Synthesis and Characterization of Silver Nanoparticles Using Alginate from the Brown Seaweed Laminaria ochroleuca: Structural Features and Antibacterial Activity

In this study, inexpensive and eco-friendly production of the silver nanoparticles (AgNPs) was explored using Laminaria ochroleuca sodium alginate as stabilizing and reducing agent. The synthesized nanoparticles were characterized by various analytical techniques such as UV–Vis spectroscopy, Energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), TEM selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The synthesis of AgNPs was elucidated by characteristic absorption peaks in the UV–Vis test. The FTIR analysis revealed the involvement of many functional groups in the bioreduction and the stabilization of AgNPs, while TEM images illustrated the spherical shape with maximum particles found in the size range of 10-20 nm. Prominent peaks and silver diffraction rings shown by the XRD spectrum and SAED pattern, respectively, confirmed the crystalline nature (fcc) of the synthesized AgNPs, which were found to be thermally stable based on TGA analysis. The AgNPs exhibited strong antibacterial activity against Gram+ and Gram– bacteria. The synthesized silver nanoparticles using Laminaria ochroleuca sodium alginate revealed interesting properties that could be potentially used for pharmaceutical applications.

Hydrothermal Processing of Laminaria ochroleuca for the Production of Crude Extracts Used to Formulate Polymeric Nanoparticles

A green extraction process using only water was proposed for the simultaneous extraction of alginate and bioactive compounds from Laminaria ochroleuca. Operation was carried out during non-isothermal heating up to maximal temperatures over the range of 70 °C to 100 °C. Once separated, the alginate and the crude extract were characterised and the biological activities and cytotoxicity of the extracts was studied, the latter in intestinal epithelial cells. Those alginates obtained at 90 °C exhibited the highest extraction yields and viscoelastic features of the corresponding hydrogels. The obtained results show that the extracts obtained by non-isothermal extraction were suitable to formulate nanoparticles, which showed the smallest size (≈250–350 nm) when the higher content of fucoidan extract was present. Given the evidenced properties, the extracts may find an application in the formulation of nanoparticulate carriers for drug delivery.

Pigments Content (Chlorophylls, Fucoxanthin and Phycobiliproteins) of Different Commercial Dried Algae

Algae are a complex, polyphyletic group of organisms, affordable and naturally rich in nutrients, but also valuable sources of structurally diverse bioactive substances such as natural pigments. The aim of this work was to evaluate the polar and non-polar pigment contents of different commercial dried algae (brown: Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca; red: Porphyra spp.; and a blue-green microalga: Spirulina spp.). The pigment extraction was carried out using different solvents (100% methanol, 100% methanol acid free, 100% ethanol, 90% acetone, N,N-dimethylformamide, dimethyl sulfoxide-water (4:1, v/v) and pH 6.8 phosphate buffer), selected according to their affinity for each class of pigments. Acetone proved to be an efficient solvent to extract chlorophylls from brown and red algae, but not from Spirulina spp. Porphyra spp. presented considerably higher levels of all pigments compared to brown algae, although Spirulina spp. presented significantly higher (p < 0.05) levels of chlorophylls, carotenoids and phycobiliproteins, compared to all macroalgae. The content of fucoxanthin extracted from the three brown algae was highly correlated to the carotenoid content. Within this group, Himanthalia elongata presented the highest fucoxanthin/total carotenoids ratio. Although the yield of extraction depended on the solvent used, the algae studied herein are an interesting source of pigments of great value for a wide range of applications.

Edible Brown Seaweed in Gluten-Free Pasta: Technological and Nutritional Evaluation

Seaweed is a novel source of important nutritional compounds with interesting biological activities that could be processed into added-value products, namely gluten-free foods. In this study, two previously developed products obtained from Laminaria ochroleuca processing (liquid extract and a purée-like mixture) were incorporated in gluten-free (GF) pasta in order to develop functional products especially designed for the celiac population. The raw and cooked pastas were characterized in terms of their cooking quality parameters, nutritional composition, texture and rheological properties, and antioxidant activity. It was found that the developed GF pastas had similar mechanical and texture characteristics to the control. Both supplemented GF pastas presented a significantly (p < 0.05) higher fibre and mineral content than the control pasta.

Psyllium and Laminaria Partnership—An Overview of Possible Food Gel Applications

Seaweeds are a novel source of important nutritional compounds with interesting biological activities that could be processed into added-value products. In this study, two previously developed products obtained by Laminaria ochroleuca processing (liquid extract and a purée-like mixture) were processed with Psyllium gel to develop functional hydrogels. The optimization of the formulation and the characterization of the Laminaria-Psyllium gels in terms of their mechanical features have allowed the proposal of potential food applications. A beneficial interaction was found between Laminaria and Psyllium in terms of the reinforcement of texture and rheological properties. The obtained outcomes could provide new healthy gelling formulations with attractive properties to alleviate the growing market demand of eco-novel food matrices.