Characterization of the Supermolecular Structure of Polydatin/6‐O‐α‐Maltosyl‐β‐cyclodextrin Inclusion Complex

Polydatin is the main bioactive ingredient in many medicinal plants, such as Hu‐zhang (Polygonum cuspidatum), with many bioactivities. However, its poor aqueous solubility restricts its application in functional food. In this work, 6‐O‐α‐Maltosyl‐β‐cyclodextrin (Malt‐β‐CD), a new kind of β‐CD derivative was used to enhance the aqueous solubility and stability of polydatin by forming the inclusion complex. The phase solubility study showed that polydatin and Malt‐β‐CD could form the complex with the stoichiometric ratio of 1:1. The supermolecular structure of the polydatin/Malt‐β‐CD complex was characterized by ultraviolet–visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffractometry (XRD), thermogravimetric/differential scanning calorimetry (TG/DSC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. The changes of the characteristic spectral and thermal properties of polydatin suggested that polydatin could entrap inside the cavity of Malt‐β‐CD. Furthermore, to reasonably understand the complexation mode, the supermolecular structure of polydatin/Malt‐β‐CD inclusion complex was postulated by a molecular docking method based on Autodock 4.2.3. It was clearly observed that the ring B of polydatin oriented toward the narrow rim of Malt‐β‐CD with ring A and glucosyl group practically exposed to the wide rim by hydrogen bonding, which was in a good agreement with the spectral data.     

Screening of β‐Glucosidase and β‐Xylosidase Activities in Four Non‐Saccharomyces Yeast Isolates

The finding of new isolates of non‐Saccharomyces yeasts, showing beneficial enzymes (such as β‐glucosidase and β‐xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non‐Saccharomyces yeasts. Four isolates were selected because of their both high β‐glucosidase and β‐xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB‐medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β‐glucosidase and β‐xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β‐glucosidase and β‐xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3‐folds) when wines were treated with non‐Saccharomyces isolates. In detail, terpineol, 4‐vinyl‐phenol and 2‐methoxy‐4‐vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2‐phenyl ethanol than those inoculated with other yeasts.     

α‐Glucosidase and α‐amylase inhibitory activities of phloroglucinal derivatives from edible marine brown alga,Ecklonia cava

BACKGROUND: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by defects in insulin secretion and action, which can lead to damaged blood vessels and nerves. With respect to effective therapeutic approaches to treatment of DM, much effort has being made to investigate potential inhibitors against α‐glucosidase and α‐amylase from natural products. The edible marine brown alga Ecklonia cava has been reported to possess various interesting bioactivities, which are studied here. RESULTS: In this study, five phloroglucinal derivatives were isolated from Ecklonia cava: fucodiphloroethol G ( 1 ), dieckol ( 2 ), 6,6′‐bieckol ( 3 ), 7‐phloroeckol ( 4 ) and phlorofucofuroeckol A ( 5 ); compounds 1, 3 and 4 were obtained from this genus for the first time and with higher yield. The structural elucidation of these derivatives was completely assigned by comprehensive analysis of nuclear magnetic spectral data. The anti‐diabetic activities of these derivatives were also assessed using an enzymatic inhibitory assay against rat intestinal α‐glucosidase and porcine pancreatic α‐amylase. Most of these phlorotannins showed significant inhibitory activities in a dose‐dependent manner, responding to both enzymes, especially compound 2 , with the lowest IC₅₀ values at 10.8 µmol L^?1 (α‐glucosidase) and 124.9 µmol L^?1 (α‐amylase), respectively. Further study of compound 2 revealed a non‐competitive inhibitory activity against α‐glucosidase using Lineweaver‐Burk plots. CONCLUSION: These results suggested that Ecklonia cava can be used for nutritious, nutraceutical and functional foods in diabetes as well as for related symptoms. Copyright © 2009 Society of Chemical Industry     

Purification and physicochemical characterization of ovine β‐lactoglobulin and α‐lactalbumin

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion‐exchange chromatography and reversed‐phase high‐performance liquid chromatography (HPLC) showed the presence of two fractions of β‐lactoglobulin but only one of α‐lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation‐mass spectrometry (ESI‐MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine β‐lactoglobulin. Amino acid compositions of the two variants of β‐lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of β‐lactoglobulin A compared to β‐lactoglobulin B at pH 2, and indicated high instability of ovine α‐lactalbumin at this pH.     

Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides

To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.     

Enzymatic Properties of β‐1,3‐Glucanase from Streptomyces sp Mo.

Streptomyces sp Mo endo‐β‐1,3‐glucanase was found to have hydrolyzing activity toward curdlan and released laminarioligosaccharides selectively. The molecular weight was estimated to be 36000 Da and its N‐terminal amino acid sequence was VTPPDISVTN. The optimal pH was 6 and the enzyme was found to be stable from pH 5 to 8. The optimal temperature was 60 °C and the activity was stable below 50 °C. The enzyme hydrolyzed selectively curdlan containing only β‐1,3 linkages. The enzyme had 89% relative activity toward Laminaria digitata laminarin, which contains a small amount of β‐1,6 linkages compared with curdlan, while Eisenia bicyclis laminarin with a higher amount of β‐1,6‐linkages, was not hydrolyzed. Mo enzyme adsorbed completely on curdlan powder. The enzymatic hydrolysis of curdlan powder resulted in the accumulation of laminaribiose (yield 81.7%). Trisaccharide was inevitably released from the hydrolysis of laminarioligosaccharides with 5 to 7 degrees of polymerization (DP). Although the enzyme cleaved off disaccharide (DP 2) from tetrasaccharide (DP 4), the reaction rate was lower than those of DP 5 to 7. The results indicated that the active site of Mo endo‐β‐1,3‐glucanase can efficiently recognize glucosyl residue chain of greater than DP 5 and hydrolyzes the β‐1,3 linkage between the 3rd and 4th glucosyl residue.     

Inhibitory potential of phenylpropanoid glycosides from Ligustrum purpurascens Kudingcha against α‐glucosidase and α‐amylase in vitro

The leaves of Ligustrum purpurascens are used in a Chinese traditional tea called small‐leaved kudingcha, which is rich in phenylpropanoid glycosides (PPGs) and has many beneficial properties. Two critical exoacting glycoside hydrolase enzymes (glucosidases) involved in carbohydrate digestion are α‐glucosidase and α‐amylase. We investigated the properties of PPGs from L. purpurascens for inhibiting α‐amylase and α‐glucosidase activity in vitro and found IC₅₀ values of 1.02 and 0.73 mg mL^?1, respectively. The patterns of inhibiting both α‐amylase and α‐glucosidase were mixed‐inhibition type. Multispectroscopy and molecular docking studies indicated that the interaction between PPGs and α‐amylase and α‐glucosidase altered the conformation of enzymes, with binding at the site close to the active site of enzymes resulting in changed enzyme activity. Our studies may help in the further health use of small‐leaved kudingcha.     

Glycyrrhetic Acid 3‐O‐Mono‐β‐d‐glucuronide (GAMG): An Innovative High‐Potency Sweetener with Improved Biological Activities

Glycyrrhetic acid 3‐O‐mono‐β‐d ‐glucuronide (GAMG) is an important derivative of glycyrrhizin (GL) and has attracted considerable attention, especially in the food and pharmaceutical industries, due to its natural high sweetness and strong biological activities. The biotransformation process is becoming an efficient route for GAMG production with the advantages of mild reaction conditions, environmentally friendly process, and high production efficiency. Recent studies showed that several β‐glucuronidases (β‐GUS) are key GAMG‐producing enzymes, displaying a high potential to convert GL directly into the more valuable GAMG and providing new insights into the generation of high‐value compounds. This review provides details of the structural properties, health benefits, and potential applications of GAMG. The progress in the development of the biotransformation processes and fermentation strategies to improve the yield of GAMG is also discussed. This work further summarizes recent advances in the enzymatic synthesis of GAMG using β‐GUS with emphasis on the physicochemical and biological properties, molecular modifications, and enzymatic strategies to improve β‐GUS biocatalytic efficiencies. This information contributes to a better framework to explore production and application of bioactive GAMG.     

Fatty acids and all‐trans‐β‐carotene are correlated in differently colored rice landraces

A set of 54 rice landrace samples was compiled from various Asian countries, including six red/brownish and eight black/purple varieties. Brown rice samples were analyzed for lipid content and fatty acid profile, as well as all‐trans‐β‐carotene content. Black/purple varieties were found to be higher in crude lipid content than the red/brownish and colorless varieties. They also had a higher β‐carotene content than the other two color classes. The highest β‐carotene content determined was 0.22 mg kg⁻¹. Black/purple varieties tended to have a higher proportion of saturated fatty acids in their lipid fraction and a lower proportion of unsaturated fatty acids. The differences were statistically significant (P < 0.05) for oleic acid, which accounted for 42.1% of the lipid fraction in black/purple varieties and for 45.3% and 46.3% in red/brownish and colorless varieties, respectively. β‐Carotene content showed a significantly positive correlation with the crude lipid content (P < 0.001) and the content of saturated fatty acids (P < 0.001) on a dry matter basis. However, it was not correlated with the unsaturated fatty acids content on a dry matter basis. Within the total lipid extract, β‐carotene showed a significantly positive correlation with the proportion of saturated fatty acids (P < 0.01), especially palmitic acid (P < 0.01), and a significantly negative correlation with unsaturated fatty acids (P < 0.001), especially oleic acid (P < 0.01). Copyright © 2005 Society of Chemical Industry     

Preparation and characterisation of selected physicochemical and functional properties of β‐chitosans from squid pen

Squid pen β‐chitosans prepared under various deacetylation conditions (30%, 35%, 40% and/or 45% NaOH for 15, 30 and/or 60 min) were characterised. β‐Chitosans (deacetylated with 35–45% NaOH for 15–60 min) had 87.1–96.2% degree of deacetylation (DD), 93.5–96.7% solubility and 120.5–654.9 mPa s viscosity. Treatment with 30% NaOH for 15–60 min yielded inadequately deacetylated β‐chitosans (DD = 51.9–80.2%). Two chitosans prepared under 35% NaOH for 15 min and 45% NaOH for 30 min (designated as 35%–15 and 45%–30, respectively) were further compared. Drying (sun‐drying vs. oven‐drying) methods did not affect DD. 35%–15 chitosan exhibited lower nitrogen, DD and bulk density, but higher viscosity compared with 45%–30 chitosan. Higher water‐ and fat‐binding capacity but lower DPPH radical scavenging activity were observed for 35%–15 chitosan compared with 45%–30 chitosan. Compared with 45%–30 chitosan, 35%–15 chitosan exhibited higher antibacterial activity against Salmonella Enteritidis and Listeria monocytogenes, but lower antibacterial activity against Escherichia coli.     

Bioequivalence of β‐carotene and retinol

For many years it was accepted that 6 mg of β‐carotene were required to produce 1 mg of vitamin A in the form of retinol. The equivalence was based on the assumptions that two‐thirds of dietary β‐carotene are not absorbed, while in the metabolism of the remaining third 1 mol of β‐carotene is converted to 1 mol retinol. Recently, the bioequivalence was raised to 12 mg β‐carotene and 1 mg retinol. The objective of this review was to re‐examine the data that were used to support the new equivalence ratio, especially since some of these data were obtained in developing countries where infestation with gut parasites and exposure to other infections is common, yet the influence of inflammation on plasma carotenoid and retinol concentrations is frequently ignored. Bioequivalence studies examined in this review include those done in developing and developed countries, depletion and repletion studies, feeding with vegetable sources of β‐carotene or pure supplements, influence of helminths, carotenoid interactions and matrix effects and studies using stable isotopes (SI). SI studies show the bioefficacy of β‐carotene conversion to retinol is generally poor even for pure β‐carotene unless the dose is small and fed regularly until equilibration is reached. Retinol formation appears to be inversely influenced by previous vitamin A intake, the amount of material given and current vitamin A status. In spite of technical complexities, more SI studies where liver reserves of vitamin A are determined pre and post intervention are needed to evaluate β‐carotene bioefficacy of different vegetable sources. Copyright © 2006 Society of Chemical Industry     

Isolation and characterization of Candida kefyr orotidine‐5′‐phosphate decarboxylase (URA3) gene

Candida kefyr is a common yeast species that can be found in fermented milk and cheeses. As a first step to developing a gene transfer system for C. kefyr, the orotidine‐5′‐phosphate decarboxylase (URA3) gene was cloned, using degenerate PCR and genome walking. The uninterrupted open reading frame of the C. kefyr URA3 gene spans 801 bp, corresponding to 267 amino acid residues. The functionality of the gene was confirmed by complementation of ura3 auxotrophs of C. albicans and Saccharomyces cerevisiae. Phylogenetic analysis of the deduced amino acid sequence indicated that it shares a high degree of homology with other Candida URA3 homologues. The GenBank Accession No. of the C. kefyr URA3 gene is FJ914763. Copyright © 2009 John Wiley & Sons, Ltd.