**8.2 Animal sources for derivation of antioxidants**

Antioxidant peptides derived from *Pinctada fucata* protein have been shown to improve collagen fiber density by increasing hydroxyproline level besides inhibiting *Skin Aging: Implications of UV Radiation, Reactive Oxygen Species and Natural Antioxidants DOI: http://dx.doi.org/10.5772/intechopen.100102*

lipid peroxidation [93]. Similar observations have also been observed with Oyster (*Crassostrea gigias*). Additionally, it could modulate AP-1 transcription factor, regulate MAPK signaling and consequently block MMP expression. It could also stimulate TGFβ/SMAD pathway enhancing collagen synthesis [94].

Usually, fish industries generate various waste products such as fish head, internal organs, scales and skin. But several investigations have shown that utilization of these resources for treatment of photoaged skin could be propitious especially in terms of waste management. One such example involves the use of gelatin polypeptides from COD fish (*Gadus microcephalus*) skin. The gelatin polypeptides contain key amino acids that are essential for collagen synthesis. They help elevate hydroxyproline level and collagen synthesis. Beside these, they are able to decrease MDA levels and improve antioxidant activities of SOD, CAT and GPx. In this way they help inhibit photoaging [95]. Similar results have also been observed for antioxidant collagen peptides obtained from Jellyfish umbrella and Silver carp (*Hypophthalmicthys molitrix*) skin [96, 97]. Tilapia (*Oreochromis niloticus*) gelatin peptides have been shown to possess hydroxyl radical scavenging property. This is crucial as hydroxyl radicals are prime ROS species that result in strong oxidative stress [98]. In a study, peptide from Tilapia gelatin hydroxylates was shown to reduce ROS levels and inhibit oxidative damage to DNA besides elevating antioxidant levels (SOD, GSH). More significantly, the peptide inhibited MMP 1 and MMP-9 expression along with regulating MAPK and NFκB pathways [99]. Similar results were also observed in another study where additionally the authors pointed out the role of C-terminus of peptide terminating with GLY-LEU in impeding MMP-1 activity [100].

#### **8.3 Derivation of antioxidants from marine sources**

Till now, different algal species have been utilized for numerous investigations aiming towards analysis of molecules effective against photoaging. *Tetraselmis suecica* microalgal extract was found to reduce MDA level while increasing SOD and GSH levels. Further, the extract could improve type I procollagen production and lower MMP-1 expression [101]. Fucoxanthin, a carotenoid found in *Undaria pinnatifida* inhibits wrinkle formation by blocking MMP-13 expression [102].

Recently, another compound known as Mycosporine like amino acid (MAA) has come into limelight. They consist of cyclic rings of aminohexenimine or aminocyclohexenone and can vary among themselves with respect to amino acids and groups attached to them [103]. They are mostly found in algal species belonging to orders Bangiales, Gracilariales, Ceramiales and Gigartinales where their prime function is to provide UV protection [104]. Production of MAA is affected by numerous factors like salt concentration, UV, amount and type of nutrient available among others [105, 106]. Recently, two MAA, Shinorine and Porphyra-334 were reported to prevent photoaging by reducing MDA levels upto ≈56% and restoring antioxidants like SOD, GSH-Px and CAT. Additionally, a reduction in NFκB, IL-1β and IL-6 was also found [107]. Porphyra-334 can further be helpful by increasing procollagen production and blocking UV induced MMP production [108]. In another study where human keratinocytes were treated with UVR, expression profiling along with functional network analysis portrayed that miRNAs regulated by porphyra-334 could modulate various genes associated with UV affected processes such as cell proliferation, apoptosis and translational elongation [109]. Another compound that has attracted the interest of many researchers is Scytonemin. It is found in polysaccharide sheath of cyanobacteria and like MAA functions as an UV protectant [105]. Like MAA, its production

is increased under photo-oxidative stress, elevated temperature osmotic stress and UVR. Recently, scytonemin from *Rivularia sp*. HKAR-4 was tested for analyzing its photoprotective function. Here, scytonemin successfully reduced intracellular ROS production along with thymine dimer formation [110]. In future it is expected that more such molecules will be revealed as research deepens in these areas with time.
