Table 4. Antioxidant activity of peptide from by-product fisheries and aquaculture

By product source	Protease / peptide extraction	Scavenging activity(Activity value or IC50 at certain condition i.e. sample concentration or certain degree hydrolysis)
		DPPH	Hydroxyl radical
Abalone Haliotis discus hannai viscera (Zhou et al., 2012)	Alkali protease	IC50; 7 mg/mL	IC50; 10 mg/mL
	Neutral protease	IC50; 4 mg/mL	IC50; 11 mg/mL
	Papain	IC50; 4 mg/mL	IC50; 17 mg/mL
	Pepsin	IC50; 4 mg/mL	IC50; 5 mg/mL
	Trypsin	IC50; 4 mg/mL	IC50; 23 mg/mL
Arrow squid Nototodarus sloanii pen (Shavandi et al., 2017)	Bacterial endopeptidase (HT)	40%-45%; 4 mg/mL	NA
	Trypsin	40%-45%; 4 mg/mL	NA
	Pepsin	35%-40%; 4 mg/mL	NA
Squid Ommastrephes bartrami (Song et al., 2016)	Endogenous protease	IC50; 0.231 mg/mL	IC50; 0.74 mg/mL
Salmon Salmo salar skin (Zhang et al., 2022)	Alcalase	NA	70%-80%; 4 mg/mL
	Neutrase	NA	50%-60%; 4 mg/mL
	Flavourzyme	NA	30%-40%; 4 mg/mL
	Protamex	NA	40%-50%; 4 mg/mL
Rainbow trout Oncorhynchus mykiss skin (Yaghoubzadeh et al., 2020)	Alcalase	40%-45%; 0.8 mg/mL	NA
	Flavourzyme	45%-50%; 0.8 mg/mL	NA
Tuna dark muscle (Saidi et al., 2018)	Prolyve BS	30%-35%; 2 mg/mL	35%-40%; 2 mg/mL
Tuna Thunnus tonggol dark muscle (Hsu, 2010)	Orientase	31.5%; 3 mg/mL	NA
	Protease XXIII	41.0%; 3 mg/mL	NA
Striped weakfish Cynoscion guatucupa skin and bones (Lima et al., 2019)	Alcalase	50%-60%; hydrolysis at 10% DH	70%-80%; hydrolysis at 10% DH
		60%-70%; hydrolysis at 15% DH	40%-50%; hydrolysis at 15% DH
	Protamex	50%-60%; hydrolysis at 10% DH	30%-40%; hydrolysis at 10% DH
		50%-60%; hydrolysis at 15% DH	40%-50%; hydrolysis at 15% DH

IC₅₀, half maximal inhibitory concentration; DPPH, 2,2-diphenyl-1-picrylhydrazyl; HT, protein/protease prepared from bacteria using high-throughput preparation; NA, not available; BS, Prolyve BS. A neutral enzyme composed of metalloprotease produced by fermentation using a selected strain of Bacillus subtilis.; DH, degree of hydrolysis.