of halogenated marine natural products discovered in the past five years. Newly discovered examples that do not report biological activity are not included.

Marine natural products

This review covers the literature published in 2012 for marine natural products, with 1035 citations (673 for the period January to December 2012) 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 (1241 for 2012), 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.