## 4 Natural Antioxidants and Their Role in Cosmetics
### Algae-Derived Antioxidants
and _Lyngbya_ sp. Extracts from these species could serve as natural photoprotectors in UV-screen cosmetic formulations [181; 183; 193]. Especially _Arthrospira platensis_ (spirulina) and _Arthrospira_ species could be of potential value in cosmeceutical, dietary, and biomedical applications. The chemical composition of spirulina comprises proteins; polysaccharides and polyunsaturated fats (including 10-30% of \(\gamma\)-linolenic acid, GLA); vitamins; and minerals and pigments, including \(\beta\)-carotene and phycocyanin. _Arthrospira_ species are used in many cosmetic products, such as balms and face masks which have anti-aging, moisturizing, brightening, and anti-acne properties, e.g., Protulines(r) by Exsymol S.A.M., Monaco--an anti-aging agent from protein-rich extract of _Arthrospira_[183; 191; 194]. The other _Cyanobacteria_ species with active antioxidant and anti-aging compounds are _Anabaena vaginicola_ (lycopene), _Aphanizomenon_ sp., _Nostoc_ sp. (MAA), and _Plankothrix mougeotii_, which seem promising in their applications in cosmeceuticals [191; 193]. 4.10.2. Phaeophyceae (Brown Algae)  
Brown seaweeds are a type of eukaryotic algae widely distributed in cold-water marine environments. They are rich in seaweed polysaccharides, including alignates, laminarans, and fucoidans, as well as proteins, amino acids, polyphenols, terpenes, mannitol, fucoxanthin, hormones, and other bioactive compounds. A unique class of active polyphenic substances extracted from Phaeophyceae are phlorotannins, a group of polymers composed of phloroglucinol. These compounds exhibit a wide range of biological properties, including antioxidant, skin-whitening, antibacterial, antiviral, anti-tumor, anti-allergic, and anti-inflammatory activities. The majority of phlorotannins and sulfated polysaccharides reported in scientific studies have been derived from _Ecklonia_ and _Eisenia_ species. Phlorotannins from marine algae, such as _Ecklonia cava_, have demonstrated the ability to protect cells from radiation-induced injury and oxidative stress. Additionally, fucoidan derived from brown algae (e.g., from _Ascophyllum nodosum_) has been reported to strongly inhibit UVB-induced MMP-1 expression in vitro. The further screening of brown algal species is needed to identify novel phlorotannins and polysaccharide derivatives that could be recommended as potential inhibitors of matrix metalloproteinases (MMPs), enzymes that contribute to collagen degradation and skin aging [180; 195]. In cosmetology, tyrosinase inhibition is the most common approach to combat skin hyperpigmentation, and the search for effective skin-whitening agents has become an important goal in the development of cosmetic formulations. Tyrosine inhibitors, regulators of melanogenesis (including fucoxanthin, phloroglucin) have been isolated from many marine species of brown algae, such as _Ecklonia cava_, _E. stolonifera_, _Fucus_veisculous, Hizikia fusiformis, Ishige foliacea, Laminaria japonica, Petalonia binghamiae, Sargasum siliquastrum, S. polycystum, and Undaria pinnatifida, which exhibit activity against melanogenesis and have a protective effect against photo-oxidative stress induced by UVB radiation [180; 181; 189; 190; 191; 192; 193; 194; 195]. The evidence indicated that bioactive compounds from seaweeds have great potential to be used as skin whitening and depigmentation agents [192]. Brown algae-derived phlorotannins and sulfated polysaccharides will be further explored in the cosmeceutical production development [181].