Bifunctionalized amphilectane diterpenes from the sponge Stylissa cf. massa

Four uncommon cycloamphilectane-type diterpenoids with antibacterial activity from the South China Sea soft coral Sinularia brassica

The chemical investigation on the soft coral Sinularia brassica collected off Xuwen Country, Guangdong Province, China, has resulted in the isolation and characterization of three uncommon cycloamphilectane-type diterpenoids, namely sinucycloamtin A-C (1-3), along with two known analogues (5 and 6). In addition, compounds 2 and 3 were hydrolyzed and their hydrolytic derivative sinucycloamtin D (4) was obtained. The structures of these previously undescribed compounds were established on the basis of extensive spectroscopic analysis, X-ray diffraction analysis, chemical conversion, as well as the comparison with the literature reported data. Compounds 1-3 represented the first examples of benzene-containing cycloamphilectane-type diterpenoids isolated from soft coral of genus Sinularia. In the in vitro bioassays, all the isolated and derived diterpenoids exhibited significant antibacterial activities against the fish pathogenic bacteria Phoyobacterium damselae FP2244 and Streptococcus parauberis SPOF3K with MIC90 values ranging from 3.7 to 9.1 μM.

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.

Chemical and biological diversity of new natural products from marine sponges: a review (2009-2018)

Marine sponges are productive sources of bioactive secondary metabolites with over 200 new compounds isolated each year, contributing 23% of approved marine drugs so far. This review describes statistical research, structural diversity, and pharmacological activity of sponge derived new natural products from 2009 to 2018. Approximately 2762 new metabolites have been reported from 180 genera of sponges this decade, of which the main structural types are alkaloids and terpenoids, accounting for 50% of the total. More than half of new molecules showed biological activities including cytotoxic, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, enzyme inhibition, and antimalarial activities. As summarized in this review, macrolides and peptides had higher proportions of new bioactive compounds in new compounds than other chemical classes. Every chemical class displayed cytotoxicity as the dominant activity. Alkaloids were the major contributors to antibacterial, antifungal, and antioxidant activities while steroids were primarily responsible for pest resistance activity. Alkaloids, terpenoids, and steroids displayed the most diverse biological activities. The statistic research of new compounds by published year, chemical class, sponge taxonomy, and biological activity are presented. Structural novelty and significant bioactivities of some representative compounds are highlighted. Marine sponges are rich sources of novel bioactive compounds and serve as animal hosts for microorganisms, highlighting the undisputed potential of sponges in the marine drugs research and development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-022-00132-3.

Trends of antimalarial marine natural products: progresses, challenges and opportunities

This review provides an overview of the antimalarial marine natural products, focusing on their chemistry, malaria-related targets and mechanisms, and highlighting their potential for drug development.

Pyrrolactams from Marine Sponge Stylissa massa Collected from Myanmar and Their Anti-Vpr Activities

A new brominated pyrrolactam stylissaol A (1) together with four known analogues, 2-bromoaldisine, aldisine, spongiacidin D, and Z-hymenialdisine, were isolated from the EtOAc extract of marine sponge Stylissa massa collected in Myanmar. The absolute configuration at C-10 of 1 was determined as R by the electronic circular dichroism (ECD) data. Among the isolated compounds, 2-bromoaldisine showed anti-Viral Protein R (Vpr) activity against TREx-HeLa-Vpr cells with an effective dose of 10 µM and its potency was comparable to that of positive control damnacanthal.

A Soft Spot for Chemistry-Current Taxonomic and Evolutionary Implications of Sponge Secondary Metabolite Distribution

Marine sponges are the most prolific marine sources for discovery of novel bioactive compounds. Sponge secondary metabolites are sought-after for their potential in pharmaceutical applications, and in the past, they were also used as taxonomic markers alongside the difficult and homoplasy-prone sponge morphology for species delineation (chemotaxonomy). The understanding of phylogenetic distribution and distinctiveness of metabolites to sponge lineages is pivotal to reveal pathways and evolution of compound production in sponges. This benefits the discovery rate and yield of bioprospecting for novel marine natural products by identifying lineages with high potential of being new sources of valuable sponge compounds. In this review, we summarize the current biochemical data on sponges and compare the metabolite distribution against a sponge phylogeny. We assess compound specificity to lineages, potential convergences, and suitability as diagnostic phylogenetic markers. Our study finds compound distribution corroborating current (molecular) phylogenetic hypotheses, which include yet unaccepted polyphyly of several demosponge orders and families. Likewise, several compounds and compound groups display a high degree of lineage specificity, which suggests homologous biosynthetic pathways among their taxa, which identifies yet unstudied species of this lineage as promising bioprospecting targets.

Antimalarial Activity of Sea Sponge Extract of Stylissa massa originating from waters of Rote Island

Research on the isolation, toxicity test, antimalarial test, and identification of the active compound from the ethyl acetate fraction of Stylissa massa sponge from Oenggae waters, Rote Island, has been conducted. This study aimed to investigate the antimalarial activity of the ethyl acetate fraction of the Stylissa massa sponge. Isolation was carried out by the extraction method using a mixed solvent of methanol: dichloromethane of 3: 2 (v/v), then the extract was partitioned in a solvent mixture of ethyl acetate: water of 1: 2 (v/v). The ethyl acetate extract obtained was separated by column chromatography using the gradient polarity system method. The toxicity test of each fraction was carried out by the Brine Shrimp Lethality Test (BSLT) method, and the antimalarial test was carried out by the haematin polymerization inhibition method. Identification of compounds from the active fraction in the antimalarial test was carried out using Liquid Chromatography-Mass Spectrometry (LC-MS). The extraction yield was 1.14 g (0.23%) of the ethyl acetate extract in the form of a dark brownish-yellow oily solid. Separation by column chromatography resulted in 15 fractions. Toxicity test results showed the four most active fractions with LC50 values, which are very promising for new drug discovery. The IC50 value in the antimalarial activity test of the four fractions indicated that the Stylissa massa sponge ethyl acetate extract was more active than the standard chloroquine compound (115 μg/mL). The LC-MS analysis indicates that fraction 11 contains two compounds that have been reported, and 1 compound is unknown. In contrast, fraction 14 indicates that it contains three compounds that have been reported and one unknown compound.

Metabolites from Marine Sponges and Their Potential to Treat Malarial Protozoan Parasites Infection: A Systematic Review

Malaria is an infectious disease caused by protozoan parasites of the Plasmodium genus through the bite of female Anopheles mosquitoes, affecting 228 million people and causing 415 thousand deaths in 2018. Artemisinin-based combination therapies (ACTs) are the most recommended treatment for malaria; however, the emergence of multidrug resistance has unfortunately limited their effects and challenged the field. In this context, the ocean and its rich biodiversity have emerged as a very promising resource of bioactive compounds and secondary metabolites from different marine organisms. This systematic review of the literature focuses on the advances achieved in the search for new antimalarials from marine sponges, which are ancient organisms that developed defense mechanisms in a hostile environment. The principal inclusion criterion for analysis was articles with compounds with IC₅₀ below 10 µM or 10 µg/mL against P. falciparum culture. The secondary metabolites identified include alkaloids, terpenoids, polyketides endoperoxides and glycosphingolipids. The structural features of active compounds selected in this review may be an interesting scaffold to inspire synthetic development of new antimalarials for selectively targeting parasite cell metabolism.

Antiplasmodial natural products: an update

Background

Malaria remains a significant public health challenge in regions of the world where it is endemic. An unprecedented decline in malaria incidences was recorded during the last decade due to the availability of effective control interventions, such as the deployment of artemisinin-based combination therapy and insecticide-treated nets. However, according to the World Health Organization, malaria is staging a comeback, in part due to the development of drug resistance. Therefore, there is an urgent need to discover new anti-malarial drugs. This article reviews the literature on natural products with antiplasmodial activity that was reported between 2010 and 2017.

Methods

Relevant literature was sourced by searching the major scientific databases, including Web of Science, ScienceDirect, Scopus, SciFinder, Pubmed, and Google Scholar, using appropriate keyword combinations.

Results and Discussion

A total of 1524 compounds from 397 relevant references, assayed against at least one strain of Plasmodium, were reported in the period under review. Out of these, 39% were described as new natural products, and 29% of the compounds had IC₅₀ ≤ 3.0 µM against at least one strain of Plasmodium. Several of these compounds have the potential to be developed into viable anti-malarial drugs. Also, some of these compounds could play a role in malaria eradication by targeting gametocytes. However, the research into natural products with potential for blocking the transmission of malaria is still in its infancy stage and needs to be vigorously pursued.

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.

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.

Two rare-class tricyclic diterpenes with antitubercular activity from the Caribbean sponge Svenzea flava. Application of vibrational circular dichroism spectroscopy for determining absolute configuration

Two new natural products, 3 and 4, and their predecessor 7-isocyanoisoneoamphilecta-1(14),15-diene (2), of the rare isoneoamphilectane class of marine diterpenes, along with the known amphilectane diterpenes 6-8, were isolated from the n-hexane extract of the marine sponge Svenzea flava collected at Great Inagua Island, Bahamas. The molecular structures of compounds 3 and 4 were established by spectroscopic (1D/2D NMR, IR, UV, HRMS) methods and confirmed by a series of chemical correlation studies. In a first ever case study of the assignment of the absolute configuration of a molecule based on the isoneoamphilectane carbon skeleton, the absolute configuration of compound 5 was established as 3S,4R,7S,8S,11R,12S,13R by application of vibrational circular dichroism (VCD). In vitro anti-TB screenings revealed that metabolites 2-4 and, in particular, semisynthetic analogue 5, are strong growth inhibitors of Mycobacterium tuberculosis H37Rv.