Astaxanthin from Haematococcus pluvialis Prevents Oxidative Stress on Human Endothelial Cells without Toxicity

Astaxanthin, a powerful antioxidant, is a good candidate for the prevention of intracellular oxidative stress. The aim of the study was to compare the antioxidant activity of astaxanthin present in two natural extracts from Haematococcus pluvialis, a microalgae strain, with that of synthetic astaxanthin. Natural extracts were obtained either by solvent or supercritical extraction methods. UV, HPLC-DAD and (HPLC-(atmospheric pressure chemical ionization (APCI)+)/ion trap-MS) characterizations of both natural extracts showed similar compositions of carotenoids, but different percentages in free astaxanthin and its ester derivatives. The Trolox equivalent antioxidant capacity (TEAC) assay showed that natural extracts containing esters displayed stronger antioxidant activities than free astaxanthin. Their antioxidant capacities to inhibit intracellular oxidative stress were then evaluated on HUVEC cells. The intracellular antioxidant activity in natural extracts was approximately 90-times higher than synthetic astaxanthin (5 µM). No modification, neither in the morphology nor in the viability, of vascular human cells was observed by in vitro biocompatibility study up to 10 µM astaxanthin concentrations. Therefore, these results revealed the therapeutic potential of the natural extracts in vascular human cell protection against oxidative stress without toxicity, which could be exploited in prevention and/or treatment of cardiovascular diseases.     

Ω3 Supplementation and Intermittent Hypobaric Hypoxia Induce Cardioprotection Enhancing Antioxidant Mechanisms in Adult Rats

Intermittent hypobaric hypoxia (IH) is linked with oxidative stress, impairing cardiac function. However, early IH also activate cardio-protective mechanisms. Omega 3 fatty acids (Ω3) induce cardioprotection by reducing infarct size and reinforcing antioxidant defenses. The aim of this work was to determine the combined effects of IH and Ω3 on cardiac function; oxidative balance and inflammatory state. Twenty-eight rats were randomly divided into four groups: normobaric normoxia (N); N + Ω3 (0.3 g·kg⁻¹·day⁻¹); IH; and IH + Ω3. IH was induced by 4 intercalate periods of hypoxia (4 days)—normoxia (4 days) in a hypobaric chamber during 32 days. At the end of the exposure, hearts were mounted in a Langendorff system and subjected to 30 min of ischemia followed by 120 min of reperfusion. In addition, we determined HIF-1α and ATP levels, as well as oxidative stress by malondialdehyde and nitrotyrosine quantification. Further, the expression of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase was determined. NF-kappaB and myeloperoxidase levels were assessed in the hearts. Relative to N hearts, IH improved left ventricular function (Left ventricular developed pressure: N; 21.8 ± 3.4 vs. IH; 42.8 ± 7.1 mmHg; p < 0.05); reduced oxidative stress (Malondialdehyde: N; 14.4 ± 1.8 vs. IH; 7.3 ± 2.1 μmol/mg prot.; p < 0.05); and increased antioxidant enzymes expression. Supplementation with Ω3 induces similar responses as IH group. Our findings suggest that both, IH and Ω3 in an independent manner, induce functional improvement by antioxidant and anti-inflammatory mechanisms, establishing cardio-protection.     

Influence of Temperature on Growth and Production of Pectenotoxin-2 by a Monoclonal Culture of Dinophysis caudata

The effects of temperature on growth and production of Lipophilic Toxins (LT) by a monoclonal culture of Dinophysis caudata was studied. The cell density of D. caudata increased significantly with increasing temperature, and was the highest under 27, 30, and 32.5 °C. Temperature affected the average specific growth rate (µ) during the exponential growth phase (EG), which increased from 15 °C to 30 °C, and then decreased at 32.5 °C. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed that this strain of D. caudata produced only pectenotoxin-2 (PTX-2) whose concentration increased significantly with incubation period, except at 32.5 °C. It was significantly different between temperatures ≤18 °C, ≥21 °C, and 32.5 °C. The cellular toxin production (CTP, pg·cell⁻¹·day⁻¹) showed variation with growth phase and temperature, except at 32.5 °C. The average net toxin production (R_tox) was not affected by temperature. During EG, the average specific toxin production rate (µ_tox) increased significantly with increase in temperature, reaching a peak of 0.66 ± 0.01 day⁻¹ at 30 °C, and then decreased. Over the entire growth span, µ_tox was significantly correlated to µ, and this correlation was most significant at 27 and 30 °C. During EG, µ_tox was affected by both temperature and growth. This study shows that temperature affects growth and toxin production of this strain of D. caudata during EG. In addition, a positive correlation was found between toxin production and growth.     

Antinociceptive and Anti-Inflammatory Activities of Crude Methanolic Extract of Red Alga Bryothamnion triquetrum

The marine environment is an extraordinary reservoir of bioactive natural products, many of which exhibit chemical and structural features not found in terrestrial natural products. In this regard, the aim of this study was to investigate the possible antinociceptive and anti-inflammatory activities of a crude methanolic extract of the red alga Bryothamnion triquetrum (BT-MeOH) in murine models. Groups of Swiss mice of both sexes (25–30 g) were used throughout the experiments. The potential antinociceptive of BT-MeOH was evaluated by means of the following tests: acetic acid-induced writhing, hot-plate test and glutamate- and formalin-induced nociception. The anti-inflammatory activity of BT-MeOH was investigated using the zymosan A-induced peritonitis test. The tests were conducted using 100 mg/kg (p.o.) BT-MeOH, 33.3 mg/kg (p.o.) dipyrone, 35.7 mg/kg (p.o.) indomethacin and 5.7 mg/kg (s.c.) morphine. The extract and all standard drugs were administered 40 min before the nociceptive/inflammatory stimulus. In the acetic acid-induced writhing test, BT-MeOH and dipyrone inhibited the nociceptive response by 55.9% (22.2 ± 2.0 writhings; p < 0.01) and 80.9% (9.6 ± 2.1 writhings; p < 0.01). In the hot-plate test, BT-MeOH did not increase the latency time of the animals in the time evaluated. In addition, BT-MeOH inhibited glutamate-induced nociception by 50.1%. While BT-MeOH did not inhibit the neurogenic phase in formalin-induced nociception, the inflammatory phase was inhibited by 53.1% (66.8 ± 14.2 s; p < 0.01). Indomethacin inhibited the inflammatory phase by 60.2% (56.8 ± 8.7 s; p < 0.01). In the zymosan-induced peritonitis test, BT-MeOH inhibited 55.6% (6.6 ± 0.2 × 10⁶ leukocytes/mL; p < 0.01) of leukocyte migration, while indomethacin inhibited 78.1% (3.2 ± 0.1 × 10⁶ leukocytes/mL; p < 0.01). Based on the results obtained in this study, we conclude that BT-MeOH has peripheral antinociceptive and anti-inflammatory activities. However, more studies need to be conducted to confirm these properties.     

Comparative Analyses of Cu-Zn Superoxide Dismutase (SOD1) and Thioredoxin Reductase (TrxR) at the mRNA Level between Apis mellifera L. and Apis cerana F. (Hymenoptera: Apidae) Under Stress Conditions

This study compared stress-induced expression of Cu-Zn superoxide dismutase (SOD1) and thioredoxin reductase (TrxR) genes in the European honeybee Apis mellifera L. and Asian honeybee Apis cerana F. Expression of both SOD1 and TrxR rapidly increased up to 5 h after exposure to cold (4°C) or heat (37°C) treatment and then gradually decreased, with a stronger effect induced by cold stress in A. mellifera compared with A. cerana. Injection of stress-inducing substances (methyl viologen, [MV] and H₂O₂) also increased SOD1 and TrxR expression in both A. mellifera and A. cerana, and this effect was more pronounced with MV than H₂O₂. Additionally, we heterologously expressed the A. mellifera and A. cerana SOD1 and TrxR proteins in an Escherichia coli expression system, and detection by SDS-PAGE, confirmed by Western blotting using anti-His tag antibodies, revealed bands at 16 and 60 kDa, respectively. Our results show that the expression patterns of SOD1 and TrxR differ between A. mellifera and A. cerana under conditions of low or high temperature as well as oxidative stress.     

Characterization of a Novel Conus bandanus Conopeptide Belonging to the M-Superfamily Containing Bromotryptophan

A novel conotoxin (conopeptide) was biochemically characterized from the crude venom of the molluscivorous marine snail, Conus bandanus (Hwass in Bruguière, 1792), collected in the south-central coast of Vietnam. The peptide was identified by screening bromotryptophan from chromatographic fractions of the crude venom. Tandem mass spectrometry techniques were used to detect and localize different post-translational modifications (PTMs) present in the BnIIID conopeptide. The sequence was confirmed by Edman’s degradation and mass spectrometry revealing that the purified BnIIID conopeptide had 15 amino acid residues, with six cysteines at positions 1, 2, 7, 11, 13, and 14, and three PTMs: bromotryptophan, γ-carboxy glutamate, and amidated aspartic acid, at positions “4”, “5”, and “15”, respectively. The BnIIID peptide was synthesized for comparison with the native peptide. Homology comparison with conopeptides having the III-cysteine framework (–CCx₁x₂x₃x₄Cx₁x₂x₃Cx₁CC–) revealed that BnIIID belongs to the M-1 family of conotoxins. This is the first report of a member of the M-superfamily containing bromotryptophan as PTM.     

Two Novel Tyrosinase Inhibitory Sesquiterpenes Induced by CuCl2 from a Marine-Derived Fungus Pestalotiopsis sp. Z233

Two new sesquiterpenes, 1β,5α,6α,14-tetraacetoxy-9α-benzoyloxy-7βH-eudesman-2β,11-diol (1) and 4α,5α-diacetoxy-9α-benzoyloxy-7βH-eudesman-1β,2β,11,14-tetraol (2), were produced as stress metabolites in the cultured mycelia of Pestalotiopsis sp. Z233 isolated from the algae Sargassum horneri in response to abiotic stress elicitation by CuCl₂. Their structures were established by spectroscopic means. New compounds 1 and 2 showed tyrosinase inhibitory activities with IC₅₀ value of 14.8 µM and 22.3 µM.     

Cytotoxic Effects of Tropodithietic Acid on Mammalian Clonal Cell Lines of Neuronal and Glial Origin

The marine metabolite tropodithietic acid (TDA), produced by several Roseobacter clade bacteria, is known for its broad antimicrobial activity. TDA is of interest not only as a probiotic in aquaculture, but also because it might be of use as an antibacterial agent in non-marine or non-aquatic environments, and thus the potentially cytotoxic influences on eukaryotic cells need to be evaluated. The present study was undertaken to investigate its effects on cells of the mammalian nervous system, i.e., neuronal N2a cells and OLN-93 cells as model systems for nerve cells and glia. The data show that in both cell lines TDA exerted morphological changes and cytotoxic effects at a concentration of 0.3–0.5 µg/mL (1.4–2.4 µM). Furthermore, TDA caused a breakdown of the mitochondrial membrane potential, the activation of extracellular signal-regulated kinases ERK1/2, and the induction of the small heat shock protein HSP32/HO-1, which is considered as a sensor of oxidative stress. The cytotoxic effects were accompanied by an increase in intracellular Ca²⁺-levels, the disturbance of the microtubule network, and the reorganization of the microfilament system. Hence, mammalian cells are a sensitive target for the action of TDA and react by the activation of a stress response resulting in cell death.     

Tasco(®), a product of Ascophyllum nodosum, imparts thermal stress tolerance in Caenorhabditis elegans

Tasco^®, a commercial product manufactured from the brown alga Ascophyllum nodosum, has been shown to impart thermal stress tolerance in animals. We investigated the physiological, biochemical and molecular bases of this induced thermal stress tolerance using the invertebrate animal model, Caenorhabiditis elegans. Tasco^® water extract (TWE) at 300 μg/mL significantly enhanced thermal stress tolerance as well as extended the life span of C. elegans. The mean survival rate of the model animals under thermal stress (35 °C) treated with 300 μg/mL and 600 μg/mL TWE, respectively, was 68% and 71% higher than the control animals. However, the TWE treatments did not affect the nematode body length, fertility or the cellular localization of daf-16. On the contrary, TWE under thermal stress significantly increased the pharyngeal pumping rate in treated animals compared to the control. Treatment with TWE also showed differential protein expression profiles over control following 2D gel-electrophoresis analysis. Furthermore, TWE significantly altered the expression of at least 40 proteins under thermal stress; among these proteins 34 were up-regulated while six were down-regulated. Mass spectroscopy analysis of the proteins altered by TWE treatment revealed that these proteins were related to heat stress tolerance, energy metabolism and a muscle structure related protein. Among them heat shock proteins, superoxide dismutase, glutathione peroxidase, aldehyde dehydrogenase, saposin-like proteins 20, myosin regulatory light chain 1, cytochrome c oxidase RAS-like, GTP-binding protein RHO A, OS were significantly up-regulated, while eukaryotic translation initiation factor 5A-1 OS, 60S ribosomal protein L18 OS, peroxiredoxin protein 2 were down regulated by TWE treatment. These results were further validated by gene expression and reporter gene expression analyses. Overall results indicate that the water soluble components of Tasco^® imparted thermal stress tolerance in the C. elegans by altering stress related biochemical pathways.     

Antioxidant,Anti-Nephrolithe Activities and in Vitro Digestibility Studies of Three Different Cyanobacterial Pigment Extracts

Phycobiliprotein-containing water and carotenoid-containing methanolic extracts of three different cyanobacteria, Pseudanabaena sp., Spirulina sp. and Lyngbya sp., were studied for their DPPH scavenging, iso-bolographic studies, and anti-nephrolithe activities. The best EC₅₀ values for DPPH scavenging were in Lyngbya water (LW, 18.78 ± 1.57 mg·mg⁻¹ DPPH) and Lyngbya methanol (LM, 59.56 ± 37.38 mg·mg⁻¹ DPPH) extracts. Iso-bolographic analysis revealed most of the combinations of extracts were antagonistic to each other, although LM—Spirulina methanol (SM) 1:1 had the highest synergistic rate of 86.65%. In vitro digestion studies showed that DPPH scavenging activity was considerably decreased in all extracts except for Pseudanabaena methanol (PM) and LM after the simulated digestion. All of the extracts were effective in reducing the calcium oxalate crystal size by nearly 60%–65% compared to negative control, while PM and Spirulina water (SW) extracts could inhibit both nucleation and aggregation of calcium oxalate by nearly 60%–80%.     

Geographic Variation of Diapause and Sensitive Stages of Photoperiodic Response in Laodelphax striatellus Fallén (Hemiptera: Delphacidae)

Large numbers of the small brown planthopper Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) occur in temperate regions, causing severe losses in rice, wheat, and other economically important crops. The planthoppers enter diapause in the third- or fourth-instar nymph stage, induced by short photoperiods and low temperatures. To investigate the geographic variation in L. striatellus diapause, we compared the incidence of nymphal diapause under various constant temperature (20 and 27°C) and a photoperiod of 4:20, 8:16, 10:14, 12:12, 14:10, and 16:8 (L:D) h regimes among three populations collected from Hanoi (21.02° N, 105.85° E, northern Vietnam), Jiangyan (32.51° N, 120.15° E, eastern China), and Changchun (43.89° N, 125.32° E, north-eastern China). Our results indicated that there were significant geographic variations in the diapause of L. striatellus. When the original latitude of the populations increased, higher diapause incidence and longer critical photoperiod (CP) were exhibited. The CPs of the Jiangyan and Changchun populations were ∼12 hr 30 min and 13 hr at 20°C, and 11 hr and 11 hr 20 min at 27°C, respectively. The second- and third-instar nymphs were at the stage most sensitive to the photoperiod. However, when the fourth- and fifth-instar nymphs were transferred to a long photoperiod, the diapause-inducing effect of the short photoperiod on young instars was almost reversed. The considerable geographic variations in the nymphal diapause of L. striatellus reflect their adaptation in response to a variable environment and provide insights to develop effective pest management strategies.     

Influence of Constant Temperature on Reproductive Parameters of Holotrichia oblita (Coleoptera: Scarabaeidae)

Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae) is a major pest both in field crops and forests because the larvae could eat the roots of most crops in the field, and the adults damage the leaves of trees and field crops. In this study, we focused on the effects of temperature on H. oblita reproductive parameters. The results indicated H. oblita female adults at 25°C could lay more eggs (84.0 eggs per female) and have the shortest preoviposition period (19.1 d), the greatest oviposition rate (2.8 eggs per female per 3 d), and largest percentage of life span spent in oviposition (59.5%). The longevity and the time to 50% egg laying decreased with increasing temperature, and female longevity was always longer than male longevity. The preoviposition and postoviposition period decreased with increasing temperature from 15 to 25°C and then increased when the temperature increased from 25 to 30°C. These results show that 25°C is the optimal temperature for reproduction of H. oblita.     

Territrem and Butyrolactone Derivatives from a Marine-Derived Fungus Aspergillus Terreus

Seventeen lactones including eight territrem derivatives (1–8) and nine butyrolactone derivatives (9–17) were isolated from a marine-derived fungus Aspergillus terreus SCSGAF0162 under solid-state fermentation of rice. Compounds 1–3 and 9–10 were new, and their structures were elucidated by spectroscopic analysis. The acetylcholinesterase inhibitory activity and antiviral activity of compounds 1–17 were evaluated. Among them, compounds 1 and 2 showed strong inhibitory activity against acetylcholinesterase with IC₅₀ values of 4.2 ± 0.6, 4.5 ± 0.6 nM, respectively. This is the first time it has been reported that 3, 6, 10, 12 had evident antiviral activity towards HSV-1 with IC₅₀ values of 16.4 ± 0.6, 6.34 ± 0.4, 21.8 ± 0.8 and 28.9 ± 0.8 μg·mL⁻¹, respectively. Antifouling bioassay tests showed that compounds 1, 11, 12, 15 had potent antifouling activity with EC₅₀ values of 12.9 ± 0.5, 22.1 ± 0.8, 7.4 ± 0.6, 16.1 ± 0.6 μg·mL⁻¹ toward barnacle Balanus amphitrite larvae, respectively.     

Phenolic Polyketides from the Co-Cultivation of Marine-Derived Penicillium sp. WC-29-5 and Streptomyces fradiae 007

Penicillium sp. WC-29-5 was co-cultured with Streptomyces fradiae 007 to produce five natural products (1–3, 4a and 4b) that were isolated and characterized by spectroscopic analysis. Interestingly, these compounds were found to be different from those produced in discrete fungal and bacterial controls. Among these compounds, the absolute configurations of compounds 4a and 4b were determined for the first time by X-ray single crystal diffraction experiments and electronic circular dichroism (ECD) calculations. An evaluation of the cytotoxic activities of these compounds revealed that 4b was moderately cytotoxic towards HL-60 and H1975 tumor cells with IC₅₀ values of 3.73 and 5.73 µM, respectively, whereas compound 4a was only moderately cytotoxic towards H1975 cells with an IC₅₀ value of 3.97 µM.     

Influence of Environmental Factors on the Paralytic Shellfish Toxin Content and Profile of Alexandrium catenella (Dinophyceae) Isolated from the Mediterranean Sea

Laboratory experiments were designed to study the toxin content and profile of the Alexandrium catenella strain ACT03 (isolated from Thau Lagoon, French Mediterranean) in response to abiotic environmental factors under nutrient-replete conditions. This dinoflagellate can produce various paralytic shellfish toxins with concentrations ranging from 2.9 to 50.3 fmol/cell. The toxin profile was characterized by carbamate toxins (GTX3, GTX4 and GTX5) and N-sulfocarbamoyl toxins (C1, C2, C3 and C4). C2 dominated at 12–18 °C, but only for salinities ranging from 10 to 25 psu, whereas GTX5 became dominant at temperatures ranging from 21 to 30 °C at almost all salinities. There was no significant variation in the cellular toxin amount from 18 °C to 27 °C for salinities ranging between 30 and 40 psu. At salinities of 10 to 25 psu, the toxin concentrations always remained below 20 fmol/cell. Toxin content was stable for irradiance ranging from 10 to 70 μmol photons/m²/s then slightly increased. Overall, the toxin profile was more stable than the toxin content (fmol/cell), except for temperature and/or salinity values different from those recorded during Alexandrium blooms in Thau Lagoon.     

Monacyclinones,New Angucyclinone Metabolites Isolated from Streptomyces sp. M7_15 Associated with the Puerto Rican Sponge Scopalina ruetzleri

During an investigation of new actinomycete species from Caribbean sponges for novel bioactive natural products, frigocyclinone (1), dimethyldehydrorabelomycin (3) and six new angucyclinone derivatives were isolated from Streptomyces sp. strain M7_15 associated with the sponge Scopalina ruetzleri. Of these, monacyclinones A–B (4–5) contain the core ring structure of dehydrorabelomycin (2) with the aminodeoxysugar found in frigocyclinone (1). Monacyclinone C (6) is a hydroxylated variant of frigocyclinone (1) and monacyclinone D (7) is a Baeyer Villiger derivative of (6) which also exists as the open chain hydrolysis product monacyclinone E (8). Monacyclinone F (9) contains two unique epoxide rings attached to the angucyclinone moiety and an additional aminodeoxysugar attached through an angular oxygen bond. All structures were confirmed through spectral analyses. Activity against rhabdomycosarcoma cancer cells (SJCRH30) after 48 h of treatment was observed with frigocyclinone (1; EC₅₀ = 5.2 µM), monacyclinone C (6; 160 µM), monacyclinone E (8; 270 µM), and monacyclinone F (9; 0.73 µM). The strongest bioactivity against rhabdomycosarcoma cancer cells and gram-positive bacteria was exhibited by compound 9, suggesting that the extra aminodeoxysugar subunit is important for biological activity.     

Anti-Inflammatory Components of the Starfish Astropecten polyacanthus

Inflammation is important in biomedical research, because it plays a key role in inflammatory diseases including rheumatoid arthritis and other forms of arthritis, diabetes, heart disease, irritable bowel syndrome, Alzheimer’s disease, Parkinson’s disease, allergies, asthma, and even cancer. In the present study, we describe the inhibitory effect of crude extracts and steroids isolated from the starfish Astropecten polyacanthus on pro-inflammatory cytokine (Interleukin-12 (IL-12) p40, interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α)) production in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells (BMDCs). Among those tested, compounds 5 and 7 showed potent inhibitory effects on the production of all three pro-inflammatory cytokines with IC₅₀ values ranging from 1.82 ± 0.11 to 7.00 ± 0.16 μM. Potent inhibitory activities were also observed for compound 1 on the production of IL-12 p40 and IL-6 with values of 3.96 ± 0.12 and 4.07 ± 0.13 μM, respectively, and for compounds 3 and 4 on the production of IL-12 p40 with values of 6.55 ± 0.18 and 5.06 ± 0.16 μM, respectively. Moreover, compounds 2 (IC₅₀ = 34.86 ± 0.31 μM) and 6 (IC₅₀ = 79.05 ± 2.05 μM) exhibited moderate inhibitory effects on the production of IL-12 p40, whereas compounds 3 (IC₅₀ = 22.80 ± 0.21 μM) and 4 (IC₅₀ = 16.73 ± 0.25 μM) moderately inhibited the production of TNF-α and IL-6, respectively.     

Purification and Characterization of a Fucoidanase (FNase S) from a Marine Bacterium Sphingomonas paucimobilis PF-1

The Search for enzyme activities that efficiently degrade marine polysaccharides is becoming an increasingly important area for both structural analysis and production of lower-molecular weight oligosaccharides. In this study, an endo-acting fucoidanase that degrades Miyeokgui fucoidan (MF), a sulfated galactofucan isolated from the sporophyll (called Miyeokgui in Korean) of Undaria pinnatifida, into smaller-sized galactofuco-oligosaccharides (1000–4000 Da) was purified from a marine bacterium, Sphingomonas paucimobilis PF-1, by ammonium sulfate precipitation, diethylaminoethyl (DEAE)-Sepharose column chromatography, and chromatofocusing. The specific activity of this enzyme was approximately 112-fold higher than that of the crude enzyme, and its molecular weight was approximately 130 kDa (FNase S), as determined by native gel electrophoresis and 130 (S1), 70 (S2) and 60 (S3) kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature of FNase S were pH 6.0–7.0 and 40–45 °C, respectively. FNase S activity was enhanced by Mn²⁺ and Na⁺ (115.7% and 131.2%), but it was inhibited by Ca²⁺, K⁺, Ba²⁺, Cu²⁺ (96%, 83.7%, 84.3%, and 89.3%, respectively), each at 1 mM. The K_m, V_max and K_cat values of FNase S on MF were 1.7 mM, 0.62 mg·min⁻¹, and 0.38·S⁻¹, respectively. This enzyme could be a valuable tool for the structural analysis of fucoidans and production of bioactive fuco-oligosaccharides.