Effect of glucose substitution by low-molecular weight chitosan-derivatives on functional, structural and antioxidant properties of maillard reaction-crosslinked chitosan-based films

In this study, the effects of different temperatures, incubation times and types of reducing sugars, including glucose and different low molecular weight (Mw) chito-oligosaccharides (COS) with varying acetylation degree (AD), on the extent of Maillard reaction (MR) on chitosan-based films were studied. Interestingly, an improvement of structural and functional properties of all MR-crosslinked films was noted, which is more pronounced by heating at higher temperature and exposure time. These findings were proved through Fourier-transform infrared and X-ray diffraction analyses. In addition, color change and Ultraviolet spectra demonstrate that glucose addition provides the high extent of MR, followed by COS1 (Mw < 4.4 kDa; AD, 18.20%) and COS2 (Mw < 4.4 kDa; AD, 10.63%). These results were confirmed by enhanced water resistance and thermal properties. Moreover, MR-chitosan/COS films showed the highest mechanical properties, whereas, glucose-loaded films were brittle, as demonstrated by scanning electron microscopy micrographs. Furthermore, MR-chitosan/COS1 films exhibited the better antioxidant behavior followed by chitosan/glucose and chitosan/COS2 films, mainly at higher heating-conditions. Thereby, MR-crosslinked chitosan/COS based films were attractive to be applied as functional and active coating-materials in various fields.

Brown seaweed Cystoseira schiffneri as a promising source of sulfated fucans: Seasonal variability of structural, chemical, and antioxidant properties

A fucoidan, sulfated polysaccharide, was extracted from the brown seaweed Cystoseira schiffneri during 4 harvest periods (December, April, July, and September) and studied for its structural and chemical properties. The Cystoseira schiffneri fucoidan (CSF) showed important variation in sulfate content ranging from 7.8% in December to 34.8% in July. This was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopies showing characteristic signals of sulfated polysaccharides. Molecular mass of the CSF varied as a function of season from 3,745 in December to 26,390 Da in July. Gas chromatography-mass spectroscopy showed that CSF fractions were "mannogalactofucans" composed mainly of mannose, fucose, and galactose with low levels of other monosaccharides. Moreover, interesting in vitro antioxidant activities that depend on the harvest season were noted for CSF. Thus, the present work might contribute to establish criteria for extracting bioactive fucoidans from an endemic Tunisian seaweed C. schiffneri.

A novel blue crab chitosan/protein composite hydrogel enriched with carotenoids endowed with distinguished wound healing capability: In vitro characterization and in vivo assessment

This work aimed to the development of chitosan and protein isolate composite hydrogels, for carotenoids-controlled delivery and wound healing. By increasing the concentration of the protein isolate, chitosan hydrogels were more elastic at a protein isolate concentration not exceeding 15% (w/w). Chitosan-protein isolate composite hydrogels revealed low cytotoxicity towards MG-63 osteosarcoma cells. Thanks to its appropriate structural, swelling and mechanical resistance properties, chitosan hydrogel (3%; w/v), reinforced with 15% (w/w) of protein isolate, was selected for the carotenoids in vitro release study. Release profiles, show delivery patterns, where carotenoids were more barely released at a pH 7.4 medium (p < .05), compared to more acidic microenvironments (pH 4.0 and pH 2.0). Thus, developed hydrogels could be applied as pH-sensitive intelligent carriers, for drugs-controlled release, with interesting antioxidant abilities. The in vivo healing potential of hydrogels in rats' models was further studied. Topical application of hydrogel-based patches allowed the acceleration of wound healing and the complete healing, for composite hydrogel enriched with carotenoids.

Conception of novel blue crab chitosan films crosslinked with different saccharides via the Maillard reaction with improved functional and biological properties

This work aimed to modify blue crab chitosan-based films through the Maillard reaction (MR) as a novel alternative to improve their functional and biological properties. To this end, different saccharides (glucose (aldohexose), fructose (ketohexose), xylose (aldopentose) and arabinose (aldopentose)), at different weight ratios 0.5, 1.0 and 2.0 % (g/100 g polymer), were studied, and films were heated at 90 °C for 24 h. Based on color changes and browning index measurements, the extent of MR was the highest with aldopentoses, whereas hexoses and particularly ketohexoses, exhibited a relative crosslinking rate. These findings were further reflected with an improvement in treated films mechanical properties and thermal degradation temperatures, and advantageously, barrier properties against UV light and water. In addition, the MR-modified Cs-based films antioxidant activity was interestingly enhanced with mainly aldopentoses. Consequently, MR crosslinked chitosan-based films are promising alternative for active and functional packaging able of food oxidation hindering, especially using aldopentoses.

Assessment of Cholesterol, Glycemia Control and Short- and Long-Term Antihypertensive Effects of Smooth Hound Viscera Peptides in High-Salt and Fructose Diet-Fed Wistar Rats

In this study, the antihypertensive activity of Purafect®-smooth hound viscera protein hydrolysate (VPH) and its peptide fraction with molecular weight (MW) below 1 kDa (VPH-I) was investigated. In addition, the lipase inhibitory activity, as well the anticoagulant potential, in vitro, were assessed. The antihypertensive effects of VPH and VPH-I were studied during 24 h (short-term effect) and 30 days (long-term effect) using high-salt (18% NaCl) and -fructose (10%) diet (HSFD)-induced hypertension. Data showed that, 4 h post-administration of VPH and VPH-I (200 mg/kg BW), the systolic blood pressure of rats was reduced by about 6 and 9 mmHg, respectively. These effects were similar to that obtained with Captopril (~9 mmHg at t = 4 h). On the other hand, exposing the rats to daily to HSFD, coupled to the administration of viscera peptides, was found to attenuate hypertension. In addition, the proteins' treatments were able to correct lipid and glycemic disorders, by reducing the total cholesterol and triglyceride contents and resorting to the plasma glucose level, compared to the HSFD group. Overall, the present findings demonstrated the preventive effect of VPH-peptides from hypertension complications, as a result of their biological properties.

Bioactive potential and structural characterization of sulfated polysaccharides from Bullet tuna (Auxis Rochei) by-products

The present study deals with the isolation of sulfated polysaccharides (Ps) from the Bullet tuna by-products (head, skin and bones). Results of chemical characterization revealed that Ps-bones showed the highest total sugar, uronic acid and sulfate group contents. Tuna extracted-Ps contained a mixture of neutral sugars, with high amounts of glucuronic and galacturonic acids and presented different molecular weights. The presence of sulfate groups in different Ps was confirmed by FTIR analysis. Interestingly, Ps-bones showed the highest antioxidant activity among all the extracted Ps. Moreover, results revealed that all polysaccharides displayed varying degrees of antibacterial activity. Ps-bones exhibited high and wide spectrum of activities, inhibiting the growth of all bacteria tested. Ps-bones incorporated during fillet cooking offered an excellent protection of fish fillet by avoiding pH change, color loss, lipid oxidation and spoilage. Overall, the results demonstrated that Ps could be potentially used as natural antioxidant and antibacterial agents.

Bioactive properties: enhancement of hepatoprotective, antioxidant and DNA damage protective effects of golden grey mullet protein hydrolysates against paracetamol toxicity

This study was undertaken to examine the hepatoprotective, antioxidant, and DNA damage protective effects of protein hydrolysates from Liza aurata, against paracetamol overdose induced liver injury in Wistar rats. L. aurata protein hydrolysates (LAPHs) were mainly constituted by glutamic acid (Glu) and glutamine (Gln) and lysine (Lys). In addition, they contained high amounts of proline (Pro), leucine (Leu) and glycine (Gly). The molecular weight distribution of the hydrolysates was determined by size exclusion chromatography, which analyzed a representative hydrolysate type with a weight range of 3–20 kDa. The hepatoprotective effect of LAPHs against paracetamol liver toxicity was investigated by in vivo assay. Rats received LAPHs daily by gavage, for 45 days. Paracetamol was administrated to rats during the last five days of treatment by intraperitoneal injection. Paracetamol overdose induced marked liver damage in rats was noted by a significant increase in the activities of serum aspartate amino transferase (AST) and alanine amino transferase (ALT), and oxidative stress which was evident from decreased activity of the enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)), and level of glutathione (GSH), and increased concentration of lipid peroxidation products (MDA). Furthermore, paracetamol increased the DNA damage with liver histopathological changes. LAPH pretreatment significantly attenuated paracetamol-induced hepatotoxic effects, including oxidative damage, histopathological lesions, and apoptotic changes in the liver tissue. Interestingly, LAPHs restored the activities of antioxidant enzymes and the level of GSH, ameliorated histological and molecular aspects of liver cells. The present data suggest that paracetamol high-dose plays a crucial role in the oxidative damage and genotoxicity of the liver and therefore, some antioxidants such us LAPHs might be safe as hepatoprotectors. Altogether, our studies provide consistent evidence of the beneficial effect of LAPHs on animals treated with a toxic dose of paracetamol and might encourage clinical trials.

This study was undertaken to examine the hepatoprotective, antioxidant, and DNA damage protective effects of protein hydrolysates from Liza aurata, against paracetamol overdose induced liver injury in Wistar rats.

Preventive effect of goby fish protein hydrolysates on hyperlipidemia and cardiovascular disease in Wistar rats fed a high-fat/fructose diet

This study was carried out to investigate the hypolipidemic, cardioprotective and anticoagulant properties of fish goby protein hydrolysates (GPHs) in rats fed a high fat and fructose diet (HFFD).

Ultrasound stroke volume variation induced by passive leg raising and fluid responsiveness: An observational cohort study

OBJECTIVE

To assess the performance of the ultrasound measurement of stroke volume (SV) coupled to passive leg raising (PLR) in predicting fluid responsiveness (FR).

DESIGN

A prospective cohort study was carried out in patients requiring volume expansion (VE). A transthoracic Doppler echocardiography (TTE) device was used for the measurement of SV. Four measurements were obtained: before and 90s after PLR, and before and after VE. The patients were subsequently classified according to their hemodynamic response to VE. Responders were defined by an increase in SV of at least 15% in response to VE.

RESULTS

Thirty maneuvers were studied. An increase in SV>15% in response to PLR was recorded in 21 cases. Hemodynamic indices taken in the first stage showed significant differences in the distensibility index of the inferior vena cava (dIVC), in the velocity-time integral of aortic blood flow (VTIAo) and in SV, with respective p-values of 0.009, 0.012 and 0.025. The SV changes induced by VE were significantly correlated to the SV changes induced by PLR, with a Spearman coefficient of 0.77 and a linear equation y=0.82 x+1.68. Fluid responsiveness can be efficiently predicted by assessing the effects of PLR on SV monitored by Doppler TTE, with a sensitivity of 94.7% and a negative predictive value of 88%.

CONCLUSION

Our data support the interest of Doppler TTE as an effective tool in predicting FR through the assessment of SV in response to PLR, in hemodynamically unstable patients.

Enhancing colour and oxidative stabilities of reduced-nitrite turkey meat sausages during refrigerated storage using fucoxanthin purified from the Tunisian seaweed Cystoseira barbata

The present study investigated the angiotensin-I converting enzyme (ACE) inhibitory activity and the antioxidant properties, in vitro and in cured meat sausages containing reduced levels of sodium nitrite, of fucoxanthin extracted from the Tunisian brown seaweed Cystoseira barbata (CBFX). Results revealed that CBFX exhibited great scavenging activities against DPPH free radicals (EC50 = 136 μg/ml), peroxyl radicals in the linoleate-β-carotene system (EC50 = 43 μg/ml) and hydroxyl radicals generated by Fenton reaction (DNA nicking assay). A considerable ferric reducing potential was also recorded for CBFX (EC50 = 34 μg/ml). It is interesting to note that CBFX was found to modulate the ACE activity, which is the key enzyme involved in the blood pressure regulation, with an EC50 of 5 μg/ml. When fucoxanthin was supplemented, the concentration of sodium nitrite added to cured turkey meat sausages was reduced from 150 to 80 ppm, coupled with the enhancement of colour and oxidative stabilities. Thus, CBFX, with noticeable antioxidant and antihyertensive effects, could be used as a natural additive in functional foods to alleviate potential human health hazards caused by carcinogenic nitrosamines formation.

Evaluation of the biotechnological potential of a novel purified protease BS1 from Bacillus safensis S406 on the chitin extraction and detergent formulation

An extracellular alkaline stable protease BS1 from a new bacteria strain, Bacillus safensis S406, isolated from the Sfax solar saltern, was purified and characterized. The enzyme was purified to homogeneity by ammonium sulfate precipitation, Sephadex G-75 gel filtration, Mono-Q anion-exchange chromatography and ultrafiltration, with a 12.70-fold increase in specific activity and 20.29% recovery. The enzyme has a molecular weight of 29kDa and appeared as a single band on native-PAGE. The optimum pH and temperature values of its proteolytic activity were pH 11.0 and 60°C, respectively. BS1 was tested for the deproteinization of shrimp wastes to extract chitin. An enzyme-protein ratio of 10U/mg of proteins allows to eliminate 93% of protein linked to the chitin after 3h hydrolysis at 45°C. Being very active in alkaline conditions, the potential application of BS1 in laundry formulation was investigated. The enzyme showed high stability in the presence of non-ionic surfactants and some commercial liquid and solid detergents, suggesting its eventual use in detergent formulations.

Novel bioactive peptides from enzymatic hydrolysate of Sardinelle (Sardinella aurita) muscle proteins hydrolysed by Bacillus subtilis A26 proteases

Sardinelle protein hydrolysate (SPH), prepared by treatment with Bacillus subtilis A26 proteases, was found to exhibit antibacterial, antioxidant and ACE-inhibitory activities. SPH, with a degree of hydrolysis of 4%, was fractionated by size exclusion chromatography on a Sephadex G-25 into five major fractions (F1-F5). F2, which exhibited the highest antibacterial and ACE-inhibitory activities, and F4, which exhibited the highest antibacterial and antioxidant activities, were further fractionated by reverse phase-high performance liquid chromatography (RP-HPLC) and then analysed using nano-ESI-LC-MS/MS to identify the sequences of peptides. Eight peptides were identified in the sub-fraction F2-A, nine peptides in the sub-fraction F4-B, and 45 peptides in F4-C. Identified peptides were found to share sequences with previously described bioactive peptides based on Biopep database. The results of this study suggest that SPH is a good source of natural bioactive peptides. Hence, it can be used as a potential ingredient in nutraceutical field.

Chitin extraction from blue crab (Portunus segnis) and shrimp (Penaeus kerathurus) shells using digestive alkaline proteases from P. segnis viscera

Since chitin is closely associated with proteins, deproteinization is a crucial step in the process of extracting chitin. Thus, this research aimed to extract chitin from Portunus segnis and Penaeus kerathurus shells by means of crude digestive alkaline proteases from the viscera of P. segnis, regarding deproteinization step, as an alternative to chemical treatment. Casein zymography revealed that five caseinolytic proteases bands exist, suggesting the presence of at least five different major proteases. The optimum pH and temperature for protease activity were pH 8.0 and 60°C, respectively, using casein as a substrate. The crude enzymes extract was highly stable at low temperatures and over a wide range of pH from 6.0 to 12.0. The crude alkaline protease extract was found to be effective in the deproteinization of blue crab and shrimp shells, to produce chitin. The best efficiency in deproteinization (84.69±0.65% for blue crab shells and 91.06±1.40% for shrimp shells) was achieved with an E/S ratio of 5U/mg of proteins after 3h incubation at 50°C. These results suggest that enzymatic deproteinization of crab and shrimp wastes by fish endogenous alkaline proteases could be a potential alternative in the chitin production process.

Beneficial effects of fermented sardinelle protein hydrolysates on hypercaloric diet induced hyperglycemia, oxidative stress and deterioration of kidney function in wistar rats

This study investigated the potential effects of fermented sardinelle protein hydrolysates (FSPHs) obtained by two proteolytic bacteria, Bacillus subtilis A26 (FSPH-A26) and Bacillus amyloliquefaciens An6 (FSPH-An6), on hypercaloric diet (HCD) induced hyperglycemia and oxidative stress in rats. Effects of FSPHs on blood glucose level, glucose tolerance, α-amylase activity and hepatic glycogen content were investigated, as well as their effect on the oxidative stress state. Biochemical findings revealed that, while undigested sardinelle proteins did not exhibit hypoglycemic activity, oral administration of FSPHs to HCD-fed rats reduced significantly α-amylase activity as well as glycemia and hepatic glycogen levels. Further, the treatment with FSPHs improved the redox status by decreasing the levels of lipid peroxidation products and increasing the activities of the antioxidant enzymes (superoxide dismutase, glutathione peroxidase and catalase) and the level of glutathione in the liver and kidneys, as compared to those of HCD-fed rats. FSPHs were also found to exert significant protective effects on liver and kidney functions, evidenced by a marked decrease in alkaline phosphatase activity and a modulation of creatinine and uric acid contents. These results indicated the beneficial effect of FSPHs on the prevention from hyperglycemia and oxidative stress.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Hypolipidemic, antiobesity and cardioprotective effects of sardinelle meat flour and its hydrolysates in high-fat and fructose diet fed Wistar rats

AIMS

The present study aims to evaluate the antiobesity, hypolipidemic and cardioprotective effects of fermented sardinelle (Sardinella aurita) protein hydrolysates (FSPHs) produced with two proteolytic bacteria, Bacillus subtilis A26 (FSPH-A26) and Bacillus amyloliquefaciens An6 (FSPH-An6).

MAIN METHODS

Wistar rats were fed during 10weeks a standard laboratory diet, a high caloric diet (HCD) and a HCD coupled with the oral administration of sardinelle meat flour (SMF) or FSPHs.

KEY FINDINGS

HCD caused hyperlipidemia and increased body weight (BW). The daily oral administration of FSPHs or SMF reduced the total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-c) serum levels, and increased the level of high-density lipoprotein cholesterol (HDL-c). Nevertheless, FSPHs were found to be more efficient than SMF. FSPHs also lowered hepatic TC and TG content and decreased the pancreatic lipase activity. Further, the administration of FSPHs or SMF decreased the BW gain, the food intake and the relative epididymal adipose tissue weight. FSPHs exhibited a potent cardioprotective effect against heart attack, which was demonstrated by returning atherogenic indexes to their normal levels and the conservation of standard histological structure of the heart and aorta.

SIGNIFICANCE

The overall results indicate that FSPHs contained bioactive peptides which significantly attenuated hyperlipidemia, and might reduce the risk of cardiovascular disease (CVD) in rats fed HCD.

Acute and sub-chronic oral toxicity profiles of lipopeptides from Bacillus mojavensis A21 and evaluation of their in vitro anticoagulant activity

The aim of the present study was to evaluate the acute and sub-chronic toxicity of lipopeptides mixture produced by Bacillus mojavensis A21 as well as their in vitro anticoagulant activity. A21 lipopeptides was given to mice at single dose from 75 mg to 1000 mg/kg body weight (bw). The median lethal dose (LD50) of A21 lipopeptides was about 550 mg/kg bw. Sub-chronic toxicity study for 28 days was done by daily oral administration of A21 lipopeptides at doses of 40 and 400 mg/kg bw in rats. Results showed that A21 lipopeptides did not cause any change in body weights and they did not produce any marked alterations in the hematological blood parameters including hematocrit concentration, hemoglobin level, white and red cells count. However, the platelets level decreased significantly compared to control value. Moreover, no significant differences in the serum biochemical characteristics were observed for rats treated by the lowest dose. In contrast, a little enhancement of alanine-aminotransferase (ALT) activity and decrease in total cholesterol were observed with the highest dose. A21 lipopeptides were also found to cause a prolongation of the thrombin time (TT), the prothrombin time (PT) and the activated partial thromboplastin time (APTT). Overall, A21 lipopeptides may be very promising compounds for therapeutic purposes.