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KWAS FERULOWY, BETA-GLUKAN I KSANTOHUMOL - BIOAKTYWNE SKŁADNIKI O POTENCJALNYM WYKORZYSTANIU PROZDROWOTNYM
Abstract
Edyta BAŃCYR and Marcin ŻYROMSKI
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Oats contain 3-5% of mixed linked beta-glucan, or (1-3), (1-4) β-D-glucan, referred to hereafter as beta-glucan. Oat beta-glucan is a viscous, and soluble dietary fibre component. Soluble and viscous dietary fibres, including the beta-glucan present in oats are associated with two major health promoting effects, i.e. the attenuation of postprandial plasma glucose and insulin levels and the control of cholesterol. Increased viscosity in the intestine delays absorption of glucose and suppresses absorption of cholesterol and reabsorption of bile acids. In spite of its apparent key role physiologically the viscosity of beta-glucan has been discussed relatively little in terms of analytical procedures. In clinical studies performed with oats, the viscosity of beta-glucan has been properly documented in only a few cases. Viscosity of beta-glucan in foods and in the food digest depends on solubility, concentration and molecular weight. A food manufacturer aiming at health-promoting products must pay attention not only to sufficient concentration of beta-glucan (dose) in the raw material, but also to the processing methods that will ensure sufficient solubility of beta-glucan and minimize enzymatic or mechanical breakdown of the beta-glucan molecule. We have been working both with different food processes utilising oat fractions high in beta-glucan and with the development of a method for viscosity determination of the soluble beta-glucan fibre. This review discusses some of the aspects related to the development with a method that could predict the behaviour of beta-glucan in oat processing with respect to its anticipated physiological functions.
Dissociation constants of four monomeric molecular models of lignin and equilibrium constants of complex with iron (III) have been determined from potentiometric measurements
The effects of fine structure and molecular size on the rheological properties of six mixed-linkage (1→3), (1→4)-β-d-glucans (β-glucans) in the solution and gel state were studied. Molecular size characterization was carried out with high-performance size exclusion chromatography combined with a refractive index detector. Samples were divided into two groups according to the values of apparent molecular weight (Mw) of the peak fraction of the main eluting peak calculated as ∼200×103 for an oat, a barley, and a wheat β-glucan and ∼100×103 for an oat and a barley β-glucan, and a lichenan sample. All polysaccharides analyzed by 2D NMR spectroscopy and high-performance anion-exchange chromatography of the cellulosic oligomers released by the action of lichenase showed the typical fine structure of mixed-linkage linear (1→3), (1→4)-β-d-glucan. Following lichenase digestion of β-glucans, the molar ratios of tri- to tetrasaccharides (DP3/DP4) were found to follow the order of lichenan (24.5)>wheat (3.7)>barley (2.8–3.0)>oat (2.1). Differences in critical concentration (c∗ ∗), viscosity, viscoelastic and shear thinning properties among samples were dependent mainly on differences in molecular size of the polymeric chains as well as on the β-glucan fine structure. All β-glucan isolates were able to form gels, as probed by dynamic rheometry; with decreasing molecular size and increasing DP3/DP4 ratio, the gelation time decreased and the gelation rate increased. Differential scanning calorimetry (DSC) showed that cereal β-glucan gels exhibit rather broad endothermic gel→sol transitions at 55–80 °C, while lichenan gels give a sharper transition, implying a more cooperative process. The DSC kinetic data showed similar responses to that from dynamic rheometry; the rate of development of the endotherm increased with increasing DP3/DP4 ratio of the polysaccharide. Furthermore, the storage modulus (G′) and the apparent melting enthalpy values (plateau ΔH) increased with decreasing molecular size and with increasing DP3/DP4 ratio. The melting temperature of the gel network, as determined by DSC and dynamic rheometry, was found to increase with the molecular size and the DP3/DP4 ratio of β-glucans; the Tm for lichenan was ∼89 °C and for cereal β-glucans varied in the narrow range of ∼65–72 °C. Large deformation mechanical tests (compression mode) up to failure revealed an increase in strength and a decrease in brittleness of mixed-linkage β-glucan gels with increasing DP3/DP4 ratio and molecular size of the polysaccharide.
The antioxidant activity of feruloyl arabinose, a model substance of cereal cell-wall fragments, in the LDL autoxidation system by CuSO4 and its absorption were studied. Ferulic acid added as free acid showed little suppressive effect on LDL oxidation. However, ferulic acid sugar esters showed a positive effect. This fact indicated that affinity of LDL particle and free or bound ferulic acid is important for the suppressive effect. The HPLC analysis showed that in rats administered feruloyl arabinose, two peaks were detected with retention times lower than those of feruloyl arabinose and ferulic acid, which appeared upon β-glucuronidase/sulfatase treatment. The study showed that the absorbed form of FAA could be a more polar compound, possibly a conjugated form. Keywords: Antioxidant; low-density lipoprotein; cereal cell wall; ferulic acid sugar ester
Oat gum was extracted from oat bran and examined chromatographically for monosaccharide constituent, presence of glycoprotein and equivalent dextran molecular weight (EDMW). Protein and ash contents were also determined. The viscosity of oat gum was studied at variable pH, temperature and concentrations of salt and sucrose. Viscosity of oat gum was compared with that of other food grade gums (xanthan, guar, gum arabic, and locust bean). TLC analysis identified only glucose and showed no evidence of xylose, arabinose or glycoprotein in the oat gum extract. The gum was 98.4% glucose as determined by high performance liquid chromatograpy. The protein and ash contents were 1.3% (N × 6.25) and 0.30%, respectively. EDMW of the extracted gum was ~882 000. Viscosity of oat gum (0.5%) was stable over a wide range of pH (2–10), decreased with increased temperature and increased in the presence of sucrose (20–45%). Oat gum was less viscous than xanthan and guar at 0.5%, but slightly more viscous than locust bean gum at the same concentration.
Application of β-glucan prepared from spent brewer's yeast as a fat replacer in mayonnaise was studied. Fat was partially substituted by β-glucan at levels of 25, 50, and 75% which were referred to as 25B, 50B, or 75B formulations, respectively. The full fat (FF) (100% oil) mayonnaise without β-glucan substitution was used as a control experiment. Physicochemical, rheological, and microbiological analyses, and sensory evaluation of the FF and reduced fat (RF) mayonnaises were performed. The results indicated that all RF mayonnaises had significantly lower energy content, but higher water content than their FF counterpart and these differences increased with increasing substitution levels of β-glucan. With regard to pH, there were no significant differences between the FF and RF mayonnaises after one-day storage. However, pH values of the RF samples decreased with an increasing degree of substitution after 2 months storage. In terms of texture, the 50B and 75B formulations showed similar firmness and adhesiveness values as those of the FF sample. Microstructure analysis showed close packing structures of large droplets for the FF and 25B and loose structures of a network of aggregated small droplets for the 50B and 75B samples. Both FF and RF mayonnaises exhibited thixothopic shear thinning behaviour under steady shear tests and were rheologically classified as weak gels under small amplitude oscillatory shear tests. Microbial loadings of all mayonnaises tested were in the acceptable limit throughout the storage time. The RF mayonnaises exhibited higher storage stability than the FF sample. Sensory evaluation demonstrated that mayonnaises substituted with β-glucan of not more than 50% were acceptable. This study shows good potential for spent brewer's yeast β-glucan to be used as a fat replacer in mayonnaise.
Oat β-glucans were extracted (water at 47 °C) from milled seeds of two Greek cultivars (A. sativa cv. Pallini and A. bysantina cv. Kassandra) and partially purified by pH adjustment of the β-glucan solutions to 4.5. Chemical analysis of the extracted gums revealed that they were composed mainly of β-glucans (>85% d.b.) together with some contaminating proteins (<9% d.b.). The fine structure of the β-glucan preparations was assessed by 13C-NMR spectroscopy and high-performance anion-exchange chromatography of the cellulosic oligomers released by the action of lichenase. The tri- and tetra-saccharides accounted for 90.9–92.3% of the total oligomers analyzed and the calculated molar ratios of trimers/tetramers varied between 1.99–2.11. Molecular size characterization was carried out with high performance size exclusion chromatography combined with a multi-angle laser light scattering and a refractive index detector; for samples with weight average molecular weight (Mw) ranging between 0.27 and 0.78×106, the values of limiting viscosity ([η]), critical concentration (c**) and coil overlap parameter (c**[η]) were within 4.9–6.4 dl/g, 1.2–2.0 g/dl and 7.8–10.1, respectively. The shear thinning behavior was dependent on the molecular weight and concentration of the β-glucan preparations. All β-glucan samples were able to form gels, as revealed by dynamic rheometry; the low molecular weight samples exhibited shorter gelation times and higher gelation rates (IE=[dlog G′/dt]max) than their high molecular weight counterparts. The gelation rate increased with increasing concentration and gel curing temperatures reaching a maximum at 32 °C; for higher temperatures the IE values decreased. For small molecular size β-glucans, a biphasic melting behavior was observed for gels at curing temperatures of 2–32 °C, whereas at higher temperatures melting of the gel network occurred as one-step process. Differential scanning calorimetry showed that gels cured at 24 °C exhibit a broad melting transition; Tm∼63 °C and ΔH∼5 mJ/mg. The mechanical properties of casted (dispersions) films from two β-glucan preparations, differing in molecular weight, with or without sorbitol, were examined by tensile measurements. The large deformation mechanical tests showed decreases in tensile (Young's) modulus (E) and strength (σmax), and an increase in percentage elongation with increasing water content and/or addition of sorbitol. The relationships between tensile parameters (E and σmax) and water content showed an increase in stiffness of the films from 2–7% moisture, and a strong softening effect at higher water contents.
Cereals β-glucans are linear homopolysaccharides of consecutively linked (1→4)-β-d-glucosyl residues (i.e. oligomeric cellulose segments) that are separated by single (1→3)-linkages. β-Glucans display all the functional properties of viscous and gel forming food hydrocolloids combined with all the physiological properties of dietary fibres. This review focuses on the relationships between the molecular–structural characteristics of β-glucans and their physicochemical properties in aqueous dispersions and in food systems as well as their physiological functions in the gastro-intestinal tract. The physical properties of β-glucans, such as solubility and rheological behaviour in the solution and gel states, are controlled by their molecular features, such as their distribution of cellulosic oligomers, their linkage pattern and their molecular weight as well as by temperature and concentration. The technological and nutritional functionality of β-glucans is often related to their rheological behaviour. Incorporation of β-glucans into various products (bread, muffins, pasta, noodles, salad dressings, beverages, soups, reduced-fat dairy and meat products) showed that attributes, such as breadmaking performance, water binding and emulsion stabilising capacity, thickening ability, texture, and appearance appear to be related to the concentration, molecular weight and structure of the polysaccharide. The health benefits of β-glucans, such as reducing blood serum cholesterol and regulating blood glucose levels, are also correlated with the amount and molecular weight of the solubilised β-glucans in the gastro-intestinal tract.
Hop acids, a family of bitter compounds derived from the hop plant (Humulus lupulus), have been reported to exert a wide range of effects, both in vitro and in vivo. They exhibit potential anticancer activity by inhibiting cell proliferation and angiogenesis, by inducing apoptosis, and by increasing the expression of cytochrome P450 detoxification enzymes. Furthermore, hop bitter acids are effective against inflammatory and metabolic disorders, which makes them challenging candidates for the treatment of diabetes mellitus, cardiovascular diseases, and metabolic syndrome. This review summarizes the current knowledge on hop bitter acids, including both phytochemical aspects, as well as the biological and pharmacological properties of these compounds.
Seven naturally derived components from hop plant (Humulus lupulus L.) extracts were tested for evaluation of biological activities affecting acne vulgaris. Five strains, Propionibacterium acnes, Staphylococcus epidermidis, Staphylococcus aureus, Kocuria rhizophila and, Staphylococcus pyogenes, were selected as the main acne-causing bacteria. Hop extracts xanthohumol and the lupulones showed strong inhibitory activities against all of the strains. Although hydrogenated derivatives did not show the same level of activity, naturally occurring xanthohumol, humulones, and lupulones all showed moderate to strong anticollagenase inhibitory activities. Antioxidant capacity was also evaluated with seven different methods based on different reactive oxygen species. Xanthohumol showed the highest activity in total oxygen radical absorbance capacity as well as singlet oxygen absorbance capacity.