Effects of a polysaccharide-rich extract derived from Irish-sourced Laminaria digitata on the composition and metabolic activity of the human gut microbiota using an in vitro colonic model.

BACKGROUND: Brown seaweeds are known to be a rich source of fiber with the presence of several non-digestible polysaccharides including laminarin, fucoidan and alginate. These individual polysaccharides have previously been shown to favorably alter the gut microbiota composition and activity albeit the effect of the collective brown seaweed fiber component on the microbiota remains to be determined. METHODS: This study investigated the effect of a crude polysaccharide-rich extract obtained from Laminaria digitata (CE) and a depolymerized CE extract (DE) on the gut microbiota composition and metabolism using an in vitro fecal batch culture model though metagenomic compositional analysis using 16S rRNA FLX amplicon pyrosequencing and short-chain fatty acid (SCFA) analysis using GC-FID. RESULTS: Selective culture analysis showed no significant changes in cultured lactobacilli or bifidobacteria between the CE or DE and the cellulose-negative control at any time point measured (0, 5, 10, 24, 36, 48 h). Following metagenomic analysis, the CE and DE significantly altered the relative abundance of several families including Lachnospiraceae and genera including Streptococcus, Ruminococcus and Parabacteroides of human fecal bacterial populations in comparison to cellulose after 24 h. The concentrations of acetic acid, propionic acid, butyric acid and total SCFA were significantly higher for both the CE and DE compared to cellulose after 10, 24, 36 and 48 h fermentation (p < 0.05). Furthermore, the acetate:propionate ratio was significantly reduced (p < 0.05) for both CD and DE following 24, 36 and 48 h fermentation. CONCLUSION: The microbiota-associated metabolic and compositional changes noted provide initial indication of putative beneficial health benefits of L. digitata in vitro; however, research is needed to clarify if L. digitata-derived fiber can favorably alter the gut microbiota and confer health benefits in vivo.

The effect of consuming Palmaria palmata-enriched bread on inflammatory markers, antioxidant status, lipid profile and thyroid function in a randomised placebo-controlled intervention trial in healthy adults.

PURPOSE: Palmaria palmata (P. Palmata) is reported to contain anti-inflammatory and antioxidant compounds albeit no study has investigated these effects in humans. METHODS: A randomised parallel placebo-controlled human intervention study was carried out to investigate the effect of consuming P. Palmata (5 g/day) incorporated into a bread on serum markers of inflammation [C-reactive protein (CRP); cytokine analysis] with secondary analysis investigating changes in lipids (cholesterol, triglycerides), thyroid function [thyroid-stimulating hormone (TSH)] and antioxidant status ferric reducing antioxidant power. ANCOVA with baseline values as covariates, controlling for age, BMI, sex and smoking status, was used to compare differences between treatment groups over time . In vitro studies investigated the inflammatory activity of P. Palmata extracts (hot water, cold water and ethanol extract), protein extracts and associated protein hydrolysates using a Caco-2 inflammation cell model. RESULTS: Consumption of P. Palmata-enriched bread significantly increased serum CRP (+16.1 %, P = 0.011), triglycerides (+31.9 %, P = 0.001) and TSH (+17.2 %, P = 0.017) when compared to the control group. In vitro evaluation of P. palmata extracts and protein hydrolysates identified a significant induction of IL-8 secretion by Caco-2 cells, and the hot water P. palmata extract was shown to increase adipocyte glycerol release (P < 0.05). CONCLUSION: Evidence from this human study suggests that P. palmata stimulates inflammation, increases serum triglycerides and alters thyroid function; however, these changes are not likely to impact health as changes remained within the normal clinical range. The data from the in vitro study provided indications that IL-8 may contribute to the apparent immunostimulation noted in the human study.

Cardioprotective potential of Irish macroalgae: generation of glycine betaine and dimethylsulfoniopropionate containing extracts by accelerated solvent extraction.

Accelerated solvent extraction (ASE®) was used to generate 18 macroalgal extracts from Irish seaweeds. The glycine betaine and dimethylsulfoniopriopionate content of the generated ASE® extracts were estimated using (1)H-NMR and confirmed for selected extracts using ultra performance liquid chromatography and mass spectrometry. Dimethylsulfoniopriopionate was only identified in the ASE® extract generated from Codium fragile ISCG0029. Glycine betaine was identified in the ASE® extract generated from Ulva intestinalis ISCG0356 using (1)H-NMR. Mass spectrometry analysis found that the seaweed species Cytoseira nodicaulis ISCG0070, Cytoseira tamariscofolia ISCG0283, and Polysiphonia lanosa ISCG0462 also had a glycine betaine content that ranged from 1.39 ng/ml to 105.11 ng/ml. Generated ASE® macroalgal extracts have potential for use as functional food ingredients in food products.

Seasonal and geographical variations in the biochemical composition of the blue mussel (Mytilus edulis L.) from Ireland.

Blue mussel (Mytilus edulis L.) farming constitutes the largest volume of the shellfish sector in Ireland. Recently, interest in mussel dietary supplements and functional foods has increased significantly. To identify the optimal harvesting time and location in Ireland, blue mussels were investigated for their biochemical composition over a period of one year. The study included samples from aquaculture facilities, wild grown mussels and waste material. Each sample was analysed at four time points to determine the total content of (i) glycogen, (ii) lipids, (iii) proteins, (iv) inorganic substances, and (v) energy. Moreover, fatty acid profiles were investigated by GC-FID revealing high contents of PUFAs and a high ω-3/ω-6 ratio. Compared to less pronounced geographical variations, distinct seasonal trends could be observed for all samples. The content of the investigated metabolite classes, inorganic substances, and energy was at a maximum level in spring or late summer.

Inclusion of Palmaria palmata (red seaweed) in Atlantic salmon diets: effects on the quality, shelf-life parameters and sensory properties of fresh and cooked salmon fillets.

BACKGROUND: The use of Palmaria palmata (PP) as a natural ingredient in farmed Atlantic salmon diets was investigated. The effect of salmon diet supplementation with P. palmata (0, 5, 10 and 15%) or synthetic astaxanthin (positive control, PC) for 16 weeks pre-slaughter on quality indices of fresh salmon fillets was examined. The susceptibility of salmon fillets/homogenates to oxidative stress conditions was also measured. RESULTS: In salmon fillets stored in modified atmosphere packs (60% N2 /40% CO2 ) for up to 15 days at 4 °C, P. palmata increased surface -a* (greenness) and b* (yellowness) values in a dose-dependent manner, resulting in a final yellow/orange flesh colour. In general, the dietary addition of P. palmata had no effect on pH, lipid oxidation (fresh, cooked and fillet homogenates) and microbiological status. 'Eating quality' sensory descriptors (texture, odour and oxidation flavour) in cooked salmon fillets were not influenced by dietary P. palmata. Salmon fed 5% PP showed increased overall acceptability compared with those fed PC and 0% PP. CONCLUSION: Dietary P. palmata was ineffective at providing red coloration in salmon fillets, but pigment deposition enhanced fillets with a yellow/orange colour. Carotenoids from P. palmata may prove to be a natural pigment alternative to canthaxanthin in salmon feeds.

The α-amylase and α-glucosidase inhibitory effects of Irish seaweed extracts.

To date, numerous studies have reported on the antidiabetic properties of various plant extracts through inhibition of carbohydrate-hydrolysing enzymes. The objective of this research was to evaluate extracts of seaweeds for α-amylase and α-glucosidase inhibitory effects. Cold water and ethanol extracts of 15 seaweeds were initially screened and from this, five brown seaweed species were chosen. The cold water and ethanol extracts of Ascophyllum nodosum had the strongest α-amylase inhibitory effect with IC50 values of 53.6 and 44.7 µg/ml, respectively. Moreover, the extracts of Fucus vesiculosus Linnaeus were found to be potent inhibitors of α-glucosidase with IC50 values of 0.32 and 0.49 µg/ml. The observed effects were associated with the phenolic content and antioxidant activity of the extracts, and the concentrations used were below cytotoxic levels. Overall, our findings suggest that brown seaweed extracts may limit the release of simple sugars from the gut and thereby alleviate postprandial hyperglycaemia.

Enrichment of polyphenol contents and antioxidant activities of Irish brown macroalgae using food-friendly techniques based on polarity and molecular size.

An efficient, food-friendly process for the enrichment of macroalgal phlorotannins from solid-liquid extracts (SLE) of three brown macroalgae, namely Fucus spiralis Linnaeus, Pelvetia canaliculata (Linnaeus) Decaisne & Thuret and Ascophyllum nodosum (Linnaeus) Le Jolis, has been demonstrated. The initial utilisation of molecular weight cut-off (MWCO) dialysis generated fractions of low molecular weight (LMW) (<3.5 kDa) and of high molecular weight (HMW) (3.5-100 kDa and >100 kDa) from cold water, hot water and aqueous ethanolic SLE extracts. An enhancement of the total phenolic content (TPC), radical scavenging abilities (RSA) and ferric reducing antioxidant power (FRAP) in the HMW fractions of 3.5-100 kDa and/or >100 kDa from the cold water and aqueous ethanolic extracts was observed. The initial weak TPC, RSA and FRAP observed in the LMW fractions relative to the HMW fractions were substantially enhanced following a reverse-phase flash chromatography fractionation method. Quadrupole time-of-flight mass spectrometry (Q-Tof-MS) suggests that phlorotannins of varying degrees of phloroglucinol polymerisation are present in LMW fractions of the three brown macroalgal species. The development of a food-friendly process for the extraction and enrichment of phlorotannins from Irish macroalgae is vital to facilitate the use of this valuable resource in future developments of macroalgal-based functional foods.

Isolation and characterization of bioactive pro-peptides with in vitro renin inhibitory activities from the macroalga Palmaria palmata.

Renin is the initial rate limiting step in the renin angiotensinogen system (RAS). To combat hypertension, various stages of the RAS can be positively affected. The aim of this study was to isolate and characterize renin inhibitory peptides from the red seaweed P. palmata for use in functional foods. Palmaria palmata protein was extracted and hydrolyzed with the food grade enzyme Papain to generate renin inhibitory peptides. Following proteolytic hydrolysis of P. palmata protein, reverse phase-high performance liquid chromatography (RP-HPLC) was employed to enrich for peptides with renin inhibitory activities. Fraction 25 (Fr-25) inhibited renin activities by 58.97% (±1.26) at a concentration of 1 mg/mL. This fraction was further characterized using nano-electrospray ionization quadropole/time-of-flight mass spectrometry (ESI-Q/TOF MS). A number of novel peptide sequences were elucidated, and the parent protein from which they were derived was determined using MS in tandem with protein database searches. All sequences were confirmed using de novo sequencing. The renin inhibitory peptide Ile-Arg-Leu-Ile-Ile-Val-Leu-Met-Pro-Ile-Leu-Met-Ala (IRLIIVLMPILMA) was chemically synthesized and its bioactivity confirmed using the renin inhibitory assay. Other stages of the RAS have recently been inhibited by bioactive peptides sourced from macroalgae, but this is the first study to isolate and characterize renin inhibitory peptides from the macroalgae.