Bifurcaria bifurcata extract exerts antioxidant effects on human Caco-2 cells.

The present research study investigated the potential protective effect of Bifurcaria bifurcata extract on cell viability and antioxidant defences of cultured human Caco-2 cells submitted to oxidative stress induced by tert-butylhydroperoxide (tert-BOOH). Aqueous extracts were firstly characterized in terms of total phenolic contents. Concentrations of reduced glutathione (GSH) and malondialdehyde (MDA), generation of reactive oxygen species (ROS), nitric oxide (NO) production, antioxidant enzymes activities [NADPH quinone dehydrogenase 1 (NQO1) and glutathione S-transferase (GST)], caspase 3/7 activity and gene expression linked to apoptosis, proinflammation and oxidative stress signaling pathways were used as markers of cellular oxidative status. B. bifurcata extract prevented the cytotoxicity, the decrease of GSH, the increase of MDA levels and the ROS generation induced by tert-BOOH. B. bifurcata extract prevented the significant decrease of NQO1 and GST activities, and the significant increase of caspase 3/7 activity induced by tert-BOOH. B. bifurcata extract also caused an over-expression of GSTM2, Nrf2 and AKT1 transcriptors, as well as reduced ERK1, JNK1, Bax, BNIP3, NFκB1, IL-6 and HO-1 gene expressions induced by tert-BOOH suggesting an increase in cellular resistance against oxidative stress. The results of the biomarkers analyzed show that treatment of Caco-2 cells with B. bifurcata extract enhance antioxidant defences, which imply an improved cell response to an oxidative challenge. B. bifurcata extract possesses strong antioxidant properties and may be a potential effective alternative to oxidant agents in the functional food industry.

Brown Macroalgae (Phaeophyceae): A Valuable Reservoir of Antimicrobial Compounds on Northern Coast of Spain.

The search for new sources of antimicrobial compounds has become an urgent need, due to the threat that the spread of bacterial resistance represents for global health and food safety. Brown macroalgae have been proposed as a great reservoir in the search for novel antimicrobial compounds. In this study, mid-polarity extracts were performed with a selection of 20 brown macroalgae species from northern Spain. The total polyphenol, carbohydrate and protein contents were quantified by spectrophotometry. The volatile organic compounds (VOCs) of whole macroalgae were also studied as a biomarker of their metabolic state in the representative species of the tested families by gas chromatography-mass spectrometry (GC-MS). The antimicrobial potential of the extracts was assessed by a disk diffusion assay against 20 target bacteria and further determinations of the minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) were performed by a microdilution assay for the active extracts. Ericaria selaginoides, Bifurcaria bifurcata and Dictyota dichotoma showed an antimicrobial effect against six Gram-positive strains: Bacillus cereus, Bacillus subtilis, Geobacillus stearothermophilus, Listeria monocytogenes, Staphylococcus aureus and Staphylococcus haemolyticus. The phenolic content was generally higher in the extracts that showed antimicrobial activity, followed by carbohydrates and low contents of proteins. The results obtained in this study reveal the potential of brown macroalgae as a promising alternative source of antimicrobial compounds as functional ingredients for the application in industrial fields.

Taurine, homotaurine, GABA and hydrophobic amino acids content influences "in vitro" antioxidant and SIRT1 modulation activities of enzymatic protein hydrolysates from algae.

Prevention and control of diseases and delaying the signs of ageing are nowadays one of the major goals of biomedicine. Sirtuins, a family of NAD+ dependent deacylase enzymes, could be pivotal targets of novel preventive and therapeutic strategies to achieve such aims. SIRT1 activating and inhibiting compounds, such as polyphenols and bioactive peptides, have been proposed to be involved in the development of many human diseases. The objective of this work was to assess and compare the antioxidant and SIRT1 modulation activities of enzymatic protein hydrolysates (EPHs) from a wide number of algae species (24 commercial samples and 12 samples harvested off the Atlantic coast of northern Spain). High antioxidant activities were observed in EPHs from red and green seaweed species. Moreover, 19 samples exhibited SIRT1 activation, while EPHs from the 16 samples were SIRT1 inhibitors. Pearson's correlation test and Principal Component Analysis revealed significant correlations between (1) total peptide and hydrophobic amino acid content in EPHs and their antioxidant activities, and (2) concentrations of taurine, homotaurine, and amino acid gamma aminobutyric acid in EPHs and their SIRT1 modulation activity.

Brown marine algae Gongolaria baccata extract protects Caco-2 cells from oxidative stress induced by tert-butyl hydroperoxide.

Gongolaria baccata (S.G. Gmelin) is marine brown seaweed mainly found on the coasts of the Baltic Sea south to the Mediterranean Sea, Canary Islands, Mauritania and Western Sahara. Herein, we report the cell viability and protective effects attributed to molecular mechanisms underlying antioxidant response to survive oxidative stress injuries. Caco-2 cells were submitted to oxidative stress by treatment with tert-butylhydroperoxide (tert-BOOH). The extract prevented cell damage and enhanced activity of antioxidant defenses (NQO1 and GST activities and GSH levels) reduced by treatment with tert-BOOH. The increases of MDA levels, the amount of intracellular ROS and caspase 3/7 activity induced by tert-BOOH were prevented when cells were treated with the G. baccata extract. Moreover, G. baccata extract caused up-regulation of GSTM2, Nrf2, and AKT1 gene expressions, as well as G. baccata extract reduced significantly Bax, BNIP3, APAF1, ERK1, JNK1, MAPK1, P38, P53, NFκB1, TNFα, IL-6, IL-1ß and HO-1 gene expressions related to apoptosis, proinflammation and oxidative stress induced by tert-BOOH. These results suggest that G.baccata extract protected the cells against oxidative damage and inflammation; protective effects that could be linked to their bioactive constituents. Hence, this brown seaweed G.baccata extract could be used for the development of functional foods and/or nutraceuticals.

Preclinical studies of toxicity and safety of the AS-48 bacteriocin.

The in vitro antimicrobial potency of the bacteriocin AS-48 is well documented, but its clinical application requires investigation, as its toxicity could be different in in vitro (haemolytic and antibacterial activity in blood and cytotoxicity towards normal human cell lines) and in vivo (e.g. mice and zebrafish embryos) models. Overall, the results obtained are promising. They reveal the negligible propensity of AS-48 to cause cell death or impede cell growth at therapeutic concentrations (up to 27 µM) and support the suitability of this peptide as a potential therapeutic agent against several microbial infections, due to its selectivity and potency at low concentrations (in the range of 0.3-8.9 µM). In addition, AS-48 exhibits low haemolytic activity in whole blood and does not induce nitrite accumulation in non-stimulated RAW macrophages, indicating a lack of pro-inflammatory effects. The unexpected heightened sensitivity of zebrafish embryos to AS-48 could be due to the low differentiation state of these cells. The low cytotoxicity of AS-48, the absence of lymphocyte proliferation in vivo after skin sensitization in mice, and the lack of toxicity in a murine model support the consideration of the broad spectrum antimicrobial peptide AS-48 as a promising therapeutic agent for the control of a vast array of microbial infections, in particular, those involved in skin and soft tissue diseases.

Control of Propionibacterium acnes by natural antimicrobial substances: Role of the bacteriocin AS-48 and lysozyme.

We report the high susceptibility of several clinical isolates of Propionibacterium acnes from different sources (skin, bone, wound exudates, abscess or blood contamination) to the head-to-tail cyclized bacteriocin AS-48. This peptide is a feasible candidate for further pharmacological development against this bacterium, due to its physicochemical and biological characteristics, even when it is growing in a biofilm. Thus, the treatment of pre-formed biofilms with AS-48 resulted in a dose- and time-dependent disruption of the biofilm architecture beside the decrease of bacterial viability. Furthermore, we demonstrated the potential of lysozyme to bolster the inhibitory activity of AS-48 against P. acnes, rendering high reductions in the MIC values, even in matrix-growing cultures, according to the results obtained using a range of microscopy and bioassay techniques. The improvement of the activity of AS-48 through its co-formulation with lysozyme may be considered an alternative in the control of P. acnes, especially after proving the absence of cytotoxicity demonstrated by these natural compounds on relevant human skin cell lines. In summary, this study supports that compositions comprising the bacteriocin AS-48 plus lysozyme must be considered as promising candidates for topical applications with medical and pharmaceutical purposes against dermatological diseases such as acne vulgaris.

LAB Bacteriocins Controlling the Food Isolated (Drug-Resistant) Staphylococci.

Staphylococci are a group of microorganisms that can be often found in processed food and they might pose a risk for human health. In this study we have determined the content of staphylococci in 7 different fresh goat-milk cheeses. These bacteria were present in all of them, ranging from 103 to 106 CFU/g based on growth on selective media. Thus, a set of 97 colonies was randomly picked for phenotypic and genotypic identification. They could be clustered by RAPD-PCR in 10 genotypes, which were assigned by 16S rDNA sequencing to four Staphylococcus species: Staphylococcus aureus, Staphylococcus chromogenes, S. simulans, and S. xylosus. Representative strains of these species (n = 25) were tested for antibiotic sensitivity, and 11 of them were resistant to at least one of the antibiotics tested, including erythromycin, amoxicillin-clavulanic acid and oxacillin. We also tested two bacteriocins produced by lactic acid bacteria (LAB), namely the circular bacteriocin AS-48 and the lantibiotic nisin. These peptides have different mechanism of action at the membrane level. Nevertheless, both were able to inhibit staphylococci growth at low concentrations ranging between 0.16-0.73 µM for AS-48 and 0.02-0.23 µM for nisin, including the strains that displayed antibiotic resistance. The combined effect of these bacteriocins were tested and the fractional inhibitory concentration index (FICI) was calculated. Remarkably, upon combination, they were active at the low micromolar range with a significant reduction of the minimal inhibitory concentration. Our data confirms synergistic effect, either total or partial, between AS-48 and nisin for the control of staphylococci and including antibiotic resistant strains. Collectively, these results indicate that the combined use of AS-48 and nisin could help controlling (pathogenic) staphylococci in food processing and preventing antibiotic-resistant strains reaching the consumer in the final products.