## 1 Introduction  
Oxidation is an important factor in the food industry because it causes a loss of nutrition, color and functionality, as well as undesirable off-flavors and toxic compounds, which further induce the deterioration of food. Furthermore, the accumulation of toxic products is dangerous to the health of consumers [1; 2]. Therefore, the inhibition of free radical formation and oxidation reactions play an important role in preventing or retarding the autoxidation of food components [3]. Many synthetic antioxidants, including butylated hydroxytoluene (BHT), butylated hydroxyansole (BHA), and tertiary butylhydroquinone (TBHQ), are widely used in the food industry for preservation and to retard lipid oxidation [4; 5]. However, the dosages of the synthetic antioxidants are under strict regulation due to their potential health hazards and toxic effects [6; 7]. Therefore, there has been a large amount of interest in researching safe antioxidants from natural sources as an alternative to synthetic antioxidants [8]. In recent years, peptides with different activities, including anticancer, antioxidant, antimicrobial, antihypertensive, and mineral-binding properties, have been isolated from various bioresources, such as byproducts from the fish processing industry [9]. Antioxidant peptides have drawn great attention and have been extensively reported as free radical scavengers, peroxide decomposers, metal inactivators and oxygen inhibitors to protect food and organisms from reactive oxygen species (ROS) [8; 10]. Arg-Gln-Ser-His-Phe-Ala-Asn-Ala-Gln-Pro (RQSHFANAQP), with molecular weight (MW) 1155 Da, from the protein hydrolysate of chickpeas showed significant dose-dependent scavenging activities on hydroxyl radicals (HO\(\bullet\)) (EC\({}_{50}\) 2.03 \(\upmu\)mol/mL), 2,2-diphenyl-1-picrylhydrazyl radicals (DPPPH\(\bullet\)) (EC\({}_{50}\) 3.15 \(\upmu\)mol/mL) and 2, 2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radicals (ABTS\({}^{+}\bullet\)) (EC\({}_{50}\) 2.31 \(\upmu\)mol/mL) [10]. Asp-Leu-Glu-Glu (DLEE), with MW 504.2 Da, was confirmed to be one of the main antioxidant peptides generated in dry-cured Xuanwei ham, and its DPPH\(\bullet\) scavenging rate was 74.45% at 0.5 mg/mL [9]. Phe-Ile-Met-Gly-Pro-Tyr (FIMGPY), Gly-Pro-Ala-Gly-Asp-Tyr (GPAGDY) and Ile-Val-Ala-Gly-Pro-Gln (IVAGPQ), with MWs of 726.90 Da, 578.58 Da and 583.69 Da, respectively, showed strong scavenging activities on DPPH\(\bullet\) (EC\({}_{50}\) 3.5768, 6.0147 and 6.733 M), HO\(\bullet\) (EC\({}_{50}\) 4.1821, 6.7752 and 8.6176 M), superoxide anion radicals (O\({}_{2}^{-}\bullet\)) (EC\({}_{50}\) 2.2149, 2.8691 and 3.1181 M) and ABTS\({}^{+}\bullet\) (EC\({}_{50}\) 1.4307, 1.3308 and 2.2101 M) [11]. In addition, FIMGPY induced HeLa cell apoptosis by up-regulating the Bax (B-cell lymphoma 2 (Bcl-2) associated X protein)/Bcl-2 ratio and caspase-3 activation [12]. Structure-activity studies on the antioxidant peptides suggested that the peptide length and the composition and position of amino acids in a peptide sequence are important determinants of the bioactivity of a specific peptide [8; 13; 14]. Cartilage is a form of connective tissue that is chemically abundant in bioactive components, and many cartilaginous proteins, low MW proteins, glycoproteins, and peptides have been prepared from various soft bone fish sources, such as bamboo and blacktip sharks [15], _Prionace glauca_[16], Amururgeon [17], spotless smoothness [7], and silvertip shark [18]. Current research has shown that those active substances could be used as angiogenesis inhibitors, tumor cells inhibitory factors, antioxidants, immune regulatory factors, and anti-invasion factors for the treatment of some diseases, especially in tumor therapy and prevention. Scalloped hammerhead (_Sphyrna lewini_), belonging to the family Triakidae, is a commercially valuable fishery resource. At present, large quantities of muscle protein and cartilages (except the cartilages from fins) from scalloped hammerhead are not used efficiently.