Codium fragile and Chondrus crispus are, respectively, green and red seaweeds which are abundant along the North Atlantic coasts. We investigated the chemical composition and antiviral activity of enzymatic extracts of C. fragile (CF) and C. crispus (CC). On a dry weight basis, CF consisted of 11% protein, 31% neutral sugars, 0.8% sulfate, 0.6% uronic acids, and 49% ash, while CC contained 27% protein, 28% neutral sugars, 17% sulfate, 1.8% uronic acids, and 25% ash. Enzyme-assisted hydrolysis improved the extraction efficiency of bioactive materials. Commercial proteases and carbohydrases significantly improved (p ≤ 0.001) biomass yield (40%–70% dry matter) as compared to aqueous extraction (20%–25% dry matter). Moreover, enzymatic hydrolysis enhanced the recovery of protein, neutral sugars, uronic acids, and sulfates. The enzymatic hydrolysates exhibited significant activity against Herpes simplex virus (HSV-1) with EC₅₀ of 77.6–126.8 μg/mL for CC and 36.5–41.3 μg/mL for CF, at a multiplicity of infection (MOI) of 0.001 ID₅₀/cells without cytotoxity (1–200 μg/mL). The extracts obtained from proteases (P1) and carbohydrases (C3) were also effective at higher virus MOI of 0.01 ID₅₀/cells without cytotoxity. Taken together, these results indicate the potential application of enzymatic hydrolysates of C. fragile and C. crispus in functional food and antiviral drug discovery.

Polysaccharides, lipids and amino acid profiles were investigated to understand the nutritional value of Caulerpa racemosa and Ulva fasciata from the Philippines. The results revealed that both species contain high amounts of proteins (8.8–19.9% for C. racemosa and 8.0–11.1% for U. fasciata). The portions of the total amino acids that were essential amino acids (EAAs) (45.28 ± 0.12% for C. racemosa and 42.17 ± 0.12% for U. fasciata) out were comparable to FAO/WHO requirements. Leucine, valine, isoleucine, and lysine are the dominant EAAs in C. racemosa, while leucine, valine, lysine, and phenylalanine are those in U. fasciata. The fatty acid profiles are dominated by monounsaturated fatty acids and polyunsaturated fatty acids in C. racemosa (56.2%), while saturated fatty acids (72.1%) are dominant in U. fasciata. High C18/C20 polyunsaturated fatty acid ratios were recorded in both species. Mineral contents for both seaweeds were within levels considered safe for functional foods. Total pigment content of C. racemosa (140.84 mg/g dw) was almost 20 times higher than that of U. fasciata (7.54 mg/g dw). Hot water extract (HWE) from C. racemosa showed in vitro antiherpetic activity without cytotoxicity. Nutritional characteristics confirmed that C. racemosa could be potentially used as a nutritious and functional food items for human consumption.

Herpes simplex virus 1 (HSV-1) remains a prominent health concern widespread all over the world. The increasing genital infections by HSV-1 that might facilitate acquisition and transmission of HIV-1, the cumulative evidence that HSV-1 promotes neurodegenerative disorders, and the emergence of drug resistance signify the need for new antiviral agents. In this study, the in vitro anti-herpetic activity of sulfated polysaccharides (SPs) extracted by enzyme or hot water from seaweeds collected in France and Mexico from stranding events, were evaluated. The anti-herpetic activity evaluation of the semi-refined-polysaccharides (sr-SPs) and different ion exchange purified fractions showed a wide range of antiviral activity. Among them, the sr-SPs from the Rhodophyta Halymenia floresii showed stronger activity EC₅₀ 0.68 μg/mL with SI 1470, without cytotoxicity. Further, the antiviral activity of the sr-SPs evaluated at different treatment schemes showed a high EC₅₀ of 0.38 μg/mL during the viral adsorption assays when the polysaccharide and the virus were added simultaneously, whilst the protection on Vero cell during the post-infection assay was effective up to 1 h. The chemical composition, FTIR and ¹H NMR spectroscopic, and molecular weights of the sr-SPs from H. floresii were determined and discussed based on the anti-herpetic activity. The potential utilization of seaweed stranding as a source of antiviral compounds is addressed.

Although the density and diversity of seaweeds in Madagascar is particularly high, these resources are underexploited and they are not part of the local population’s eating habits. No study has been carried out on the nutritional properties and seasonal variation of Eucheuma species harvested in Madagascar. In this study, Eucheuma denticulatum was harvested monthly over two years (2021 and 2022) on the northeast coast of Madagascar (Sainte Marie Island). The compositional analysis revealed prominent sugars and minerals up to 41.0 and 39.5% dw, respectively. E. denticulatum showed slight variability over the seasons in the macroelements and oligoelements (Ca, K, Na, Mg, Fe, Mn) ranging from 22.8 ± 0.2 to 25.3 ± 0.1% dw in 2021 and 22.1 ± 0.3 to 26.5 ± 0.3% dw in 2022. Total amino acids varied from 2.3 ± 0.6 to 2.5 ± 0.6% dw during the two years. Seaweed extracts showed antioxidant activity by the in vitro method ranging from 2026 ± 2 to 2998 ± 4 μg.mL⁻¹ in 2021, and from 1904 ± 2 to 2876 ± 4 μg.mL⁻¹ in 2022. Finally, the principal component analysis (PCA) showed a correlation between protein content and environmental parameters. The nutritional characteristics therefore confirmed that E. denticulatum could potentially be used as a nutritious and functional food and could be incorporated in the diet of local populations.

Marine seaweeds are recognized as a rich source of structurally diverse bioactive compounds, particularly sulfated polysaccharides with promising biomedical applications. In the present study, a sulfated polysaccharide Codium tomentosum fraction (PSCT) was extracted from the Moroccan green seaweed Codium tomentosum and subjected to comprehensive chemical, structural, and biological characterization. The extraction yield reached 22.01%, and the polysaccharide fraction was mainly composed of neutral sugars (66.84%), along with significant levels of sulfate groups (8.73%) and uronic acids (4.13%). Monosaccharide analysis revealed a predominance of galactose and arabinose, indicating a complex heteropolysaccharide structure. Spectroscopic and morphological analyses (FTIR, XRD, UV–Vis, and SEM–EDS) suggested predominantly amorphous characteristics and confirmed the sulfated profile of the extract. Biological evaluation demonstrated that PSCT exhibits multifunctional bioactivities. The extract showed notable antiviral activity against Herpes Simplex Virus 1 (HSV1), with an EC₅₀ value of 12.22 ± 2.90 µg/mL and no detectable cytotoxicity (CC₅₀ > 200.00 µg/mL). In addition, PSCT displayed strong antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, with remarkably low MIC values ranging from 0.05 to 0.78 mg/mL. Furthermore, antioxidant assays revealed concentration-dependent activity, with up to 68% DPPH radical scavenging and an IC₅₀ of 1.25 mg/mL, indicating a moderate antioxidant potential, along with notable reducing power in the FRAP assay. Overall, these findings highlight the potential of C. tomentosum-derived polysaccharides as multifunctional natural agents with antiviral, antimicrobial, and antioxidant properties, supporting their prospective application in pharmaceutical and biomedical fields.