## 4 Discussion  
Marine seaweeds have a rich and diverse biochemical profile, containing primary and secondary metabolites such as pigments, phenolic compounds, polysaccharides, fatty acids and proteins. These compounds can be used in the development of various innovative products in many industries, particularly in the food industry. Abiotic factors such as changing nutrient levels, UV radiation, temperature, and salinity can cause environmental stress, leading to metabolic changes and variations in metabolites' production. Therefore, the biochemical profile of seaweed changes in response to these stressors [44]. Given that the aim of this study was to evaluate the biochemical composition and antioxidant activity of _L. ochroleuca_ (wild), _S. polyschides_ (wild), _M. pyrifera_ (cultivated) and the residual pulp of cultivated _M. pyrifera_, the results show differences among the  
Figure 4: Total phenolic content (TPC), expressed as mg GAE\(\cdot\)g\({}^{-1}\), in hydroethanolic kelp extracts. Data are presented as mean \(\pm\) standard deviation (\(n\) = 3). Different letters above the bars indicate statistically significant differences between the extracts (\(p\) < 0.05). Figure 5: Ferric reducing antioxidant power (FRAP), expressed as mmol Fe\({}^{2+}\) equivalents\(\cdot\)g\({}^{-1}\) of extract, in hydroethanolic kelp extracts. Data are presented as mean \(\pm\) standard deviation (\(n\) = 3). Different letters above the bars indicate statistically significant differences between the extracts (\(p\) < 0.05). species, which is in line with previously published data demonstrating the highly diverse biochemical composition of brown seaweeds. The fresh biomass of _Laminaria chroleuca_ and _Saccorhiza polyschides_ had a high moisture content, as is usual for seaweeds, in line with or slightly higher than the values found by other authors (85-94%) [44; 45; 46]. The ash content represents the inorganic content of the sample [35]. For _S. polyschides_, large discrepancies were found between our study and previously published studies (20-44.6% dw) [44; 45; 46], indicating large environmental variations in nutrient availability between sampling sites. The remarkably high ash content found in _M. pyrifera_ (48.94% dw) cultivated in Luderitz, Namibia is even higher than that found by [PERSON] and [PERSON] [36], indicating a high concentration of mineral salts and inorganic elements in the dry biomass. This may be related to the high availability of inorganic elements in the marine environment due to the Benguela Current and the seawater hydrodynamics that mobilise minerals by suspending them in seawater, making them available for absorption by the seaweed [47; 48]. Finally, the reduction in the inorganic matter content of the pulp may be due to the previous aqueous extraction process. The work of [PERSON] et al. [49] showed the same downward trend during phycocolloid extraction, suggesting that inorganic matter may be lost to the liquid fraction during extraction. The protein content of brown macroalgae usually varies between 5% and 20% of dry weight (dw), depending on species, season, and environmental conditions [29; 50; 51]. Specifically, _S. polyschides_ has been reported to contain between 7% and 18% dw protein [52], _L. achroleuca_ exhibits values ranging from 7.5% to 18% [44], while _M. pyrifera_ is known to have a protein content between 5% and 15% of its dry weight [53; 54]. Our results are in line with these authors, demonstrating that seaweed biomass may be an interesting alternative protein source, suitable as a functional or supplementary food. This is particularly relevant given the growing global demand for sustainable protein sources to reduce reliance on animal-derived products. Although brown algae tend to have a lower average protein content than red or green algae, their nutritional and functional potential remains substantial [51].