Now showing 1 - 9 of 9
  • Publication
    Polysaccharides from macroalgae: Recent advances, innovative technologies and challenges in extraction and purification
    Polysaccharides obtained from macroalgae have promising prospects and could contribute greatly to the future of a marine based bio-economy. Specifically, laminarin and fucoidan from brown macroalgae have a wide variety of potential industrial applications including functional foods and nutraceuticals, due to their broad range of biological activities. These beneficial biological activities are related to the chemical composition and structure of the macroalgal polysaccharides. The molecular weight, monosaccharide composition and sulphate content of these polysaccharides could be influenced by both macroalgal biology (i.e. variations in polysaccharide composition due to macroalgae species and their biological cycle) and different extraction/purification techniques employed to obtain polysaccharide enriched products (i.e. de-sulphation or fragmentation of sulphated polysaccharides). This review focuses on the extraction and purification methods for the macroalgal polysaccharides laminarin and fucoidan used in the recent literature. The application of innovative extraction technologies (such as ultrasound, microwave and enzyme-assisted extractions), as well as new purification techniques (i.e. membrane separation), are also discussed together with the challenges concerning molecule structure-function relationship and macroalgal variability.
    Scopus© Citations 241  3298
  • Publication
    Effect of seasons on the proximate composition of Laminaria hyperborea from Irish Atlantic coast
    This study aimed to analyze the seasonal variation in the proximate composition of Laminaria hyperborea collected in 2016 and 2017, off the west coast of Ireland.
      48
  • Publication
    Optimization and validation of reverse phase HPLC method for qualitative and quantitative assessment of polyphenols in seaweed
    (Elsevier, 2018-01-30)
    A simple reverse phase-high performance liquid chromatography (RP–HPLC) coupled to a diode array detector (DAD) and negative ion electrospray mass spectrometer (ESI–MS) method was developed for simultaneous identification and quantification of phenolic antioxidants in seaweed. The proposed method was validated in terms of linearity, limits of detection (LOD), limits of quantification (LOQ), recovery and intermediate precision. The calibration curves were linear with correlation coefficient ranging from 0.9909 to 0.9997 while the values of LOD (0.26–0.82 mg/L), LOQ (0.77–2.50 mg/L), recovery (≥97.2%) and precision in terms of retention time (%RSD ≤2.27) and peak area (% RSD ≤5.11) were satisfactory. Brown seaweed Himanthalia elongata used in this study was extracted with 60% methanol and the crude extract was cleaned with SPE (Solid Phase Extraction) cartridge. HPLC-DAD-MS/MS analysis of the SPE fraction allowed the identification of 7 phenolic compounds comprising phlorotannins, hydroxybenzoic acid, hydroxycinnamic acid and flavonols subclasses of polyphenols. Quantitative analysis of these compounds revealed the presence of phloroglucinol (394.1 ± 4.33 μg/g), gallic acid (96.3 ± 3.12 μg/g), chlorogenic acid (38.8 ± 1.94 μg/g), caffeic acid (44.4 ± 2.72 μg/g), ferulic acid (17.6 ± 0.85 μg/g), myricetin (8.6 ± 0.85 μg/g) and quercetin (4.2 ± 0.15 μg/g), in the extract. The SPE fraction were tested for antioxidant capacity which were significantly (P < 0.05) higher (EC50; 14.5 ± 0.57 mg/g) than the ascorbic acid (EC50; 35.8 ± 0.59 mg/g) and the crude extract (EC50; 46.3 ± 0.48 mg/g). The occurrence of all these phenolic antioxidant compounds in H. elongata extract suggested that the developed method is sensitive enough and reproducible and could be used for qualitative and quantitative assessment of polyphenols in seaweed.
    Scopus© Citations 74  777
  • Publication
    Enhancing the extraction of polysaccharides and antioxidants from macroalgae using sequential hydrothermal-assisted extraction followed by ultrasound and thermal technologies
    Fucose sulphated polysaccharides (FSPs) and glucans have recently attracted the attention of the scientific community due to their wide range of biological activities. Both polysaccharides should ideally be selectively extracted using innovative technologies with high extraction efficiency. This study aims to: (1) Optimise the extraction variables used in hydrothermal-assisted extraction (HAE) to obtain high yields of FSPs, total glucans, and antioxidants from Laminaria hyperborea; (2) to apply these optimised protocols to other brown macroalgae; and (3) to explore the application of ultrasound and thermal technologies to increase the recovery of polysaccharides from the residual biomass. Box-Behnken design (three-factor, four-levels) was employed to optimise the HAE variables, and principal component analysis was used to evaluate the recovery of polysaccharides from the residual biomass. The optimal HAE conditions were 120 ◦C, 80.9 min, and 12.02 mL/g macroalgae from L. hyperborea. The best sequential application of ultrasound and thermal treatment achieved an additional 2971.7 ± 61.9 mg fucose/100 g dried macroalgal residue (dmr) from Ascophyllum nodosum and 908.0 ± 51.4 mg total glucans/100 g dmr from L. hyperborea macroalgal residues.
    Scopus© Citations 59  228
  • Publication
    Characterization of dietary fucoxanthin from Himanthalia elongata brown seaweed
    This study explored Himanthalia elongata brown seaweed as a potential source of dietary fucoxanthin which is a promising medicinal and nutritional ingredient. The seaweed was extracted with low polarity solvents (n-hexane, diethyl ether, and chloroform) and the crude extract was purified with preparative thin layer chromatography (P-TLC). Identification, quantification and structure elucidation of purified compounds was performed by LC-DAD-ESI-MS and NMR (1 H and 13 C). P-TLC led purification yielded 18.6 mg/g fucoxanthin with 97% of purity based on the calibration curve, in single-step purification. LC-ESI-MS (parent ion at m/z 641 [M + H-H2O] +) and NMR spectra confirmed that the purified band contained all-trans-fucoxanthin as the major compound. Purified fucoxanthin exhibited statistically similar (p > 0.05) DPPH scavenging capacity (EC 50:12.9 μg/mL) while the FRAP value (15.2 μg trolox equivalent) was recorded lower (p < 0.05) than the commercial fucoxanthin. The promising results of fucoxanthin purity, recovery and activity suggested that H. elongata seaweed has potential to be exploited as an alternate source for commercial fucoxanthin production.
    Scopus© Citations 70  593
  • Publication
    Evaluation of Ultrasound, Microwave, Ultrasound–Microwave, Hydrothermal and High Pressure Assisted Extraction Technologies for the Recovery of Phytochemicals and Antioxidants from Brown Macroalgae
    This study aims to explore novel extraction technologies (ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), ultrasound–microwave-assisted extraction (UMAE), hydrothermal-assisted extraction (HAE) and high-pressure-assisted extraction (HPAE)) and extraction time post-treatment (0 and 24 h) for the recovery of phytochemicals and associated antioxidant properties from Fucus vesiculosus and Pelvetia canaliculata. When using fixed extraction conditions (solvent: 50% ethanol; extraction time: 10 min; algae/solvent ratio: 1/10) for all the novel technologies, UAE generated extracts with the highest phytochemical contents from both macroalgae. The highest yields of compounds extracted from F. vesiculosus using UAE were: total phenolic content (445.0 ± 4.6 mg gallic acid equivalents/g), total phlorotannin content (362.9 ± 3.7 mg phloroglucinol equivalents/g), total flavonoid content (286.3 ± 7.8 mg quercetin equivalents/g) and total tannin content (189.1 ± 4.4 mg catechin equivalents/g). In the case of the antioxidant activities, the highest DPPH activities were achieved by UAE and UMAE from both macroalgae, while no clear pattern was recorded in the case of FRAP activities. The highest DPPH scavenging activities (112.5 ± 0.7 mg trolox equivalents/g) and FRAP activities (284.8 ± 2.2 mg trolox equivalents/g) were achieved from F. vesiculosus. Following the extraction treatment, an additional storage post-extraction (24 h) did not improve the yields of phytochemicals or antioxidant properties of the extracts.
      127Scopus© Citations 24
  • Publication
    Exploring ultrasound-assisted extraction to recover high valuable polysaccharides from brown macroalgae and its related antioxidant activities
    This study aimed to optimize the ultrasound-assisted extraction (UAE) parameters of temperature, time and amplitude on the yields of fucose and glucans and their antioxidant activities (FRAP and DPPH) of extracts from Laminaria digitata and to evaluate the application of these optimum UAE parameters in other brown macroalgae (L. hyperborea and Ascophyllum nodosum).
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  • Publication
    Seasonal Variation of the Proximate Composition, Mineral Content, Fatty Acid Profiles and Other Phytochemical Constituents of Selected Brown Macroalgae
    The main objective was to determine the chemical, phytochemical, fatty acid and mineral profiles of three commercially relevant brown macroalgae (Laminaria digitata, Laminaria hyperborea and Ascophyllum nodosum) collected each season for two years off the west coast of Ireland. All the chemical, phytochemical, fatty acid and minerals analysed varied significantly depending on the macroalgal species, season and year of collection. Overall, the protein contents of macroalgae were negatively correlated with carbohydrate content. Protein (2–11%) was at its highest during winter and/or spring, decreasing to a minimum during summer and/or autumn. The three macroalgal species analysed in this study had clearly differentiated fatty acid profiles. The concentration of fatty acids was higher in A. nodosum compared with both Laminaria species. The mineral profile of the three macroalgal species was rich in essential metals, particularly Ca, Mg and P, while the levels of I were approximately 9- to 10-fold higher in both Laminaria spp. compared with A. nodosum. The levels of toxic metals (Cd, Hg and Pb) in all the macroalgal species studied were low in the current study; while the levels of total As were high (49–64 mg/kg DW macroalgae) compared with previous reports.
    Scopus© Citations 31  279
  • Publication
    Extraction and yield optimisation of fucose, glucans and associated antioxidant activities from laminaria digitata by applying response surface methodology to high intensity ultrasound-assisted extraction
    The objectives of this study were to employ response surface methodology (RSM) to investigate and optimize the effect of ultrasound-assisted extraction (UAE) variables, temperature, time and amplitude on the yields of polysaccharides (fucose and total glucans) and antioxidant activities (ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity (DPPH)) from Laminaria digitata, and to explore the suitability of applying the optimum UAE conditions for L. digitata to other brown macroalgae (L. hyperborea and Ascophyllum nodosum). The RSM with three-factor, four-level Box-Behnken Design (BBD) was used to study and optimize the extraction variables. A second order polynomial model fitted well to the experimental data with R2 values of 0.79, 0.66, 0.64, 0.73 for fucose, total glucans, FRAP and DPPH, respectively. The UAE parameters studied had a significant influence on the levels of fucose, FRAP and DPPH. The optimised UAE conditions (temperature = 76 ◦C, time = 10 min and amplitude = 100%) achieved yields of fucose (1060.7 ± 70.6 mg/100 g dried seaweed (ds)), total glucans (968.6 ± 13.3 mg/100 g ds), FRAP (8.7 ± 0.5 µM trolox/mg freeze-dried extract (fde)) and DPPH (11.0 ± 0.2%) in L. digitata. Polysaccharide rich extracts were also attained from L. hyperborea and A. nodosum with variable results when utilizing the optimum UAE conditions for L. digitata.
    Scopus© Citations 70  263