Marine Drugs

Aminopolysaccharide chitin is one of the main structural biopolymers in sponges that is responsible for the mechanical stability of their unique 3D-structured microfibrous and porous skeletons. Chitin in representatives of exclusively marine Verongiida demosponges exists in the form of biocomposite-based scaffolds chemically bounded with biominerals, lipids, proteins, and bromotyrosines. Treatment with alkalis remains one of the classical approaches to isolate pure chitin from the sponge skeleton. For the first time, we carried out extraction of multilayered, tube-like chitin from skeletons of cultivated Aplysina aerophoba demosponge using 1% LiOH solution at 65 °C following sonication. Surprisingly, this approach leads not only to the isolation of chitinous scaffolds but also to their dissolution and the formation of amorphous-like matter. Simultaneously, isofistularin-containing extracts have been obtained. Due to the absence of any changes between the chitin standard derived from arthropods and the sponge-derived chitin treated with LiOH under the same experimental conditions, we suggest that bromotyrosines in A. aerophoba sponge represent the target for lithium ion activity with respect to the formation of LiBr. This compound, however, is a well-recognized solubilizing reagent of diverse biopolymers including cellulose and chitosan. We propose a possible dissolution mechanism of this very special kind of sponge chitin. Full article

Among neglected tropical diseases, leishmaniasis is one of the leading causes, not only of deaths but also of disability-adjusted life years. This disease, caused by protozoan parasites of the genus Leishmania, triggers different clinical manifestations, with cutaneous, mucocutaneous, and visceral forms. As existing treatments for this parasitosis are not sufficiently effective or safe for the patient, in this work, different sesquiterpenes isolated from the red alga Laurencia johnstonii have been studied for this purpose. The different compounds were tested in vitro against the promastigote and amastigote forms of Leishmania amazonensis. Different assays were also performed, including the measurement of mitochondrial potential, determination of ROS accumulation, and chromatin condensation, among others, focused on the detection of the cell death process known in this type of organism as apoptosis-like. Five compounds were identified that displayed leishmanicidal activity: laurequinone, laurinterol, debromolaurinterol, isolaurinterol, and aplysin, showing IC₅₀ values against promastigotes of 1.87, 34.45, 12.48, 10.09, and 54.13 µM, respectively. Laurequinone was the most potent compound tested and was shown to be more effective than the reference drug miltefosine against promastigotes. Different death mechanism studies carried out showed that laurequinone appears to induce programmed cell death or apoptosis in the parasite studied. The obtained results underline the potential of this sesquiterpene as a novel anti-kinetoplastid therapeutic agent. Full article

The enzymatic degradation of different chitin polymers into chitin oligosaccharides (COSs) is of great significance given their better solubility and various biological applications. Chitinase plays a pivotal role in the enzymatic preparation of COSs. Herein, a cold-adapted and efficient chitinase (ChiTg) from the marine Trichoderma gamsii R1 was purified and characterized. The optimal temperature of ChiTg was 40 °C, and the relative activity at 5 °C was above 40.1%. Meanwhile, ChiTg was active and stable from pH 4.0 to 7.0. As an endo-type chitinase, ChiTg exhibited the highest activity with colloidal chitin, then with ball-milled and powdery chitin. In addition, ChiTg showed high efficiency when hydrolyzing colloidal chitin at different temperatures, and the end products were mainly composed of COSs with one to three degrees of polymerization. Furthermore, the results of bioinformatics analysis revealed that ChiTg belongs to the GH18 family, and its acidic surface and the flexible structure of its catalytic site may contribute to its high activity in cold conditions. The results of this study provide a cold-active and efficient chitinase and ideas for its application regarding the preparation of COSs from colloidal chitin. Full article

Microalgal biomass is characterized by high protein, carbohydrates, and lipids concentrations. However, their qualitative and quantitative compositions depend not only on the cultivated species but also on the cultivation conditions. Focusing on the microalgae’s ability to accumulate significant fatty acids (FAs) amounts, they can be valorized either as dietary supplements or for biofuel production, depending on the accumulated biomolecules. In this study, a local isolate (Nephroselmis sp.) was precultured under autotrophic conditions, while the Box–Behnken experimental design followed using the parameters of nitrogen (0–250 mg/L), salinity (30–70 ppt) and illuminance (40–260 μmol m⁻² s⁻¹) to evaluate the accumulated biomolecules, with an emphasis on the amount of FAs and its profile. Regardless of the cultivation conditions, the FAs of C14:0, C16:0, and C18:0 were found in all samples (up to 8% w/w in total), while the unsaturated C16:1 and C18:1 were also characterized by their high accumulations. Additionally, the polyunsaturated FAs, including the valuable C20:5n3 (EPA), had accumulated when the nitrogen concentration was sufficient, and the salinity levels remained low (30 ppt). Specifically, EPA approached 30% of the total FAs. Therefore, Nephroselmis sp. could be considered as an alternative EPA source compared to the already-known species used in food supplementation. Full article

The skin is the largest organ of the human body, composed of a diverse range of cell types, non-cellular components, and an extracellular matrix. With aging, molecules that are part of the extracellular matrix undergo qualitative and quantitative changes and the effects, such as a loss of skin firmness or wrinkles, can be visible. The changes caused by the aging process do not only affect the surface of the skin, but also extend to skin appendages such as hair follicles. In the present study, the ability of marine-derived saccharides, L-fucose and chondroitin sulphate disaccharide, to support skin and hair health and minimize the effects of intrinsic and extrinsic aging was investigated. The potential of the tested samples to prevent adverse changes in the skin and hair through stimulation of natural processes, cellular proliferation, and production of extracellular matrix components collagen, elastin, or glycosaminoglycans was investigated. The tested compounds, L-fucose and chondroitin sulphate disaccharide, supported skin and hair health, especially in terms of anti-aging effects. The obtained results indicate that both ingredients support and promote the proliferation of dermal fibroblasts and dermal papilla cells, provide cells with a supply of sulphated disaccharide GAG building blocks, increase ECM molecule production (collagen and elastin) by HDFa, and support the growth phase of the hair cycle (anagen). Full article

Glioblastoma (GBM) is a major type of primary brain tumor without ideal prognosis and it is therefore necessary to develop a novel compound possessing therapeutic effects. Chrysomycin A (Chr-A) has been reported to inhibit the proliferation, migration and invasion of U251 and U87-MG cells through the Akt/GSK-3β signaling pathway, but the mechanism of Chr-A against glioblastoma in vivo and whether Chr-A modulates the apoptosis of neuroglioma cells is unclear. The present study aims to elucidate the potential of Chr-A against glioblastoma in vivo and how Chr-A modulates the apoptosis of neuroglioma cells. Briefly, the anti-glioblastoma activity was assessed in human glioma U87 xenografted hairless mice. Chr-A-related targets were identified via RNA-sequencing. Apoptotic ratio and caspase 3/7 activity of U251 and U87-MG cells were assayed via flow cytometry. Apoptosis-related proteins and possible molecular mechanisms were validated via Western blotting. The results showed that Chr-A treatment significantly inhibits glioblastoma progression in xenografted hairless mice, and enrichment analysis suggested that apoptosis, PI3K-Akt and Wnt signaling pathways were involved in the possible mechanisms. Chr-A increased the apoptotic ratio and the activity of caspase 3/7 in U251 and U87-MG cells. Western blotting revealed that Chr-A disturbed the balance between Bax and Bcl-2, activating a caspase cascade reaction and downregulating the expression of p-Akt and p-GSK-3β, suggesting that Chr-A may contribute to glioblastoma regression modulating in the Akt/GSK-3β signaling pathway to promote apoptosis of neuroglioma cells in vivo and in vitro. Therefore, Chr-A may hold therapeutic promise for glioblastoma. Full article

In this study, we characterized the bioactive properties of three important brown seaweed species, Sargassum thunbergii, Undaria pinnatifida, and Saccharina japonica, by subcritical water extraction (SWE), as these species are well known for their beneficial health effects. Their physiochemical properties, including potential antioxidant, antihypertensive, and α-glucosidase inhibitory activity, and the antibacterial activity of the hydroysates were also analyzed. The highest total phlorotannin, total sugar content, and reducing sugar content in the S. thunbergii hydrolysates were 38.82 ± 0.17 mg PGE/g, 116.66 ± 0.19 mg glucose/g dry sample, and 53.27 ± 1.57 mg glucose/g dry sample, respectively. The highest ABTS⁺ and DPPH antioxidant activities were obtained in the S. japonica hydrolysates (124.77 ± 2.47 and 46.35 ± 0.01 mg Trolox equivalent/g, respectively) and the highest FRAP activity was obtained in the S. thunbergii hydrolysates (34.47 ± 0.49 mg Trolox equivalent/g seaweed). In addition, the seaweed extracts showed antihypertensive (≤59.77 ± 0.14%) and α-glucosidase inhibitory activity (≤68.05 ± 1.15%), as well as activity against foodborne pathogens. The present findings provide evidence of the biological activity of brown seaweed extracts for potential application in the food, pharmaceutical, and cosmetic sectors. Full article

To discover bioactive natural products from mangrove sediment-derived microbes, a chemical investigation of the two Beibu Gulf-derived fungi strains, Talaromyces sp. SCSIO 41050 and Penicillium sp. SCSIO 41411, led to the isolation of 23 natural products. Five of them were identified as new ones, including two polyketide derivatives with unusual acid anhydride moieties named cordyanhydride A ethyl ester (1) and maleicanhydridane (4), and three hydroxyphenylacetic acid derivatives named stachylines H–J (10–12). Their structures were determined by detailed nuclear magnetic resonance (NMR) and mass spectroscopic (MS) analyses, while the absolute configurations were established by theoretical electronic circular dichroism (ECD) calculation. A variety of bioactive screens revealed three polyketide derivatives (1–3) with obvious antifungal activities, and 4 displayed moderate cytotoxicity against cell lines A549 and WPMY-1. Compounds 1 and 6 at 10 μM exhibited obvious inhibition against phosphodiesterase 4 (PDE4) with inhibitory ratios of 49.7% and 39.6%, respectively, while 5, 10, and 11 showed the potential of inhibiting acetylcholinesterase (AChE) by an enzyme activity test, as well as in silico docking analysis. Full article

Conotoxins are a class of disulfide-rich peptides found in the venom of cone snails, which have attracted considerable attention in recent years due to their potent activity on ion channels and potential for therapeutics. Among them, α-conotoxin RgIA, a 13-residue peptide, has shown great promise as a potent inhibitor of α9α10 nAChRs for pain management. In this study, we investigated the effect of substituting the naturally occurring L-type arginine at position 11 of the RgIA sequence with its D-type amino acid. Our results indicate that this substitution abrogated the ability of RgIA to block α9α10 nAChRs, but instead endowed the peptide with the ability to block α7 nAChR activity. Structural analyses revealed that this substitution induced significant alteration of the secondary structure of RgIA[11r], which consequently affected its activity. Our findings underscore the potential of D-type amino acid substitution as a promising strategy for designing novel conotoxin-based ligands targeting different types of nAChRs. Full article

Based on the marine natural products piperafizine B, XR334, and our previously reported compound 4m, fourteen novel 3,6-diunsaturated 2,5-diketopiperazine (2,5-DKP) derivatives (1, 2, 4–6, 8–16), together with two known ones (3 and 7), were designed and synthesized as anticancer agents against the A549 and Hela cell lines. The MTT assay results showed that the derivatives 6, 8–12, and 14 had moderate to good anticancer capacities, with IC₅₀ values ranging from 0.7 to 8.9 μM. Among them, compound 11, with naphthalen-1-ylmethylene and 2-methoxybenzylidene functions at the 3 and 6 positions of 2,5-DKP ring, respectively, displayed good inhibitory activities toward both A549 (IC₅₀ = 1.2 μM) and Hela (IC₅₀ = 0.7 μM) cancer cells. It could also induce apoptosis and obviously block cell cycle progression in the G2/M phases in both cells at 1.0 μM. The electron-withdrawing functions might not be favorable for the derivatives with high anticancer activities. Additionally, compared to piperafizine B and XR334, these semi-N-alkylated derivatives have high liposolubilities (>1.0 mg mL⁻¹). Compound 11 can be further developed, aiming at the discovery of a novel anticancer candidate. Full article

Sodium alginate (SALG) is a substance derived from brown seaweed that has been shown to reduce blood pressure (BP). However, its effects on renovascular hypertension caused by 2-kidney, 1-clip (2K1C) are not yet clear. Previous research suggests that hypertensive rats have increased intestinal permeability, and that SALG improves the gut barrier in inflammatory bowel disease mouse models. Therefore, the goal of this study was to determine whether the antihypertensive effects of SALG involve the intestinal barrier in 2K1C rats. Rats were fed either a 1.0% SALG diet or a control diet for six weeks after being subjected to 2K1C surgery or a sham operation. The systolic BP was measured weekly, and the mean arterial BP was measured at the end of the study. Intestinal samples were taken for analysis, and plasma lipopolysaccharide (LPS) levels were measured. The results showed that BP in 2K1C rats was significantly higher than in SHAM rats when fed CTL, but not when fed SALG. The gut barrier in 2K1C rats was improved by SALG intake. Plasma LPS levels also differed depending on the animal model and diet. In conclusion, dietary SALG may alleviate 2K1C renovascular hypertension by altering the gut barrier. Full article

Polyphenols are compounds found in various plants and foods, known for their antioxidant and anti-inflammatory properties. Recently, researchers have been exploring the therapeutic potential of marine polyphenols and other minor nutrients that are found in algae, fish and crustaceans. These compounds have unique chemical structures and exhibit diverse biological properties, including anti-inflammatory, antioxidant, antimicrobial and antitumor action. Due to these properties, marine polyphenols are being investigated as possible therapeutic agents for the treatment of a wide variety of conditions, such as cardiovascular disease, diabetes, neurodegenerative diseases and cancer. This review focuses on the therapeutic potential of marine polyphenols and their applications in human health, and also, in marine phenolic classes, the extraction methods, purification techniques and future applications of marine phenolic compounds. Full article

Puupehenone and puupehedione are natural products isolated from marine organisms. These compounds display a broad spectrum of biological activities, the in vitro antitubercular activity of puupehenone being a stand out, and are equipped with an interesting structural complexity. These products have served to stimulate the continual interest of the synthetic community. The first part of this article is a review of their total synthesis, using natural compounds which have the potential to be transformed into these marine compounds as starting materials; the synthetic routes employed to generate the basic skeleton; and the advances made to synthesize the pyran C ring with the required diastereoselectivity to obtain the natural products. Finally, this perspective shows a personal reflection of the authors on a possible unified and efficient retrosynthetic route that could allow easy access to these natural products, as well as their epimers at the C8 carbon and which could be used to address future biological issues in the production of pharmacologically active compounds. Full article

The biomass of microalgae and the compounds that can be obtained from their processing are of great interest for various economic sectors. Chlorophyll from green microalgae has biotechnological applications of great potential in different industrial areas such as food, animal feed, pharmaceuticals, cosmetics, and agriculture. In this paper, the experimental, technical and economic performance of biomass production from a microalgal consortium (Scenedesmus sp., Chlorella sp., Schroderia sp., Spirulina sp., Pediastrum sp., and Chlamydomonas sp.) was investigated in three cultivation systems (phototrophic, heterotrophic and mixotrophic) in combination with the extraction of chlorophyll (a and b) on a large scale using simulation; 1 ha was established as the area for cultivation. In the laboratory-scale experimental stage, biomass and chlorophyll concentrations were determined for 12 days. In the simulation stage, two retention times in the photobioreactor were considered, which generated six case studies for the culture stage. Subsequently, a simulation proposal for the chlorophyll extraction process was evaluated. The highest microalgae biomass concentration was 2.06 g/L in heterotrophic culture, followed by mixotrophic (1.98 g/L). Phototrophic and mixotrophic cultures showed the highest chlorophyll concentrations of 20.5 µg/mL and 13.5 µg/mL, respectively. The simulation shows that higher biomass and chlorophyll production is attained when using the mixotrophic culture with 72 h of retention that we considered to evaluate chlorophyll production (a and b). The operating cost of the entire process is very high; the cultivation stage has the highest operating cost (78%), mainly due to the high energy consumption of the photobioreactors. Full article

Tetrodotoxin (TTX) and its analogues are naturally occurring toxins historically responsible for human poisoning fatalities in Eastern Asia. It is typically linked to the consumption of pufferfish and, to a lesser extent, marine gastropods and crabs. In the scope of a comprehensive project to understand the prevalence of emergent toxins in edible marine organisms, we report, for the first time, the detection of TTX analogues in the soft tissues of edible crabs, the European fiddler crab (Afruca tangeri) and green crab (Carcinus maenas), harvested in southern Portugal. No TTX was detected in the analyzed samples. However, three TTX analogues were detected—an unknown TTX epimer, deoxyTTX, and trideoxyTTX. These three analogues were found in the European fiddler crab while only trideoxyTTX was found in the green crab, suggesting that the accumulation of TTX analogues might be influenced by the crabs’ different feeding ecology. These results highlight the need to widely monitor TTX and its analogues in edible marine species in order to provide adequate information to the European Food Safety Authority and to protect consumers. Full article

One possible scheme of Rugulopteryx okamurae biomass valorization based on a green, rapid and efficient fractionation technique was proposed. Microwave-assisted pressurized hot water extraction was the technology selected as the initial stage for the solubilization of different seaweed components. Operation at 180 °C for 10 min with a 30 liquid-to-solid ratio solubilized more than 40% of the initial material. Both the alginate recovery yield (3.2%) and the phenolic content of the water-soluble extracts (2.3%) were slightly higher when distilled water was used as solvent. However, the carbohydrate content in the extract (60%) was similar for both solvents, but the sulfate content was higher for samples processed with salt water collected from the same coast as the seaweeds. The antiradical capacity of the extracts was related to the phenolic content in the extracts, but the cytotoxicity towards HeLa229 cancer cells was highest (EC₅₀ = 48 µg/mL) for the extract obtained with distilled water at the lowest temperature evaluated. Operation time showed a relevant enhancement of the extraction performance and bioactive properties of the soluble extracts. The further fractionation and study of this extract would be recommended to extend its potential applications. However, due to the low extraction yield, emphasis was given to the solid residue, which showed a heating value in the range 16,102–18,413 kJ/kg and could be useful for the preparation of biomaterials according to its rheological properties. Full article

Studies estimate that nearly 2 million new cases of gastric cancer will occur worldwide during the next two decades, which will increase mortality associated with cancer and the demand for new treatments. Marine algae of the Laurencia genus have secondary metabolites known for their cytotoxic action, such as terpenes and acetogenins. The species Laurencia obtusa has demonstrated cytotoxicity against many types of tumors in previous analyses. In this study, we determined the structure of terpenes, acetogenins, and one fatty acid of Laurencia using mass spectrometry (ESI-FT-ICR/MS). In vitro cytotoxicity assays were performed with adenocarcinoma gastric cells (AGS) to select the most cytotoxic fraction of the crude extract of L. obtusa. The Hex:AcOEt fraction was the most cytotoxic, with IC₅₀ 9.23 µg/mL. The selectivity index of 15.56 shows that the Hex:AcOEt fraction is selective to cancer cells. Compounds obtained from L. obtusa were tested by the analysis of crystallographic complexes. Molecular docking calculations on the active site of the HIF-2α protein showed the highest affinity for sesquiterpene chermesiterpenoid B, identified from HEX:AcOEt fraction, reaching a score of 65.9. The results indicate that L. obtusa presents potential compounds to be used in the treatment of neoplasms, such as gastric adenocarcinoma. Full article

The incorporation of bromine, iodine or fluorine into the tricyclic core structure of thiaplakortone A (1), a potent antimalarial marine natural product, is reported. Although yields were low, it was possible to synthesise a small nine-membered library using the previously synthesised Boc-protected thiaplakortone A (2) as a scaffold for late-stage functionalisation. The new thiaplakortone A analogues (3–11) were generated using N-bromosuccinimide, N-iodosuccinimide or a Diversinate™ reagent. The chemical structures of all new analogues were fully characterised by 1D/2D NMR, UV, IR and MS data analyses. All compounds were evaluated for their antimalarial activity against Plasmodium falciparum 3D7 (drug-sensitive) and Dd2 (drug-resistant) strains. Incorporation of halogens at positions 2 and 7 of the thiaplakortone A scaffold was shown to reduce antimalarial activity compared to the natural product. Of the new compounds, the mono-brominated analogue (compound 5) displayed the best antimalarial activity with IC₅₀ values of 0.559 and 0.058 μM against P. falciparum 3D7 and Dd2, respectively, with minimal toxicity against a human cell line (HEK293) observed at 80 μM. Of note, the majority of the halogenated compounds showed greater efficacy against the P. falciparum drug-resistant strain. Full article

The pharmacological treatment of cancer-related pain is unsatisfactory. Tetrodotoxin (TTX) has shown analgesia in preclinical models and clinical trials, but its clinical efficacy and safety have not been quantified. For this reason, our aim was to perform a systematic review and meta-analysis of the clinical evidence that was available. A systematic literature search was conducted in four electronic databases (Medline, Web of Science, Scopus, and ClinicalTrials.gov) up to 1 March 2023 in order to identify published clinical studies evaluating the efficacy and security of TTX in patients with cancer-related pain, including chemotherapy-induced neuropathic pain. Five articles were selected, three of which were randomized controlled trials (RCTs). The number of responders to the primary outcome (≥30% improvement in the mean pain intensity) and those suffering adverse events in the intervention and placebo groups were used to calculate effect sizes using the log odds ratio. The meta-analysis showed that TTX significantly increased the number of responders (mean = 0.68; 95% CI: 0.19–1.16, p = 0.0065) and the number of patients suffering non-severe adverse events (mean = 1.13; 95% CI: 0.31–1.95, p = 0.0068). However, TTX did not increase the risk of suffering serious adverse events (mean = 0.75; 95% CI: −0.43–1.93, p = 0.2154). In conclusion, TTX showed robust analgesic efficacy but also increased the risk of suffering non-severe adverse events. These results should be confirmed in further clinical trials with higher numbers of patients. Full article