Towards the Use of Adsorption Methods for the Removal of Purines from Beer.

Beer corresponds to a fermented alcoholic beverage composed of several components, including purine compounds. These molecules, when ingested by humans, can be catabolized into uric acid, contributing to uric acid's level increase in serum, which may lead to hyperuricemia and gout. To assure a proper management of this disease, physicians recommend restrictive dietary measures, particularly by avoiding the consumption of beer. Therefore, it is of relevance to develop efficient methods to remove purine compounds from alcoholic beverages such as beer. In this review, we provide an introduction on fermented alcoholic beverages, with emphasis on beer, as well as its purine compounds and their role in uric acid metabolism in the human body in relation to hyperuricemia and gout development. The several reported enzymatic, biological and adsorption methods envisaging purine compounds' removal are then reviewed. Some enzymatic and biological methods present drawbacks, which can be overcome by adsorption methods. Within adsorption methods, adsorbent materials, such as activated carbon or charcoal, have been reported and applied to beer or wort samples, showing an excellent capacity for adsorbing and removing purine compounds. Although the main topic of this review is on the removal of purine compounds from beer, other studies involving other matrices rather than beer or wort that are rich in purines are included, since they provide relevant clues on designing efficient removal processes. By ensuring the selective removal of purine compounds from this beverage, beer can be taken by hyperuricemic and gouty patients, avoiding restrictive dietary measures, while decreasing the related healthcare economic burden.

Genome Mining and Enzymatic Total Biosynthesis of Purincyclamide.

A cyclodipeptide synthase-containing gene cluster (pcm) was identified in Streptomyces chrestomyceticus NA4264 through genome mining. Heterologous expression of the cryptic pcm gene cluster in Streptomyces albus led to the production of a new highly modified cyclodipeptide named purincyclamide (1). Bioinformatic analysis and gene knockout experiments revealed the biosynthetic pathway. The production of 1 was achieved through a one-pot enzymatic reaction.

Cauliflower-like resin microspheres with tuneable surface roughness as solid-phase extraction adsorbent for efficient extraction and determination of plant growth regulators in cucumbers.

New cauliflower-like phloroglucinol-glyoxylic acid resin microspheres (PGRMs) with controllable diameters and tuneable surface roughness were prepared using a one-step environmentally-friendly method without a catalyst. The PGRMs obtained exhibited a rough surface, narrow size distribution, and excellent adsorption capacity for polar compounds. The PGRMs were employed as an adsorbent for solid phase extraction (SPE) of kinetin (KT) and 6-benzyladenine (6-BA) in cucumbers and demonstrated better extraction recoveries and purification efficiency than phloroglucin-formaldehyde resin and common commercial adsorbents. Our PGRMs-SPE-HPLC method showed good linearity (r ≥ 0.9997) ranging from 0.04 to 4.00 µg/g for KT and 6-BA, and recoveries at three spiked concentration ranged from 77.8% to 104.4% with RSDs ≤ 6.8%. This PGRMs-SPE-HPLC method was applied successfully to determine of KT and 6-BA in cucumbers.

Polyhedral oligomeric silsesquioxane grafted silica-based core-shell microspheres for reversed-phase high-performance liquid chromatography.

Polyhedral oligomeric silsesquioxane (POSS) was used to modify spherical silica to fabricate core-shell POSS@SiO2 microspheres. The material was characterized by Fourier transform infrared experiments, scanning electron microscopy, thermogravimetric analysis and elemental analysis. The material was also used as a stationary phase for HPLC separation. The POSS@SiO2 column exhibits a reverse-phase liquid chromatography (RPLC) retention mechanism. The column efficiency of alkylbenzenes reaches 67,200 plates·m-1. The POSS@SiO2 column was also utilized for separation of basic anilines and polycyclic aromatic hydrocarbons. Compared with the commercial C8 column, the POSS@SiO2 column exhibits enhanced separation selectivity. The column was also used for the separation of synthetic cytokinins 6-benzylaminopurine and 6-furfurylaminopurine in bean sprout after extraction. In addition, the methacrylate groups on the surface of the POSS@SiO2 microsphere were further functionalized so as to facilitate the fabrication of versatile stationary phases with various separation mechanisms. Graphical abstract Schematic presentation of the two-step fabrication of polyhedral oligomeric silsesquioxane grafted silica-based (POSS@SiO2) core-shell microspheres for use in HPLC.

Cupric ion functionalized polydopamine coated magnetic microspheres as solid-phase adsorbent for the extraction of purines in plasma.

In this paper, Cu2+ functionalized Fe3O4@polydopamine core-shell (Fe3O4@PDA@Cu2+) magnetic microspheres were prepared by the chelation between Cu2+ and catechol of polydopamine surface. The synthetic magnetic adsorbent was characterized by Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, scanning electron microscope and transmission electron microscopy. Four purines include guanine, adenine, hypoxanthine and xanthine were selected as model compounds to evaluate the applicability of this adsorbent. Several parameters that effected the extraction efficiency, such as extraction time, adsorbent amount, solution pH, ionic strength, eluent type, concentration of eluent and eluent time, were investigated. Under the optimized conditions, good linearity was obtained with correlation coefficients between 0.9983 and 0.9999 for the four analytes, and their LOD and LOQ were 0.42-2.15 ng/mL and 1.41-6.50 ng/mL, respectively. Meanwhile, the RSDs of intra-day and inter-day precision were in the range of 1.43%-5.55% and 4.56%-7.01%, respectively. The spiked recoveries of four purines in real sample were 70.01%-102.42%, indicating this proposed method might have potential applications for the analysis of purines in real samples. In addition, the developed method was used to monitor the concentrations of adenine in rat plasma at different time points after intragastric administration.

ZIF-8@SiO2 core-shell microsphere extraction coupled with liquid chromatography and triple quadrupole tandem mass spectrometry for the quantitative analysis of four plant growth regulators in navel oranges.

Monodisperse silica spheres that comprised a rhombic-dodecahedral zeolitic imidazolate framework core-shell microsphere were applied in the sample pretreatment of navel orange. A rapid and efficient liquid chromatography with triple quadrupole tandem mass spectrometry method was established for simultaneously quantifying four plant growth regulators, 6-benzylaminopurin, indole-3-acetic acid, indolepropionic acid, 3-indolebutyric acid, in navel oranges. A satisfactory result was obtained, i.e., the peak area of the four plant growth regulators against concentration was linear with good correlation coefficients of 0.99987-0.99991. Under optimized conditions, the limits of detection were 3.0-59.4 µg/L for the four plant growth regulators. This method was applied to the simultaneous analysis of the four plant growth regulators in commercial samples, and all the detections were confirmed by acquiring transitions for each pesticide in the samples.

Sulfated Purine Alkaloid Glycosides from the Pupal Case Built by the Bruchid Beetle Bruchidius dorsalis Inside the Seed of Gleditsia japonica.

Three new sulfated isoguanine alkaloid glycosides, designated as saikachinoside A monosulfate (1), saikachinoside A disulfate (2), and locustoside B disulfate (3), have been isolated from the pupal case of the wild bruchid seed beetle Bruchidius dorsalis (Chrysomelidae, Bruchinae) infesting the seed of Gleditsia japonica Miq. (Fabaceae). Their structures were determined by spectroscopic methods and the inhibitory activity of 2 and 3 against acid phosphatase was evaluated.

Simultaneous quantification of three alkylated­purine adducts in human urine using sulfonic acid poly(glycidyl methacrylate­divinylbenzene)-based microspheres as sorbent combined with LC-MS/MS.

Three alkylated DNA adducts, N3­methyladenine, N3­ethyladenine and N7­ethylguanine, have been proved to be potential biomarkers for DNA injury caused by exposure to cigarette smoke. In this study, a highly specific and sensitive method using a new mixed-mode sulfonate-functionalized poly(glycidyl methacrylate-divinylbenzene) as a solid-phase extraction sorbent was developed for the analysis of these three alkylated-purine adducts in human urine. Under optimized conditions, the prepared sorbent interacts strongly with these urinary adducts, demonstrating high clean-up efficiency and extraction recovery. The method detection limits (S/N ≥ 3) of N3-MeA, N3-EtA and N7-EtG were 1.75, 0.20, and 0.15 pg mL-1, respectively, while the method quantitation limits were found to be 5.78, 0.66, and 0.49 pg mL-1 for N3-MeA, N3-EtA and N7-EtG, respectively. The intra-day and inter-day precisions were investigated, of which were in the range of 1.6-3.8% and 3.2-5.6%, respectively. The recovery values of the alkylated DNA adducts in spiked urine sample were ranged 89.7-104.5%. Their concentrations were statistically significantly higher in smokers than in nonsmokers. These results show that the proposed method is suitable for the analysis of alkylated DNA adducts.

[Determination of 6-benzylaminopurine in edible mushrooms by solid liquid extraction with low-temperature partition and high performance liquid chromatography-mass spectrometry].

A simple method based on solid liquid extraction with low-temperature partition (SLE-LTP) coupled with high performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for the determination of 6-benzylaminopurine (6-BA) in edible mushrooms. The samples were extracted with acetonitrile followed by low-temperature partition at -30℃ for 4 h. The separation was performed on a Hitachi LaChrom C18 column (250 mm×4.6 mm, 5 µm) with 0.02 mol/L ammonium acetate (containing 0.1% (v/v) glacial acetic acid)-methanol (6:4, v/v) as the mobile phases with isocratic elution. The compound was detected in positive electrospray ionization mode, and quantified by external standard method. The results showed that the limit of detection (LOD, S/N>3) for the analyte was 0.006 mg/kg, and the limit of quantification (LOQ, S/N>10) was 0.02 mg/kg. The calibration curve showed good linear in the range of 0.05-2.0 mg/L, and the correlation coefficient (r2) was 1.0000. The spiked recoveries were between 81.3% and 93.7% with the relative standard deviations (RSDs, n=6) of 0.7%-2.4% at the spiked levels of 0.1 mg/kg and 0.5 mg/kg. The developed method is simple, reliable and can be applied for the accurate determination of 6-BA residue in edible mushrooms.

Marine Alkylpurines: A Promising Group of Bioactive Marine Natural Products.

Marine secondary metabolites with a purine motif in their structure are presented in this review. The alkylpurines are grouped according to the size of the alkyl substituents and their location on the purine ring. Aspects related to the marine source, chemical structure and biological properties are considered together with synthetic approaches towards the natural products and bioactive analogues. This review contributes to studies of structure-activity relationships for these metabolites and highlights the potential of the sea as a source of new lead compounds in diverse therapeutic fields.

Poly(glyceryl monomethacrylate-co-ethylene glycol dimethacrylate) monolithic columns with incorporated bare and surface modified gluconamide fumed silica nanoparticles for hydrophilic interaction capillary electrochromatography.

This research article presents the preparation and characterization of monolithic capillary columns with incorporated bare fumed silica nanoparticles (FSNPs) and surface coated gluconamide FSNPs and their subsequent use in hydrophilic interaction capillary electrochromatography (HI-CEC) of small relatively polar solutes. The monolithic support was based on the in situ polymerization of glyceryl monomethacrylate (GMM) and ethylene glycol dimethacrylate (EDMA) yielding the poly(GMM-co-EDMA) monolith for the incorporation of bare and gluconamide-FNSPs. The poly(GMM-co-EDMA) monolith functioned as a true "support" for both types of polar FSNPs "stationary phases". In other words, monolithic capillary columns with "FSNPs stationary phases" were obtained in the sense that the contribution of the monolith proper to solute' retention was at its minimum. The gluconamide-FSNPs were obtained by reacting the FSNPs with the polar organosilane N-(3-triethoxysilylpropyl)gluconamide either by a pre- or on-column approach yielding p-gluconamide-FSNPs or o-gluconamide-FSNPs, respectively. While the p-gluconamide-FSNPs was coated by an oligosiloxane gluconamide layer as revealed by thermogravimetric analysis, the o-gluconamide-FSNPs are thought to be covered with a monomeric layer of gluconamide ligands as was manifested by the higher plate number obtained on the latter than on the former gluconamide-FSNPs incorporated monolithic columns. In the on-column modification process of FSNPs, the reaction was performed in a closed system whereby atmospheric water vapor are not available to cause the polymerization of the trifunctional organosilane N-(3-triethoxysilylpropyl)gluconamide. Also, the fact that the o-gluconamide-FSNPs incorporated monoliths were made from bare-FSNPs incorporated monoliths may indicate that the bare FSNPs were better dispersed into the monolithic matrix than the p-gluconamide-FSNPs, a condition that might have further contributed to the lower plate count obtained on p-gluconamide- than o-gluconamide-FSNPs incorporated monolithic columns. Overall, o-gluconamide-FSNPs stationary phases and to a lesser extent bare-FSNPs stationary phases proved useful in HI-CEC of small polar solutes, including DMF, formamide, thiourea, some phenols and nucleobases.

Ionic Liquid-Hybrid Molecularly Imprinted Material-Filter Solid-Phase Extraction Coupled with HPLC for Determination of 6-Benzyladenine and 4-Chlorophenoxyacetic Acid in Bean Sprouts.

A new method involving ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled to high-performance liquid chromatography (IL-HIM-FSPE-HPLC) was developed for the simultaneous isolation and determination of 6-benzyladenine (6-BA) and 4-chlorophenoxyacetic acid (4-CPA) in bean sprouts. Sample preconcentration was performed using a modified filter, with the new IL-HIM as the adsorbent, which shows double adsorption. The first adsorption involves special recognition of molecular imprinting, and the second involves ion exchange and electrostatic attraction caused by the ionic liquid. This method combines the advantages of ionic liquids, hybrid materials, and molecularly imprinted polymers and was successfully applied to determine 6-BA and 4-CPA in bean sprouts. The adsorption of 6-BA to IL-HIM is based on selective imprinted recognition, whereas the adsorption of 4-CPA is mainly dependent on ion-exchange interactions.

A method for assessing efficiency of bacterial cell disruption and DNA release.

BACKGROUND: DNA-based testing is becoming the preferred method both for identifying microorganisms and for characterizing microbial communities. However, no single DNA extraction method exists that is suitable for all types of microorganisms because bacteria are variable in their susceptibility to lysis by available extraction procedures. To develop and test new DNA extraction procedures, it would be helpful to determine their efficiencies. While the amount of extracted DNA can readily be measured by different methods, calculation of true efficiency requires knowledge of the initial amount of DNA in the starting bacterial sample, which cannot be done with precision by any existing method. In the process of developing a new extraction procedure, we developed a method that can be used to determine the total amount of both DNA and RNA in bacteria. The amount of DNA can be calculated from the amount of purines released after mild acid and alkali treatment. The amount of RNA in the same extract can also be calculated from the amount of ribonucleoside monophosphates. The released purines and ribonucleoside monophosphates can be quantified by absorbance using HPLC, with reference to appropriate standards. RESULTS: The acid/HPLC method was used to measure the efficiency of commonly used bead-beating and chemical protocols for releasing DNA from a particularly hardy organism, Mycobacterium smegmatis as well as several other species (Bacillus subtilis vegetative cells and spores; Francisella philomiragia; Pseudomonas aeruginosa; Moraxella catarrhalis; Bacillus thuringiensis; Staphylococcus aureus). Surprisingly large differences in efficiency between methods were found. CONCLUSIONS: The acid/HPLC method is a new tool to determine DNA extraction efficiencies and should aid in the development of improved protocols for releasing DNA from a broad range of microorganisms.

Novel skeleton compound Allomyrinanoid A and two purine alkaloids from the adult of Allomyrina dichotoma L.

Three new compounds were isolated from the adult insect of Allomyrina dichotoma L. for the first time. A new skeleton compound is named as Allomyrinanoid A (1) originated from the familiar norbornane derivatives and two new compounds of purine alkaloid are named as adenine-9-methylaldehyde oxime B (2) and 6-N-methyleneimine-adenine-9-methylaldehyde oxime B (3). The compounds (2) and (3) are the tautomers of imine-enamine and creatively separated form the solvent using column chromatography method. The structures of all isolated compounds were established by spectroscopic methods including analyses of their 1D, 2D NMR and HRESI-MS data, and confirmed by comparison of the literature data. These new components displayed antibacterial activities against both Gram-positive and Gram-negative strain.

Purine analogue ENERGI-F706 induces apoptosis of 786-O renal carcinoma cells via 5'-adenosine monophosphate-activated protein kinase activation.

Purine compounds are known to activate 5'-adenosine monophosphate-activated protein kinase (AMPK), which has important roles in treatments for renal cell carcinoma. The present study was aimed to investigate the effects of the purine analogue ENERGI­F706 on the human renal carcinoma cell line 786­O and the underlying mechanisms. The results revealed that ENERGI­F706 (0.2­0.6 mg/ml) significantly decreased the cell viability to up to 36.4±2.4% of that of the control. Compared to 786­O cells, ENERGI­F706 exerted less suppressive effects on the viability of the human non­tumorigenic renal cell line HK­2. Flow cytometric analysis showed that ENERGI­F706 contributed to cell cycle arrest at S­phase and triggered apoptosis of 786­O cells. Immunoblot analysis revealed that anti­apoptotic B­cell lymphoma 2 (Bcl­2) levels were reduced and pro­apoptotic Bcl­2­associated X protein levels were diminished. In addition, activation of caspase­9, caspase­3 and poly(adenosine diphosphate ribose) polymerase (PARP) was promoted in 786­O cells in response to ENERGI­F706. Effects of ENERGI­F706 on AMPK cascades were investigated and the results showed that ENERGI­F706 enhanced phosphorylation of AMPKα (T172) and p53 (S15), a downstream target of AMPK. In addition, the AMPK activation, p53 (S15) phosphorylation, reduction of Bcl­2, cleavage of caspase­3 and PARP as well as suppressed cell viability induced by ENERGI­F706 were reversed in the presence of AMPK inhibitor compound C (dorsomorphin). In conclusion, the findings of the present study revealed that ENERGI­F706 significantly suppressed the viability of 786­O cells via induction of cell cycle arrest and apoptosis, attributing to AMPK and p53 activation and subsequent cell cycle regulatory and apoptotic signaling. It was therefore indicated that ENERGI­F706 may be suitable for the treatment of renal cell carcinoma.

Endophytic bacteria from Pinellia ternata, a new source of purine alkaloids and bacterial manure.

CONTEXT: Pinellia ternata (Thunb.) Berit., a perennial herb belonging to Araceae, is one of the few medicinal plants to produce purine alkaloids. It is speculated that endophytic bacteria from P. ternata may produce guanosine or inosine. However, there is no report about endophytic bacteria in P. ternata. OBJECTIVE: In this study, endophytic bacteria were isolated from P. ternata and examined for the first time. This study finds a novel way to increase the yield of P. ternata herb, and to provide some new alkaloid producers. MATERIALS AND METHODS: Plant material includes leaves, tubers, and roots of cultivated and wild P. ternata. The dilutions were smeared onto beef extract-peptone medium and cultured at 28 °C in darkness for 48-72 h. Co-culture treatments were prepared by inoculating 100 mL liquid 1/2 MS medium with bacterial culture broth at concentrations of 0 (control), 0.5%, and 1.5% (v/v). RESULTS: Of the 34 endophytic bacterial colonies isolated from P. ternata leaves, roots, and tubers, five strains were able to produce purine alkaloids. Results from 16s rDNA sequence analysis indicated that the bacteria belonged to Bacillus cereus, Aranicola proteolyticus, Serratia liquefaciens, Bacillus thuringiensis, and Bacillus licheniformis. Co-culture with living Serratia liquefaciens cells increased PLB growth by 58-71%. Co-culture with living Bacillus licheniformis cells increased PLB growth by 4-11%. CONCLUSION: This study provides a novel way for improving the yield of P. ternata herb, and for the production of purine alkaloids by the fermentation industry.

Click N-benzyl iminodiacetic acid: novel silica-based tridentate zwitterionic stationary phase for hydrophilic interaction liquid chromatography.

Iminodiacetic acid (IDA) is dicarboxylic acid amine, which may produce stronger interaction with polar or charged compounds than bidentate α,ß-amino acid. In this article, a novel type of tridentate zwitterionic HILIC stationary phase was prepared by covalently bonding N-benzyl IDA on silica gel via copper(I) catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition (CuAAC). The structure of this stationary phase and all related intermediates was confirmed by NMR, FT-IR, MS spectrum and elemental analysis. The new stationary phase showed good HILIC characteristics and high column efficiency (the theoretical plate number is up to 44000 plates m(-1) in the case of guanosine) in the application of separation of polar compounds, including organic acids, organic bases, as well as highly polar and hydrophilic compounds, such as cephalosporins and carbapenems. Most of them displayed good peak shape and selectivity.

Quantitative online liquid chromatography-surface-enhanced Raman scattering of purine bases.

Raman spectroscopy has been of interest as a detection method for liquid chromatographic separations for a significant period of time, due to the structural information it can provide, allowing the identification and distinction of coeluting analytes. Combined with the rapidly advancing field of enhanced Raman techniques, such as surface-enhanced Raman scattering (SERS), the previous low sensitivity of Raman measurements has also been alleviated. At-line LC-SERS analyses, where SERS measurements are taken of fractions collected during or after HPLC separation have been shown to be sensitive and applicable to a wide variety of analytes; however, quantitative, real-time, online LC-SERS analysis at comparable sensitivity to existing methods, applicable to high-throughput experiments, has not been previously demonstrated. Here we show that by introducing silver colloid, followed by an aggregating agent into the postcolumn flow of an HPLC system, we can quantitatively and reproducibly analyze mixtures of purine bases, with limits of detection in the region of 100-500 pmol. The analysis is performed without the use of a flow cell, thereby eliminating previously detrimental memory effects.

Magnetic solid-phase extraction based on methylcellulose coated-Fe3O4-SiO2-phenyl for HPLC-DAD analysis of sildenafil and its metabolite in biological samples.

In the present study, magnetic nanoparticles (MNPs) with phenyl functionalized core and a hydrophilic methylcellulose coating were synthesized. The functionalized MNPs showed excellent dispersibility in aqueous solution and they were applied to magnetic solid phase extraction (MSPE) of sildenafil and its metabolite, desmethyl sildenafil, from human urine and plasma samples followed by high performance liquid chromatographic analysis. The factors that may influence the extraction, including the amount of MNPs, pH and salt concentration of sample solution, extraction and desorption time, and the volume of desorption solvent, were investigated in detail. Under the optimum MSPE conditions, the developed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 8.2% and low limits of detection of 0.41-0.96 ng mL(-1) from urine and plasma samples. The proposed material possessed good water compatibility and demonstrated excellent applicability for biological samples.

[High-sensitivity analysis of purines in alcoholic beverages using hydrophilic interaction chromatography coupled with tandem mass spectrometry].

In this study, we established a high-sensitivity analytical method for purines in alcoholic beverages using hydrophilic interaction chromatography coupled with tandem mass spectrometry. The alcoholic beverages were hydrolyzed with perchloric acid (60%) and subjected to strong cation exchange solid-phase extraction (Bond Elut SCX). The four purine bases (hypoxanthine, adenine, xanthine, guanine) in the extracted solution were separated by hydrophilic interaction chromatography with TSKgel Amide-80 as a separation column, 10 mM ammonium formate (pH 2.0) as mobile phase A, and acetonitrile/100 mM ammonium formate (pH 2.0) (90/10) as mobile phase B. The detection of purine bases was performed by tandem mass spectrometry with ESI. The linearity of this analytical method was not less than 0.996, and the repeatability was not more than 8.4% for each purine base. The recovery was in the range of 60-105%, and the detection limit was not more than 0.005 mg/100 mL. This established method is expected to be useful for quality control and surveillance of purines in alcoholic beverages.