# Marine Bioactives and Their Application in the Food Industry: A Review
## 2 Marine Sources of Bioactive Molecules
### Marine Algae
#### 2.2.1 Macroalgae
Additionally, protein hydrolyses sourced from macrolgae have been identified as a promising source of antioxidants. The principal constituents of free amino acids in seaweed encompass aminobutyric acid, taurine, alanine, citrulline, ornithine, and hydroxyproline, with their proportions depending upon seaweed species. Taurine (2-aminoethanesulfonic acid) stands out among these amino acids, playing a critical role in various biological functions such as blood pressure regulation, conjugating bile acids, and acting as an anti-inflammatory, antioxidant, and hypocholesterolemomic agent [73]. Additionally, various types of seaweeds contain uncommon amino acids, including mycosporine-like amino acids (MAAs), which are renowned for their antioxidant properties [49]. Nevertheless, the most extensively studied functional algal proteins fall into two main categories: phycobiliproteins (phycocyanins, phycoerythrin, and allophyocyanins) and lectins. Phycobiliproteins form complexes of proteins and pigments (phycobilins) and are considered highly soluble fluorescent proteins. These are broadly applied as fluorescent markers in the biotechnology field and serve as natural colorants for the cosmetic and food industries. Furthermore, certain phycobiliproteins exhibit anti-inflammatory, antioxidant, antiviral, hypocholesterolememic, neuroprotective, and lipase inhibition activities [74]. On the other hand, macrolalgal lectins, which are typically bound with glycoproteins and carbohydrates, have also been obtained from both green and red algae (e.g., _Ulma_ sp.). These bioactive lectins play diverse roles in biological processes, including antibacterial and antiviral activities, intercellular communication, antitumor and anti-inflammatory effects, and binding and recognition of carbohydrates [75; 76]. Nonetheless, seaweed proteins face limitations in digestibility due to their elevated phenolic content, especially in brown algae. Conversely, red and green algae generally offer better protein availability due to their low phenolic content [77]. Aside from phenolic compounds, the digestibility of proteins can also be influenced by abundant dietary fibers, polysaccharides, and lectins, as well as the extent of protein glycosylation. Consequently, augmenting the digestibility of these proteins can be accomplished by eliminating polysaccharides through enzymatic methods. However, more research is required to uncover the in vivo digestibility of algal proteins while devising effective strategies for enhancing the bioaccessibility of these proteins [49; 55]. Macroalgae Lipids and Fatty Acids  
Phospholipids and glycolipids are the predominant lipid types in seaweed, making up roughly 1-5% of their cell walls. While seaweed has a lower lipid level than terrestrial plants like soy and sunflower, it contains a high amount of PUFAs. The lipid composition of seaweed differs based on factors such as species, season, location, salinity, temperature, and light intensity [49]. In particular, lower temperatures lead to increased PUFA accumulation in algae [78]. Various species of macrolgae have substantial quantities of EPA and DHA. Specifically, EPA stands out as the primary fatty acid in most seaweeds, making up over 50% of the total fatty acids. Notably, brown and red algae are rich in EPA, linoleic acid, and \(\alpha\)-linolenic acid, whereas green seaweeds have higher levels of oleic, hexadecetraenoic, and palmitic acids. For example, _Ulva_ sp. (e.g., _Ulva pertusa_) are high in hexadecetraenoic acid, while _Laminaria_ sp. (e.g., _Laminaria ochroleuca_ and _Undaria pinnuatifida_) are abundant in octadecetraenoic acid [79]. Nevertheless, their role as a food energy source seems limited due to their relatively low lipid level (\(\sim\)4.5%).