Mohamed Hajji

Structural, physicochemical and antioxidant properties of sodium alginate isolated from a Tunisian brown seaweed

An original sodium alginate from Tunisian seaweed (Cystoseira barbata) was purified and characterized by circular dichroism (CD) and ATR-FTIR spectroscopies. ATR-FTIR spectrum of C. barbata sodium alginate (CBSA) showed the characteristic bands of mannuronic (M) and guluronic acids (G). The M/G ratio was estimated by CD (M/G = 0.59) indicating that CBSA was composed of 37% mannuronic acid and 63% guluronic acid. The analysis of viscosity of CBSA showed evidence of pseudoplastic fluid behaviour. The emulsifying capacity of CBSA was evaluated at different concentrations (0.25-3%), temperatures (25-100 °C) and pH (3.0-11.0). Compared to most commercial emulsifiers, the emulsion formulated by CBSA was found to be less sensitive to temperature changes and more stable at acidic pH. CBSA was examined for antioxidant properties using various antioxidant assays. CBSA exhibited important DPPH radical-scavenging activity (74% inhibition at a concentration of 0.5 mg/ml) and considerable ferric reducing potential. Effective hydroxyl-radical scavenging activity (82% at a concentration of 5 mg/ml) and potent protection activity against DNA breakage were also recorded for CBSA. However, in the linoleate-β-carotene system, CBSA exerted moderate antioxidant activity (60% at a concentration of 1.5 mg/ml). Therefore, CBSA can be used as a natural ingredient in food industry or in the pharmaceutical field.

Fucans from a Tunisian brown seaweed Cystoseira barbata: Structural characteristics and antioxidant activity

Sulfated polysaccharides from brown seaweeds are known to be a topic of numerous studies, due to their beneficial biological properties including antioxidant activity. Fucans were isolated from the brown seaweed Cystoseira barbata harvested in Tunisia. ATR-FTIR and (1)H-NMR spectroscopies demonstrated that C. barbata sulfated polysaccharides (CBSPs) consisted mainly of 3-linked-α-l-fucopyranosyl backbone, acetylated and mostly sulfated at C-4. Molar degrees of sulfation and acetylation of CBSPs were 0.79 and 0.27, respectively. Neutral sugars analysis determined by gas chromatography-mass spectrometry (GC-MS) showed that CBSPs were mainly composed of fucose (44.6%) and galactose (34.32%) with few amounts of other sugars such as glucose (7.55%), rhamnose (6.41%), xylose (4.21%) and mannose (2.91%). CBSPs were examined for in vitro antioxidant properties using various antioxidant assays. CBSPs exhibited important DPPH radical-scavenging activity (100% inhibition at a concentration of 1.5mg/ml) and considerable ferric reducing potential (24.62 mg ascorbic acid equivalents). Effective chelating activity and significant protection activity against hydroxyl radical induced DNA breakage were also recorded for CBSPs. However, in the linoleate-β-carotene system, CBSPs exerted moderate antioxidant activity (62% inhibition at a concentration of 1.5mg/ml). Therefore, CBSPs can be used as a potent natural antioxidant in food industry or in the pharmaceutical field.

A peptidomic approach for the identification of antioxidant and ACE-inhibitory peptides in sardinelle protein hydrolysates fermented by Bacillus subtilis A26 and Bacillus amyloliquefaciens An6

Antioxidant and angiotensin I-converting enzyme (ACE)-inhibitory activities of sardinelle (Sardinella aurita) protein hydrolysates (SPHs) obtained by fermentation with Bacillus subtilis A26 (SPH-A26) and Bacillus amyloliquefaciens An6 (SPH-An6) were investigated. Both hydrolysates showed dose-dependent antioxidant activities evaluated using various in vitro antioxidant assays. Further, they were found to exhibit ACE-inhibitory activity. Peptides from SPH-A26 and SPH-An6 were analyzed by nESI-LC-MS/MS and approximately 800 peptides were identified. Identified peptides derived mainly from myosin (43% and 31% in SPH-An6 and SPH-A26, respectively). Several peptides identified in both hydrolysates were found to share sequences with previously identified antioxidant and ACE-inhibitory peptides based on Biopep database. Some of these peptides were selected for synthesis and their biological activities were evaluated. Among the synthesized peptides, NVPVYEGY and ITALAPSTM were found to be the most effective ACE-inhibitors with IC50 values of 0.21 and 0.23mM, respectively. On the other hand, NVPVYEGY, which exhibited the highest ACE-inhibitory activity, showed the highest reducing power and peroxyl radical scavenging activities, followed by SLEAQAEKY and GTEDELDKY. The results of this study suggest that fermented sardinelle protein hydrolysates are a good source of natural antioxidant peptides and could have the potential to act as hypotensive nutraceutical ingredients.

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 10 weeks 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. HighlightsFermented sardinelle protein hydrolysates (FSPHs) were prepared by two proteolytic bacteria.Hypercaloric diet (HCD) induced obesity and hyperlipidemia.FSPHs were found to attenuate obesity and hyperlipidemia in HCD‐fed rats.FSPHs exhibited a potent cardioprotective effect.FSPHs could be used as ingredients to formulate functional foods.

Polyphenolic-protein-polysaccharide ternary conjugates from Cystoseira barbata Tunisian seaweed as potential biopreservatives: Chemical, antioxidant and antimicrobial properties

The present study investigated the antioxidant and antimicrobial activities of naturally occurring Cystoseira barbata seaweed glyco-conjugates (CBGs), with a view to developing safer food preservatives. CBGs were successfully isolated, then chemically and structurally characterized. CBGs contained a high amount of polysaccharides (49.76%) that consisted mainly of neutral sugars (47.67%) and uronic acids (2.09%). The carbohydrate fraction was sulfated (13.81%) and conjugated with proteins (9.86%) and phenolic compounds (4.98%). Infrared spectroscopy of CBGs showed interactions between polyphenols, proteins and polysaccharides, which were characterized by α-type glycosidic bond and sulfate groups in the axial position of sugar residues. Neutral sugars analysis of CBGs by GC-MS revealed that conjugated polysaccharides were mainly composed of galactose (34.02%), fucose (26.25%) and mannitol (21.25%) with few amounts of other sugars such as glucose (5.78%), rhamnose (4.9%), xylose (3.22%) and mannose (2.22%). Analysis of the amino acid composition of CBGs showed a high level of essential amino acids (40.36%), in which threonine was the most relevant (10.28%). LC-QTOF-MS analysis of the phenolic fraction of CBGs showed a variety of phenolic compounds including flavonoids, phlorotannins and anthraquinone glycosides. CBGs exhibited potent antioxidant activities including radical scavenging activity, chelating ability and reducing power, and displayed noticeable antibacterial and antifungal activities, which may open the way to the development of a natural biopreservation strategy based on algae.

Safer and healthier reduced nitrites turkey meat sausages using lyophilized Cystoseira barbata seaweed extract

Abstract Background Nitrite salts are still common additives in the meat industry. The present study provides a first approach on the employment of the lyophilized aqueous extract (WE) of the Tunisian seaweed Cystoseira barbata for the quality enhancement of turkey meat sausage. Methods WE was supplemented as a natural antioxidant agent to investigate its effectiveness in delaying lipid oxidation turkey meat sausages containing reduced amounts of sodium nitrites. Results On storage day 5, all concentrations of WE (0.01–0.4 %) reduced the meat lipid oxidation by approximately 36 %, as compared to the negative control containing only 80 mg/kg of meat of sodium nitrites as antioxidant. It was noted that within 15 days of refrigerated storage, a meat system containing 80 mg/kg of meat of sodium nitrites and 0.02 % and 0.04 % of WE had similar Thiobarbituric Acid Reactive Substances (TBARS) levels (19±1.32 and 17±1.12 µmol/kg of meat, respectively), which were comparable to the positive control containing sodium nitrites (150 mg/kg of meat) and 0.045 % vitamin C (18.46±1.27 µmol/kg of meat). In-depth, the metabolomic profiling using gas chromatography–mass spectrometry (GC/MS) and liquid chromatography–quadripole–time–of–flight–mass spectrometry (LC-QTOF-MS) analyses of the Tunisian seaweed C. barbata solvent extracts showed that the main active compounds were phenolic compounds, fatty acids and sterols. Conclusions Overall, the cold medium containing C. barbata lyophilized aqueous extrac, with strong antioxidant activity and antihypertensive properties, may open the way to the development of a natural quality enhancement strategy for new functional and ever healthier reduced nitrites meat sausages based on algae.

Antioxidant, antibacterial and in vivo wound healing properties of laminaran purified from Cystoseira barbata seaweed

Laminaran, a polysaccharide extracted from marine algae, exhibits attractive properties being non-toxic, hydrophilic and biodegradable. The aim of this study was to investigate the effectiveness of a cream based on the brown seaweed Cystoseira barbata laminaran (CBL) for healing full thickness wounds induced on rats. The antibacterial activity of CBL was evaluated against Gram positive and Gram negative bacteria and the antioxidant properties were assessed using five different assays. To highlight the healing effectiveness of CBL-based cream, the response to treatment was assessed by macroscopic, histologic and biochemical parameters and was compared to controls. CBL, recovered (7.27%) by ultrafiltration (1-10 kDa) and predominantly consisted of (1 → 3)-linked β-d-glucopyranose residues with a small level of (1 → 6)-glycosidic bonds, showed noticeable antioxidant and antibacterial properties. The cream containing CBL as an active ingredient exerted a promoting healing effect. The wound contraction reached 98.57 ± 1.31% after thirteen days of treatment. The derma in CBL treated group is properly arranged and revealed an improved collagen deposition and an increased fibroblast and vascular densities compared with the control groups. Overall, these results established, for the first time, a scientific in vivo evidence of the efficiency of CBL as a wound healing agent of interest in modern medicine.

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.