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This study focusses on the valorization of the red seaweed Mastocarpus stellatus, collected in the Northern coast of Portugal, as a natural source of high value compounds due to its beneficial properties. An annual monitoring of the seaweed was performed by determining its lipids, ash, carbohydrates, phycobiliproteins, total phenolic compounds, antioxidant capacity and carrageenan from three different rocky shores located in the north of Portugal. The results showed a seasonal and spatial variability of the studied compounds between October 2018 and September 2019 depending on the climatic variables of temperature, precipitation, and solar radiation. The most productive season coincided with the warmest months, except for carbohydrates and phycobiliproteins, which were promoted in the colder season. The spatial variation also could be explained by the proximity to water channel discharges at the sampling sites. Complementary studies on the carrageenan fraction were conducted in one of the shores due to the high biopolymer content, to determine their carrageenan proportion between the summer and winter period and establish their rheological capabilities for the formulation of gelling matrices. The extracted biopolymers exhibited typical structural and viscoelastic characteristics of kappa/iota-hybrid carrageenans, suggesting notably differences depending on the harvest season, which is critically relevant to define future applications.

Ultrasound-assisted water extraction was optimized to recover gelling biopolymers and antioxidant compounds from Mastocarpus stellatus. A set of experiments following a Box–Behnken design was proposed to study the influence of extraction time, solid liquid ratio, and ultrasound amplitude on the yield, sulfate content, and thermo-rheological properties (viscoelasticity and gelling temperature) of the carrageenan fraction, as well as the composition (protein and phenolic content) and antiradical capacity of the soluble extracts. Operating at 80 °C and 80 kHz, the models predicted a compromise optimum extraction conditions at ~35 min, solid liquid ratio of ~2 g/100 g, and ultrasound amplitude of ~79%. Under these conditions, 40.3% carrageenan yield was attained and this product presented 46% sulfate and good mechanical properties, a viscoelastic modulus of 741.4 Pa, with the lowest gelling temperatures of 39.4 °C. The carrageenans also exhibited promising antiproliferative properties on selected human cancer cellular lines, A-549, A-2780, HeLa 229, and HT-29 with EC50 under 51.9 μg/mL. The dried soluble extract contained 20.4 mg protein/g, 11.3 mg gallic acid eq/g, and the antiradical potency was equivalent to 59 mg Trolox/g.

Antiproliferative and antioxidant activities and mycosporine-like amino acid (MAA) profiles of methanol extracts from edible wild-harvested (Chondrus crispus, Mastocarpus stellatus, Palmaria palmata) and cultivated (C. crispus) marine red macroalgae were studied herein. Palythine, asterina-330, shinorine, palythinol, porphyra-334 and usujirene MAAs were identified in the macroalgal extracts by LC/MS/MS. Extract reducing activity rankings were (p < 0.001): wild P. palmata > cultivated C. crispus = wild M. stellatus > wild low-UV C. crispus > wild high-UV C. crispus; whereas oxygen radical absorbance capacities were (p < 0.001): wild M. stellatus > wild P. palmata > cultivated C. crispus > wild low-UV C. crispus > wild high-UV C. crispus. Extracts were antiproliferative against HeLa and U-937 cells (p < 0.001) from 0.125–4 mg/mL, 24 h. Wild P. palmata and cultivated C. crispus extracts increased (p < 0.001) HeLa caspase-3/7 activities and the proportion of cells arrested at Sub G1 (apoptotic) compared to wild-harvested C. crispus and M. stellatus extracts. HeLa cells incubated with wild P. palmata and cultivated C. crispus extracts also exhibited morphological changes characteristic of apoptosis (shrinkage, rounding). Thus, extracts rich in low-polarity usujirene and polar palythine and asterina-330 MAAs were antiproliferative as inducers of apoptosis in HeLa cells.

Polyunsaturated fatty acids are well known for their protective properties in relation to different skin diseases. Although seaweeds possess a low lipid fraction, they could act as an alternative renewable source of polyunsaturated fatty acids whenever other valuable seaweed components are also valorized. In this study, a biorefinery process using Mastocarpus stellatus as a model seaweed was proposed. The process started with the supercritical carbon dioxide extraction of the lipid and phenolic fractions. The influence of pressure during extraction with pure supercritical CO2 was studied while operating at a selected temperature and solvent flow rate. Kinetic data obtained during the ethanol-modified supercritical CO2 extraction were fitted to the spline model. Sequential processing was proposed with (i) pure CO2 to obtain a product with 30% PUFA content and ω-3:ω-6 ratio 1:1, (ii) ethanol-modified CO2 to extract phenolics, and (iii) microwave-assisted subcritical water extraction operating under previously optimized conditions for the extraction of phenolics, carrageenan and protein fractions. The composition of the supercritical extracts showed potential for use in both dietary and topical applications in skin care products. The remaining solids are suitable for the extraction of other valuable fractions.

This study was designed to analyze the chemical composition and in vitro rumen fermentation of eight seaweed species (Brown: Alaria esculenta, Laminaria digitata, Pelvetia canaliculata, Saccharina latissima; Red: Mastocarpus stellatus, Palmaria palmata and Porphyra sp.; Green: Cladophora rupestris) collected in Norway during spring and autumn. Moreover, the in vitro ruminal fermentation of seventeen diets composed of 1:1 oat hay:concentrate, without (control diet) or including seaweeds was studied. The ash and N contents were greater (p < 0.001) in seaweeds collected during spring than in autumn, but autumn-seaweeds had greater total extractable polyphenols. Nitrogen in red and green seaweeds was greater than 2.20 and in brown seaweeds, it was lower than 1.92 g/kg DM. Degradability after 24 h of fermentation was greater in spring seaweeds than in autumn, with Palmaria palmata showing the greatest value and Pelvetia canaliculata the lowest. Seaweeds differed in their fermentation pattern, and autumn Alaria esculenta, Laminaria digitata, Saccharina latissima and Palmaria palmata were similar to high-starch feeds. The inclusion of seaweeds in the concentrate of a diet up to 200 g/kg concentrate produced only subtle effects on in vitro ruminal fermentation.

The red algae, a remarkably diverse group of organisms, are difficult to identify using morphology alone. Following the proposal to use the mitochondrial cytochrome c oxidase subunit I (cox1) for DNA barcoding animals, we assessed the use of this gene in the identification of red algae using 48 samples plus 31 sequences obtained from GenBank. The data set spanned six orders of red algae: the Bangiales, Ceramiales, Corallinales, Gigartinales, Gracilariales and Rhodymeniales. The results indicated that species could be discriminated. Intraspecific variation was between 0 and 4 bp over 539 bp analyzed except in Mastocarpus stellatus (0-14 bp) and Gracilaria gracilis (0-11 bp). Cryptic diversity was found in Bangia fuscopurpurea, Corallina officinalis, G. gracilis, M. stellatus, Porphyra leucosticta and P. umbilicalis. Interspecific variation across all taxa was between 28 and 148 bp, except for G. gracilis and M. stellatus. A comparison of cox1 with the plastid Rubisco spacer for Porphyra species revealed that it was a more sensitive marker in revealing incipient speciation and cryptic diversity. The cox1 gene has the potential to be used for DNA barcoding of red algae, although a good taxonomic foundation coupled with extensive sampling of taxa is essential for the development of an effective identification system.

Many of the pathologies leading to premature death from cardiovascular diseases (CVDs) in humans are influenced by an individual's nutritional habitus. Diet-related risk factors for these pervasive, noncommunicable diseases include obesity, hypertension, endothelial dysfunction, diabetes, and disproportionate cellular free-radical production. CVDs are the number one cause of premature death globally, and effective methods for ameliorating CVD risk factors associated with diet should be a primary target. Although various intervention strategies are being developed and implemented, such as healthy lunch programs, improved menus in school cafeterias, and government mandates for food manufacturers regarding the reduction of salt and trans fats in processed products, a broader, more universal approach is in order. The proliferation and ready availability of high-calorie, nutrient-poor foods and the powerful marketing tools used by multinational food companies seriously compromise the health and wellness potential of a significant proportion of the global population. In this review, some of the underlying mechanisms contributing to cardiovascular health are discussed in terms of human nutritional status. Unhealthy plasma cholesterol levels, obesity, nutritional energy imbalances, and inflammatory responses are identified as some of the likely precursors in the manifestation of cardiovascular issues. The favourable therapeutic impact dietary macroalgae could have by the provision of robust antioxidant suites, macro- and micronutritional elements, fibre content, and fatty acid profiles makes seaweeds viable and important contenders for involuntary intervention strategies related to food manufacturing. These components are discussed in relation to their functionality with respect to human health, and numerous edible macroalgae, such as Hypnea charoides, Mastocarpus stellatus, Palmaria palmata, Laminaria japonica, and Ulva pertusa are mentioned in light of their amelioration value. Opportunities for the practical utilization of marine macroalgae into ordinary foodstuffs are highlighted.

The effect of the seaweed drying temperatures (35, 45, 55 and 85 °C), prior to the biopolymer extraction, on the rheological properties of kappa/iota-hybrid carrageenan (KI) gels in NaCl extracted from Mastocarpus stellatus seaweed is reported, together with the thermal stability of obtained gels. The average molecular mass (ranged between 2.25 × 10 6 and 1.02 × 10 6  kg kmol −1 ) of extracted KI, determined by gel permeation chromatography, and estimated intrinsic viscosities (ranged between 0.935 and 0.258 m 3  kg −1 ), conducted in a capillary viscometer, decreased with increase of the seaweed drying temperatures. The parameters ( K and a ) of the Mark-Houwink-Sakurada (MHS) equation for KI are also reported. Thermo-rheological oscillatory measurements were conducted in a stress-controlled rheometer in order to clarify the kinetics of gel formation and to characterize the structure of the matured gels. Rheological results indicated a weakening of the KI gelling properties at smaller average molecular masses (i.e. larger seaweed drying temperatures, above 45 °C). Even so, KI samples exhibited stable and weak gel properties (i.e. elastic modulus <200 Pa). KI gels reached stability after 20 min of maturation. Cooling and heating profiles showed a strong temperature dependency. Gel setting temperatures significantly depended on the biopolymer content, whereas gel melting temperatures (68.0 ± 0.3 °C) were unvaried. No complete thermal stability was observed for gels formed with tested biopolymers, the most thermal stable being those prepared with KI with larger molecular masses (i.e. lower seaweed drying temperatures, below 45 °C).

Kelp ecology is heavily biased toward the conspicuous sporophyte stage, whereas understanding of the microscopic gametophyte remains limited. Given that kelp gametophytes are known to grow in/on other species of algae, we sought to determine if species-specific polymerase chain reaction could detect kelp gametophytes in situ from coextracted host DNA. Upon verifying our molecular results, we also assessed distributional patterns of the kelp gametophytes according to site, host species, and vertical placement in the intertidal zone. We sampled Chondrus crispus, Mastocarpus stellatus, and Palmaria palmata (Florideophyceae) at Wallace Cove, New Brunswick, Canada, on 13 September 2016, where kelp sporophytes were abundant, and at an adjacent location without obvious sporophyte presence, L'Etete, on 26 September 2016. Species-specific primers were used to assess the presence of Alaria esculenta and Laminaria digitata DNA from coextracted red algal DNA. We successfully amplified kelp DNA from the host tissue of each red algal species, indicating that gametophytes were present at Wallace Cove and L'Etete during the fall of 2016, with significantly less gametophyte presence at L'Etete. Although no significant differences in gametophyte presence occurred according to host species, P. palmata had significantly less gametophyte presence when sampled from its upper range in the intertidal. Microscopy and additional field observations confirmed the presence of brown endophytes in a variety of hosts, including C. crispus and P. palmata. Our study showcases a simple method for detecting kelp gametophytes, with our preliminary results demonstrating that the distributional and ecological range of kelp gametophytes is broader than that of the sporophytic counterparts.

Eight carrageenophytes, representing seven genera and three families of Gigartinales (Florideophyceae), were studied for 15 months. The reproductive status, dry weight, and carrageenan content have been followed by a monthly random sampling. The highest carrageenan yields were found in Chondracanthus acicularis (61.1%), Gigartina pistillata (59.7%), and Chondracanthus teedei var. lusitanicus (58.0%). Species of Cystocloniaceae family produces predominantly iota-carrageenans; Gigartinaceae family produces hybrid kappa-iota carrageenans (gametophytic plants) and lambda-family carrageenans (sporophytic plants); Phyllophoraceae family produces kappa-iota-hybrid carrageenans. Quadrate destructive sampling method was used to determine the biomass and line transect. Quadrate nondestructive sampling method, applied along a perpendicular transect to the shoreline, was used to calculate the carrageenophytes cover in two periods: autumn/winter and spring/summer. The highest cover and biomass were found in Chondrus crispus (3.75%–570 g/m2), Chondracanthus acicularis (3.45%–99 g/m2), Chondracanthus teedei var. lusitanicus (2.45%–207.5 g/m2), and Mastocarpus stellatus (2.02%–520 g/m2).