Purification and identification of three novel antioxidant peptides from protein hydrolysate of bluefin leatherjacket (Navodon septentrionalis) skin

Skin protein from a bluefin leatherjacket (Navodon septentrionalis) processing by-product was hydrolyzed by trypsin, flavourzyme, neutrase, papain, alcalase, and pepsin, and protein hydrolysate (BSH) prepared using alcalase showed the highest DPPH, HO, and O₂⁻ · scavenging activities among all hydrolysates. Using ultrafiltration and consecutive chromatography, three novel peptides with strong antioxidant properties were purified from BSH, and their sequences were determined as Gly-Ser-Gly-Gly-Leu (GSGGL, BSP-A), Gly-Pro-Gly-Gly-Phe-Ile (GPGGFI, BSP-B), and Phe-Ile-Gly-Pro (FIGP, BSP-C) with molecular weights of 389.41, 546.63, and 432.52 Da, respectively. BSP-C exhibited the highest scavenging activities on DPPH (EC₅₀ 0.118 mg/ml), HO (EC₅₀ 0.073 mg/ml), and O₂⁻ · (EC₅₀ 0.311 mg/ml) among the three peptides. In addition, BSP-C could effectively inhibit autooxidation in a linoleic acid model system. The antioxidant activities of BSP-A, BSP-B, and BSP-C might be due to the small molecular sizes and the hydrophobic and/or aromatic amino acid residues in their amino acid sequences. The present results suggested that peptides purified from the skin protein hydrolysate of bluefin leatherjacket were excellent antioxidants and could be effectively used as food ingredients and additives, and pharmaceuticals.     

Purification and identification of antioxidant peptides from corn gluten meal

Corn gluten meal was hydrolyzed by alkaline protease and Flavourzyme to obtain the antioxidant peptides. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging capacity (1,1-diphenyl-2-picrylhydrazyl/2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt/hydroxyl radical/superoxide radical anion), metal ion (Fe²⁺/Cu²⁺) chelating activity and lipid peroxidation inhibitory capacity. The hydrolysates were separated by ultrafiltration, and those with molecular weight <10 kDa exhibited highest antioxidant activity in all relevant assays. The hydrolysates were subsequently purified by gel filtration chromatography, and fraction F3 showed the highest antioxidant activity. Three peptides were identified from fraction F3 using LC–ESI–Q–TOF MS/MS as Leu-Pro-Phe (375.46 Da), Leu-Leu-Pro-Phe (488.64 Da) and Phe-Leu-Pro-Phe (522.64 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. Thus, corn gluten meal may be used as a potential source of antioxidant peptides for food and nutraceutical applications.     

A novel antioxidant and antimicrobial peptide from hen egg white lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolyzed with papain, trypsin and a combination of the two to isolate antioxidant peptides. The prepared hydrolysates were evaluated for antioxidant activity using DPPH and ABTS radical scavenging, metal ion chelation and lipid peroxidation inhibition. The obtained hydrolysate by a combination of the two enzymes exhibited the highest antioxidant activity compared to other hydrolysates and elected for isolation of antioxidant peptides by reverse-phase high-performance liquid chromatography (RP-HPLC). A most potent fraction namely F2 fraction, identified to be NTDGSTDYGILQINSR (MW: 1753.98 ± 0.5 Da) using tandem mass spectrometry. The antimicrobial activity of the F2 peptide was tested using radial diffusion assay (RDA). Our results showed that this peptide has inhibitory effects on both Gram-negative and Gram-positive bacteria. Minimum inhibition concentration (MIC) values of the F2 peptide against Escherichia coli and Leuconostoc mesenteroides bacteria were 355.64 (±2.2) and 442.25 (±2.8) μg/ml, respectively.     

Antioxidant properties of hot water extracts from Ganoderma tsugae Murrill

Ganoderma tsugae Murrill (Ganodermataceae) were available in the form of mature and baby Ling chih, mycelia and fermentation filtrate. From these four forms, hot water extracts were prepared and their antioxidant properties were studied. Hot water extracts from mature and baby Ling chih showed high antioxidant activities (78.5% and 78.2%) at 20 mg/ml, and had EC₅₀ values of 7.25 and 5.89 mg extract/ml, respectively. EC₅₀ values in reducing power were 1.12, 1.37, 2.48 and 1.41 mg extract/ml, whereas those in scavenging abilities of 1,1-diphenyl-2-picrylhydrazyl radicals were 0.30, 0.40, 0.72 and 5.00 mg extract/ml for Ling chih, baby Ling chih, mycelia and filtrate, respectively. At 20 mg/ml, scavenging abilities on hydroxyl radicals were in the descending order of Ling chih>baby Ling chih>mycelia>filtrate. Total phenols were the major naturally occurring antioxidant components found in hot water extracts and in the range of 40.86–42.34 mg/g. From EC₅₀ values obtained, fruit bodies of G. tsugae (Ling chih and baby Ling chih) were good in antioxidant properties, except for the chelating ability on ferrous ions.     

Purification and identification of antioxidative peptides from loach (Misgurnus anguillicaudatus) protein hydrolysate by consecutive chromatography and electrospray ionization-mass spectrometry

Loach protein was hydrolyzed by papain to obtain antioxidative peptides. The results showed that the loach protein hydrolysate (LPH) could scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) (IC₅₀ = 17.0 ± 0.54 mg/mL) and hydroxyl radicals (IC₅₀ = 2.64 ± 0.29 mg/mL). It could chelate cupric ion and inhibit the lipid peroxidation in a linoleic acid emulsion system. The hydrolysate was isolated and purified by ultrafiltration and consecutive chromatographic methods including ion-exchange chromatography, gel filtration chromatography and a two-step reverse high-performance liquid chromatography (RP-HPLC). The purified antioxidant peptide was identified as Pro-Ser-Tyr-Val (464.2 Da) using RP-HPLC connected on-line to an electrospray ionization (ESI) mass spectrometer. The purified peptide showed a 9.14-fold higher scavenging activity for hydroxyl radical compared with the crude LPH. Therefore, it is possible to produce natural antioxidative peptides from loach protein by enzymatic hydrolysis and purification.     

Intracellular ROS scavenging and antioxidant enzyme regulating capacities of corn gluten meal-derived antioxidant peptides in HepG2 cells

The objective of this study was to investigate the intracellular reactive oxygen species (ROS) scavenging activities and antioxidant enzyme regulating capacities of corn gluten peptide fractions (CPFs) in HepG2 cells. A cellular antioxidant activity (CAA) assay was used to assess their antioxidant activities and revealed that both CPF1 (molecular weight < 1 kDa) and CPF2 (molecular weight between 1 and 3 kDa) exhibited high cellular antioxidant activities with EC₅₀ values of 2.85 ± 0.19 mg/mL and 5.05 ± 0.32 mg/mL, respectively. Both CPFs also exhibited cytoprotective effects and intracellular ROS scavenging activities in HepG2 cells subjected to oxidative stress by oxidation with H₂O₂. In addition, at concentrations of 2.50 mg/mL, the CPFs increased the activity levels of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), as well as the total glutathione (GSH) levels in oxidized HepG2 cells (from 86.54% to 114.14% (CPF1) or 109.72% (CPF2) for SOD activity; from 71.91% to 107.64% (CPF1) or 106.50% (CPF2) for CAT activity; from 70.52% to 103.01% (CPF1) or 104.10% (CPF2) for GR activity; and from 81.39% to 114.00% (CPF1) or 108.82% (CPF2) for total GSH levels). These results suggested that both CPF1 and CPF2 exhibited positive effects on the activities of the intracellular antioxidant enzymes SOD, CAT and GR, as well as on the total GSH levels in HepG2 cells under conditions of oxidative stress. Furthermore, size exclusion gel chromatography and MALDI-TOF/TOF mass spectrometry revealed that the molecular weights of the antioxidant peptides in CPF1 were between 500 Da to 900 Da, and a novel antioxidant peptide consisting of GLLLPH (Gly-Leu-Leu-Leu-Pro-His) was identified in CPF1.     

Evaluation of antioxidant activity of parsley (Petroselinum crispum) essential oil and identification of its antioxidant constituents

Antioxidant capacities of the essential oil extracted from parsley (Petroselinum crispum) were evaluated by three different in vitro assays: β-carotene bleaching assay, DPPH free radical scavenging assay and Fe²⁺-metal chelating assay. Results showed that the parsley oil (PO) possessed a certain degree of antioxidant activities in terms of β-carotene bleaching capacity and free radical scavenging activity, but its metal chelating capacity was negligible. The antioxidant EC₅₀ values of the β-carotene bleaching assay and DPPH free radical scavenging assay of the crude PO dissolved in methanol were measured in about 5.12 and 80.21 mg/mL, respectively. However, these values were much weaker than those of BHT in 0.01 and 0.58 mg/mL, and of α-tocopherol in 0.01 and 0.10 mg/mL. Isolation and identification of the inherent antioxidants in PO involved using various chromatographic techniques including silica gel open column chromatography, normal phase-HPLC and GC–MS. Myristicin in PO was found as a dominant compound (32.75%) that exhibited a moderate antioxidant activity. Apiol was the second dominant compound (17.54%), but it might be the major contributor to the antioxidant activity of PO. These results suggest that the PO and its two major components can be potential alternative natural antioxidants.     

Influence of postharvest gamma irradiation treatment on the content of bioactive compounds and antioxidant activity of fenugreek (Trigonella foenum–graceum L.) and spinach (Spinacia oleracea L.) leaves

Fenugreek and spinach leaves after irradiation in the dose range of 0.25–1.5 kGy were evaluated for the content of bioactive compounds and antioxidant activity using DPPH radical scavenging, ferric reducing ability power (FRAP), hydroxyl radical scavenging and ferrous ion chelating assays. Results of the study revealed that bioactive content except total ascorbic acid was significantly (p ≤ 0.05) higher in fenugreek compared to spinach. Data analysis revealed that gamma irradiation treatment significantly (p ≤ 0.05) enhanced the content of individual as well as total bioactive components of both vegetables. Positive correlation (r = 0.92) existed between gamma irradiation and total phenolics. The results of the antioxidant activity as determined by above mentioned assays revealed a significant (p ≤ 0.05) decrease in EC₅₀ values and a corresponding increase in antioxidant content and activity due to irradiation. Comparison of the increase in inhibition percentage, reducing power and chelating efficiency revealed that treatment of irradiation was significantly (p ≤ 0.05) effective in enhancing the ferric reducing power of both the vegetables (3.1–37.5% for fenugreek, 4.1–42.8% for spinach) and OH radical scavenging for spinach (1.5–22.4%) compared to fenugreek (0.78–13.1%). The present investigation suggested that postharvest radiation treatment to fenugreek and spinach has a potential to enhance their antioxidant content and activities, besides acting as a photo-sanitary treatment.Industrial relevanceThe increasing demand of convenience, wholesome and health promoting foods has resulted in search of new technologies to improve the shelf-life and at the same time preserve the nutritional quality. Prolonging postharvest storage, while enhancing the content of bioactive compounds will have a positive impact on both the industry and consumers. The present study demonstrated that postharvest radiation treatment of fenugreek and spinach can be used a novel approach to enhance their bioactive composition and antioxidant activity.     

Chemical composition of wild edible mushrooms and antioxidant properties of their water soluble polysaccharidic and ethanolic fractions

Mushrooms have become attractive as functional foods and as a source of physiologically beneficial bioactive compounds. Herein, we describe and compare the chemical constituents (phenolic compounds, macronutrients, sugars, fatty acids, tocopherols and ascorbic acid) of four wild edible mushrooms widely appreciated in gastronomy: Armillaria mellea (Vahl) P. Kumm., Calocybe gambosa (Fr.) Donk, Clitocybe odora (Fr.) P. Kumm., Coprinus comatus (O.F. Müll.) Pers. Furthermore, the antioxidant activity of their water soluble polysaccharidic and ethanolic fractions was studied by three different in vitro assays. C. comatus revealed the highest concentrations of sugars (43.23/100 g dry weight), PUFA (77.46%), phenolic compounds (45.02 mg/kg), tocopherols (301.03 μg/100 g) and, among all of the fractions tested, its ethanolic fraction showed the highest antioxidant activity (EC₅₀ < 2.6 mg/ml). C. odora revealed one of the highest ascorbic acid (172.65 mg/100 g) contents and its water soluble polysaccharidic fraction showed the best antioxidant properties (EC₅₀ < 3.6 mg/ml) among the polysaccharidic fractions. The studied mushrooms species could potentially be used in well-balanced diets and as a source of bioactive compounds.     

Antioxidant properties of methanolic extracts from Ganoderma tsugae

Ganoderma tsugae Murrill was available in the form of mature and baby Ling chih, mycelia and fermentation filtrate. From these four forms, methanolic extracts were prepared and their antioxidant properties were studied. Methanolic extracts from mature and baby Ling chih showed high antioxidant activities (96.8% and 93.6%) at 20 mg ml⁻¹, and had EC₅₀ values of 0.53 and 1.11 mg ml⁻¹, respectively. EC₅₀ values in reducing power were 5.00, 2.28, 0.93 and 2.15 mg ml⁻¹ for Ling chih, baby Ling chih, mycelia and filtrate, respectively. Methanolic extracts from mature and baby Ling chih scavenged 1,1-diphenyl-2-picrylhydrazyl radicals by 88.4% and 93.8% at 5 mg ml⁻¹, whereas those from mycelia and filtrate scavenged by 85.7% and 79.3% at 10 mg ml⁻¹, respectively. EC₅₀ values in chelating ability on ferrous ions were 4.82, 3.05, 1.10 and 3.41 mg ml⁻¹ for Ling chih, baby Ling chih, mycelia and filtrate, respectively. Total phenols were the major naturally occurring antioxidant components found in all methanolic extracts and in the range of 24.0–35.6 mg g⁻¹. Based on EC₅₀ values, G. tsugae was good in antioxidant properties except for the scavenging ability on hydroxyl radicals.     

Purification,characterization, and in vitro digestion of novel antioxidant peptides from chicken blood hemoglobin

The study aimed to purify and characterize antioxidant peptides from chicken blood hemoglobin hydrolysate. The fraction M₂ (< 3 KDa) with the strongest antioxidant activity was isolated by ultrafiltration, and its DPPH (1,1-diphenyl-2-picryl-hydrazyl radical) free radical scavenging rate, ABTS [2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate)] free radical scavenging rate, and iron ion chelation activity were 82.91%, 77.49%, and 80.99%, respectively. After in vitro digestion, the antioxidant capacity of chicken blood hydrolysate was significantly higher than that before digestion (p < 0.05). M₂ exhibited the strongest antioxidant activity after stomach digestion, with a DPPH radical scavenging rate and iron ion chelating power of 82.91% and 79.61%, respectively. Component A was purified from M₂ by Sephadex G-25 gel chromatography. The peptide sequences were identified by LC-MS/MS from fraction A, and four peptides, AEDKKLIQ (944.54 Da), APAPAAK (625.36 Da), LSDLHAHKL (1033.57 Da), and LSNLHAYNL (1044.54 Da) were synthesized using the solid-phase peptide method, among which APAPAAK was a novel antioxidant peptide. Molecular docking was used to simulate the binding of these four peptides to the key active site of Keap1 via hydrogen bonding. This study suggests that chicken blood may provide a new natural source of antioxidant peptides.     

Antioxidant activity of protein hydrolysates obtained from discarded Mediterranean fish species

In this study, five discarded species in the Mediterranean Sea, namely sardine, horse mackerel, axillary seabream, bogue and small-spotted catshark, were evaluated as raw material for obtaining fish protein hydrolysates exhibiting antioxidant activity. The DH of the hydrolysates ranged from 13.2 to 21.0%, with a protein content varying from 60.7 to 89.5%. The peptide profile of all hydrolysates was very similar, except for the hydrolysate of small-spotted catshark. Their lipid content was found to be between 4.6 and 25.3%. The highest DPPH scavenging activity was found for the hydrolysates of sardine and horse mackerel with EC₅₀ values varying from 0.91 to 1.78 mg protein/mL. Sardine and small-spotted catshark hydrolysates exhibited the highest ferrous chelating activity with an EC₅₀ value of 0.32 mg protein/mL. Moreover, sardine and bogue hydrolysates presented the highest reducing power. Finally, a total of six antioxidant peptides were theoretically identified within the structure of myosin and actin proteins from sardine and small-spotted catshark. The potential antioxidant activity exhibited by the hydrolysates suggests that it is feasible to obtain added-value products such as natural antioxidants from these discarded species.     

Isolation of antioxidative and ACE inhibitory peptides from protein hydrolysate of skipjack (Katsuwana pelamis) roe

Bioactive peptides from protein hydrolysate of defatted skipjack (Katsuwonus pelamis) roe with 5% degree of hydrolysis (DH) prepared by Alcalase digestion were isolated and characterised. Two active fractions with ABTS radical scavenging activity (973.01–1497.53 μmol TE/mg sample) and chelating activity (0.05–0.07 μmol EE/mg sample) from consecutive purification steps including ultrafiltration, cation exchange column chromatography and reverse phase high performance liquid chromatography (RP-HPLC), were subjected to analysis of amino acid sequence by LC–MS/MS. Seven dominant peptides with 6–11 amino acid residues were identified as DWMKGQ, MLVFAV, MCYPAST, FVSACSVAG, LADGVAAPA, YVNDAATLLPR and DLDLRKDLYAN. These peptides were synthesised and analysed for ACE-inhibitory activity and antioxidative activities. MLVFAV exhibited the highest ACE inhibitory activity (IC₅₀ = 3.07 μM) (p < 0.05) with no antioxidative property, whilst DLDLRKDLYAN showed the highest metal chelating activity, ABTS radical and singlet oxygen scavenging activities. Therefore, peptides prepared from skipjack roe could be further employed as a functional food ingredient.     

In vitro antioxidant activity of a peptide isolated from Nile tilapia (Oreochromis niloticus) scale gelatin in free radical-mediated oxidative systems

In the present study, a peptide possessing antioxidant properties was isolated from Nile tilapia (Oreochromis niloticus) scale gelatin. Gelatin protein was hydrolyzed using alcalase, pronase E, trypsin and pepsin. Antioxidant efficacy of respective hydrolysates were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide radical anion scavenging activities. Moreover, protective effect on DNA damage caused by hydroxyl radicals generated was determined. Further, the level of reactive oxygen species (ROS) was determined using a fluorescence probe, 2′,7′-dichlorofluorescin diacetate (DCFH-DA), which could be converted to highly fluorescent dichlorofluorescein (DCF) with the presence of intracellular ROS on mouse macrophages, RAW 264.7 cells. Among hydrolysates, alcalase-derived hydrolysate exhibited the highest antioxidant activity compared to other enzymatic hydrolysates. Therefore, it was further analyzed and the sequence of an active peptide present in it was identified as Asp-Pro-Ala-Leu-Ala-Thr-Glu-Pro-Asp-Pro-Met-Pro-Phe (1382.57 Da). This peptide showed no cytotoxic effect on mouse macrophages (RAW 264.7) and human lung fibroblasts (MRC-5). In addition, it scavenged hydroxyl, DPPH and superoxide radicals at the IC₅₀ values of 7.56, 8.82 and 17.83 μM, respectively. These results suggest that the peptide derived from Nile tilapia (O. niloticus) scale gelatin acts as a candidate against oxidative stress and could be used as a potential functional food ingredient.     

Antioxidant activity of dulse (Palmaria palmata) extract evaluated in vitro

Palmaria palmata (dulse) is traditionally consumed as a snack food and garnish; but, little is known about its potential as a source of antioxidants. A 1-butanol soluble fraction extracted from dulse exhibited OH scavenging activity ± EDTA (non-site and site specific activity) in a deoxyribose assay. EC₅₀ concentrations of dulse extract to quench DPPH and ABTS⁺ free radicals were 12.5 and 29.5 mg/ml. Dulse extract inhibited (p < 0.05) conjugated diene production in a linoleic acid emulsion at 24, 48 and 52 h, 38 °C; and inhibited (p = 0.044) thiobarbituric acid reactive substances (TBARS) production at 52 h. One milligram dulse extract exhibited reducing activity = 9.68 μg l-ascorbic acid and total polyphenol content = 10.3 μg gallic acid; the dulse extract did not chelate transition metal ions. The antioxidant activity of the dulse extract was associated with aqueous/alcohol-soluble compounds characterized by phenolic functional groups with reducing activity.     

Antioxidant activities of enzymatic rapeseed protein hydrolysates and the membrane ultrafiltration fractions

In this study, rapeseed protein isolate was hydrolyzed with various proteases to obtain hydrolysates that were separated by membrane ultrafiltration into four molecular size fractions (<1, 1–3, 3–5, and 5–10 kDa). Alcalase hydrolysis significantly (p < 0.05) produced the highest yield of protein hydrolysate while Flavourzyme produced the least. The <1 kDa fraction was the most abundant after the membrane ultrafiltration of the protein hydrolysates, which indicates that the proteases were efficient at reducing the native rapeseed proteins into low molecular weight peptides. Antioxidant properties of the resulting hydrolysates and membrane fractions were characterized and results showed the Pepsin + Pancreatin (P + P) protein hydrolysate had significantly highest (p < 0.05) scavenging activity against DPPH radical among the unfractionated enzymatic hydrolysates. But the P + P hydrolysate was not as effective as other hydrolysates during long-term inhibition of linoleic acid oxidation. For most of the samples, fractionation into the <1 kDa peptides significantly (p < 0.05) improved DPPH and superoxide scavenging properties when compared to the unfractionated protein hydrolysates. Only the <1 kDa fraction showed ferric reducing antioxidant power and the effect was dose-dependent. Overall, Alcalase and Proteinase K seem to be more efficient proteases to release antioxidant peptides from rapeseed proteins when compared to P + P, Flavourzyme and Thermolysin.     

A Comparative Study on Antioxidant and DNA Protective Activity of Different Skin Coloured Brinjal (Solanum Melongena)

The aim of this study was to investigate the in vitro antioxidant activity and DNA damage inhibition potential of aqueous extract of S. melongena with different skin colours. Water extracts of brinjal with four different skin colours: moderately purple (S1), light purple (S2), dark purple (S3) and purple with green lines (S4) were tested for their antioxidant and radical scavenging activities. The total phenolic content (TPC) was quantified using Folin-Ciocalteau's method. The effectiveness of brinjal extracts in preventing radical induced DNA damage was also determined. There was a significant difference (p<0.0001) between the skin colour andantioxidant activity. Brinjal with S3skin colour showed the highest TPC and antioxidant activity measured by FRAP while, S2 showed the least. S1 displayed the highest percentage of DPPH radical scavenging activity with an IC₅₀ value of 3.51±0.62 mg/ml while, S3 demonstrated the strongest total antioxidant capacity with an inhibition percentage of 40.45±1.17. In the FTC (Ferric Thiocyanate) and egg yolk model, S1 and S3 showed better antioxidantactivity than S2 and S4. The in vitro freeradical quenchingand antioxidant results well correlated with the in vitro lipid peroxidation assays. All extracts were able to effectively retain DNA against AAPH induced radical damage at the concentration levels (25 and 75 mg/ml) tested. All the extracts showed moderate to potent antioxidant activity, among which S3 and S1, intensely coloured skins, demonstrated better antioxidant activity which may be attributed to the higher phenolic content since a linear relation was observed between the TPC and the antioxidant parameters.     

Phenolic composition,antioxidant and antimicrobial activities of free and bound phenolic extracts of Moringa oleifera seed flour

Phenolic compounds, antioxidant and antibacterial activities of defatted Moringa oleifera seed flour (DMF) were investigated. The total phenolic and flavonoid contents were measured using colorimetric methods. Free phenolic acid and flavonoid profiles were analyzed by high performance liquid chromatography, while antioxidant capacities were evaluated using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), ferric reducing antioxidant power and total antioxidant capacity. The results showed that extractability of phenolic compounds was significantly higher (p < 0.05) in bound phenolic extract (4173.00 ± 32.22 mg gallic acid equivalents (GAE)/100 g) than in free phenolic extract (780.00 ± 14.2 mg GAE/100 g) and it showed higher antioxidant and antimicrobial activities. The IC₅₀ value for DPPH radical scavenging activity was 0.9 ± 0.05 and 14.9 ± 0.07 mg/mL for bound phenolic and free phenolic extracts, respectively. Bound phenolic extract was more effective (minimum inhibitory concentration (MIC), 0.06–0.157%) than free phenolic extract (MIC, 0.117–0.191%) against tested bacteria. Ten phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, caffeic acid, protocatechuic acid, cinnamic acid, catechin, epicatechin, vanillin and quercetin) were identified and quantified in both extracts. These natural plant phenolics from Moringa seeds could be a good source of antioxidants and antibacterials for food and pharmaceutical industries.     

Antiphotoaging effect and purification of an antioxidant peptide from tilapia (Oreochromis niloticus) gelatin peptides

In this study, the effect of tilapia gelatin peptides (TGP) on UV-induced damages to mice skin was evaluated. The antioxidant indicators, lipid, collagen and glycosaminoglycan of mice skin were determined and histological changes of the collagen were depicted. The results showed TGP could alleviate the UV-induced abnormal changes of antioxidant indicators, and the protective effect was in dose-dependent manners. TGP could protect skin lipid and collagen from the UV radiation damages, and the change of glycosaminoglycan was also recovered significantly. The action mechanisms of TGP mainly involved the antioxidant properties and the repairing to endogenous collagen synthesis. Therefore, the key antioxidant peptide was further purified from TGP. Finally, one antioxidant peptide was identified and the amino acid sequence was Leu-Ser-Gly-Tyr-Gly-Pro (592.26 Da). The IC₅₀ value of this peptide on hydroxyl radical scavenging activity was 22.47 μg/mL. TGP could be a novel antiphotoaging agent from natural resources.     

Effect of blanching on the antioxidant properties of some tropical green leafy vegetables

Eight popularly consumed green leafy vegetables in Nigeria namely: Structium sparejanophora, Amarantus cruentus, Telfairia occidentalis, Baselia alba, Solanum macrocarpon, Corchorus olitorus, Vernonia amygdalina, and Ocimum gratissimum were blanched in hot water for 5 mins. The antioxidant properties of the fresh and blanched green leafy vegetables were subsequently determined. The total phenol, ascorbic acid and the antioxidant potentials as typified by reducing property and free radical scavenging activity was also determined. The results of the study revealed that blanching cause a significant (P<0.05) increase in the total phenol [fresh (0.1–0.3 g/100 g), blanched (0.2–0.6 g/100 g)] content of the green leafy vegetables except in Amarantus cruentus and Vernonia amygdalina where there was no change. Conversely, there was a significant (P<0.05) decrease in the vitamin C [fresh (43.5–148.0 mg/100 g), blanched (15.8–27.3 mg/100 g)], reducing property [fresh (0.5–1.5 absorbance), blanched (0.1–0.6 absorbance)] and free radical scavenging ability [fresh (20.0–51.4%), blanched (16.4–47.1%)] of the blanched green leafy vegetables except in Structium sparejanophora, where there was no change in the reducing property (0.6 absorbance) and free radical scavenging ability (59.8%) of the blanched vegetable. In view of this it could be concluded that blanching of vegetables though makes green leafy vegetables more palatable and less toxic, however it reduces their antioxidant properties drastically.