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This study aimed to biosynthesize zinc oxide nanoparticles (ZnO-NPs) using extracts from various seaweeds, including Ulva lactuca, Ulva intestinalis (Chlorophyta), and Sargassum muticum (Phaeophyceae). The biosynthesized ZnO-NPs were characterized using UV spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and zeta potential analysis. Their antimicrobial activity was assessed using the disk diffusion method, revealing significant efficacy against two bacterial species (Klebsiella pneumoniae and Escherichia coli) and two fungal species (Candida albicans and Aspergillus niger). Additionally, the antioxidant potential of the ZnO-NPs was evaluated based on the total antioxidant capacity, ferric reducing antioxidant power, and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assays. The antioxidant activity of the ZnO-NPs was confirmed using the three antioxidant assays. The ZnO-NPs of U. lactuca recorded the highest antioxidant activity. The cytotoxicity of the ZnO-NPs was tested on different cell lines using the MTT assay. The ZnO-NPs of U. lactuca showed very weak cytotoxic effects on WI 38 (84.98 ± 4.6 µg/mL) and 23, and this result confirmed its safety on normal cells. The ZnO-NPs of U. lactuca showed moderate cytotoxic effects on the HepG-2 (46.66 ± 2.8 µg/mL) and MCF-7 (30.60 ± 2.1 µg/mL) cell lines. In an in vivo study, the ZnO-NPs of U. lactuca showed a decrease in tumor volume, weight, and serum malondialdehyde in experimental mice, while the total antioxidant capacity of the serum was increased. Histopathological changes in ZnO-NPs indicated a reduction in tumor size, a lower number of mitosis divisions, and a rise in apoptosis correlated with the ZnO-NPs of the U. lactuca-treated groups. In conclusion, biosynthesized ZnO-NPs from seaweed showed potent antimicrobial, antioxidant, and antitumor activities, which can be used in the pharmaceutical industry.

Green algae, phylum Chlorophyta, due to their green appearance as higher plants, are seen as one of the raw materials to be widely used by humanity for different purposes. How can these different purposes achieve ONU Sustainable Development Goals? The genus Ulva sp. is widely distributed through all continents, tolerating different ecosystems (freshwater and marine), different intensities of light, temperature, and salinity. The Ulva sp. life cycle is isomorphic and biphasic type, also affected by biotic factors such as thallus age, phytohormones, microbiome, sporulation inhibitors and metabolomic. Due to that, types of farming can be implemented depending on the cultivation method and it is final biomass exploitation. Thus, this critical review analyzes the laminar Ulva species from the ecology and demonstrates that the seaweed biomass application, may make significant contributions to marine ecosystems, humans, aquaculture, and biotechnological innovation, indicating its importance in both environmental and socioeconomic contexts based on experiments across the world, time and critical thinking. This means that explaining the actual road and future roads of laminar Ulva into a multi-tool development from humankind welfare. With right management of resources and human empowerment, Ulva sp. products can be produced facing climate change and support different industries. However, responsible management of Ulva populations and farming is essential to prevent overgrowth, green floods, and maintain environmental equilibrium.

Seaweeds have been explored as a natural resource of compounds of interest due to their bioactivities. Although many studies report the interest and the application of seaweeds in various areas, from food or human health to the economy, these data mostly focus on raw extracts and not on specific compounds, such as seaweed pigments. Fungal infections of the skin, nails, and hair caused by dermatophytes are the most common fungal infections worldwide. These pathologies require long periods of topical and/or systemic treatment associated with adverse effects and increased antifungal resistance. So, this study had two objectives: the first was to isolate and characterize the pigments of the seaweeds Calliblepharis jubata and Fucus vesiculosus; the second was to assess their antifungal activity. The extraction of pigments was performed using a method of extraction by exhaustion, and the purification was achieved via column chromatography. Three techniques were used to characterize the pigments: thin-layer chromatography (TLC), UV–visible spectrophotometry, and Fourier-transform infrared spectroscopy (FTIR). The antifungal activity against the three most common dermatophytes, Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum canis, was evaluated using a microdilution methodology, following the EUCAST international standards. It was possible to observe that the extracts obtained from the seaweed C. jubata, corresponding to the purified pigment phycobiliprotein, and the crude extract (an enriched extract) showed antifungal activity against the three fungal agents of human skin infection.

The important purpose of this work is to evaluate the biostimulant activity of the algae Chlorella vulgaris and Ulva lactuca extracts on the crop plants Lactuca sativa, to compare the effect of these two green algae on plant growth and development as a part of a sustainable plant production method and show that these extracts can be a promissory source for replacing chemical fertilization. The study faces all the phases of plant growth, from the germination of the seeds to the greenhouse plant growth and treatment, matched with the chemical characterization of both the green algae used and the lettuce plants. This work is meant to define a tool to be improved by more experiments and studies in order to suggest a sustainable method that could ensure an adequate use of organic fertilizer. After the identification of the best concentration of the respective extracts of C. vulgaris and U. lactuca, the experiment affirmed that a low concentration (15% C. vulgaris and 25% U. lactuca) of the extracts contributed to the production of plants with a satisfying nutritional profile, while a high concentration (75% U. lactuca) is conducive to lettuce production with some parameters not suitable for human diet and health.

The seaweed-based biostimulants available in the market are proven to achieve better results than synthetic commercial fertilizers in plant growth parameters. There are many compounds present in seaweeds that are responsible for the plant bioactivities. Seaweed polysaccharides, such as agar, alginate, and carrageenan, make up most of the seaweed biomass and are proven to achieve excellent results in agricultural crops (in poly- and oligosaccharides formula). These types of compounds are reported to improve seed germination and plant vigor, increase the uptake of soil nutrients, and protect plants against several abiotic and biotic stresses such as salinity, drought, temperature, and pathogens. When applied to the soil directly or sprayed on the foliage, seaweed poly- and oligosaccharides can protect plants against pathogens by stimulating a plant to produce secondary metabolites and manage its defense pathways. Therefore, seaweed poly- and oligosaccharides constitute an important source of potential elicitors in plants and have a particular interest for agriculture. Thus, in this review, the focus is on the potential application of these compounds in the agricultural domain: problems, obstacles, and possibilities.

With the notable scarcity of Chondrus crispus on the Portuguese coast, and interest in exploiting compounds such as carrageenan, this study focuses on investigating different aquaculture methods and recording the yield of carrageenan from specimens grown by different methods. We compare the growth of Chondrus crispus in aquaculture using Free Floating, Cages, Attempted Fixation on Rock, and Fixed Line similar to Long Line. The best method was Free Floating where Nursery 0 had a 24-day Specific Growth Rate (SGR) of 2.08 ± 0.47%/day. The worst method in terms of growth was Nursery 2 (Attempted Fixation on Rock) where the SGR at 28 days was 0.33 ± 0.69%/day, and no fixation was observed. In terms of carrageenan extraction, all culture methods gave rise to biomass that had a lower extraction yield than wild specimens, at 50.95 ± 4.10%. However, the Free-Floating method from Nursery 1 showed an acceptable carrageenan content (31.43 ± 7.00%). Therefore, we demonstrate that the concept of C. crispus cultivation may be key to promoting the sustainability and stability of this species.

Seaweeds have been incorporated in the daily diet of several human cultures since ancient times, due to their nutritional characteristics and healthy properties. The brown seaweeds Undaria pinnatifida, Saccharina latissima, Sacchoriza polyschides, and Laminaria ochroleuca were collected in the Viana do Castelo (Portugal) bay to assess their proximate composition analysis. As a result, the algal biomass was dried, and its moisture and ash content were determined. The dried biomass was then analyzed for total nitrogen/total protein (using the Kjeldahl method), total fiber content (through fiber analyzer digestion), total lipids (in a Soxhlet apparatus), and fatty acid characterization (by gas chromatography-mass spectrometry). Apart from phosphorus, which was analyzed by spectrophotometry, the ashes were employed for mineral and trace element characterization via dry mineralization and quantified using flame atomic absorption spectrometry. Moreover, the total phenolic content was assessed spectrophotometrically by the Folin-Ciocalteu method in the algal aqueous extracts. Analyses showed that their protein concentrations ranged from 12 to 24% dry weight (DW), while lipid concentrations varied between 0.51% and 1.52% DW. Regarding the carbohydrate concentration in these seaweeds, a concentration between 48% and 60% DW was observed. The S. polyschides had the highest overall total phenolic content (6.19 × 10−3 g GAE/100 g of dried algae), while L. ochroleuca had the lowest amount (3.72 × 10−3 g GAE/100 g of dried algae). U. pinnatifida had the highest total fatty acid content (35.13 mg/g DW), whereas S. latissima presented the lowest value (22.59 mg/g DW). Significant concentrations of highly unsaturated fatty acids (HUFA) were observed in both seaweeds, with U. pinnatifida having the highest value (10.20 mg/g DW) and S. latissima the lowest content (4.81 mg/g DW). It is also highlighted that these seaweeds have a nutritional relevance as a source of essential nutrients, including nitrogen, potassium, sodium, calcium, magnesium, and iron.

Macroalgae are a biological group that has mainly been used in Asian countries; however, the interest shown by Western society is recent, its application in the industrial sector having increased in the last few decades. Seaweeds are filled with properties which are beneficial to our health. To use them as food and enhance these properties, heat has been used on them. This process alters the bioactive compounds. If we study the levels of moisture, they can vary according to the drying methods used. High values of moisture can lead to a short shelf life due to oxidation, microbial or enzyme activity, so controlling these values is highly recommended. Heat causes enzymatic activity as well as oxidation, which leads to degradation of phenolic compounds in comparison with freeze-drying, which causes fewer losses of these components. Due to the same occurrences, lipid content can also vary, modifying the bioactive compounds and their benefits. Pigments are some of the components most affected by heat, since, through this process, seaweeds or seaweed products can suffer a change in color. Iodine in macroalgae can decrease drastically; on the other hand, protein yield can be greatly enhanced. Some studies showed that the amount of arsenic in raw seaweeds was higher than when they were heat processed, and that arsenic values varied when different heat treatments were applied. Additionally, another study showed that heat can alter protein yield in specific species and have a different effect on other species.

Alginates are one of the most important compounds of brown seaweeds. These compounds are employed in the food area, because of their important rheological properties, such as viscosity, gelling, and stabilizing features and as dietary fiber source. In this study, five species of dominant brown seaweeds were collected in the Red Sea (Padina boergesenii, Turbinaria triquetra, Hormophysa cuneiformis, Dictyota ciliolata, and Sargassum aquifolium) so as to characterize the alginate yield and its properties. The analysis demonstrated differences in the alginate yield among the seaweeds. The highest yield of alginate was recorded in the species T. triquetra (22.2 ± 0.56% DW), while the lowest content was observed in H. cuneiformis (13.3 ± 0.52% DW). The viscosity from the alginates varied greatly between the species, whereas the pH varied slightly. The alginate exhibited a moisture content between 6.4 and 13.1%, the ash content ranged between 12.3 and 20% DW, the protein reached values from 0.57 to 1.47% DW, and the lipid concentration varied from 0.3 to 3.5% DW. Thus, the phytochemical analysis demonstrated that the extracted alginates can be safely applied in the food industry. Furthermore, the alginate yield reveals the potential application of these seaweeds as a nutraceutical raw source, which can be exploited by the food industry.

Seaweed-based cosmetics are being gradually used by consumers as a substitute of synthetic equivalent products. These seaweed-based products normally contain purified compounds or extracts with several compounds. Several seaweeds’ molecules already demonstrated a high potential as a cosmetic active ingredient (such as, mycosporine-like amino acids, fucoidan, pigments, phenolic compounds) or as a key element for the products consistency (agar, alginate, carrageenan). Moreover, seaweeds’ compounds present important qualities for cosmetic application, such as low cytotoxicity and low allergens content. However, seaweeds’ biochemical profile can be variable, and the extraction methods can cause the loss of some of the biomolecules. This review gives a general look at the seaweed cosmetics benefits and its current application in the cosmetic industry. Moreover, it focuses on the ecological and sustainable scope of seaweed exploitation to guarantee a safe source of ingredients for the cosmetic industry and consumers.

Calliblepharis jubata is an edible red seaweed and a carrageenan primary producer, considered native in Figueira da Foz (Portugal). C. jubata has the particularity of producing only one kind of carrageenan, the iota fraction. However, this seaweed is not yet valuable for the food industry or even for human consumption. In this work, we characterize important biochemical compounds of C. jubata growing up within different cultivation techniques and wild specimens. The aim of this work is to know if there are differences between the biological compounds of interest and identify the advantages for human consumption and the food industry. The results supported the nutritional value of the seaweed, where the ones from inshore cultivation (T) were more identical to the wild specimens (F), than the indoor C. jubata (A, B, C). The parameters analyzed were fatty acids, carbohydrates and carrageenan content.