Perennial halophyte Salicornia neei Lag.: Cell wall composition and functional properties of its biopolymers.

Salicornia neei halophyte extends in Argentina seashores. To envisage potential applications, cell wall sequential extraction performed on dry plant yielded 1.1, 2.4, 0.3 and 0.9% of pectin fractions respectively extracted by room temperature water, 90 °C-water, CDTA and Na2CO3. They contained 21-33% uronic acids (UA) with low degree of methylation and 0.5-1.2 M ratios of neutral sugars to UA. High arabinose level suggests that long arabinan side-chains maintain cell wall flexibility in water deficit. Fractions also contained 10-36% of proteins. The KOH-soluble fractions (4.3%) were mainly arabinoxylans. At 2.0% w/v, pectin fractions developed "weak gel"-type networks with Ca2+, while arabinoxylans generated "dilute solutions". Cellulose (28%) and lignin (45.1%) were the main biopolymers in the final residue, which showed low water swelling capacity (3.6 mL/g) due to lignin, increasing when arabinoxylans were also present. Phenolics (9.8%) were mainly water-extractable. Salicornia is a source of biopolymers and antioxidants potentially useful for food applications.

Compositional changes in cell wall polysaccharides from apple fruit callus cultures modulated by different plant growth regulators.

The cell wall composition of apples callus cultures showed changes in the presence of 5 mg l(-1) of three different plant growth regulators (PGRs), namely picloram, abscisic acid and gibberellic acid. Although the structural functions of cell walls do not generally allow for pronounced variations of the total pectin and matrix glycan content, this work provides evidence that the addition of these plant growth regulators can rule, at least partly, cell wall metabolism in apple callus cultures. The chelator- and carbonate-extracts always had the analytical characteristics of pectins, with high proportions of uronic acids, arabinose and galactose as the main monosaccharides, and a significant proportion of rhamnose, but the cross-linking glycan fractions were still rich in RG-I-like material. The application of PGRs produced shifts of uronic acid and neutral sugars between fractions. Arabinose was the neutral sugar exhibiting more variations in apple callus cell wall. Picloram and abscisic acid produced an increase of the uronic acid contents of the cell walls. The AIRs obtained from calluses treated with different PGRs did not show large amounts of high molecular weight products, as determined by size-exclusion chromatography. For the carbonate-extract only the callus treated with picloram displayed two separated peaks for products of different molecular weights. The chromatographic profiles for the 4% KOH-extract displayed two peaks for all the treatments, one very sharp with high molecular weight, and another one wider of smaller molecular weight, whereas the difference between treatments can only be appraised through the areas of the peaks. This is the first report on cell wall composition from fruit calluses supplemented with different PGRs.

Effect of extraction time and temperature on the characteristics of loosely bound pectins from Japanese plum.

The cell wall composition of Japanese plums (Prunus salicina) at six developmental stages was previously evaluated (Ponce et al., J. Agric. Food Chem. 2010, 58, 2562-2570). This fruit is an interesting source of pectins, polysaccharides of valuable functionality for pharmaceutical and food formulations. In the present work it was investigated how the different conditions for the aqueous extraction of pectins from Japanese plums affect the yield as well as their chemical and rheological characteristics. It has been determined that extraction with water at room temperature for periods longer than 2h did not produce additional increment of yield (12%) but decreased the average molecular weights of the extracted pectins. Pectins with a degree of methylation ≈40% with high viscosity in water and with adequate molecular weights (≈72,000) were obtained. Conversely, utilization of boiling water for extraction increased considerably the yields (33-38%) but the extracted pectins showed significant lower viscosity in water in spite of their higher molecular weights. The poorer thickening ability was associated to the lower proportion of arabinose residues present in the hairy regions of the pectin macromolecules extracted by hot water, which led the polymers to interact more transiently in a 2% w/v water solution.

Characterization of acid-extracted pectin-enriched products obtained from red beet (Beta vulgaris L. var. conditiva) and butternut (Cucurbita moschata Duch ex Poiret).

Chemical and rheological characteristics of fractions enriched in soluble dietary fiber are reported. These fractions were obtained through acid hydrolysis of butternut (Cucurbita moschata Duch ex Poiret) and red beet (Beta vulgaris L. var. conditiva) cell wall enriched powders. Hydrolysis was performed using citric acid at different pH values and reaction times (2 and 3 h). Yields obtained for butternut fractions were between 21 and 28 g/100 g; for red beet, yields were 24 and 31 g/100 g for pH 1.5 and 11 and 17 g/100 g for pH 2.0 for previously mentioned times; in general, the increase of the yield was directly correlated with the decrease of pH and the increase of reaction time. Products enriched in low methoxyl pectins were obtained in all cases. At the lowest pH assayed, pectins were essentially constituted by homogalacturonan; a significant content of neutral sugars was determined at the higher extraction pH. Neutral sugars were constituted mainly by arabinose, galactose, rhamnose, and glucose in different proportions for each fraction; in general, butternut fractions showed high glucose contents. Flow behavior for 2.00% (w/v) aqueous systems of the different products was evaluated. Data obtained for fractions isolated at pH 1.5 fit to Herschel-Bulkley and Cross models while those isolated at pH 2.0 fit to Ostwald and Cross models. All samples showed low viscosity and, hence, poor thickening properties.

Antiretroviral activity of fucoidans extracted from the brown seaweed Adenocystis utricularis.

Treatment of human immunodeficiency virus type 1 (HIV-1, causative agent of AIDS) infection represents a major challenge in antiviral therapeutics. Many difficulties are associated with the treatment, including toxicity, resistance and high costs. Taking this into account, research for novel compounds able to overcome these limitations is needed. Sulfated polysaccharides appear to be interesting, given their abundance as components of seaweeds. Herein, a series of fractions obtained from the brown seaweed Adenocystis utricularis was analysed for in vitro anti-HIV-1 activity. These fractions, which have anti-herpes simplex virus activity, were determined previously to belong to the family of fucoidans, sulfated polysaccharides obtained from the cell walls of brown seaweeds. Assays in human PBMC primary cell culture demonstrated that two of the five fractions analysed had potent anti-HIV-1 activity both against WT and drug-resistant HIV-1 strains. For active fractions, it was also shown that the inhibitory effect was not due to an inactivating effect on the viral particle (i.e. no virucidal activity was detected) but rather to a blockade of early events of viral replication. Given these encouraging results, these seaweed-derived fractions appear as good candidates for further studies on their potential for in vivo therapy and/or prophylaxis of HIV-1 infection.