Peptides derived from dietary proteins, have been reported to display significant antioxidant activity, which may exert notably beneficial effects in promoting human health and in food processing. Recently, much research has focused on the generation, separation, purification and identification of novel peptides from various protein sources. Some researchers have tried to discover the structural characteristics of antioxidant peptides in order to lessen or avoid the tedious and aimless work involving the ongoing generated peptide preparation schemes. This review aims to summarize the current knowledge on the relationship between the structural features of peptides and their antioxidant activities. The relationship between the structure of the precursor proteins and their abilities to release antioxidant fragments will also be summarized and inferred. The preparation methods and antioxidant capacity evaluation assays of peptides and a prediction scheme of quantitative structure–activity relationship (QSAR) will also be pointed out and discussed.

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The Structure-Activity Relationship of the Antioxidant Peptides from Natural Proteins.

High-throughput assay comparison and standardization for metal chelating capacity screening: A proposal and application

In this work, the nanoemulsion of essential oil from Citrus medica L. var. sarcodactylis was prepared using a spontaneous emulsification method. Meanwhile, the effect of nanoemulsification on the antioxidant, antibacterial and antibiofilm activity of essential oil was evaluated. GC–MS analysis indicated nineteen compounds in the essential oil, and the essential oil was dominated by d -Limonene (50.04%). The minimum and stable droplets (73 nm) of essential oil nanoemulsion were formulated when the concentration of essential oil in oil phase was 50% (w/w). The hydroxyl radicals, DPPH radicals scavenging ability, iron reducing power, antibacterial and antibiofilm activity of nanoemulsified essential oil were significantly higher than those of pure essential oil at same concentration. Moreover, the nanoemulsified essential oil exhibited higher inhibitive effect on the bacteria in tofu than pure essential oil. Therefore, nanoemulsification significantly enhanced the antioxidant, antibacterial and antibiofilm activity/efficiency of essential oils, which will promote the abroad utilization of essential oils.

The antioxidant, antibacterial, antibiofilm activity of essential oil from Citrus medica L. var. sarcodactylis and its nanoemulsion

Lead (Pb)-induced reproductive toxicity is a well-characterized adverse effect associated with this heavy metal. It has been found that Pb exposure is associated with altered spermatogenesis, increased testicular degeneration, and pathological sperm alterations. On the other hand, it has been reported that Pb-induced reproductive toxicity is associated with increased reactive oxygen species (ROS) formation and diminished antioxidant capacity in the reproductive system. Hence, administration of antioxidants as protective agents might be of value against Pb-induced reproductive toxicity. This study was designed to investigate whether carnosine (CAR) and histidine (HIS) supplementation would mitigate the Pb-induced reproductive toxicity in male rats. Animals received Pb (20 mg/kg/day, oral, 14 consecutive days) alone or in combination with CAR (250 and 500 mg/kg/day, oral, 14 consecutive days) or HIS (250 and 500 mg/kg/day, oral, 14 consecutive days). Pb toxicity was evident in the reproductive system by a significant increase in tissue markers of oxidative stress along with severe histopathological changes, seminal tubule damage, tubular desquamation, low spermatogenesis index, poor sperm parameters, and impaired sperm mitochondrial function. It was found that CAR and HIS supplementation blunted the Pb-induced oxidative stress and mitochondrial dysfunction in the rat reproductive system. Thereby, antioxidative and mitochondria-protective properties serve as primary mechanisms for CAR and HIS against Pb-induced reproductive toxicity.

Carnosine and Histidine Supplementation Blunt Lead-Induced Reproductive Toxicity through Antioxidative and Mitochondria-Dependent Mechanisms.

Protein hydrolyzates of Stripped weakfish (Cynoscion guatucupa) industrial byproducts were prepared, and their antimicrobial and antioxidant activities, as well as bioaccessibility were evaluated. Byproducts were hydrolyzed by Alcalase (HA) and Protamex (HP) to achieve degrees of hydrolysis (DH) of 5, 10 and 15%, respectively. Resulting hydrolyzates were enzymatically digested with pepsin and pancreatin to determine the in vitro bioaccessibility. The highest antimicrobial activity was verified for HA with DH 5% (HA5) against Escherichia coli O157:H7 (5.50 ± 0.17 mm). Whereas HP with DH 5% (HP5) showed the highest antioxidant activity for the tested assays. After simulated in vitro gastrointestinal digestion, all samples were bioaccessible and showed an increase for the ABTS and hydroxyl radical scavenging with the highest activities for HA5 (87.7 ± 0.21%) and HP5 (87.5 ± 0.34%) and HP5 (96.7 ± 0.86%) and HP15 (97.5 ± 0.15%), respectively. We then submitted HA5 and HP5 to peptide sequences analysis, the bioactivities were attributed to the presence of amino acid such Phe, Leu, and Trp in the peptide sequences and peptide sequences like WDDMEK (HP5). The developed peptides present a potential for use as natural antimicrobial and antioxidant preservatives in food.

Bioactivity and bioaccessibility of protein hydrolyzates from industrial byproducts of Stripped weakfish (Cynoscion guatucupa)

Determination of reducing power and metal chelating ability of antioxidant peptides: revisited methods.

The purpose of this study was to improve two common assays used for antioxidant capacity measurements, i.e. the reducing power and chelating ability measurements, for appropriate comparisons between the molecules tested and chosen references, as the usual methods are often performed in a qualitative way rather than a quantitative way. After revision, it was then possible to determine an AERC index (Ascorbate Equivalent Reducing Capacity) and a CECC (Carnosine Equivalent Chelating Capacity) or EECC (EDTA Equivalent Chelating Capacity) index according to the chosen standard, by analogy to the TEAC indice (Trolox Equivalent Antioxidant Capacity) already used in many reported works to determine the free radical scavenging activity. Thus, the determination of these relative indices enables the comparison of antioxidative capacities obtained in various studies. The adaptation of these two assays to micro-scales and the calculation of AERC, EECC and CECC were performed on model peptides.

Violette Kessler

Papers

Determination of reducing power and metal chelating ability of antioxidant peptides: revisited methods.

Determination of reducing power and metal chelating ability of