New bioactive sulfated metabolites from the Mediterranean tunicate Sidnyum turbinatum

Marine Natural Products from Tunicates and Their Associated Microbes

Marine tunicates are identified as a potential source of marine natural products (MNPs), demonstrating a wide range of biological properties, like antimicrobial and anticancer activities. The symbiotic relationship between tunicates and specific microbial groups has revealed the acquisition of microbial compounds by tunicates for defensive purpose. For instance, yellow pigmented compounds, "tambjamines", produced by the tunicate, Sigillina signifera (Sluiter, 1909), primarily originated from their bacterial symbionts, which are involved in their chemical defense function, indicating the ecological role of symbiotic microbial association with tunicates. This review has garnered comprehensive literature on MNPs produced by tunicates and their symbiotic microbionts. Various sections covered in this review include tunicates' ecological functions, biological activities, such as antimicrobial, antitumor, and anticancer activities, metabolic origins, utilization of invasive tunicates, and research gaps. Apart from the literature content, 20 different chemical databases were explored to identify tunicates-derived MNPs. In addition, the management and exploitation of tunicate resources in the global oceans are detailed for their ecological and biotechnological implications.

The Ascidian-Derived Metabolites with Antimicrobial Properties

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.

Antitumoral compounds from vertebrate sister group: A review of Mediterranean ascidians

Among the diseases that afflict the human population, cancer is one for which many drug treatments are not yet known or effective. Moreover, the pharmacological treatments used often create serious side effects in sick patients and for this reason, it is essential to find effective and less harmful treatments. To date, marine biodiversity is a real source of metabolites with antitumoral activity and among invertebrates' ascidians have been the main source to obtain them. Mediterranean area is the richest in biodiversity and contains several ascidian species used in drugs development during the years. However, many more Mediterranean ascidian species have not been studied and could be a source of useful bioactive compounds. This review aims to summarize the scientific studies that analyzed the antitumor compounds obtained from different Mediterranean ascidians species, encouraging them to search further compounds in other new species to improve pharmacological treatments and human population life.

Natural Products Diversity of Marine Ascidians (Tunicates; Ascidiacea) and Successful Drugs in Clinical Development

This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications, challenges and recent developments in marine drug discovery reported during 1994-2014, highlighting the structural activity of compounds produced by these specimens. Till date only 5% of living ascidian species were studied from <3000 species, this study represented from family didemnidae (32%), polyclinidae (22%), styelidae and polycitoridae (11-12%) exhibiting the highest number of promising MNPs. Close to 580 compound structures are here discussed in terms of their occurrence, structural type and reported biological activity. Anti-cancer drugs are the main area of interest in the screening of MNPs from ascidians (64%), followed by anti-malarial (6%) and remaining others. FDA approved ascidian compounds mechanism of action along with other compounds status of clinical trials (phase 1 to phase 3) are discussed here in. This review highlights recent developments in the area of natural products chemistry and biotechnological approaches are emphasized.

XAS spectroscopy, sulfur, and the brew within blood cells from Ascidia ceratodes

We report the first use of K-edge X-ray absorption spectroscopy (XAS) as a direct spectroscopic probe of pH and cytosolic emf within living cells. A new accuracy metric of model-based fits to K-edge spectra is further developed. Sulfur functional groups in three collections of living blood cells and one sample of cleared blood plasma from the tunicate Ascidia ceratodes were speciated using K-edge XAS. Cysteine and cystine, the preferred thiol-disulfide model, averaged about 12% of total sulfur. Sulfate monoesters and cyclic diesters unexpectedly constituted 36% of blood cell sulfur. Soluble sulfate averaged about 25% across the three blood cell samples, while the ratio of SO4(2-) to HSO4(-) implied average signet ring vacuolar pH values of 0.85, 1.4, or 3.1. Intracellular (VSO4)(+) was unobserved, while [V(RSO3)n]((3-n)+) was detected in the two lowest pH blood cell samples. About 5% of sulfur was distributed as mono- or dibenzothiophene or ethylene-epi-sulfide, or as a thiadiazole reminiscent of the polycarpathiamines. Blood plasma was dominated by sulfate (83%), but with 15% of an alkylsulfate ester and about 2% of low-valent sulfur. Gravimetric analysis of soluble sulfate yielded average concentrations of blood cell sulfur. Average [cysteine] and [cystine] (ranging ~10-30 mM and ~20-90 mM, respectively) implied blood-cell cytosolic emf values of approximately -0.20 V. High cellular [cysteine] is consistent with the proposed model for enzymatic reduction of vanadate by endogenous thiol, wherein the trajectory of metal site-symmetry is controlled and directed through to a thermodynamically favored 7-coordinate V(III) product.

New bioactive sulfated alkenes from the sea cucumber Apostichopus japonicus

Two new alkene sulfates, (5Z)-dec-5-en-1-yl sulfate (4) and (3E)-dec-3-en-1-yl sulfate (5), together with three known sulfated alkanes, 2,6-dimethylheptyl sulfate (1), octyl sulfate (2), and decyl sulfate (3), were isolated from the sea cucumber Apostichopus japonicus. The structures of the new compounds 4 and 5 were elucidated by spectroscopic analysis, including ¹H-, ¹³C-, and 2D-NMR, ESI-MS, and HR-ESI-MS. Compounds 2 and 3 were isolated from natural sources for the first time. In preliminary bioassays in vitro, compounds 4 and 5 showed antibacterial, antifungal, and cytotoxic activities.

New bioactive alkyl sulfates from Mediterranean tunicates

Chemical investigation of two species of marine ascidians, Aplidium elegans and Ciona edwardsii, collected in Mediterranean area, led to isolation of a series of alkyl sulfates (compounds 1-5) including three new molecules 1-3. Structures of the new metabolites have been elucidated by spectroscopic analysis. Based on previously reported cytotoxic activity of these type of molecules, compounds 1-3 have been tested for their effects on the growth of two cell lines, J774A.1 (BALB/c murine macrophages) and C6 (rat glioma) in vitro. Compounds 1 and 2 induced selective concentration-dependent mortality on J774A.1 cells.

Diving for drugs: tunicate anticancer compounds

The marine biosphere boasts tremendous biodiversity replete with structurally unique, active and selective secondary metabolites. Bioprospecting for antitumor compounds has been rewarding, and tunicates have been especially successful in yielding prospective cancer therapies. These compounds are now subjected to clinical trials in Europe and the USA. With the ongoing search for potent and specific anticancer drugs, in this article we discuss the unique perspectives, compounds and opportunities afforded by this rich source of potential pharmaceuticals. We discuss marine-derived antitumor drugs, their structures, and their various types and levels of antitumor activities in bench and bedside efforts.

Sodium 1-(12-hydroxy)octadecanyl sulfate, an MMP2 inhibitor, isolated from a tunicate of the family Polyclinidae

Sodium 1-(12-hydroxy)octadecanyl sulfate (1) was isolated from a marine tunicate as a matrix metalloproteinase 2 (MMP2) inhibitor.(1) The structure was elucidated by a combination of spectroscopic and chemical methods. Compound 1 inhibited MMP2 with an IC(50) value of 9.0 microg/mL.

Turbinamide, a new selective cytotoxic agent from the Mediterranean tunicate Sidnyum turbinatum

A unique cytotoxic metabolite, turbinamide (1), has been isolated from the marine tunicate Sidnyum turbinatum through a bioassay-guided approach. Its structure has been elucidated by an extensive spectroscopic analysis. Turbinamide demonstrated a strong and selective cytotoxic effect against neuronal cells rather than immune system cells. Structure: see text.