桑叶多糖的分离纯化及对α - 葡萄糖苷酶的抑制活性

利用Sephadex-G50 从桑叶多糖中分离纯化得到两种不同多糖组分MLP1 和MLP2,经过高效凝胶色谱(GPC)分析表明,MLP1 的纯度为94.55%,重均相对分子质量MW 为11800,多分散性系数为1.25,MLP2 的纯度为96.64%,重均相对分子质量MW 为7630,多分散性系数为1.12。并利用α- 葡萄糖苷酶抑制活性体外筛选模型,对MLP1 和MLP2 进行活性研究,结果表明两个组分对α- 葡萄糖苷酶均具有较好的抑制活性。     

The determination of flavonoid contents in mulberry and their scavenging effects on superoxide radicals

Flavonoid content of mulberry leaves of 19 varieties of species, determined spectrophotometrically in terms of rutin equivalent, varied from 11.7 to 26.6 mg g⁻¹ in spring leaves and 9.84 to 29.6 mg g⁻¹ in autumn leaves. Fresh leaves gave more extract than air-dried or oven-dried ones. HPLC showed that mulberry leaves contain at least four flavonoids, two of which are rutin and quercetin. The percentage superoxide ion scavenged by extracts of mulberry leaves, mulberry tender leaves, mulberry branches and mulberry bark were 46.5, 55.5, 67.5 and 85·5%, respectively, at a concentration of 5 μg ml⁻¹. The scavenging effects of most mulberry extracts were greater than those of rutin (52.0%).     

Antioxidant and antiproliferative effects of methanol extracts from raw and fermented parts of mulberry plant (<Emphasis Type="Italic">Morus alba</Emphasis> L.)

Total phenolic content, phenolic acids, radical scavenging activity and antiproliferative properties of different parts of mulberry (Morus alba L.) were determined. The highest phenolic content was found in methanol extracts of mulberry root (117.7 ± 2.0), followed by leaves (71.4 ± 2.4), branches (49.0 ± 1.5) and fruit (11.2 ± 0.3) [mg ferulic acid equivalents (FAE) kg⁻¹ dry weight (DW)] (P < 0.05). The highest level of total phenolics in the fractions was in roots (166.2 ± 7.5 and 160.8 ± 7.2 mg kg⁻¹ DW for BuOH and EtOAC, respectively). Methanol extracts and their fractions dose dependently increased radical scavenging activity of mulberry branches, roots and leafs (more than 70%). Total phenolic content of the tested plant extracts was highly correlated with the radical scavenging activity. The antiproliferative effect of mulberry parts on human cell lines was different and connected to the concentrations of the investigated extracts. The fermentation of the mulberry leaves did increase their methanol extract antiproliferative effect only on human gastric carcinoma (SNU-601) cell line in concentration of 1,000 mg mL⁻¹. In conclusion, some plant parts of the Korean mulberry could be recommended as preventative and therapeutic agents, based on their antioxidant and antiproliferative properties.     

Kernel partial least squares model for pectin content in peach using near-infrared spectroscopy

Pectin is a class of complex galacturonic acid-rich polysaccharides that are related to the texture of fruit and vegetables. The objective of this study was to develop, using near-infrared (NIR) spectroscopy, the best model for the determination of pectin content in peach fruit. A total of 100 samples divided into lossy and lossless samples were used to collect NIR raw spectra in the range of 1000–2500 nm. NIR absorption spectra were then obtained after pre-processing. Finally, four methods were used to establish lossy and lossless spectral models. The 10-fold cross-validation coefficient of determination R² of the lossy model was between 0.364 and 0.628, whereas that of the lossless model was between 0.187 and 0.288, indicating that the lossy model was better than the lossless model. Among all samples, the kernel partial least squares (KPLS) lossy model was better, with coefficient of determination R² = 0.628, root mean square error (RMSE) = 0.069 and mean absolute error (MAE) = 0.061. This is the first study to evaluate the prediction of peach pectin content using NIR spectroscopy, and the model can be used for rough screening.     

Influence of fermentation parameters on phytochemical profile and volatile properties of mulberry (Morus nigra) wine

In the present study Box–Behnken Design was employed to analyse the effects of fermentation parameters such as temperature (T _F), pH, inoculum size (I _S) and °Brix (B_X) on total phenolic concentration (TPC), total flavonoid concentration (TFC), total anthocyanin concentration (TAC), ethanol concentration (ETHC), total higher alcohol concentration (THAC) and total ester concentration (TESC) for the development of a phytochemical‐rich wine using mulberry as a substrate. The results demonstrated that fermentation parameters significantly alter the wine characteristics. Hence, a wine with excellent consumer preference (overall acceptability of 8.51) and high concentration of phytochemicals (TPC = 6014.03 ± 27.80 mg L⁻¹, TFC = 4791.35 ± 21.22 mg L⁻¹, TAC = 1480.72 ± 5.33 mg L⁻¹) as well as good aromatic properties (ETCH =82.85 ± 0.87 g L⁻¹, THAC =249.91 ± 0.31 mg L⁻¹ and TESC =52.55 ± 0.17 mg L⁻¹) with high antioxidant activity (DPPH =220.18 mmol·l⁻¹) was obtained at optimized fermentation conditions of T _F = 25°C, pH = 4.00, I _S = 10% (v /v) and B_X = 26. The results from the present study might contribute to strengthening the development of wine containing high concentrations of phytochemical compounds with attractive olfactory attributes. Copyright © 2017 The Institute of Brewing & Distilling     

Effects of different prebiotic stabilisers and types of molasses on physicochemical,sensory, colour and mineral characteristics of probiotic set yoghurt

The physicochemical, sensory, properties and mineral profile of probiotic set yoghurts prepared with different prebiotic stabilisers (pectin and guar) at 0.5% (w/v) and different molasses (grape, mulberry and carob) at 10% (v/v) were investigated. Guar‐supplemented yoghurts had the lowest titratable acidity values (P < 0.01) also the highest water‐holding capacity values (P < 0.01). However, guar had a negative effect on gel firmness and sensory properties of yoghurts. The effect of different stabilisers and molasses on colour L* and a*values was statistically significant (P < 0.01). Panelists gave the highest flavour scores to the pectin‐added yoghurts during storage period (P < 0.01).     

Evaluation of flavonoid and polyphenol constituents in mulberry leaves using HPLC fingerprint analysis

The mulberry leaf is a promising dietary source of antioxidants due to its high levels of beneficial compounds. To further examine its antioxidant properties, twelve batches of authenticated mulberry leaf, with total flavonoid contents (TFC) ranging from 24.34 mg g⁻¹ DW to 58.42 mg g⁻¹ DW and total polyphenol content (TPC) ranging from 11.49 mg g⁻¹ DW to 30.03 mg g⁻¹ DW, were investigated. According to Spearman’s coefficient, antioxidant activities, including the DPPH radical scavenging assay and the ferric reducing antioxidant power (FRAP), were positively correlated with TFC and TPC. The HPLC-DAD analysis results identified the characteristic fingerprint peaks in mulberry leaves as chlorogenic acid, rutin, quercetin 3-O-glucoside and kaempferol 3-O-glucoside, all of which directly contribute to the antioxidant capacity of mulberry leaves. Notably, young mulberry leaves showed higher antioxidant capacity than those of mature leaves. These promising results help create a compelling case for future development of mulberry leaf products.     

Dietary polysaccharide extracts of Agaricus brasiliensis fruiting bodies: chemical characterization and bioactivities at different levels of purification

Polysaccharides of the European strain of A. brasiliensis were obtained by hot water extraction and ethanol precipitation (HWPE I) of fruiting bodies, and further purified by dialysis (HWPE II) and pronase incubation (PPE). These polysaccharides consisted mainly of (1 → 6)-β-d-glucans. PPE was free of proteins and polyphenols as demonstrated by quantitative assays and NMR profiling. They showed a clear IFN-γ inducing activity in human PBMCs, which suggests these polysaccharides to have proinflammatory effects. Treatment by β-glucosidase caused the polysaccharides to be degraded into smaller fragments and at the same time increased their IFN-γ inducing activity in PBMCs fourfold.In vitro, PPE showed a dose-dependent inhibition of the proliferation of the human leukemia Jurkat cell. At 100 μg/mL the cells’ viability was decreased by appr. 51% compared to the control. EPR spin trapping demonstrated a high antioxidative activity against ^•OH and ^•O2⁻ radicals of HWPE I and PPE. Further, the results of the antioxidant assays indicated that antioxidant activity against ^•OH radicals in the Fenton system was achieved through scavenging or through chelating iron mechanisms.The good immunomodulating and antioxidative properties of A. brasiliensis polysaccharide extract obtained by hot water extraction and ethanol precipitation make it suitable for everyday use as an inexpensive dietary supplement.     

Comparison of analytical methods for measuring proanthocyanidins in wines and their relationship with perceived astringency

The concentration of proanthocyanidins from twenty red wines from cv. Cabernet Sauvignon, five rosé wines from cv. Cabernet Sauvignon and five white wines from cv. Sauvignon Blanc was quantified using four analytical methodologies, and their relationship with the perceived astringency was investigated. Proanthocyanidin concentrations were determined by a methylcellulose precipitation assay, a protein precipitation assay and two colourimetric methods (Bate‐Smith and vanillin assay). The four methodologies showed high repeatability but differed widely in proanthocyanidin concentrations. The methylcellulose and protein precipitation assays could not quantify proanthocyanidins in rosé and white wines. The protein precipitation assay gave the lowest concentration of proanthocyanidins in all of the red wines. The methylcellulose precipitation assay (r = 0.7725; r² = 0.59) and the protein precipitation assay (r = 0.6828; r² = 0.47) showed a strong correlation with the perceived astringency compared with the colourimetric methods. The strong correlation of the methylcellulose precipitation method with the perceived astringency could be a useful tool to estimate red wine astringency.     

Characterisation of whey protein isolate–gum tragacanth electrostatic interactions in aqueous solutions

The main objectives of this study were to measure molecular parameters of gum tragacanth by GPC‐MALLS system and investigate the complexation behaviour of whey protein isolate/gum tragacanth mixed dispersions (0.5 wt% total biopolymer concentration) as a function of pH (7.00–2.00) and the biopolymer mixing ratio (r = 0.1–10) using spectrophotometric, zeta potential and precipitate yield determination methods. GPC‐MALLS revealed that gum tragacanth contains relatively heterogeneous particles with high weight‐average and number‐average (M_w = 7.74 × 10⁵ g mol^?1 and M_n = 3.87 × 10⁵ g mol^?1) molecular mass and high dispersity index (~2.04 ± 0.3). Results of complexation displayed that as the biopolymer mixing ratio increases, the net neutrality shifts to the higher pHs. The critical values associated with the complex structure formation were found at r = 2 in which the charge density of the mixture was near zero at a wide range of pH (3.0–4.0). However, the highest precipitate yield achieved in pH 3.4.     

Determination of Pectin in the Presence of Food Polysaccharides

A selective and specific method to assay pectin in mixtures of polysaccharides using pectinase was developed. The mixture was extracted with 99.5% (v/v) ethanol to remove gum arabic and any other ethanol-soluble saccharides and polysaccharides; pectin was then hydrolyzed with pectinase. The hydrolyzed pectin was recovered by solution in 80% (v/v) ethanol and assayed by the m-hydroxybiphenyl method. The assay was not affected by agar and gums of tragacanth, karaya, guar, and locust bean in the mixture. Alginate and xanthan gum in the mixture repressed the development of color by this method, but this effect could be offset by modification of the pectinase reaction system.     

Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC‐CO₂). Addition of ethanol to the SC‐CO₂ at 2% (v/v) caused greater inactivation than SC‐CO₂ alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC‐CO₂ remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.     

Ultrasound-assisted extraction of polysaccharides from mulberry leaves

Ultrasound-assisted extraction (UAE) of polysaccharides from mulberry leaves was studied. The effects of four factors on the yield of polysaccharides were investigated. The results showed that optimum conditions were extraction power of 60 W, extraction temperature of 60 °C, extraction time of 20 min and ratio of water to raw material of 15:1 (ml/g). The three different methods (UAE, MAE and CSE) were compared for extracting polysaccharides from the mulberry leaves by SEM images. Totally, UAE had the largest yield of polysaccharides. The crude polysaccharides obtained from UAE were purified and two components (MPS-1 and MPS-2) were obtained. Their structure was analysed with chemical methods. From FT-IR, they were polysaccharides. MPS-1 had more functional groups than MPS-2. From HP GPC analysis, molecular weights of MPS-1 and MPS-2 were 24898D and 61131D, respectively. From GC analysis, MPS-1 was composed of Sor, Ara, Xyl and Glc, and MPS-2 was composed of Rha, Ara, Xyl, Glc, Gal and Man.     

Rheological properties of whey protein isolate stabilized emulsions with pectin and guar gum

Dynamic oscillatory and steady-shear rheological tests were carried out to evaluate the rheological properties of whey protein isolate (WPI) stabilized emulsions with and without hydrocolloids (pectin and guar gum) at pH 7.0. Viscosity and also consistency index of emulsions increased with hydrocolloid concentration. At γ = 20 s⁻¹, the value of viscosity of the emulsion with 0.5% (w/v) pectin was about fivefold higher than that of the emulsion without pectin. Flow curves were analyzed using power law model through a fitting procedure. Flow behaviour index of all emulsions except for containing 0.5% (w/v) guar gum was approximately in the range of 0.9–1.0, which corresponds to near-Newtonian behaviour. The shear thinning behaviour of emulsions containing 0.5% (w/w) guar gum was confirmed by flow behaviour index, n, of 0.396. Both storage (G′) and loss modulus (G″) increased with an increase in frequency. Emulsions behaved like a liquid with G″ > G′ at lower frequencies; and like an elastic solid with G′ > G″ at higher frequencies. Effect of guar gum was more pronounced on dynamic properties. Phase angle values decreased from 89 to <10° with increasing frequency and indicated the viscoelasticity of WPI-stabilized emulsions with and without pectin/guar gum.     

Effects of the proteinaceous moiety on the emulsifying properties of sugar beet pectin

The role of the proteinaceous moiety in emulsifying was investigated using pectin from sugar beet as a model polysaccharide. Physicochemical and macromolecular characteristics of sugar beet pectin were examined with or without an enzymatic modification using multiple acid-proteinases. The enzymatic modification decreased the total protein content from 1.56±0.15% to 0.13±0.02% by the Bradford method without significant change in ferulic acid or most constitutional sugars. It also decreased the weight-average molecular weight (M_w) from 517±28 to 254±20 kg/mol and the z-average root-mean-square radius of gyration from 43.6±0.8 to 35.0±0.6 nm. Emulsifying properties of the polysaccharide with or without the enzymatic modification were evaluated by emulsion droplet size and creaming stability of O/W emulsions (pH 3.0) containing 15 w/w% middle-chain triglyceride and 1.5 w/w% sugar beet pectin as main constituents. The modification increased the average diameter (d_3,2) of emulsion droplets from 0.56±0.04 to 3.00±0.25 μm immediately after the preparation, suggesting a decrease in the emulsifying activity. It caused the creaming of the emulsions during incubation at 60 °C, which was in line with the finding that macroscopic phase separation occurred only in the presence of the modified pectin after storage at 20 °C for a day, suggesting a decrease in the emulsion stabilizing ability. The modification also decreased significantly the amount of the pectin fraction that adsorbed onto the surface of emulsion droplets from 14.58±2.21% to 1.22±0.03% and the interfacial concentration of the polysaccharide from 1.42±0.23 to 0.45±0.05 mg/m², where the proteinaceous materials in the pectin molecules activated the oil-water interface. Results from the present study suggest an important role of the proteinaceous moiety to explain the emulsifying properties of sugar beet pectin as in the case of gum arabic and soy soluble polysaccharide.     

Rheological behaviour of uncross-linked and cross-linked gelatinised waxy maize starch with pectin gels

Rheological characterisation of uncross-linked (UPS) and cross-linked (CPS) waxy maize starch with pectin was conducted to determine the influence of pectin on the properties of the starch. The viscoelastic behaviour of 5% (w/v) gel systems containing UPS and CPS polysaccharides at 25 °C was evaluated by small angle deformation oscillation rheometry. Viscoelasticity measurements of the cross-linked polysaccharides indicated that the elastic component increased after cross-linking. Among all gels studied, the properties of the CPS mixtures (ratios 2:3 and 3:2) showed quite high storage (G′) and loss (G″) moduli (compared with gels of other ratios), indicating that gels of these two particular ratios had the greatest degree of elasticity and were very well structured. The results suggest that cross-linking between starch and pectin molecules can give rise to novel rheological properties.     

Effect of flavonol glycoside in mulberry (Morus alba L.) leaf on glucose metabolism and oxidative stress in liver in diet‐induced obese mice

BACKGROUND: Mulberry therapies on type 2 diabetic patients or streptozotocin‐induced diabetic rats have been reported to improve fasting blood glucose levels. We investigated the effects of dietary consumption of mulberry‐leaf powder and purified quercetin 3‐(6‐malonylglucoside), the quantitatively major flavonol glycoside in mulberry leaves, on glucose and lipid metabolism in high‐fat diet‐induced obese mice. Male C57BL/6J mice aged 8 weeks were assigned to three groups (control, mulberry leaf powder (MLP), and quercetin 3‐(6‐malonylglucoside) (Q3MG)) and treated with their respective diets for 8 weeks. RESULTS: We found that dietary supplementation of 10 g MLP kg^?1 or 1 g Q3MG kg^?1 in high‐fat diet effectively suppressed blood glucose levels. We also noted increased expression of glycolysis‐related genes and suppression of thiobarbituric acid reactive substances concentrations in the liver of Q3MG group compared to control mice. CONCLUSION: Dietary consumption of Q3MG, the quantitatively major flavonol glycoside in mulberry leaves, improved hyperglycemia in obese mice and reduced oxidative stress in the liver. Copyright © 2010 Society of Chemical Industry     

Stimulation of polygalacturonase production in an immobilized system by <Emphasis Type="Italic">Aspergillus</Emphasis> sp.: effect of pectin and glucose

The synthesis of polygalacturonases (PG) is known to be influenced by Aspergillus growth conditions, namely, environmental factors and pectin content in the cultivation medium containing a mixed carbon source. Optimal conditions were attained at a temperature of 30 °C and an initial pH of 4.5. PG activity (3.29 and 2.48 U/mL) was determined after a two-day culture of Aspergillus sp. HC1 and Aspergillus sp. CC1, respectively, in a basic medium containing 2% citrus pectin as the sole carbon source. The addition of glucose (2% w/v) to the basic medium led to a 2-fold increase in PG production. However, enzyme synthesis was repressed when a higher concentration of glucose was used in the medium containing the mixed carbon source. Spores from the two fungi were immobilized in a 3% Ca–alginate system and the mechanical strength of the gel beads allowed the use of this process system 6-fold longer (288 h) than the free culture. In the Aspergillus sp. CC1 immobilized system, PG production increased nearly 10-fold in the medium with 2% glucose added (5.95 U/mL) in comparison to the medium without sugar (0.55 U/mL). The results demonstrate that a different response in activity was produced by free and entrapped spore systems. PG production remained approximately constant throughout the six 48 h cycles in the medium containing citrus pectin (2% w/v) as the sole carbon source.     

Pulsed electric fields- and ultrasound-assisted green extraction of valuable compounds from Origanum vulgare L. and Thymus serpyllum L.

This work compared the effects of pulsed electric fields (PEF) and ultrasound (US) technologies on the extent of cell disintegration of two Mediterranean herb tissues (Origanum vulgare L., Thymus serpyllum L.), as well as on the extractability of phenolic compounds during the subsequent hydroalcoholic extraction (0%–50% ethanol in water, v/v) for up to 4 h. The rate of phenolic compounds extraction decreased with time and was predicted rather satisfactorily (R² = 0.898–0.989) by the Peleg’s model. The application of either PEF or US treatment prior to solid–liquid extraction (SLE) has the potential to reduce duration and concentration of ethanol to achieve the same recovery yield of phenolic compounds. Under optimised PEF (3 kV cm⁻¹, 10 kJ kg⁻¹) and US (400 W, 20 min) treatment conditions, the extracts obtained from either PEF or US pretreated herb samples showed higher total phenolic yield (36% on average) and antioxidant activity (FRAP) (36% on average) as compared to the control extraction, especially when 25% ethanol was used as a solvent. GC/MS analyses revealed no evidence of degradation of individual phenolics due to either PEF or US application.     

桑叶茯砖茶多糖的响应面提取工艺优化及其体外抗氧化降血脂作用

以桑叶茯砖茶为原料,研究水提取法对其中的多糖提取效果的影响以及桑叶茯砖茶多糖的抗氧化和降血脂作用。通过单因素实验考察了提取时间、提取温度、液料比以及提取次数等对多糖得率的影响,在此基础上,采用响应面分析法优化提取工艺,确定了桑叶茯砖茶多糖最佳提取工艺为:提取时间1.6 h,液料比16:1 mL/g,提取温度51 ℃,提取次数1次,在该最佳条件下,桑叶茯砖茶多糖得率为10.43%,与模型预测值基本吻合,表明该提取工艺稳定可行。体外抗氧化和降血脂实验发现,当桑叶茯砖茶多糖质量浓度为80 μg/mL时,对DPPH自由基的清除率达84.35%,当质量浓度达到130 μg/mL时,其对ABTS+·的清除率可达72.30%,当桑叶茯砖茶多糖浓度为1.75 mg/mL时,对·OH的清除率为74.08%,表明抗氧化效果较好。当桑叶茯砖茶多糖质量浓度为3.50 mg/mL时,其对牛磺胆酸盐和甘氨胆酸盐的结合率分别达到59.96%和41.97%,表明具有较好的降血脂作用。