Selective elution of tea catechins and caffeine from polyvinylpolypyrrolidone

Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n‐hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N‐dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H‐bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be <40% (v/v) for DMSO or 20% (v/v) for DMF. Desorption would get to equilibrium within 1 h and followed the pseudo‐second‐order model. Caffeine and catechins could be separately desorbed through two‐stage elution procedure, that is, water or 20% aqueous ethanol for desorbing caffeine and part of nongalloylated catechins and DMSO/ethanol (8/2, v/v) for eluting the remaining catechins. Highly purified catechins (~95%) with high level (~70%) galloylated catechins would be achieved when the desorption procedure was applied in column chromatograph.     

Polyvinylpolypyrrolidone-Supported Chlorosulfonic Acid: An Efficient Catalyst for One-Pot Synthesis of Dihydropyrimidinones and Octahydroquinazolin-2,5-diones

Polyvinylpolypyrrolidone-supported chlorosulfonic acid has been successfully applied to perform one-pot reaction of arylaldehydes, urea, ethylacetoacetate, or cyclic 1,3-diketo compounds under solvent-free condition at 70°C to provide a series of dihydropyrimidinones and octahydroquinazolin-2,5-diones in good to excellent yields. The method offers several advantages such as high yield, short reaction time, simple workup, easy preparation, and reusability of the catalyst. The [PVPP-SO₃H]⁺Cl^? catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). Moreover, the catalyst could be recycled several times without significant loss of its catalytic activity. Clean methodologies, easy work-up procedure, high yield, and simple preparation of the catalyst are some advantages of this article.     

PVPP在原啤酒处理中的作用

探讨了PVPP对啤酒中多酚类物质的去除率，结果表明，PVPP对啤酒中多酚的去除率达到90%左右，可有效延长啤酒的贮存期，效果优于硅藻土等。与抗氧化剂Vc协同使用效果更佳。     

Study of a novel disintegrable oleanolic acid-polyvinylpolypyrrolidone solid dispersion

Novel solid dispersions of oleanolic acid-polyvinylpolypyrrolidone (OLA-PVPP SDs) were designed and prepared to improve the apparent solubility of drug, as well as to improve the stability, fluidity and compressibility of SDs. Disintegrable OLA-PVPP SDs were then evaluated both in vitro and in vivo. DSC, XRD, IR and SEM analysis proved the formation of OLA-PVPP SD and its amorphous state. The results of fluidity study, moisture absorption test and stability test showed that OLA-PVPP SD with good fluidity and qualified stability was successfully obtained. Meanwhile excellent dissolution rate was achieved for in vitro studies; dissolution test showed that ～50–75% of OLA was dissolved from SDs within the first 10?min, which is about 10–15 times of free OLA. In vivo study indicated that the formation of solid dispersion could largely improve the absorption of OLA, resulting in a much shorter T_max (p?C_max (p?0→∞ of OLA-PVPP SDs (1:6) were 155.4?±?37.24?h·ng/mL compared to the 103.11?±?26.69?h·ng/mL and 94.92?±?13.05?h·ng/mL of OLA-PVPP physical mixture (1:6) and free OLA, respectively. These proved PVPP could be a promising carrier of solid dispersions and was industrially feasible alternative carrier in the manufacture of solid dispersions.     

Removal of Dissolved Brown Algal Phlorotannins Using Insoluble Polyvinylpolypyrrolidone (PVPP)

Tannins, a large and diverse group of phenolic secondary metabolites, are common in terrestrial plants and marine brown algae. It is sometimes desirable to remove the tannins from plant or algal extracts, e.g., when isolating enzymes and nucleic acids, when using certain colorimetric methods to quantify the tannin content, or to create reliable controls when using tannins in experimental studies. Insoluble polyvinylpolypyrrolidone (PVPP) can be used to specifically remove tannins from solution. In the present study, we evaluated the effect of different factors (amount of PVPP, number of PVPP treatments, type of solvent, pH, and incubation time) on the PVPP removal of dissolved brown algal phlorotannins. Our results imply that there is a limited amount of phlorotannins that can bind to a given amount of PVPP, and that it is preferable to use low quantities of PVPP repeatedly, compared to using fewer treatments with a high amount of PVPP. Furthermore, we found no consistent effect on the removal of phlorotannins due to solvent type (acetone, methanol, distilled water or filtered seawater). There was a slight decrease in the amount of phlorotannins removed from extracts with increasing pH when repeatedly treated with PVPP. All phlorotannins were removed from extracts with pH 6.2, and 89% of the initial phlorotannin content was removed at pH 9.7. These results are compared with previous methodological studies on tannin removal with PVPP. Furthermore, the implications of phlorotannin removal in analytical and ecological investigations are discussed.     

Influence of malt on the xanthohumol and isoxanthohumol behavior in pale and dark beers: A micro-scale approach

The main objective of this work was to understand which compounds are responsible for the partial inhibition of xanthohumol (XN) thermal isomerization during wort boiling of dark malts. With such purpose, worts from different kinds of malt (pale, caramel and roasted) were chemically characterized (e.g. antioxidant activity, polyphenols and melanoidins contents) and studied by several chromatographic techniques. Molecular exclusion chromatography experiments showed that adsorption of XN to polyvinylpolypyrrolidone is lower for the high molecular weight fractions. It seems likely that this is due to the reaction between XN and coloured substances that changes chemical properties of XN or, at least, results in the formation of complexes that have different chemical properties. This leads to an inhibition of XN isomerization observed in this work. It was also verified that the melanoidins content was significantly higher in the higher molecular weight fractions, suggesting that probably these compounds are the main responsible for the XN isomerization inhibiting effect.     

Antioxidant activities of solid-state fermentation derived proteins and peptides from heat-stabilized defatted rice bran

The response surface methodology was used to optimize the effect of three parameters, Bacillus subtilis (natto) Takahashi inoculum log (5–7 log CFU/g HDRB), initial water content (25%–45% w/v), and fermentation time (24–72 h), as independent variables on the extraction of the maximum water-soluble proteins and peptides (WSPP) from heat-stabilized defatted rice bran (HDRB). The optimum conditions were achieved by fitting the second-order polynomial equation. The result showed that all the factors, initial water content, inoculum log, and fermentation time, were critical in extracting WSPP from HDRB. The predicted optimum conditions for highest amount of WSPP extracted were 40.96% w/v water content, 6.27 log CFU/g HDRB inoculum log, and 61.01 h fermentation time. Under these optimized conditions of solid-state fermentation (SSF), 64.6% ± 0.7% of total protein in HDRB was extracted as WSPP which was closer to the predicted value of 63.3%. While the WSPP extracted from nonfermented HDRB was 20.6%. The majority of the WSPP from SSF-HDRB had MW <5 kDa. The WSPP from SSF-HDRB showed significant radical scavenging activities (56%, 44.4%, and 84.5%) in comparison to that from HDRB (12.5%, 9.3%, and 35.5%), of free radical (DPPH), superoxide radicals, and hydroxyl radicals, respectively. The SSF method is an efficient method to extract proteins and hydrolysates from HDRB and can find application as an ingredient in suitable products. Furthermore, the higher antioxidant activity is indicative of its potential function in controlling the oxidative stability in food products.     

A Comparison of Polyvinylpolypyrrolidone (PVPP), Silica Xerogel and a Polyvinylpyrrolidone (PVP)–Silica Co‐Product for Their Ability to Remove Polyphenols from Beer

Proanthocyanidins have been characterized and levels compared in an ale and a lager using normal‐phase liquid chromatography– mass spectroscopy (LC/MS) after a pre‐concentration step employing Sephadex LH‐20 chromatography. Twenty proanthocyanidins were identified including both non‐galloylated and galloylated forms of the monomers, dimers and trimers. Oligomers greater than trimer were not detected. A proportion of all classes of proanthocyanidin adsorbed non‐specifically to a silica xerogel product, but polyvinylpolypyrrolidone (PVPP) and a product that comprises polyvinylpyrrolidone (PVP) on a surface of amorphous silica displayed greater capability (i.e. specificity) for binding these materials. Of the two specific adsorbents, it was the PVPP that had the greater binding capability compared to the PVP‐silica co‐product.     

Prediction of Colloidal Stability of Highly Stabilized Beers by a Modified Chapon Tannoid Content Test

The tannoid content test, introduced by Chapon, is accepted as a recommended MEBAK analytical method for the detection of haze‐forming polyphenols in beer and other intermediates. Under certain conditions, the results can be used directly for predicting the colloidal stability of beer. Its disadvantage is that it does not provide detectable results for beers stabilized by high doses of polyvinylpolypyrrolidone (PVPP). A test modification is proposed that increases the test sensitivity and gives non‐zero results, even for highly stabilized samples that are not measurable by the standard test. The modification is based on adding saturated ammonium sulphate solution (SASS) to the sample to reach 9% saturation (0.5 mL of SASS to 5 mL sample volume) before the actual test performance. The results of the modified test can simply be converted to results obtained by the standard method. Tannoid content correlates linearly with the content of haze‐forming polyphenols and with chill haze produced after defined accelerated aging. In a set of beer samples of one brand having different degrees of stabilization, a high correlation was determined between test results and long‐term colloidal stability. The modified test can be used as a rapid and simple test for checking the stabilization process. It is particularly suitable for Pilsner type beer of long (more than 6 months) colloidal stability controlled by stabilization on the side of polyphenols.