Effect of low‐temperature physical aging on the dynamic transitions of atactic polystyrene in the glassy state

The local and cooperative dynamics of atactic PS (a‐PS) were studied by broadband dielectric relaxation spectroscopy (BDRS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR). The a‐PS has been subjected to thermal rejuvenation and subsequent quenching, short‐term aging (6 weeks), and long‐term aging (1 year) at ambient conditions. Where for the rejuvenated sample only an α‐ and a γ‐relaxation is observed, short‐term aging results in an additional β*‐relaxation that merges with the α‐relaxation at longer aging times. The γ‐relaxation is increasing in intensity and activation energy during aging. The α‐process shows no spectral changes and shift in the relaxation time upon aging. This may be attributed to a possible erasure of history of the material during the temperature‐sweep mode measurement. Fourier transform infrared spectroscopy (FTIR) results suggest that the energetically favorable trans‐trans (tt) conformers are increased in population with aging. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1394–1401     

Chiral separation of isoxanthohumol and 8‐prenylnaringenin in beer,hop pellets and hops by HPLC with chiral columns

Xanthohumol, isoxanthohumol, and 8‐prenylnaringenin in beer, hop and hop pellet samples were analyzed by HPLC using an InertSustain phenyl column and the mobile phase containing 40% methanol and 12% 2‐propanol. Fractions of isoxanthohumol and 8‐prenylnaringenin obtained by the above HPLC were separately collected. Isoxanthohumol and 8‐prenylnaringenin were enantioseparated by HPLC using a Chiralcel OD‐H column with a mobile phase composed of hexane–ethanol (90:10, v/v) and a Chiralpak AD‐RH column with a mobile phase composed of methanol–2‐propanol–water (40:20:40, v/v/v), respectively. Isoxanthohumol and 8‐prenylnaringenin from beer, hop and hop pellet samples were found to be present in a racemic mixture. This can be explained by the fact that the two analytes were produced by a nonenzymatic process. The effects of boiling conditions on the conversion of xanthohumol into isoxanthohumol were also studied. A higher concentration of ethanol in heating solvent resulted in a decrease in the conversion ratio and the conversion was stopped by addition of ethanol at >50% (v/v). The isomerization was significantly affected pH (2−10) and the boiling medium at pH 5 was minimum for the conversion. Therefore, it was suggested that xanthohumol was relatively difficult to convert to isoxanthohumol in wort (pH 5−5.5) during boiling.     

A Metabolomic Approach to Beer Characterization

The consumers’ interest towards beer consumption has been on the rise during the past decade: new approaches and ingredients get tested, expanding the traditional recipe for brewing beer. As a consequence, the field of “beeromics” has also been constantly growing, as well as the demand for quick and exhaustive analytical methods. In this study, we propose a combination of nuclear magnetic resonance (NMR) spectroscopy and chemometrics to characterize beer. ¹H-NMR spectra were collected and then analyzed using chemometric tools. An interval-based approach was applied to extract chemical features from the spectra to build a dataset of resolved relative concentrations. One aim of this work was to compare the results obtained using the full spectrum and the resolved approach: with a reasonable amount of time needed to obtain the resolved dataset, we show that the resolved information is comparable with the full spectrum information, but interpretability is greatly improved.     

Two Rare α‐Pyrone (=2H‐Pyran‐2‐one) Derivatives from Gentiana rhodantha Franchet

Two new rare α‐pyrone (=2H‐pyran‐2‐one) derivatives, rhodanthpyrones A and B ( 1 and 2 , resp.), together with fourteen known compounds, 3 – 16 , were isolated from the whole plants of Gentiana rhodantha. The structures of these compounds were elucidated by spectroscopic analyses. This is the first report on the occurrence of α‐pyrone derivatives in the genus Gentiana.     

Determination of Volatile Markers from Magnum Hops in Beer by In-Tube Extraction—Gas Chromatography—Mass Spectrometry

ABSTRACT

A chromatographic method was developed for the identification of volatile markers from Magnum hops in two types of beer. The study was initially performed with Magnum hop pellets and hop essential oil and subsequently with traditional and flavored beer during the primary fermentation. The volatile compounds were isolated employing the in-tube extraction (ITEX) technique followed by identification and quantification through gas-chromatography—mass spectrometry (GC-MS) operating in scan mode. The main authentication markers identified in traditional beer were from aromatic compounds, aldehydes and alcohol esters. The most predominant authentication marker compounds in beer flavored with Magnum hop essential oil were obtained from terpenoids, followed by acid esters, alcohol esters and alcohol classes. A unique feature of this study was represented by the discriminant markers for the authentication of Magnum hop variety, identified in hop pellets, hop essential oil and flavored beer. The application of this methodology can be used for optimization of brewing technology and process parameters in view of prolonging fruity hop flavor stability of Romanian beers.     

Construction of a comprehensive beer proteome map using sequential filter‐aided sample preparation coupled with liquid chromatography tandem mass spectrometry

The quality traits of beer, which include flavor, texture, foam stability, gushing, and haze formation, rely on contributions from beer proteins and peptides. Large‐scale proteomic analysis of beer is gaining importance, not only with respect to authenticity of raw material in beer but also to improve quality control during beer production. In this work, foam proteins were first isolated from beer by virtue of their high hydrophobicity. Then sequential filter‐aided sample preparation coupled with liquid chromatography and tandem mass spectrometry was used to analyze both beer protein and foam protein. Finally, 4692 proteins were identified as beer proteins, and 3906 proteins were identified as foam proteins. In total, 7113 proteins were identified in the beer sample. Several proteins contributing to beer quality traits, including lipid transfer protein, serpin, hordein, gliadin, and glutenin, were detected in our proteins list. This work constructed a comprehensive beer proteome map that may help to evaluate potential health risks related to beer consumption in celiac patients.     

Feasibility of Defatted Juice from Sea-Buckthorn Berries (Hippophae rhamnoides L.) as a Wheat Beer Enhancer

Juice made from sea-buckthorn berries (Hippophae rhamnoides L.) is a valuable source of bioactive compounds, vitamins, as well as micro- and macronutrients. By applying defatted sea-buckthorn juice, it is possible to enhance wheat beer and change its sensory properties and the contents of bioactive compounds in the finished product. A sensory assessment showed that wheat beers with a 5% v/v addition of sea-buckthorn juice were characterised by a balanced taste and aroma (overall impression). Physicochemical analyses showed that, compared to the control samples, wheat beers enhanced with defatted sea-buckthorn juice at a rate of 5% v/v or 10% v/v had high total acidity with respective mean values of 5.30 and 6.88 (0.1 M NaOH/100 mL), energy values lower on average by 4.04% and 8.35%, respective polyphenol contents of 274.1 mg GAE/L and 249.7 mg GAE/L, as well as higher antioxidant activity (measured using DPPH, FRAP, and ABTS assays). The findings show that the samples of wheat beer enhanced with sea-buckthorn juice had average ascorbic acid contents of 2.5 and 4.5 mg/100 mL (in samples with 5% v/v and 10% v/v additions, respectively) and contained flavone glycosides, e.g., kaempferol-3-O-glucuronide-7-O-hexoside. Based on the current findings, it can be concluded that wheat beer enhanced with sea-buckthorn juice could emerge as a new trend in the brewing industry.     

Cardenolide and pregnane derivatives from the roots of Trachycalymma fimbriatum (Weimark) Bullock. Glycosides and aglycones. 322

The roots of Trachycalymma fimbriatum (WEIMARCK ) BULLOCK contain both cardenolide and pregnaneglycosides. Elimination of 2-deoxysugars by mild acid hydrolysis gave a mixture from which some anhydroderivatives and the following compounds could be isolated: uzarigenin ( l ), ascleposide = 3-O-(6-deoxy-β-D -allopyranosyl)-uzarigenin ( 4 ), coroglaucigenin ( 6 ) and two pregnane derivatives (H and J). Compound H could be identified as 3β,14β-dihydroxy5α, 17α-pregnan-20-one ( 10 ). Compound J is probably a new substance, for which we tentatively assign structure 18 , i.e. 3β8β,14β-trihydroxy-5α,17α-pregnan-20-one. We suspect H and J to be artefacts produced from the corresponding 17b-derivatives during acid hydrolysis. 17-iso-H is probably a precursor in the biosynthesis of uzarigenin. The cardenolides of Trachycalymma fimbriatum are the same as found in Asclepias glaucophylla, a closely related species, while the pregnane derivatives of the latter are distinctly higher hydroxylated.     

A New Peroxy‐multiflorane Triterpene Ester from the Processed Seeds of Trichosanthes kirilowii

A new peroxy‐multiflorane triterpene ester, (3α,5α,8α,20α)‐5,8‐epidioxymultiflora‐6,9(11)‐diene‐3,29‐diol 3,29‐dibenzoate ( 1 ), was isolated from the processed seeds of Trichosanthes kirilowii, together with the two known related derivatives 2 and 3 , and the two known steroids 4 and 5 . Compounds 2, 4 , and 5 were isolated from the genus Trichosanthes for the first time. The structure of compound 1 was established by NMR, HR‐MS, and CD analyses. Compounds 1 – 3 were tested for their in vitro cytotoxicity against human‐tumor cell lines (Hela, HL‐60, and MCF‐7) and anti‐inflammatory activity (LPS‐induced B lymphocyte cells) with the MTT method.     

Oleanane‐Type Triterpenoids from the Endophytic Fungus Pestalotiopsis clavispora Isolated from the Chinese Mangrove Plant Bruguiera sexangula

Three new triterpenoid derivatives, named (15α)‐15‐hydroxysoyasapogenol B ( 1 ), (7β,15α)‐7,15‐dihydroxysoyasapogenol B ( 2 ), and (7β)‐7,29‐dihydroxysoyasapogenol B ( 3 ), were isolated from cultures of the plant endophytic fungus Pestalotiopsis clavispora. Their structures and relative configurations were elucidated by extensive spectroscopic analysis and X‐ray crystallography.     

Synthesis of α‐Nitro‐α‐diazocarbonyl Derivatives and Their Applications in the Cyclopropanation of Alkenes and in O?H Insertion Reactions

A facile and highly efficient method for the preparation of α‐nitro‐α‐diazocarbonyl derivatives by a diazo‐transfer reaction involving (trifluoromethyl)sulfonyl azide has been developed. These substrates undergo a rhodium‐catalyzed cyclopropanation reaction with a variety of alkenes. A systematic study of the reaction indicated that the diastereoselectivity of the cyclopropanation could be effectively controlled through the modification of the steric bulk of the diazo reagent. A novel O? H insertion reaction of the metal? carbene complex derived from the α‐nitro‐α‐diazocarbonyl reagent afforded the corresponding novel α‐nitro‐α‐alkoxy carbonyl derivatives.     

Two new polyhydroxysterols produced by Fusarium solani,an endophytic fungus from Chloranthus multistachys

A highly antagonistic endophytic fungus, designated strain CL39, was originated from the leaves of Chloranthus multistachys collected in Wulong of Chongqing municipality of China in November 2015. The strain was identified as Fusarium solani based on morphological characteristics, 5.8S gene and internal transcribed spacer sequence analysis. Two new compounds, 2β, 9α-dihydroxy-5α-methoxyergosta-7, 22-diene (1), 2β, 6β-dihydroxy-5α-methoxyergosta-7, 22-diene (2) have been isolated from the culture broth of the strain. Structures of the new compounds were elucidated by detailed analysis of their spectroscopic data aided by the comparison with reported data of related derivatives, and found to belong to the polyhydroxylated steroids with a hydroxyl at C-2 instead of C-3, a rare structure among the steroids. The extract of this strain and all isolated compounds were evaluated for their antagonistic activities.     

New Patchoulol‐Type Sesquiterpenoids from Pogostemon cablin

Four new patchoulol derivatives, 8α,9α‐dihydroxypatchoulol ( 1 ), 3α,8α‐dihydroxypatchoulol ( 2 ), 6α‐hydroxypatchoulol ( 3 ), and 2β,12‐dihydroxypatchoulol ( 4 ), were isolated from the aerial part of Pogostemon cablin (Labiatae), together with nine known compounds, sesquiterpenoids 5 – 8 and flavonoids 9 – 13 . Their structures were elucidated by detailed spectroscopic analysis, using 1D‐ and 2D‐NMR techniques.     

A Chiral Recognition Mechanism Proposed for Resolving π-Acidic Racemates on π-Acidic Chiral Stationary Phases Derived from (S)-Leucine

A chiral recognition mechanism which can rationalize the resolution of N-(3,5-dinitrobenzoyl)-α-amino amides on chiral stationary phases (CSPs) obtained from N-(3,5-dinitrobenzoyl)leucine amide derivatives has been proposed on the basis of the chromatographic resolution behavior of various N-(3,5-dinitrobenzoyl)-α-amino acid derivatives and N-(various benzoyl)leucine N-propyl amides. The proposed chiral recognition mechanism utilizes two hydrogen bonding interactions between the CSP and the analyte and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) groups of the CSP and the analyte. From the chiral recognition mechanism proposed, it has been concluded that the resolution of π-acidic N-(3,5-dinitrobenzoyl)-α-amino acid derivatives on π-acidic CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide delivatives is not unusual, but is merely the extension of the resolution of the π-basic racemates on π-acidic CSPs. However, the chromatographic behavior of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives on CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide derivatives is different from that of the resolution of other N-(3,5-dinitrobenzoyl)-α-amino acid derivatives. To rationalize this exceptional behavior, a second chiral recognition mechanism which utilizes two hydrogen bonding interactions (which are different from those of the first chiral recognition mechanism) between the CSP and the analytes and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) group of the CSP and the phenyl group of the analytes has been proposed to compete with the first chiral recognition mechanism. In this instance, it has been proposed that the separation factors and the elution orders of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives are dependent on the balance of the two competing chiral recognition mechanisms.     

Dimedone‐catalyzed Addition of Amines into Cyano Group: Facile Synthesis of Thiazol‐2‐yl Substituted E‐Acrylonitriles

An efficient dimedone‐catalyzed synthesis of highly functionalized thiazol‐2‐yl substituted E‐acrylonitrile derivatives has been established through two‐step reaction of α‐thiocyanate ketones with malononitrile and amines. The α‐thiocyanate ketones were subjected with malononitrile to provide thiazol‐2‐ylidenemalononitrile derivatives, followed with various amines in the present of dimedone to yield the final thiazol‐2‐yl substituted acrylonitrile derivatives.     

Antioxidant and alpha-glucosidase inhibitory activities of isoflavonoids from the rhizomes of Ficus tikoua Bur

A new unique isoflavone derivatives with a cyclic-monoterpene-substituent, ficusin C (1), together with five known compounds (2–6), were isolated from the rhizomes of Ficus tikoua. Their structures were elucidated on the basis of spectroscopic data interpretation, mass spectrometric analysis and comparison with literature data of related compounds. Antioxidant and α-glucosidase inhibitory activities of these compounds were evaluated by 1,1-diphenyl-2-picryhydrazyl (DPPH) radical-scavenging assay and α-glucosidase inhibitory experiment, respectively.     

Computer-assisted design and lactonization of model seco-acid derivatives of lankanolide

In some cases, seco-acid derivatives (a precursor of macrolactone) did not cyclize to form the corresponding macrolactone. To design easily cyclizable seco-acid derivatives of lanaknolide, the conformation of several model seco-acids was calculated, and lactonization experiments of the seco-acids prepared from oleandomycin were carried out to elucidate the efficiency of the cyclization of the model seco-acid. The easily cyclable seco-acid was designed to be C8 exomethylene derivative of lankanolide seco-acid. On the other hand, seco-acid derivative having tertiary alcohol at C8 was predicted not to cyclize to form macrolactone.     

Reaktionen von Steroiden mit Dialkylaminoschwefeltrifluoriden. I. 11β-Hydroxysteroide. Über STeroide, 233. Mitteilung

Reactions of Steroids with Dialkylaminosulfur Trifluorides. I. 11β-Hydroxysteroids. Reactions of three types of 11β-hydroxy steroids with dialkylaminosulfur trifluorides (DAST) have been studied. 9Δ-unsubstituted 11-alcohols are dehydrated with DAST to Δ⁹⁽¹¹⁾-unsaturated compounds under very mild conditions. 9α-Chloro-11β-hydroxy steroids are quantitatively fluorinated in position 11 yielding the known 9α-chloro-11β-fluoro derivatives. Finally, 9α, 11Δ-fluorohydrins at 0–25° are selectively transformed with DAST into Δ¹¹-9α-fluorides. When the latter reaction is run at lower temperature, the corresponding 11-piperidinesulfinates, products of partial hydrolysis of the alkoxy-dialkylaminosulfur difluoride intermediates postulated by Middleton, can be isolated in high yields. A rational explanation of the results is presented.     

Polar steroid derivatives from the Vietnamese starfish Astropecten polyacanthus

Five polar steroid derivatives, including one new glycosylated polyhydroxysteroid namely polyacanthoside A (1), were isolated from the water-soluble materials from the MeOH extract of the Vietnamese starfish Astropecten polyacanthus using various chromatographic separations. The structure elucidation was confirmed by spectroscopic experiments such as HR-ESI-MS, 1D and 2D NMR. Among the isolated compounds, (20R,24S)-3β,6α,8,15β,24-pentahydroxy-5α-cholestane (3) showed significant cytotoxic effect against five human cancer cell lines as HepG2, KB, LNCaP, MCF7 and SK-Mel2 with the IC₅₀ values from 18.03 ± 2.63 to 21.59 ± 3.23 μM.     

From 2011 to 2022: The development of pyrazole derivatives through the α,β-unsaturated carbonyl compounds

The synthesis of pyrazole derivative using α,β-unsaturated carbonyl compounds has attracted increasing attention of the synthetic organic chemist community. Interestingly, the simplicity of the synthetic method, high reactivity, and ease of incorporating diversity into the desired prototype have contributed a lot toward the exploration of α,β-unsaturated carbonyl compounds by various research groups. Due to the tremendous pharmacological significance of pyrazole derivatives, their synthesis has been one of the leading research frontiers in recent years. As prime examples, sildenafil, zometapin, Celebrex, and rimonabant have been successfully commercialized in the market to treat various life-challenging diseases. Considering the great profile of α,β-unsaturated carbonyl compound in the synthesis of biologically active pyrazole derivatives, this review incorporates contemporary literature (2011–2022) on the synthesis of pyrazole and its derivatives using α,β-unsaturated carbonyl compound as a starting precursor.