Pea-Derived Antioxidant Peptides: Applications, Bioactivities, and Mechanisms in Oxidative Stress Management

Abstract

Chronic injuries and diseases related to oxidative stress are major global concerns as they impose a great medical burden and lead to serious public health issues. Antioxidant peptides derived from pea protein can serve as potent antioxidants and food additives, contributing to address the challenges posed by oxidative stress. This review will focus on the antioxidant effects of pea peptides demonstrated in various in vitro chemical, cellular, and in vivo antioxidant models. Additionally, this review also summarizes the regulatory role of pea peptides on the Nrf2 (NF-E2-related factor 2)/Kelch-like ECH-associated protein 1 (Keap1) pathway, aiming to elucidate their antioxidant mechanisms. Our review found that pea peptides with smaller molecular weights (<1 kDa) obtained through enzymatic hydrolysis or fermentation and/or those containing amino acids such as Glu, Asp, Gly, Pro, and Leu tend to exhibit higher antioxidant activity. These pea peptides exert their antioxidant effects by scavenging free radicals, chelating pro-oxidative transition metals, reducing hydrogen peroxide, inactivating reactive oxygen species, enhancing the expression of antioxidant enzymes, and reducing the accumulation of lipid peroxides. Our study provides a theoretical foundation for the development of pea resources and the processing of pea-related functional foods.

1. Introduction

Free radicals are defined as any species with unpaired electrons capable of existing independently that originate from both endogenous and exogenous pathways [1]. The former comes from external or environmental origins such as air pollutants, smoke, and radiation, while the latter primarily derives from byproducts of metabolic or inflammatory reactions synthesized within the body [1,2,3,4]. Generally, free radicals include various forms such as peroxyl radicals (ROO·), hydroxyl radicals (OH·), nitric oxide (NO·), and superoxide radicals (O₂·), which can attack macromolecules in the human body, including membrane lipids, proteins, and DNA [5,6]. Aerobic organisms possess an antioxidant defense system to counteract the destructive effects of oxidative stress [7]. In healthy individuals, there is a balance between oxidative stress and antioxidant defenses, enabling the body to resist low levels of oxidative stress [8]. Conversely, the above balance might be disrupted by overloading exogenous pro-oxidants (including reactive oxygen species (ROS) species in environmental pollution and in cigarette smoke), making challenging the elucidation of the toxic effects and representing problems for toxicology and ecotoxicology [9,10]. Furthermore, excessive free radical attack also lead to dysfunction of cells, tissues, and organs and the development of chronic diseases such as diabetes, neurodegenerative disorders, cancer, and inflammatory diseases [11,12,13,14].

Oxidative reactions also occur in food, often leading to deterioration in quality attributes such as flavor, aroma, texture, and color, which shortens shelf life and further causes food spoilage [15,16]. Many synthetic antioxidants, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), are used as food additives to prevent spoilage [17,18]. However, some studies suggest that these synthetic antioxidants may cause DNA damage and toxicity, raising concerns about their negative effects on human health, leading to restrictions on their use [19,20,21]. In recent years, the isolation of new, safe antioxidants from natural foods has attracted the interest of researchers. A variety of natural antioxidants, including polyphenols, anthocyanins, polysaccharides, and bioactive peptides, have been isolated and applied in fields like food preservation and chronic disease treatment [22,23,24,25]. Among these, bioactive peptides are specific protein fragments composed of approximately 2–20 amino acid residues, typically exerting beneficial or physiological effects on living organisms [26]. The advantages of bioactive peptides lie in their low cost, simple preparation, large-scale production, and high bioactivity, prompting scientists to identify many bioactive peptides from various organisms and extensively study their biological activities [27].

Pea (Pisum sativum L.), more specifically the yellow or green cotyledon varieties known as dry, smooth or field pea, is the second most important crop in the Leguminosae family [28]. Peas are cultivated in nearly all countries worldwide and are regarded as an essential component of the human diet [29]. Canada is the largest global producer of peas, followed by China, Russia, and India. Typically, peas exhibit two phenotypic forms: smooth peas and wrinkled peas, with seed coats that may be cream-yellow, yellow-green, light green, green, olive green, dark green, brown, or orange-brown [29]. From a nutritional perspective, peas consist mainly of protein (20–25%), fat (1.5–2.0%), starch-based carbohydrates (24–49%), and total dietary fiber (60–65%). Minor components include vitamins (primarily B vitamins), minerals (K (1.04%), P (0.39%), Mg (0.10%), Ca (0.08%)), phytic acid, saponins, polyphenols, and oxalates [28]. Peas are rich in lysine and threonine but deficient in sulfur-containing amino acids (methionine and cysteine); thus, they are often consumed in combination with cereals to enhance absorption [30]. However, peas also contain some anti-nutritional compounds, such as alkaloids, phytic acid, phenolic compounds, lectins, chymotrypsin inhibitors, trypsin inhibitors, antifungal peptides, and ribosomes [31]. These anti-nutritional compounds have negative effects on human and animal health, impairing growth and metabolic activities. The high nutritional density of peas makes them a valuable food source capable of addressing the dietary needs of approximately 800–900 million malnourished individuals globally [32]. The USDA MyPlate guidelines recommend consuming at least three cups of dried beans and peas per week; however, the majority of the U.S. population falls short of this recommendation. In recent years, the strong demand for peas has been driven by their use in sports nutrition supplements and gluten-free products [33]. Additionally, peas can be utilized in a variety of products, including plant-based cheeses, meat alternatives, beverages, and baked goods [34,35,36,37,38]. Furthermore, peas can also be consumed as sprouts and microgreens after germination [29]. Several commercial pea-based products have been developed and are available in the market, such as pea flour, pea protein, pea hull fiber, and pea cell wall fiber.

Among leguminous protein sources that can serve as alternatives to animal protein and/or soy protein, pea protein is widely recognized for its nutritional value, abundance, non-GMO status, and low allergenicity [39,40]. Currently, pea protein is one of the fastest-growing plant proteins in the global alternative product market, with its rapid growth attributed to the agronomic benefits of pea cultivation, low production costs, and acceptable nutritional quality [34,39]. The common extraction method for pea protein is wet processing, with extraction efficiency dependent on pH, solubilizing agents, and the extraction process [41]. Specifically, pea flour is dispersed in water and the pH is adjusted to 9–10 to solubilize the proteins. The slurry is then centrifuged to separate proteins from carbohydrates, followed by further adjusting the pH of the supernatant to the isoelectric point (4.3–4.5) to precipitate the proteins. Finally, the precipitated protein extract is neutralized and either spray-dried or freeze-dried into protein powder. Generally, pea protein can be categorized into pea protein concentrate (PPC) and pea protein isolate (PPI), with the former having a slightly lower protein content of 38–65%, while the latter generally contains over 80% protein [34]. In terms of protein composition, pea protein consists of 55–65% buffer-extractable globulins and 18–25% water-soluble albumins. The globulins serve as seed storage proteins and comprise two main subcomponents: legumin (pI 5–6) and vicilin (pI 4–6), corresponding to 11S and 7S seed storage proteins, respectively [34,39]. The albumins include metabolic and enzymatic proteins of the pea [34]. Pea protein exhibits several excellent functional properties, such as water-holding capacity, emulsification, foaming, gelation, oil retention, and fat replacement ability [35,41]. These properties can be further improved through various modification techniques, including polysaccharide conjugation, enzymatic treatment, acylation, deamidation, and physical modification, which also contributes to lighter beany taste [41].

Pea bioactive peptides are defined as specific amino acid sequences derived from pea protein that possess potential physiological properties beyond basic nutritional functions [42]. In their native state within pea proteins, these sequences remain inactive; however, they can demonstrate diverse bioactivities upon release, including antioxidant, anticancer, anti-inflammatory, hypoglycemic, and antihypertensive effects [26,43]. The hydrolysis of pea proteins is essential for generating bioactive peptides, which can be liberated through microbial fermentation, germination, enzymatic hydrolysis, or in vitro/digestive proteolysis of precursor proteins [44]. Commonly used proteases include pepsin, trypsin, chymotrypsin, pancreatin, alcalase, flavourzyme, and bromelain, while typical fermentation strains include Lactobacillus plantarum, Bacillus licheniformis, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus reuteri, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus acidophilus, and Lactobacillus helveticus [45,46,47,48]. The bioactivity of released pea peptides depends on multiple factors, such as the type of pea protein, the enzymes/fermentation strains employed, and the processing conditions applied (

Table 1. Production methods, sequences, and in vitro antioxidant activity of peptides from pea protein.

Sources	Processing	Sequences	Antioxidant Capacity	References
PPH	7% pea protein, 3.8% (enzyme/substrate ratio) alcalase protease, 50 °C for 3 h	YLVN, EEHLCFR, TFY	DPPH: IC50: EEHLCFR = 0.027 mg/mL; TFY = 1.492 mg/mL; ABTS: IC50: YLVN = 0.002 mg/mL; EEHLCFR = 0.019 mg/mL; TFY = 0.006 mg/mL; OH·: IC50: EEHLCFR = 2.796 mg/mL; O2-: IC50: YLVN = 1.357 mg/mL; EEHLCFR = 1.247 mg/mL; ORAC: IC50: YLVN = 1.12 μmol TE/μmol Peptide; EEHLCFR = 0.921 TE/μmol Peptide; TFY = 0.484 µmol TE/μmol Peptide	[52]
PPH	Alkaline proteases; substrate concentration (2, 3, 4, and 5%), enzyme to substrate ratio (4, 6, 8, 10, and 12%), temperature (40, 45, 50, 55, and 60 °C), and pH (7.0, 8.0, 9.0, and 10.0)	YSSPIHIW, ADLYNPR, HYDSEAILF, AGVLPGIK, GHYPNPDIEYG, SQISPLPVLK, KFTPPHVI, KINPDAPLDKV, RDDNEDLRVL, HTDADYILV; ATDDQIMDGVR, QIENPVKEL, HIISPELQ, TVVVNFSV	DPPH increased as enzyme to substrate ratio increase; DPPH increased and then decreased as pH, temperature and substrate concentration increase; the antioxidant activity of peptides followed the order of YSSPIHIW > ADLYNPR > HYDSEAILF	[53]
PPH	Alcalase (50 °C, pH 8.0), pepsin (37 °C, pH 2.0), trypsin (37 °C, pH 8.0), chymotrypsin (37 °C, pH 8.0), flavourzyme (50 °C, pH 8.0), and pancreatin (37 °C, pH 7.5)	Pea protein peptides with MW < 1 kDa and 1–3 kDa	High HRSA and SRSA, high linoleic acid peroxidation inhibition activity	[54]
PPH	pH 6, 6.58 and 8.0, 60 °C for 120 min	Peptide mixture	High FRAP, ORAC and DPPH value	[46]
PPIH	Sample was mixed with 3.5 mL of electrolite solution, 0.5 mL of α-amylase, 25 μL 0.3 mol/L CaCl2, and 975 μL H2O and incubated at 37 °C for 2 min. After that, the resulting solution was mixed with 7.5 mL of simulated gastric fluid and 1.6 mL of pepsin solution at 37 °C for 2 h and then mixed with 11.0 mL of the simulated intestinal fluid and 5.0 mL of pancreatin solution at 37 °C for 2 h	Peptide mixture	ORAC: ranged from 0.07 to 0.31 mg/mL; IC50 of HRSA: 3–10 mg/mL	[55]
Pea flour	1.2 g portion of legume flour was mixed with 1.8 g of water, and the suspension was mixed in a ratio 1:1 with digestive fluid (oral, gastric, duodenal, and jejunal-ileal digestion phases) to perform the digestion	NYDEGSEPR, NQLDSTPR, EDVPNHGT, GGSSTHPYP, NDLGNPDHGEH, LGNPDSGENH, NDLGNPDSGENH, IGANEPSEH, LGNPDSGENH, NDLGNPDHGEH, NYDEGSEPR, YDEGSEPR, NDLGNPDHGEH, SDDEDTAPPR, GDGMPGGGSNGSGPGPK, QEEDEDEEKQPR, KEDEDEDEEEEE, NDLGNPDSGENH	Pea peptides had lower antioxidant capacity than faba bean, but higher antioxidant capacity than soybean	[56]
Pea peptides	Purchased from Shuangta Biochemical Technology	200–5000 Da	The HRSA, SRSA and ABTS activity of pea peptides were improved after encapsulated in maltodextrin and gum tragacanth	[57]
PPH	pH 6.2, 0–8 h in a 43 °C water bath	GRNEDEEKGAIVKVKGGL, GRRGGQQQEEESEEQNEGNSVLSG, KDFPFPSSAL, LGGNPETEFPETQEEQQGRHRQ, QRPVKELAFPG, RRGGQQQEEESEEQNEGNSVL, RRGGQQQEEESEEQNEGNSVLSGF, SLDLWDPFQ, SLDVWDPLK	IC50: 0.774 mg/mL (DPPH), 0.305 mg/mL (ABTS)	[47]
Pea oligopeptide	Alcalase 2.4 L, pH 9.0, 80 °C for 30 min	TGRGAP, PPKIYP, HQMPKP, TSSLP	Se-pea oligopeptide had higher DPPH and HRSA than pea oligopeptide and sodium selenite	[58]
PPH	1% Alcalase® (1 h, pH 8.0) + Flavourzyme® (1 h, pH 7.0) or Protamex® (2 h, pH 7.0) + Flavourzyme® (2 h, pH 7.0), 55 °C	APQE, ELTP, LPQ, LSSIL, NVISQ, PNY, QLEEL, SEPFN, SLSLL, SPDIY, TPGEVL, TPVIA	IC50: 14.57–14.99 mg/mL (iron chelating activity); 4.24–5.62 mg/mL (reducing activity); 0.041–0.045 mg/mL (ABTS)	[48]
PPH	Enzyme to substrate ratio 1:100, pH 7.0, 50 °C, 1.5 h	>5 kDa; 3–5 kDa; 1–3 kDa; <1 kDa	55% (DPPH); the 50 kGy pre-irradiated hydrolysates have the strongest ABTSscavenging effect	[59]
PPH	Enzyme concentration of 12.0%, temperature of 60.2 °C, pH 6.5, substrate concentration of 7.1%	Peptide mixture	98.1% (DPPH) at the optimal hydrolysis conditions	[60]
PPH	2% enzyme/substrate (neutral protease/validase/alkaline protease), 6 h, 55 °C, pH 7.0	>10 kDa; 3–10 kDa; 1–3 kDa; <1 kDa	Peptides with MW < 1 kDa had the highest ORAC (55.2–81.6 μmol TE/g), DPPH (70.5%), ABTS (52.5 μmol TE/g) and lipid peroxidation values	[61]
PPH	1% enzyme/substrate, pH 8.0, 25 min/120 min	Peptide mixture	The lowest antioxidant activity was found at pH 8.0; when the hydrolysis takes place to a great extent, the antioxidant activity decreases significantly against any reagent (DPPH, ABTS or FC)	[62]
Pea Pentapeptide	Chemical synthesis	VNRFR	VNRFR had lower DPPH and ABTS compared to quercetin and rutin; but when VNRFR was bound with quercetin or rutin, their antioxidant capacity decreased due to antagonistic effects between them	[63]
Pea seed hydrolysate	The seeds were cooked in water at a legume:water ratio of 1:6 (w/v), by three different household processing methods: (a) ordinary cooking, at 100 °C for 40 min; (b) pressure cooking, at 8.7 psi for 15 min; and (c) microwave cooking, at 800 W for 30 min	Peptide mixture	Peptide mixture had high DPPH, ABTS and FRAP value	[64]
PPH	30 min, 50 °C, pH 7.0, enzyme/substrate (E/S) ratio of 1:50	Peptide mixture	The ABTS and reducing powder of PPH increased after loading with curcumin and treated using pH-driven method and ethanol-induced method	[65]
PPH	4% alcalase, 4 h, pH 4.0, 50 °C	Peptide mixture	The ORAC, DPPH, SRSA, HRSA, FRAP and MCA of PPH increased after 400 and/or 600 Mpa pretreatment; heat pretreatment of PPH resulted in reduced DPPH	[66]
PPH	pH 8 and 55 °C for Alcalase; pH 6.5 and 40 °C for Neutrase; pH 6 and 60 °C for Flavourzyme	TVTSLDLPVLRW, IGPSSSPDIYNPEAGRIK, ENLQNYRLL, GPIYSNEFGKFF, AEYVRLY, TVTSLDLPVLRW, NIGPSSSPDIYNPEAGRIK, AMFVPH, GPIYSNEFGKFF, NILEASYNTR	The ABTS, DPPH, SRSA and HRSA of TVTSLDLPVLRW were 579.5, 5078.2, 422.0 and 1533.8 mmol GSH/mol peptide, respectively; AEYVRLY were 492.3, 5316.4, 1394.4 and 1584.7 mmol GSH/mol peptide, respectively; and FVPY were 491.9, 6108.4, 1088.7 and 976.3 mmol GSH/mol peptide, respectively	[67]
Yellow pea flour hydrolysates	In the first one, flour was dispersed in distilled water in a ratio of 1/1.75 (similar to tube assay), and the mixture was incubated at 30 °C for 24 h (FF1). In the second, the flour/distilled water ratio was 1/6, and the fermentation was conducted at 37 °C for 24 h (FF2)	Peptide mixture	IC50: FF1: 0.071 mg SP/mL, FF2: 0.033 mg SP/mL (ORAC)	[68]
PPH	0.5 h, flavourzyme, 50 °C, pH 6.0, 1% enzyme-protein ratio	Peptide mixture	PPH had higher ABTS and reducing power than PF and PPI; the production of TBARS and protein carbonyls were inhibited	[69]

PPH, pea protein hydrolysates; DPPH, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity; ABTS, 2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulphonic acid) ammonium salt radical scavenging activity; ORAC, oxygen radical absorbance capacity; HRSA, hydroxy radical scavenging activity; SRSA, superoxide radical scavenging activity; MW, molecular weight; FRAP, ferric reducing antioxidant power; PPIH, pea protein isolate hydrolysate; MCA, metal chelating activity; PF, pea flour; PPI, pea protein isolate; TBARS, 2-thiobarbituric acid reactive substances.

). Many pea-derived bioactive peptides share common structural features, including relatively short residue lengths, hydrophobic/acidic amino acid residues, and the presence of Glu, Asp, Gly, and Pro [47]. These pea-derived bioactive peptides can be absorbed by human body through intestinal peptide transporter PepT1, paracellular movement, and translocation across the plasma membrane [49]. Given their broad health benefits and high bioactivity, pea peptides are widely incorporated as primary or supplementary ingredients in functional foods, nutraceuticals, and cosmetics, such as pea-based yogurt, fermented pea milk, pea-based Mozzarella cheeses, and pea extract formulations [35,50,51]. Overall, peas, pea protein, and pea peptides are all high-nutritional-value products, and their bioactivity warrants further exploration for broad applications in the functional food industry.

Given the high activity and broad food application value of pea antioxidant peptides, we first conducted a literature search on the study of antioxidant peptides in peas and processed pea products, and compiled the sources, sequences, antioxidant activity results of pea peptides reported in these studies. Additionally, we discussed the activation of the Nrf2 (NF-E2-related factor 2)/Kelch-like ECH-associated protein 1 (Keap1) pathway by these pea peptides. This study will facilitate the rapid identification of antioxidant peptides from other food sources and support the development of functional pea-based foods.

2. Antioxidant Activity of Pea Peptides

Pea-derived bioactive peptides have garnered increasing attention due to their remarkable antioxidant properties, which play a crucial role in mitigating oxidative stress—a key contributor to chronic diseases and aging. These peptides, generally released through enzymatic hydrolysis, exhibit potent free radical scavenging, metal ion chelation, and lipid peroxidation inhibition capabilities (Table 1). Additionally, their antioxidant efficacy has also been extensively studied via cellular, and in vivo mouse models, demonstrating significant potential in ROS scavenging and upregulation of antioxidant enzyme expression. Most of these in vitro chemical antioxidant models were used in evaluating the antioxidant activity of pea peptides.

2.1. In Vitro Antioxidant Activity and Reliability of Pea Peptides

2.1.1. In Vitro Antioxidant Activity of Pea Peptides

There are many types of in vitro antioxidant models, which can be classified into the following categories based on their reaction mechanisms: 1. Hydrogen atom transfer (HAT)-based methods. These methods typically measure the ability to quench free radicals by donating hydrogen, such as total radical-trapping antioxidant parameter, ORAC, and inhibition of induced low-density lipoprotein oxidation [70]. 2. Single electron transfer (SET)-based methods. These methods detect the ability to transfer an electron to reduce any compound (such as metals, carbonyls, and radicals), resulting in a color change when the compound is reduced. Examples containing ferric ion reducing antioxidant power (FRAP) assay, trolox equivalent antioxidant capacity (TEAC) assay, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and 2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulphonic acid) ammonium (ABTS) salt radical scavenging assay [70]. 3. Metal chelation-based assays. In these assays, antioxidants chelate transition metals such as Fe(II) and Cu(II). These are referred to as the ferrous ion chelation activity test and the cuprous ion chelation activity test, which are two common metal chelation-based methods for evaluating antioxidant capacity [71]. 4. Lipid peroxidation and ROS/ reactive nitrogen species (RNS) scavenging activity assays, including thiobarbituric acid method (TBA), H₂O₂ scavenging method, ferric thiocyanate method (FTC), nitric oxide scavenging activity, peroxynitrite radical scavenging activity, superoxide radical scavenging activity (SRSA), and xanthine oxidase method [71]. Therefore, the application of these in vitro chemical antioxidant models in evaluating the antioxidant activity of pea peptides were introduced.

As indicated above, the bioactivity of released pea peptides generally depends on type of pea protein, enzymes/fermentation strains, and processing conditions, etc. Therefore, some researchers have investigated the effects of processing methods on the antioxidant activity of pea peptides. Ordinary cooking, pressure cooking, and microwave cooking lead to different digestibility of pea protein, resulting in varying antioxidant activities of pea bioactive peptides [64]. After microwave treatment, the TCA-soluble peptide content in peas reached its highest level in both undigested and oral digestion states, while pressure-cooked peas exhibited the highest TCA-soluble peptide content after gastric and intestinal digestion, indicating that these two methods are more effective in producing high-antioxidant pea peptide hydrolysates. DPPH and ABTS experimental results confirmed this, showing that pressure-cooked and microwave-treated pea samples generally exhibited slightly higher antioxidant activity than those subjected to ordinary cooking. The efficiency of different proteases in digesting pea protein also influences the antioxidant activity of the resulting bioactive peptides. Zhu et al. [61] used three proteases to treat pea protein, and the results showed that small molecular pea protein hydrolysate fractions (<1 kDa) treated with neutral protease exhibited the highest ORAC value, followed by alkaline protease-treated peptides (<1 kDa) and validase-treated peptides (<1 kDa). However, the DPPH assay indicated that alkaline protease-treated pea peptides (<1 kDa) displayed the highest antioxidant activity, followed by validase-treated peptides (1–3 kDa), suggesting that same pea peptides may exhibit different free radical scavenging activities in different antioxidant assays. ABTS results further demonstrated that neutral protease- and alkaline protease-treated pea peptides (<1 kDa) had higher ABTS scavenging activity compared to validase-treated peptides. In summary, low-molecular-weight pea peptides tend to exhibit higher antioxidant activity, and neutral protease and alkaline protease are more effective in producing highly antioxidative pea peptides. The finding that smaller molecular weight pea peptide mixtures exhibit higher antioxidant activity has also been validated in the study of Asen and Aluko [54]. They reported that pea protein hydrolysates digested by flavourzyme or pepsin with a molecular weight < 1 kDa demonstrated higher hydroxyl and superoxide radical scavenging activities compared to those of the 1–3 kDa fractions. However, this trend is not always entirely accurate. For instance, in the case of alkaline protease and trypsin-treated pea peptides, the 1–3 kDa fraction exhibited higher superoxide radical scavenging activity than the <1 kDa fraction.

Enzymatic treatment is a crucial processing method for pea protein and has been widely used by researchers to obtain antioxidant peptides from pea protein. Felix et al. [62] treated pea protein concentrate (PPC) with trypsin and found that as the enzymatic hydrolysis time increased, the DPPH and ABTS radical scavenging activities of the pea peptide mixture decreased slightly. In addition, pH also affects the antioxidant activity of pea protein peptides. The ABTS and DPPH radical scavenging activities as well as total phenolic content of PPC peaked at pH 6.5, pH 8.0, and pH 2.0 (protein hydrolysate gelling pH), respectively, providing a reference for other researchers studying the antioxidant activity of plant protein peptides [62]. Some scholars have optimized processing methods to obtain pea protein hydrolysates with the highest antioxidant activity. Zhou et al. [60] found that under processing conditions of 12.0% enzyme concentration, 60 °C, pH 6.5, and substrate concentration of 7.1% (w/v), the resulting pea protein hydrolysate exhibited the highest DPPH scavenging activity. Similarly, different fermentation conditions can also lead to variations in the antioxidant activity of pea protein hydrolysates. Babini et al. [67] observed that pea protein fermented with L. plantarum 98A resulted in hydrolysates with the highest DPPH radical scavenging activity, followed by L. paracasei 1122-treated hydrolysates and L. brevis 3BHI-treated hydrolysates, while pea protein fermented with L. rhamnosus C249 exhibited the lowest DPPH radical scavenging activity.

The variety of peas can also influence the antioxidant activity of pea peptides. Research by Cipollone and Tironi [55] found that after digestion, Navarro pea flour hydrolysates exhibited a higher ORAC value compared to Yams pea flour hydrolysates, although their hydroxyl radical scavenging activities were similar. This may be attributed to differences in the molecular composition of the digested protein products between the two pea varieties. Additionally, some studies have explored the effects of processing methods, such as high pressure, heat treatment, and electron beam irradiation, on the antioxidant activity of pea protein peptides. Girgih et al. [66] revealed that as the pressure of high-pressure pretreatment increased, alkaline protease-hydrolyzed pea peptides exhibited higher ORAC values, suggesting that pressure may alter the hydrolysis pattern of pea protein, ultimately enhancing its ORAC activity. However, in DPPH experiments, pea protein hydrolysates pretreated at 400 MPa showed approximately 18% higher DPPH radical scavenging activity compared to those pretreated at 200 MPa and 600 MPa, while heat pretreatment led to a slight decrease in DPPH radical scavenging activity. Superoxide radical scavenging activity (SRSA) and hydroxyl radical scavenging activity (HRSA) experiments indicated that high pressure slightly reduced the antioxidant activity of pea protein hydrolysates. In contrast, FRAP (ferric reducing antioxidant power) experiments found that high-pressure pretreatment did not cause significant changes in FRAP values, whereas heating promoted the release of bioactive peptides, thereby enhancing their interaction with ferric ions and further leading to a notable increase in FRAP. This study demonstrated that different in vitro antioxidant assays exhibited varying sensitivity to high-pressure pretreatment, but the underlying mechanisms and patterns require further investigation. Wang et al. [59] observed that as the intensity of pre-irradiation increased, the DPPH and ABTS radical scavenging activities of pea protein hydrolysates demonstrated intensity-dependent activity, achieving the highest radical scavenging values at a pre-irradiation intensity of 50 kGy. Similarly, the reasons behind these changes induced by pre-irradiation treatment warrant deeper exploration.

In addition to the aforementioned methods, chemiluminescence assays and direct current (DC) polarographic assays have also been employed to evaluate the antioxidant activity of bioactive peptides. The chemiluminescence method offers advantages such as high sensitivity, rapid response, and simple operation [72]. Since ROS are known to generate excited states during reactions, manifesting as chemiluminescence, the scavenging of ROS by antioxidants leads to chemiluminescence quenching. Therefore, ROS levels are negatively associated with antioxidant activity [73]. Generally, studies on the antioxidant properties of plant-derived peptides may utilize luminol as a chemiluminescent probe or rely on peroxyl-radical-mediated excited-state generation through the oxidation of appropriate hydrocarbons [73]. The latter approach is commonly combined with other antioxidant assays mentioned earlier. The DC polarographic assay has also been used to assess the antioxidant activity of pea peptides. This method is based on the reduction in anodic current, measured using a dropping mercury electrode (DME) in an alkaline hydrogen peroxide solution, upon the addition of antioxidants [74]. However, the application of these two methods in evaluating pea-derived antioxidant peptides remains very limited. Further research is needed to validate their effectiveness in assessing the antioxidant potential of pea peptides.

Considering the high antioxidant activity of PPH, several antioxidant peptides have been identified, including YLVN, EEHLCFR, TFY, YSSPIHIW, ADLYNPR, HYDSEAILF, and GGSSTHPYP (Table 1). Overall, these pea protein peptides are rich in amino acids such as Glu, Asp, Gly, Pro, and Leu, while containing fewer residues such as Met and Cys. Zhao and Liu [52] identified three antioxidant peptides (YLVN, EEHLCFR, TFY) from PPH, with ABTS radical scavenging activity ranked as YLVN > TFY > EEHLCFR, and ORAC activity ranked as TFY > EEHLCFR > YLVN. Comparatively, these peptides exhibited weaker hydroxyl radical and superoxide anion scavenging activities. Ding et al. [53] processed pea protein under optimal hydrolysis conditions (55 °C, 3.15% substrate concentration, and 9.2% enzyme-to-substrate ratio) and found that lower molecular weight components (MW < 1 kDa) exhibited the highest antioxidant activity. Further studies identified 14 peptides from PPH, with YSSPIHIW, ADLYNPR, and HYDSEAILF demonstrating the strongest antioxidant potential. A limitation of these studies was the lack of synthetic validation of these peptides to confirm their bioactivity. Dual-enzyme hydrolysis significantly enhanced the degree of hydrolysis of pea protein, resulting in a richer variety of active peptides in the hydrolysates. Flavourzyme combined with protamex treated pea protein resulted in higher ABTS scavenging activity and reducing activity compared to alcalase combined with protamex-treated pea protein, which may be attributed to the greater number of active peptides present in the flavourzyme + protamex hydrolysates (85 vs. 48) [48]. Further investigation revealed that flavourzyme + protamex PPH contained a higher abundance of pentapeptides, including GDIIA, GDTIK, GGLIE, LPAGT, LSSVL, NVISQ, PGDVF, and SEPFN. Both hydrolysates contained peptides rich in Asp, Glu, Pro, Leu, Val, and Gly, consistent with our observations that peptides enriched in these residues exhibit excellent antioxidant activity. Babini, Tagliazucchi, Martini, Più and Gianotti [67] identified several bioactive peptides from pea flour hydrolysates, such as TVTSLDLPVLRW, VTSLDLPVLRW, TSLDLPVLRW, and AEYVRLY. These bioactive peptides showed ABTS radical scavenging capacities ranging from 492.3 to 624.1 mmol GSH/mol peptide, DPPH radical scavenging capacities from 5078.2 to 6501.1 mmol GSH/mol peptide, superoxide anion scavenging capacities from 389.3 to 1394.4 mmol GSH/mol peptide, and hydroxyl radical scavenging capacities from 1438.3 to 1584.7 mmol GSH/mol peptide, indicating that the antioxidant activity of PPH primarily derives from these antioxidant peptides.

Certain modifications and processing methods can further enhance the antioxidant activity of pea peptides, such as selenium chelation. A novel organic selenium supplement (Se-POP) was synthesized using pea peptides and sodium selenite [58]. Se-POP exhibited significantly greater DPPH and iron-reducing capacities compared to either component alone, suggesting that the structure of the pea peptides may have changed or a synergistic effect occurred between the pea peptides and sodium selenite. LC-MS/MS analysis revealed the sequences of the active peptides, including FLIGAP, TGRGAP, VYLAGA, PPKIYP, HQMPKP, and TSSLP. Notably, PPKIYP exhibited the highest ABTS scavenging capacity, although the study did not elucidate the underlying mechanism for this enhanced activity. It is important to note that pea peptides may exhibit antagonistic effects when co-administered with polyphenols, leading to a reduction in their antioxidant activity [63]. For instance, a peptide-quercetin mixture showed lower DPPH and ABTS radical scavenging capacities than quercetin alone, indicating that it is not advisable to consume peas alongside quercetin-rich vegetables and fruits.

Due to the high antioxidant activity of pea peptides, researchers have explored applications of pea peptides in food preservation. Studies demonstrated that incorporating highly antioxidative PPH into cooked cured beef effectively mitigated color deterioration, inhibited the decline of red pigment content, and reduced accumulation of TBARS and protein carbonyl compounds during refrigerated storage, suggesting an extension of the shelf life of the beef [69]. However, a limitation of this study is that it did not identify the types of active peptides in PPH, nor did it explore the effects of PPH on other indicators of cooked cured beef, such as protein secondary structure or textural properties. Future research could consider incorporating PPH into edible coatings to enhance its preservative effects [16].

2.1.2. Reliability of In Vitro Methods for Evaluating the Antioxidant Activity of Peptides

Although in vitro methods are widely used for screening the antioxidant activity of pea protein peptides, their reliability remains challenging. The primary drawback of in vitro chemical antioxidant assays is the significant variability in results across different methods. Therefore, researchers often employ multiple in vitro chemical antioxidant approaches, such as using ABTS, DPPH, FRAP, HRSA, SRSA, and ORAC to evaluate pea protein peptides, thereby enhancing the reliability of the assessments (Table 1). Moreover, oxidation and reduction reactions are highly sensitive to their chemical environment, particularly to factors such as oxygen levels, transition metal ion concentrations, and the presence of redox-active compounds [75]. These variables can lead to discrepancies in experimental results. Consequently, researchers typically use in vitro chemical antioxidant methods as a reference for in vivo studies or employ multiple in vitro assays to comprehensively evaluate the antioxidant properties of pea peptides. Unpurified pea protein hydrolysates often contain residual polyphenols, which may lead to an overestimation of the measured antioxidant activity. For instance, small-molecule polyphenols such as quercetin, rutin, and gallic acid (naturally present in peas) exhibit significant antioxidant activity, leading to an overestimation of the hydrolysate’s overall antioxidant capacity [76]. Additionally, potential antagonistic interactions between bioactive peptides and polyphenols may weaken the antioxidant effects of peptides. As reported by Wah, Flores, Mosibo, Aluko, Fatoki and Udenigwe [63], ROS fluorescence intensity experiments demonstrated that pretreatment with peptide-quercetin or peptide-rutin mixtures produced higher fluorescence signals than when using the individual polyphenols or peptides alone, which suggests low ROS scavenging capacity caused by antagonistic effect between the peptides and polyphenols. Finally, unpurified pea protein peptides may also face compatibility issues with the assay medium. For example, when unpurified hydrolysates are mixed with methanolic DPPH reagent in an aqueous medium, DPPH precipitation occurs, leading to an overestimation of radical scavenging activity. In summary, while in vitro antioxidant assays are widely adopted due to their convenience, rapid reaction, and ability to simultaneously detect multiple radical-scavenging activities, they suffer from limitations such as poor reliability, high variability in results, and potential discrepancies with in vivo antioxidant outcomes.

2.2. Cellular Antioxidant Activity of Pea Peptides

Despite the cost-effectiveness, speed, simplicity, and reproducibility of in vitro chemical antioxidant methods, they have several drawbacks and limitations [77]. For instance, the results obtained from these methods often differ significantly from the actual effects of antioxidants in vivo, and there is considerable variability in data across different in vitro chemical antioxidant assays. Cellular models can provide more comprehensive insights into the physiological effects of natural antioxidant peptides. Given that animal models and human clinical trials are expensive, time-consuming, and complex, cellular antioxidant assays serve as effective tools for preliminary evaluation and screening of potential natural antioxidant peptides prior to in vivo studies [78]. The protective effects of natural antioxidant peptides against oxidative stress-induced cellular damage reflect their underlying protective mechanisms. Various mammalian cell lines are commonly employed to establish oxidative stress models, including human embryonic kidney 293 cells (HEK293), human hepatocarcinoma cells (HepG2), rat adrenal pheochromocytoma cells (PC12), cervical adenocarcinoma cells (HeLa), red blood cells, and human neuroblastoma cells (SH-SY5Y) [78,79]. Frequently used oxidative stress inducers include hydrogen peroxide (H₂O₂), lipophilic tert-butyl hydroperoxide (t-BHP), and 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) [79,80,81]. Generally, the oxidative stress inhibitory capacity of active peptides can be evaluated by measuring levels of ROS, cell viability, expression of antioxidant enzymes, and the level of oxidative byproducts such as malondialdehyde (MDA) [78].

Several studies have investigated the protective effects of pea-derived peptides in cellular oxidative stress models. Research has demonstrated that pea protein isolate hydrolysates can effectively mitigate hydrogen peroxide-induced damage in mouse skeletal muscle cells (C₂C₁₂), while other studies showed that pea-derived peptides significantly reduced ROS and MDA elevation in Caco-2 cells induced by α-gliadin peptide, decreased cell viability, and enhanced the production of antioxidant enzymes including SOD, CAT, GSH-Px, and GR [82,83]. However, the specific bioactive peptide components and their underlying mechanisms remain unclear. Further research has identified the amino acid sequences of key antioxidant peptides in pea protein hydrolysates. For instance, studies revealed that YLVN, EEHLCFR, and TFY all alleviated H₂O₂-induced LO2 cell death, with efficacy following the order of EEHLCFR > YLVN > TFY [52]. These peptides also upregulated antioxidant enzyme production (GSH-Px, CAT, and SOD↑) and reduced ROS levels. Similarly, Similarly, peptides identified by Li et al. [84], such as EFEGMTFLL, KGOTPLFPR, KYSSPIHIW, KKADLYNPR, EHYDSEAILF, and KYGPTPVRDGFK, provided substantial protection against Pb-induced oxidative stress in PC12 cells, thus reducing ROS and MDA accumulation while enhancing the synthesis of SOD, CAT, GR, and GSH-Px. These studies indicate that pea active peptides possess protective effects against oxidative damage in liver, intestinal epithelial, and neuronal cells. Interestingly, some short peptides from peas, such as VLP, LLP, VA, LL, and LRW (

Table 2. Production methods, sequences, and in vivo antioxidant activity of peptides from pea protein.

Sources	Processing	Sequences	Model	Antioxidant Capacity	Mechanism	References
Pea peptides	Chemical synthesis	EFEGMTFLL, KGOTPLFPR, KYSSPIHIW, KKADLYNPR, EHYDSEAILF, KYGPTPVRDGFK	Pb treated PC12 cells	Pea peptides increased cell viability and inhibited ROS generation; pea peptides increased SOD, CAT, GR and GSH-Px accumulation and inhibited MDA levels	Activating Nrf2 pathway	[84]
Pea peptides	Chemical synthesis	KEDDEEEEQGEEE, GQTPLFPR, IPVNRPGQLQ, VTPGATDDQIMDGVRK, YGPTPVRDGFK, HYDSEAILF, ADLYNPR, IR, YSSPIHIW, KF, EF	Caco-2 cells	Cell viability, SOD, CAT, GST, GSH-Px ↑; ROS, MDA ↓	Activating Nrf2 pathway	[83]
PPH	Bromelain (1000 CDU/mL), Neutrase (0.0024 AU-N/mL) and Flavourzyme (3.3 LAPU/mL); 45 °C for 24 h	Peptide mixture	H2O2-injured C2C12 cells	Cell viability, crystal violet intensity ↑	/	[82]
PPH	1% (w of enzyme/w of pea protein) Flavourzyme® at 50 °C for 6 h	NKFGKFF, GGPFKSPF and RPVLGGSSTFPYP	Retinoic acid-injured human neuroblastoma SH-SY5Y cells	Cell viability ↑; ROS ↓	Nrf2/HO-1 pathway ↑	[86]
Pea Pentapeptide	Chemical synthesis	VNRFR	C. elegans species exposed to fresh NGM medium plates containing 400 mM juglone	VNRFR improved survival rate of C. elegans species and inhibited its ROS production	/	[63]
Pea peptides	Chemical synthesis	VLP, LLP, VA, LL	HepG2 containing insulin	Cell viability increased at low peptide concentrations but decreased at high VA and LL concentrations; ROS ↓	/	[87]
PPH	7% pea protein, 3.8% (enzyme/substrate ratio) alcalase protease, 50 °C for 3 h	YLVN, EEHLCFR, TFY	0.5, 1, 2, 4, 6, and 8 mmol/L of H2O2 injured LO2 cells;	Cell viability, GSH-Px, CAT, SOD ↑; ROS ↓	Binding with keap1; binding energy: YLVN = −8.2 kcal/mol; EEHLCFR = −7.2 kcal/mol; TFY = −8.9 kcal/mol	[52]
Pea peptides	The pea protein was loaded into the steam explosion equipment and treated at 1.0 MPa for 40 s	Peptide mixture	HepG2 cells treated with FFA; C57BL/6 J mice fed with high-fat diet	Cell viability ↑	Nrf2/HO-1 pathway ↑	[88]
Pea peptides	Chemical synthesis	LRW	A7r5 cells treated with Ang II	Ang II-stimulated oxidative stress ↓	NF-κB pathway ↓	[85]

↑ indicates upregulation; ↓ indicates downregulation; ROS, reactive oxygen species; GSH-Px, glutathione peroxidase; CAT, catalase; SOD, superoxide dismutase; MDA, lipid peroxidation; GR, glutathione reductase; C2C12, mouse skeletal muscle cell line; HepG2, Human liver hepatocellular cell; FFA, free fatty acids.

), exhibited significant antioxidant activity, comparable to that of longer-chain antioxidant peptides. Specifically, LRW was found to mitigate superoxide generation stimulated by Ang II in vascular smooth muscle cells, demonstrating excellent antioxidant activity; however, this study did not evaluate other antioxidant parameters [85]. Currently, research exploring the relationship between the primary and secondary structures of pea peptides and their cellular antioxidant activity remains limited.

2.3. In Vivo Antioxidant Activity of Pea Peptides

Although the activity and potential action mechanisms of pea antioxidant peptides can be assessed through in vitro and cellular antioxidant experiments, animal studies are essential for further evaluating the antioxidant capacity and bioavailability of these peptides [78]. However, due to the high costs and lengthy testing periods associated with animal research and human trials, studies investigating the in vivo effects of pea antioxidant peptides using various animal models are scarce. Moreover, in addition to cellular effects, animal experiments can be influenced by a range of biological effects induced by antioxidant actions, such as reduced inflammation, improved blood glucose balance, decreased acetylcholine levels, and lowered cancer risks [78,89,90,91]. Similarly to the indicators used in cellular antioxidant models, common assessment parameters in in vivo antioxidant models include ROS, SOD, CAT, GSH-Px, and MDA [92,93]. Aging models and fatigue models based on rats or mice are the most commonly employed in vivo antioxidant models [89,94].

Pea antioxidant peptides demonstrate significant regulatory effects on oxidative stress in murine models, which effectively suppresses systemic ROS levels while upregulates antioxidant enzyme synthesis. Specifically, Feng et al. [95] found that pea peptides (molecular weight < 2000 Da) prolonged the swimming time of weight-loaded mice, inhibited the accumulation of exercise metabolic waste, increased the synthesis of SOD and GSH-Px, reduced MDA accumulation, and improved parameters related to insulin and immune factors (IL-2, IL-4, IL-6, IFN-γ, TNF-α), ultimately resulting in the suppression of exercise-induced fatigue. High doses of pea peptides exhibited the best performance among all treatment groups, outperforming isolated pea protein, low doses of pea peptides and medium doses of pea peptides. Steam-explosion modified pea peptides exhibited beneficial effects in high-fat diet-fed C57BL/6J mice, as evidenced by improved serum lipid profiles (triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol) and upregulated expression of Nrf2 and HO-1 proteins [88]. Nevertheless, as this study employed a non-standard antioxidant evaluation model, it provided limited assessment of oxidative stress-related biomarkers. Future research should employ aging mouse models to systematically explore the effects of pea protein peptides, particularly those with different molecular weights, on the modulation of oxidative stress in mice.

3. Antioxidant Mechanism of Pea Peptides

Nrf2, a Cap’n’collar (CNC) transcription factor family member, consists of 605 amino acids and features seven conserved functional domains (Neh1-Neh7) [96]. Its stability and ubiquitination are regulated by Keap1, which is a cysteine-rich protein containing 624 amino acids and 27 Cys residues [97,98]. Specifically, the N-terminal domain of Nrf2 mediates Keap1-dependent degradation, while the Neh5 domain is responsible for its cytoplasmic localization. Under normal circumstances, Nrf2 is sequestered in the cytoplasm by Keap1, which promotes its ubiquitination and subsequent proteasomal degradation [99]. However, in response to oxidative stress or Nrf2 activators, Nrf2 separates from Keap1 and moves into the nucleus. There, it forms a heterodimer with small Maf proteins and activates a set of genes containing antioxidant response elements (AREs), leading to the production of antioxidant enzymes such as SOD and GSH, as well as the transcription of heme oxygenase-1 (HO-1) [100]. HO-1, an inducible isoform and rate-limiting enzyme, facilitates the breakdown of heme into carbon monoxide and free iron, and converts biliverdin into bilirubin, thus providing free radical scavenging and cytoprotection. If this signaling pathway is disrupted, the levels of antioxidant enzymes may decrease, hindering the clearance of ROS [101]. Therefore, the ability of pea peptides to regulate Nrf2 determines its antioxidant properties.

Both pea peptide mixtures and pea-derived antioxidant peptides have demonstrated regulatory effects on the Nrf2/Keap1 pathway (Figure 1). For instance, studies by Gao, Cui, Yan, Li, Sun, Wang and Wang [83] have shown that GQTPLFPR, YGPTPVRDGFK, and HYDSEAILF can mitigate α-gliadin peptide-induced oxidative stress by upregulating Keap1 and downregulating Nrf2. Additionally, these three peptides modulated the expression of glutamate-cysteine ligase catalytic subunit (GCLC) and glutamate-cysteine ligase modifier (GCLM), both of which are Nrf2-targeted antioxidant genes. GCLC is the catalytic subunit of the rate-limiting enzyme in GSH synthesis, and its transcriptional expression limits the capacity for GSH production, thereby reducing the body’s ability to scavenge free radicals [102]. In contrast, GCLM contributes to GSH synthesis, and the activation of GCLM by pea peptides is beneficial for the timely clearance of free radicals and bolster the body’s antioxidant capacity [103]. Among these peptides, YGPTPVRDGFK exhibits the strongest regulatory effect on the Nrf2/Keap1 pathway, though the underlying mechanism remains unclear. Similarly, SE-modified pea peptides also demonstrated regulatory effects on the Nrf2 pathway in a high-fat diet model, indicated by the upregulation of Nrf2 and HO-1 in a clear dose-dependent manner [88]. Thus, SE-modified pea peptides contribute to alleviating oxidative stress induced by high-fat diets, thereby improving obesity-related non-alcoholic fatty liver disease. Similarly, the peptides KYSSPIHIW, KKADLYNPR, and KYGPTPVRDGFK can mitigate oxidative stress-induced damage to neuronal cells by modulating the Nrf2/Keap1 pathway, with KKADLYNPR showing the best efficacy [84]. In addition to using Western blot analysis to assess protein expression in the Nrf2/Keap1 pathway, some studies have employed molecular docking to predict the regulatory capabilities of pea peptides. Studies reveal that YLVN, EEHLCFR, and TFY bind to Keap1 with binding energies of −8.2, −7.2, and −8.9 kcal/mol, respectively, indicating a relatively strong interaction with Keap1 [52]. Furthermore, the study revealed that these peptides can enter the Kelch domain pocket, primarily binding to amino acid residues on Keap1 through hydrogen bonds and hydrophobic interactions, thereby sterically hindering Nrf2-Keap1 binding. The activation of the Keap1-Nrf2-ARE signaling pathway subsequently leads to increased expression of downstream antioxidant proteins such as SOD, CAT, and GSH-Px. Current research on the regulation of pea peptides on the Keap1-Nrf2-ARE pathway still presents several unresolved questions. For instance, which amino acids in pea peptides have the most significant activating effects on the Keap1-Nrf2-ARE pathway? Does the peptide chain length affect the activation of the Keap1-Nrf2-ARE pathway? Future research should focus on addressing these issues.

4. Conclusions

Pea antioxidant peptides are unique antioxidants because they can mitigate oxidative stress-induced damage through various ways, such as scavenging free radicals, chelating pro-oxidative transition metals, reducing hydrogen peroxide, inactivating reactive oxygen species, enhancing the expression of antioxidant enzymes, and reducing the accumulation of lipid peroxides. Pea peptides with high antioxidant activity typically have a molecular weight below 1 kDa and are often rich in amino acids like Glu, Asp, Gly, Pro, and Leu, while containing fewer amino acids such as Met and Cys. These peptides exert their antioxidant effects by regulating the expression of proteins associated with the Nrf2/Keap1 pathway, facilitating the timely clearance of ROS and promoting the expression of antioxidant enzymes (SOD, CAT, GSH-Px). Understanding the relationship between the composition of pea peptides and their antioxidant activity may lead to the successful development of a new class of highly effective, multifunctional, and widely recognized safe antioxidants, as well as contribute to the production and commercialization of functional foods containing pea peptides.