Seaweeds are well-known for their exceptional capacity to accumulate essential minerals and trace elements needed for human nutrition, although their levels are commonly very variable depending on their morphological features, environmental conditions, and geographic location. Despite this variability, accumulation of Mg, and especially Fe, seems to be prevalent in Chlorophyta, while Rhodophyta and Phaeophyta accumulate higher concentrations of Mn and I, respectively. Both red and brown seaweeds also tend to accumulate higher concentrations of Na, K, and Zn than green seaweeds. Their valuable mineral content grants them great potential for application in the food industry as new ingredients for the development of numerous functional food products. Indeed, many studies have already shown that seaweeds can be used as NaCl replacers in common foods while increasing their content in elements that are oftentimes deficient in European population. In turn, high concentrations of some elements, such as I, need to be carefully addressed when evaluating seaweed consumption, since excessive intake of this element was proven to have negative impacts on health. In this regard, studies point out that although very bioaccessible, I bioavailability seems to be low, contrarily to other elements, such as Na, K, and Fe. Another weakness of seaweed consumption is their capacity to accumulate several toxic metals, which can pose some health risks. Therefore, considering the current great expansion of seaweed consumption by the Western population, specific regulations on this subject should be laid down. This review presents an overview of the mineral content of prevalent edible European macroalgae, highlighting the main factors interfering in their accumulation. Furthermore, the impact of using these marine vegetables as functional ingredients or NaCl replacers in foods will be discussed. Finally, the relationship between macroalgae’s toxic metals content and the lack of European legislation to regulate them will be addressed.

Ulva macroalgae species are recognized to be an underexploited source of key nutrients, including proteins, fibers and minerals. The present work evaluated the nutritional value protein, ash, mineral composition, fat, fatty acid profile and dietary fiber of the green macroalgae Ulva rigida produced in an open land-based integrated multi-trophic aquaculture (IMTA) system, over four seasons. Overall, protein and fat content of the farmed algae ranged between 7.6 and 25.8% DW and between 0.2 and 1.3% DW, respectively, reaching the highest levels during autumn/winter seasons. In turn, total dietary fiber and ashes showed a contrary seasonal tendency, reaching maximum levels in spring (40.9–58.3% DW and 25.5–38.8% DW, respectively). Notably, the latter were particularly characterized by their richness in potassium, magnesium and iron, and a sodium/potassium ratio bellow 1.7. Variable cultivation conditions of stocking density (Sd) and flow rate (Fr) were also tested, allowing to confirm that manipulation of cultivation conditions in an IMTA system may help to improve the nutritional value of this macroalga and to boost its market value through its use as a functional food ingredient.

Brown macroalgae are rich sources of nutrients and health-promoting compounds. Nevertheless, their consumption is still limited by their strong organoleptic characteristics, thus requiring the development of extraction strategies to profit from their nutritional value. To fulfil this, two sequential extraction approaches were developed, differing in the solvent used in the first extraction step, water in approach 1 or food-grade ethanol in approach 2, to obtain economic and affordable extracts rich in specific compounds from Fucus vesiculosus. The use of water in the first step of extraction allowed us to recover water-soluble phlorotannins, laminarans and mannuronic-rich alginates, making the subsequent 70% ethanol extract richest in fucoxanthin (0.07% algae DW), and the hot water fractions purest in fucoidans and alginates with a lower mannuronic-to-guluronic (M/G) ratio (2.91). Conversely, when beginning extraction procedures with 96% ethanol, the recovered yields of phlorotannins increased (0.43 g PGE/100 g algae DW), but there was a concomitant seven-fold decrease in the recovery of fucoxanthin in the subsequent 70% ethanol extract. This approach also led to less pure hot water fractions containing fucoidans, laminarans and alginates with a higher M/G ratio (5.50). Overall, this work unveiled the potential of the first extraction steps in sustainable and holistic cascade strategies to modulate the composition of food-grade extracts, creating prospects of their application as tailored functional ingredients in food products.

A phlorotannin extract was obtained from Himanthalia elongata, revealing a profile rich in fucophlorethol-type and carmalol-type compounds. When subjected to simulated gastrointestinal digestion, its levels of total phlorotannins and antioxidant activity, measured in vitro via NO^● and O₂^●− scavenging assays, were reduced, thus suggesting that these compounds’ integrity and bioactivity are negatively affected by the digestive process. Nevertheless, when undigested vs. digested extracts were used on lipopolysaccharide-stimulated Raw 264.7 macrophages, both showed a strong inhibitory effect on the cellular NO^● production. In fact, although not statistically significant, the digested extract revealed a tendentially stronger effect compared to its undigested counterpart, suggesting that even though there is a decrease in the phlorotannins’ concentration after digestion, with a consequent loss of their scavenging properties, the possible degradation products being formed may exert their effects through the modulation of the intracellular signaling mechanisms. Overall, this study not only contributes to a better understanding of the phlorotannins’ composition of the species H. elongata, but also shows that, although the digestive process may affect the integrity and concentration of these compounds, this does not necessarily translate into loss of bioactivity, in particular the anti-inflammatory activity, probably owing to the bioactive effects that the degradation products of these phenolics may have at an intracellular level.

Phloroglucinol is a powerful antioxidant compound and an active pharmaceutical ingredient used in the management of intestinal spasms. In this report, we describe the interaction of γ-cyclodextrin with phloroglucinol to readily form a solid inclusion compound with 1:1 by co-dissolution and freeze-drying. Solid-state characterisation using FT-IR, thermal analyses (TGA and DTA) and X-ray powder diffraction confirmed the formation of a true inclusion compound (γ-CD·PG) in which the molecules of γ-CD are stacked into channels. This spatial arrangement is typical of γ-CD inclusion compounds, and it allows for the guest molecules to be located inside these channels. The evaluation of the antiradical potential of γ-CD·PG (against O₂^•− and NO^•) on different steps of the digestive process (mouth, gastric and intestinal phases) led us to conclude that the inclusion of phloroglucinol promoted better antioxidant activity at the end of the digestion when compared to the free phloroglucinol.

Water deficit negatively affects crop yield and quality. Biostimulants, such as brown seaweed extracts, offer a sustainable solution to mitigate these effects. This study evaluated the impact of Laminaria digitata ‐aqueous extract (LE) on tomato performance and its potential to alleviate drought stress by examining morphological, physiological, and metabolic responses. Two‐week‐old tomato plants were foliar‐sprayed with LE (0.0, 0.1, and 1.0 g L ⁻¹ ) and split into well‐watered (WW) and water‐limited (WL) groups. WW plants received regular irrigation, while WL faced a one‐week drought. Then, half of the WL plants were rewatered and allowed to recover for 24 h (REC group). In general, LE effects were influenced by irrigation conditions, mainly impacting physiological and metabolomic parameters. Under WW conditions, LE decreased chlorophyll content, improved energy conversion by regulating photosystem antenna size, enhanced photochemical efficiency (ΦPSII) and gas exchange parameters ( g _s , C _i , P _N ), and promoted photosynthesis through stomatal modulation and RuBisCO activity. Conversely, under WL conditions, LE (especially 0.1 g L ⁻¹ ) decreased gas exchange parameters, but increased water use efficiency by inducing stomatal closure without impairing CO₂ assimilation. LE‐treated plants exhibited ROS detoxification and phytohormone downregulation, which in turn negatively affected the content of certain secondary metabolites (e.g., catechin). Phytohormone modulation may result from reduced ROS levels or crosstalking with LE compounds, including mannitol, alginates, laminarans, minerals, and phlorotannins, which likely act synergistically to improve physiological regulation. Overall, LE application improved drought tolerance by enhancing photosystem regulation, phytohormone modulation, and antioxidant capacity in tomato plants, highlighting its potential use as a biostimulant for sustainable agriculture.