Recent advances on bioactive polysaccharides from mulberry.

Mulberry (Moraceae family), commonly considered as a folk remedy, has a long history of usage in many regions of the world. Polysaccharides regarded as one of the major components in mulberry plants, and they possess antioxidant, antidiabetic, hepatoprotective, prebiotic, immunomodulatory and antitumor properties, among others. In recent decades, mulberry polysaccharides have been widely studied for their multiple health benefits and potential economic value. However, there are few reviews providing updated information on polysaccharides from mulberry. In this review, recent advances in the study of isolation, purification, structural characterization, biological activity and the structure-activity relationship of mulberry polysaccharides are summarized and discussed. Furthermore, a thorough analysis of the current trends and perspectives on mulberry polysaccharides is also proposed. Hopefully, these findings can provide a useful reference value for the development and application of natural polysaccharides in the field of functional food and medicine in the future.

Effect of Curcumin Addition on the Properties of Biodegradable Pectin/Chitosan Films.

A pectin/chitosan matrix-loaded curcumin film (PCCF) with a deep eutectic solvent (DES) as the solvent and plasticizer was prepared in this study. Different quantities of curcumin (identified as PCCF-0, PCCF-1, PCCF-2. PCCF-3) were loaded on the pectin/chitosan film in order to evaluate their effects on the film properties. Results showed that curcumin could interact with the pectin/chitosan matrix and form a complex three-dimensional network structure. PCCF could promote the thickness, tensile strength, thermal properties, antioxidant and antiseptic capacities, but deteriorate the light transmission and elongation at the same time. The addition of curcumin would change the color of the film, without significantly affecting the moisture content. The tensile strength of PCCF-3 reached the maximum value of 3.75 MPa, while the elongation decreased to 10%. Meanwhile, the water-resistance properties of PCCF-3 were significantly promoted by 8.6% compared with that of PCCF-0. Furthermore, PCCF showed remarkable sustained antioxidant activities in a dose-dependent manner. PCCF-3 could inhibit DPPH and ABTS free radicals by 58.66% and 29.07%, respectively. It also showed antiseptic capacity on fresh pork during storage. Therefore, curcumin addition could improve the barrier, mechanical, antioxidant and antiseptic properties of the polysaccharide-based film and PCCF has the potential to be used as a new kind of food packaging material in the food industry.

Comparative assessment of phytochemical profiles and antioxidant and antiproliferative activities of kiwifruit (Actinidia deliciosa) cultivars.

The present study was designed to analyze and compare phytochemical activities of four different cultivars of kiwifruit. Among all investigated varieties, Hua You (HY) and Cui Xiang (CUX) displayed the maximum concentration of phytochemical content, and the highest total phenolic results were observed in HY and CUX cultivars with 220.20 ± 1.12 mg GAE/100 g and 218.04 ± 1.11 mg GAE/100 g FW, respectively. Likewise, the richest total flavonoids results were estimated in red kiwifruit (RKF) and CUX varieties with 49.082 ± 0.14 mg CE/100 g FW and 48.327 ± 0.14 mg CE/100 g FW, respectively. Moreover, tests for oxygen radical scavenging capacity (ORAC) and peroxyl radical scavenging capacity (PSC) were observed maximum in RKF cultivar showing 131.229 ± 5.91 µM Trolox equivalent/g FW and 85.957 ± 11.75 µM vitamin C equivalent/g FW, respectively. Furthermore, the highest cellular antioxidant activity (CAA) with No PBS wash protocol was depicted in RKF 237.544 ± 4.12 µM QE equivalent/g FW with the lowest EC50 0.0128 mg/ml. In addition, high-performance liquid chromatography (HPLC) analysis confirmed the presence of ferulic acid, naringin, gallic acid, syringic acid, caffeic acid, rutin, protocatechuic acid, salicylic acid, and catechin in kiwifruit. Catechin as one main content in our study is consistent with the recent reports. The result suggested that the phytochemical profile and bioactivities were significantly affected by the type of cultivars. PRACTICAL APPLICATIONS: Kiwifruit is widely consumed over the world for its rich nutritious and medicinal values. Currently, phytochemicals are considered as one of the main bioactive components of kiwifruits, which are responsible for lots of bioactivities, such as antitumor, anti-inflammatory, antioxidant, hypoglycemic, and hypolipidemic activities. There are varieties of kiwifruits, and the bioactive components and bioactivities are greatly affected by the cultivars. But there have been no comparative studies on the phytochemicals from different varieties. This study aimed to make a comprehensive assessments of the free, bound, and total phenolics and flavonoids, as well as the chemical-based and cell-based antioxidant activities of four different subspecies of kiwifruit. This work would be beneficial to elucidate the function differences of different kiwifruit phytochemicals, promote its further research, as well as provide a basis for selecting cultivars.

Antihyperglycemic and antihyperlipidemic activities of a polysaccharide from Physalis pubescens L. in streptozotocin (STZ)-induced diabetic mice.

In this study, a polysaccharide was extracted from Physalis pubescens L. (named PP). Its antihyperglycemic and antihyperlipidemic activities were evaluated in STZ-induced diabetic mice. Results showed that PP was determined to be composed of rhamnose (Rha), arabinose (Ara), fucose (Fuc), xylose (Xyl), mannose (Man), glucose (Glc) and galactose (Gal) with molar percentages of 4.65%, 17.34%, 1.43%, 6.24%, 5.52%, 45.5%, and 19.31%, respectively. The average molecular weight (Mw) was found to be 20.0 kDa. It had a strong α-glucosidase inhibitory activity in vitro. PP treatment could enhance the oral glucose tolerance, and increase the levels of SOD, GSH, CAT, vitamin C, vitamin E, HDL-c, C-peptide, GCK and hepatic glycogen in diabetic mice. Besides, PP treatment could also decrease the levels of MDA, TG, TC, LDL-c, BUN and G-6-Pase. The regulating effects were stronger in high dose PP treatment than those in the low and medium dose treatments. In short, PP played an important role in protecting STZ-induced diabetic mice, and the effect was closely related to its activities in antioxidation and regulating glucose and lipid metabolism.

A comparison study on polysaccharides extracted from Fructus Mori using different methods: structural characterization and glucose entrapment.

In this study, the structure characteristics and the hypoglycemic and antioxidant activities of mulberry fruit polysaccharides obtained by the commonly used hot water (MFPh)-, ultrasonic (MFPu)-, acid (MFPc)- and alkali (MFPa)-assisted extraction methods were investigated. NMR analysis indicated that the four polysaccharides had similar glycosidic linkage patterns. Scanning electron microscopy analyses showed that the surface morphology of the polysaccharides was greatly affected by the extraction methods. The results of the bioactivity assays indicated that MFPh exhibited stronger antioxidant and α-amylase inhibitory activities than the other polysaccharides. Moreover, all the polysaccharides showed good α-glucosidase inhibitory activities except for MFPu with the lowest molecular weight. These results suggested that acid, alkali, and ultrasonic-assisted extractions have different effects on the degradation of polysaccharides without changing the main structure compared with hot water extraction. In addition, the molecular weight of polysaccharides plays a key role in the bioactivity of the mulberry fruit polysaccharides.

Comparative study on the physicochemical properties and bioactivities of polysaccharide fractions extracted from Fructus Mori at different temperatures.

This study examined the effects of different extraction temperatures (30 °C and 90 °C) on the physicochemical properties and bioactivities of polysaccharides (MFPs-30-60, MFPs-30-80, MFPs-90-40, MFPs-90-60 and MFPs-90-80) extracted at same ethanol gradation (40, 60 and 80%). The polysaccharides were extracted from Fructus Mori, and their antioxidant, hypoglycemic and hypolipidemic activities were evaluated. The results showed that all the polysaccharide fractions contained the same monosaccharides but at different molar ratios. MFPs-30-80 had the highest content of glucose (30.33%), and MFPs-90-40 had the highest content of uronic acid (43.46%). In addition, compared to the extraction temperature of 30 °C, the higher temperature (90 °C) caused the degradation of the extracted polysaccharides. Generally, MFPs-30-80 showed superior antioxidant activity, MFPs-90-40 displayed good bile acid-binding ability, and both MFPs-30-80 and MFPs-90-40 exhibited the strongest inhibitory effects on α-amylase and α-glucosidase activity. This study concludes that the bioactivities of mulberry fruit polysaccharides depend on a combination of structural factors that are greatly affected by the extraction temperature.

Synthesis of multifunctional Fe3O4@PLGA-PEG nano-niosomes as a targeting carrier for treatment of cervical cancer.

A new folic acid (FA)-conjugated poly (lactic-co-glycolicacid) (PLGA)-polyethylene glycol (PEG) nano-noisome was prepared. The noisome was employed as a drug delivery system to load curcumin (Cur) as a model drug and fluorescent probe for cervical cancer therapy and cell imaging. The Fe3O4@PLGA-PEG@FA noisomes were prepared through facile emulsion solvent evaporation and conjugation chemistry method, possessing the properties of high rapid magnetic separation and targeting character. X-ray photoelectron spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM) were adopted to characterize the chemical structure and properties of these niosomes. MTT assay revealed that the blank noisomes exhibited excellent biocompatibility. The in vitro drug loading and release behavior studier showed the as prepared nano-noisome presented ultrahigh performance as drug carrier. The confocal laser scanning microscopy (CLSM) and flow cytometry (FCM) experiments demonstrated that Cur-loaded Fe3O4@PLGA-PEG@FA niosomes achieved significantly high targeting efficiency for cervical cancer. Additionally, the FA-targeted niosomes exhibited higher antitumor efficiency than free Cur. Cell morphology, the mitochondrial membrane potential and cell cycle changes indicated that Cur-loaded niosomes induced HeLa229 cells to apoptosis by destroying mitochondrion of cervical tumor cells, simultaneously changing nuclear morphology and blocking tumor cell proliferation. These results demonstrate that Fe3O4@PLGA-PEG@FA noisomes have promising applications as targeted drug delivery system for sustained drug release in cancer treatment.

Modulation of gut microbiota by mulberry fruit polysaccharide treatment of obese diabetic db/db mice.

Increasing evidence indicates that gut microbiota is an important factor in mediating the development of metabolic disorders, especially type 2 diabetes. Herein, we investigated the protective effects of polysaccharides from mulberry fruit on diabetic db/db mice. We observed an inhibition in the body weight increase, a decrease in the blood glucose levels, and an improvement in glucose tolerance. Furthermore, our data showed increased enzymatic activities as evidenced by parameters such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT). In addition, high density lipoprotein cholesterol (HDL-C) increased, while total cholesterol (TC), triacylglycerol (TG), low density lipoprotein cholesterol (LDL-C), lipid peroxide content malonaldehyde (MDA), and free fatty acid (FFA) levels decreased, accompanied by the recovery from damage to the liver, kidneys and pancreas. Meanwhile, metformin and polysaccharide similarly shifted the abundance of the main gut microbiota, Bacteroidetes and Firmicutes, in diabetic mice toward levels observed in healthy mice. Especially at the genus level, the enrichment of some key bacteria like Bacteroidales, Lactobacillus, Allobaculum, Bacteroides, and Akkermansia was observed. Taken together, our findings suggest that polysaccharides from the mulberry fruit modulate gut microbiota, including enriching functional bacteria and reducing microbial diversity, which may contribute to their antidiabetic effects.

Averrhoa carambola free phenolic extract ameliorates nonalcoholic hepatic steatosis by modulating mircoRNA-34a, mircoRNA-33 and AMPK pathways in leptin receptor-deficient db/db mice.

The objective of the present study is to investigate the hepatic steatosis relieving effect of Averrhoa carambola free phenolic extract (ACF) on leptin receptor-deficient (db/db) mice and elucidate the modulation hepatic lipogenesis mechanisms. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) assays, accompanying hematoxylin and eosin (H&E) staining, were applied to identify the alleviation of liver histopathological changes. Serum and hepatic lipid assays, combined with oil red O staining, were used to investigate the amelioration of lipid accumulation. Further assessments by quantitative real-time PCR and western blot assays were used to elucidate the suppression of the fatty acid and triglyceride (TG) synthesis mechanisms underlying ACF protection. These results indicated that ACF treatment significantly reduced the liver TG of db/db mice (p < 0.05). The mechanisms are partly through phosphorylation of AMPK α and down-regulation of SREBP-1c expression, and further down-regulation of FAS and SCD1 (p < 0.05). In addition, the expression levels of mircoRNA-34a and mircoRNA-33, which modulate this signaling pathway, were significantly down-regulated by ACF treatment (p < 0.05). Collectively, these results revealed that ACF exhibited a potent hepatic steatosis relieving effect partly by inhibiting the signal transduction of hepatic lipogenesis.

Fractionation, preliminary structural characterization and bioactivities of polysaccharides from Sargassum pallidum.

Sargassum pallidum polysaccharides were fractioned using a DEAE-Sepharose fast-flow column and four polysaccharide fractions (SP-P1, SP-P2, PV-P3 and SP-P4) were obtained. Structural analyses indicated that SP-P2 and SP-P4 had higher molecular weights than SP-P1 and SP-P3. SP-P2, SP-P3 and SP-P4 comprised of fucose, rhamnose, arabinose, galactose, glucose, xylose, and mannose in a similar molar ratio, while SP-P1 did not contain arabinose. SP-P2 and SP-P4 had a similar number of (1→6) or (1→) glycosidic linkages (1→2) or (1→4) glycosidic linkages and (1→3) glycosidic linkages, while SP-P1 and SP-P3 contained a small number of (1→3) glycosidic linkages. SP-P2 exhibited better bioactivities than SP-P1, SP-P3 and SP-P4, including antioxidant, anti-hemolysis inhibitory, α-amylase and α-glucosidase inhibitory and antiproliferative activities. These data suggest that S. pallidum has four polysaccharide fractions with different structural features and bioactivities and SP-P2 has potential to be explored as a functional food or complementary medicine.

Major triterpenoids in Chinese hawthorn "Crataegus pinnatifida" and their effects on cell proliferation and apoptosis induction in MDA-MB-231 cancer cells.

The cytotoxicity and antiproliferative effect of phytochemicals presenting in the fruits of Chinese hawthorn (Crataegus pinnatifida) were evaluated. Shanlihong (Crataegus pinnatifida Bge. var. major N.E.Br.) variety possessed significant levels of flavonoids and triterpenoids, and showed potent antiproliferative effect against HepG2, MCF-7 and MDA-MB- 231 human cancer cells lines. Triterpenoids-enriched fraction (S9) prepared by Semi-preparative HPLC, and its predominant ingredient ursolic acid (UA) demonstrated remarkably antiproliferative activities for all the tested cancer cell lines. DNA flow cytometric analysis showed that S9 fraction and UA significantly induced G1 arrest in MDA-MB-231 cells in a dose-dependent manner. Western blotting analysis revealed that S9 fraction and UA significantly induced PCNA, CDK4, and Cyclin D1 downregulation in MDA-MB-231 cells, followed by p21Waf1/Cip1 up-regulation. Additionally, flow cytometer and DNA ladder assays indicated that S9 fraction and UA significantly induced MDA-MB-231 cells apoptosis. Mitochondrial death pathway was involved in this apoptosis as significantly induced caspase-9 and caspase-3 activation. These results suggested that triterpenoids-enriched fraction and UA exhibited antiproliferative activity through the cell cycle arrest and apoptosis induction, and was majorly responsible for the potent anticancer activity of Chinese hawthorn.

Antioxidant, antitumor and immunomodulatory activities of water-soluble polysaccharides in Abrus cantoniensis.

Abrus cantoniensis is a vegetative food in tropical areas of Asia and claimed as folk beverages and soups consumed for cleansing liver toxicants and preventing liver diseases. Polysaccharides (ACP-І and ACP-II) were extracted with hot water from A. cantoniensis, and isolated by DEAE cellulose chromatography. The chemical properties as well as antioxidant, antitumor and immunomodulatory activities of ACP-I and ACP-II were investigated. The results showed that the ACP-I (9.09kDa) contained only glucose and ACP-II (38.45kDa) consisted of rhamnose, arabinose, galactose and glucose. ACP-II exhibited higher oxygen radical absorbance capacity (ORAC) and hydroxyl radical prevention capacity (HRPC) than ACP-I with ORAC values and HRPC values of 53.42±3.32µmol Trolox equiv./g DW and 34.84±5.07µmol Trolox equiv./g DW. Besides, in the wound healing assay, ACP-II exhibited potent migration inhibitory effects on MCF-7 cells. ACP-II could also significantly stimulate the proliferation of splenocytes and thymocytes, and enhanced NO production of peritoneal macrophages. These findings suggest that the polysaccharide ACP-II in A. cantoniensis could be served as a novel potential functional food.

Characterization of polysaccharide fractions in mulberry fruit and assessment of their antioxidant and hypoglycemic activities in vitro.

The present study aimed to characterize and investigate the polysaccharide fractions of mulberry fruit, and their antioxidant and hypoglycemic activities. Mulberry fruit polysaccharides (MFP) were extracted by using hot water as the solvent and fractioned by using a DEAE-Sepharose fast-flow column. In total four eluents of water (MFP-1), 0.1 M NaCl (MFP-2), 0.2 M NaCl (MFP-3) and 0.3 M NaCl (MFP-4) were fractionated. Arabinose, galactose, glucose, xylose and mannose were the main components present in MFP-1, while MFP-2 and MFP-3 were composed of arabinose and galactose, and MFP-4 of arabinose, galactose and glucose. High-performance gel permeation chromatography (HP-GPC) analysis indicated a narrower molecular weight distribution in the MFP-1 fraction. Scanning electron microscopy (SEM) exhibited a smooth surface for MFP-1 and MFP-3 fractions, whereas MFP-2 and MFP-4 have pore openings and flocculent fibers on a smooth surface. Tertiary structure analyses indicated that none of the fractions had a triple-helical conformation. On the whole, MFP-3 and MFP-4 showed better antioxidant activity and inhibitory effects on α-amylase and α-glucosidase compared to MFP-1 and MFP-2. These results show significant potential for the antioxidant and hypoglycemic activities of MFP-3 and MFP-4 indicating the need for their further exploration as potential antidiabetic agents.

Phenolic contents and cellular antioxidant activity of Chinese hawthorn "Crataegus pinnatifida".

It is evident from various epidemiological studies that consumption of fruits and vegetables is essential to maintain health and in the disease prevention. Present study was designed to examine phenolic contents and antioxidant properties of three varieties of Crataegus pinnatifida (Chinese hawthorn). Shanlihong variety exhibited elevated levels of total phenolics and flavonoid contents, including free and bond phenolics. Procyanidin B2 was most abundant phenolic compound in all samples, followed by epicatechin, chlorogenic acid, hyperoside, and isoquercitrin. The free ORAC values, and free hydro-PSC values were 398.3-555.8 µmol TE/g DW, and 299.1-370.9 µmol VCE/g DW, respectively. Moreover, the free cellular antioxidant activity (CAA) values were 678-1200 µmol of QE/100 g DW in the no PBS wash protocol, and 345.9-532.9 µmol of QE/100 g DW in the PBS wash protocol. C. pinnatifida fruit could be valuable to promote consumer health.

Identification of phenolics in litchi and evaluation of anticancer cell proliferation activity and intracellular antioxidant activity.

Litchi leaf is a good resource for phenolics, which are good candidates for medicines. In this work, three phenolics were isolated from litchi leaf by column chromatography. Their structures were identified by electrospray ionization-mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy as secoisolariciresinol 9'-O-ß-D-xyloside (1), 4,7,7',8',9,9'-hexahydroxy-3,3'-dimethoxy-8,4'-oxyneolignan (2), and cinnamtannin B1 (3). Cinnamtannin B1 showed better extra- and intracellular antioxidant activities than Compounds 1 and 2. The intracellular antioxidant activity of cinnamtannin B1 was related to the upregulation of endogenous antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase), and inhibition of ROS generation. Furthermore, cinnamtannin B1 exhibited strong antiproliferative effects against HepG2 and Siha cell lines with no significant cytotoxicities. In the case of the HepG2 cell line, cell cycle arrest and apoptosis induction were the underlying anticancer mechanisms of cinnamtannin B1. The results indicated that cinnamtannin B1 was a potent cancer cell proliferation inhibitor and a good intracellular antioxidant.

Structural characterization and immunomodulatory activity of a new heteropolysaccharide from Prunella vulgaris.

A new heteropolysaccharide, here called P1, was isolated from the fruit clusters of Prunella vulgaris using a hot water extraction method. Chemical and physical analyses indicated that P1 had a spherical conformation with an average molecular weight of 1750 kDa and consisted of arabinose (28.37%), xylose (54.67%), mannose (5.61%), glucose (5.46%), and galactose (5.89%). The main types of P1 linkages were proved to be (1→5)-linked α-L-Ara, (1→)-linked α-L-Ara, (1→3)-linked α-D-xyl, (1→3)-linked ß-D-Gal, (1→3,6)-linked ß-D-Gal, (1→3,6)-linked α-D-Man and (1→6)-linked α-D-Glc according to the periodate oxidation-Smith degradation and NMR analyses. P1 could significantly enhance the secretion of NO, TNF-α, and IL-6 in murine RAW 264.7 cells, involving the toll-like receptor 2 (TLR2), TLR4 and complement receptor 3 (CR3). Further studies showed that P1 exhibited stable immune activities in the pH range of 4.0-10.0 and below 121 °C. The results suggested that P1 could be used as a potent immunomodulatory agent in functional foods and pharmacological fields.

Characterization, antioxidant and immunomodulatory activities of polysaccharides from Prunella vulgaris Linn.

Water-soluble polysaccharides from Prunella vulgaris Linn (P. vulgaris) were fractionated using DEAE-Sepharose fast-flow column to obtain several eluents of water (PV-P1), 0.1M NaCl (PV-P2) and 0.2M NaCl (PV-P3). Structural analyses showed that PV-P1 had a higher molecular weight and degree of branching as compared to PV-P2 and PV-P3. Tertiary structure analyses indicated that PV-P1, PV-P2 and PV-P3 did not have triple-helical conformation. PV-P2 and PV-P3 showed stronger antioxidant activities than PV-P1, as measured radical scavenging capacities. PV-P1 showed stronger immunomodulatory activities than PV-P2 and PV-P3 in term of stimulation of the production of pro-inflammatory cytokines, including nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in murine macrophage RAW 264.7 cells. PV-P1, PV-P2 and PV-P3 did not exhibit cytotoxicities against RAW 264.7 at the concentrations tested. These results suggest that P. vulgaris polysaccharides could be explored as potential antioxidant and immunomodulatory agents for the complementary medicine or functional foods.

Antioxidant capacity of anthocyanins from Rhodomyrtus tomentosa (Ait.) and identification of the major anthocyanins.

The anthocyanins in the fruits of Rhodomyrtus tomentosa (ACN) were extracted by 1% TFA in methanol, and then purified by X-5 resin column and C18 (SPE) cartridges. The purified anthocyanin extract (ART) from the fruits of R. tomentosa showed strong antioxidant activities, including DPPH radical-scavenging capacity, ABTS radical scavenging capacity, reducing power and oxygen radical absorbance capacity (ORAC). The purified anthocyanin extract was analyzed by high performance liquid chromatography (HPLC). The major anthocyanins were purified by semi-preparative HPLC and Sephadex LH-20 column chromatography, and were identified as cyanidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside, petunidin-3-O-glucoside, delphinidin-3-O-glucoside and pelargonidin-3-glucoside by HPLC-ESI/MS and nuclear magnetic resonance spectroscopy (NMR). Cyanidin-3-O-glucoside was considered as the most abundant anthocyanin, which was 29.4 mg/100 g dry weight of R. tomentosa fruits. Additionally, all the major anthocyanins were identified from R. tomentosa fruit for the first time.

Isolation and characterization of an oxygen radical absorbance activity peptide from defatted peanut meal hydrolysate and its antioxidant properties.

Defatted peanut meal hydrolysate (DPMH) was purified using ultrafiltration, gel filtration chromatography, and high-performance liquid chromatography. A tripeptide with strong oxygen radical absorbance capacity (ORAC) was isolated and identified as Tyr-Gly-Ser by ESI-MS/MS. It was then synthesized to measure its antioxidant properties in different systems. The ORAC value of Tyr-Gly-Ser was 3-fold higher than that of glutathione (GSH), and it displayed a stronger protective effect on linoleic acid peroxidation and H(2)O(2)-induced oxidative injury in rat pheochromocytoma line PC12 cells than GSH (p < 0.05). However, Tyr-Gly-Ser showed negligible DPPH radical scavenging activity, reducing power, and no metal chelating ability. The results suggested that Tyr-Gly-Ser displayed antioxidant activity via the hydrogen atom transfer mechanism, and the Tyr at the N-terminal was the hydrogen donor. The ORAC assay was recommended as a reliable and effective method to measure the antioxidant activity in the course of antioxidant peptide isolation.

Effects of supplementation with grass carp protein versus peptide on swimming endurance in mice.

OBJECTIVE: We investigated the effects of grass carp protein or peptide administration on swimming endurance in mice. METHODS: Grass carp protein or peptide was intragastrically administered to male National Institutes of Health mice at low [1 mg/(g·d)] and high [5 mg/(g·d)] doses, continuously once per day before swimming exercise. After training for 28 d, fatigue-related biochemical parameters, including liver glycogen, gastrocnemius muscle glycogen, plasma glucose, serum lactic acid, blood urea nitrogen, superoxide dismutase (SOD), glutathione peroxidase, and catalase (CAT), were assayed. RESULTS: Compared with the control group, all treatments applied significantly prolonged the exercise time, and high-dose peptide administration was the most effective (P<0.001). Liver glycogen was remarkably increased by seven times or more by protein or peptide ingestion compared with that of the control group. High-dose protein or peptide addition significantly elevated liver glycogen, muscle glycogen, glucose level, and the removal of metabolites, serum lactic acid, and blood urea nitrogen was greater after exercise. In terms of the comparison between protein versus peptide, high-dose peptide addition significantly enhanced CAT (P=0.016) and SOD (P=0.007), while no significant differences were observed for glutathione peroxidase, glucose, liver glycogen, or muscle glycogen between high-dose peptide and protein addition. The difference between low-dose protein and peptide supplementation was not significant. CONCLUSION: Grass carp protein or peptide significantly improved the endurance capacity of mice. The superiority of peptide over protein was observed at high-dose supplementation, which was mainly attributed to the significant enhancement of antioxidant enzyme levels (CAT and SOD).