Glycosidic Cleavage Research Articles

One-step extraction and hydrolysis of crocin into crocetin by recyclable deep eutectic solvents

Crocetin, an aglycone derived from crocin, is synthesized in biological systems through the hydrolysis of crocin as a bioactive metabolite, which is closely associated with its pharmacodynamic effects. This research demonstrates, for the first time, that deep eutectic solvents (DES) could not only exhibit excellent solubilizing properties for crocin-based compounds, but also offer a protic medium capable of catalyzing the cleavage of glycosides to yield crocetin. A series of bifunctional and recyclable DES was proposed and characterized using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), differential scanning calorimeter (DSC), and cytotoxicity analysis. The benzyltriethylammonium chloride-oxalic acid dihydrate (TEBAC-OA, 1:1.5, mol/mol) was tailor-made for the simultaneous extraction and conversion process with a solid-to-liquid ratio of 1:20 and heating at 80 °C for 30 min. The yield of crocetin could reach 8.485 mg/g. Following the processing, DES and crocetin were successfully recovered separately, resulting in a 94% recovery rate for crocetin. The used DES was then utilized in the subsequent processing step, maintaining a production efficiency of 95.8%. Additionally, the cytotoxicity assessment revealed that the final used eutectic systems exhibited lower cytotoxicity compared to other commonly used solvents. The hydrogen bonding energy between DES and crocin, as well as the acidity of DES, were found to have a strong correlation with the yield of crocetin. Consequently, this study has successfully developed a sustainable, efficient, and simple technique for the one-step production of crocetin from gardenia fruit.

Achieving Cross-Ring Fragmentation of N-Linked Glycans by IR-MALDESI.

Glycans are complex structures that require MS/MS for detailed structural elucidation. Incorporating metals can provide more structural information by inhibiting glycosidic cleavage and enhancing cross-ring fragmentation. A direct analysis was performed using lithium doping and IR-MALDESI to induce cross-ring fragmentation of glycans. The protonated and lithiated versions of the two glycans were isolated and subjected to HCD. For protonated glycans, only glycosidic cleavages were observed. Using lithium doping, MS/MS consisted of abundant cross-ring fragments. Seventeen cross-ring fragments were detected across both glycans using lithium-doped ESI. This is the first incorporation of metal doping in IR-MALDESI to achieve cross-ring fragments in MS/MS analysis.

Metabolism investigation of the peptide-drug conjugate LN005 in rats using UHPLC[sbnd]HRMS

LN005, as a peptide-drug conjugate (PDC), is a conjugate of the homing peptide VAP and doxorubicin (DOX). The exceptional targeting ability of the homing peptide VAP is directed toward glucose-regulated protein (GRP78), a highly expressed protein primarily found in the endoplasmic reticulum of various solid tumors. However, there are limited reports regarding the metabolism of peptide-drug conjugates (PDCs), and the in vivo metabolism of LN005 has yet to be investigated. After intravenous injection of 18 mg/kg LN005 in SD rats, biological samples including plasma, urine, fecal, and bile samples, were collected and analyzed by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A total of 11 possible metabolites of LN005 were identified. Unchanged LN005 was found to be the main component in rat blood and urine, accounting for 46.46% and 63.79% of the total peak areas, respectively. M1057 was the most abundant metabolite in feces, accounting for 57.65% of the total peak area. Only one metabolite, M398, was identified in rat bile. The metabolism of LN005 is closely related to DOX, and the primary metabolic pathways involved oxidative deamination or hydrolysis, reductive glycosidic cleavage, hydrolytic glycosidic cleavage, and dehydrogenation.

The catalytic domains of Streptococcus mutans glucosyltransferases: a structural analysis.

Streptococcus mutans, found in the human oral cavity, is a significant contributor to the pathogenesis of dental caries. This bacterium expresses three genetically distinct types of glucosyltransferases named GtfB (GTF-I), GtfC (GTF-SI) and GtfD (GTF-S) that play critical roles in the development of dental plaque. The catalytic domains of GtfB, GtfC and GtfD contain conserved active-site residues for the overall enzymatic activity that relate to hydrolytic glycosidic cleavage of sucrose to glucose and fructose, release of fructose and generation of a glycosyl-enzyme intermediate in the reducing end. In a subsequent transglycosylation step, the glucosyl moiety is transferred to the nonreducing end of an acceptor to form a growing glucan polymer chain made up of glucose molecules. It has been proposed that both sucrose breakdown and glucan synthesis occur in the same active site of the catalytic domain, although the active site does not appear to be large enough to accommodate both functions. These three enzymes belong to glycoside hydrolase family 70 (GH70), which shows homology to glycoside hydrolase family 13 (GH13). GtfC synthesizes both soluble and insoluble glucans (α-1,3 and α-1,6 glycosidic linkages), while GtfB and GtfD synthesize only insoluble or soluble glucans, respectively. Here, crystal structures of the catalytic domains of GtfB and GtfD are reported. These structures are compared with previously determined structures of the catalytic domain of GtfC. With this work, apo structures and inhibitor-complex structures with acarbose are now available for the catalytic domains of GtfC and GtfB. The structure of GtfC with maltose allows further identification and comparison of active-site residues. A model of sucrose binding to GtfB is also included. The new structure of the catalytic domain of GtfD affords a structural comparison of the three S. mutans glycosyltransferases. Unfortunately, the catalytic domain of GtfD is not complete since crystallization resulted in the structure of a truncated protein lacking approximately 200 N-terminal residues of domain IV.

Mechanism for dissociative hydrolysis of pyrimidine nucleoside d4N: Inversion vs retention

Employing the microhydration model that involves two to five explicit water molecules, two plausible dissociative hydrolysis pathways of 2′,3′-didehydro-2′,3′-dideoxyuridine (d4U), α-path with configuration-inversion and β-path with configuration-retention, have been investigated by M06-2X(CPCM)/6–31++G(d,p) method. Using this model, inclusion of three explicit water molecules (n = 3) is shown to be the smallest system that gives the minimal activation free energy for α-path and β-path. Our results suggest that the glycoside cleavage is the RDS, and α-path is more favorable kinetically than β-path. Whereas β-path with exergonic formation of β-dihydrofuran-like sugar with keto pyrimidine complex possesses thermodynamic preference over α-path, where the formation of α-dihydrofuran-like sugar with enol pyrimidine complex is endergonic. The free energy barriers of RDSs for d4U (25.8 kcal mol−1) and d4T (27.3 kcal mol−1) suggest that the glycosidic bond in d4T is more stable than that in d4U. The relative lower stability of d4U is probably an important factor for less antiviral activity of d4U. The small free energy barrier differences of ∼ 1 kcal mol−1 for β-path over α-path, and the reaction free energy differences of ∼ -12 kcal mol−1 for β-path lower than α-path in d4T and d4U suggest a competitive β-path in pyrimidine d4Ns. The higher free energy barriers of RDSs in ddU (27.6 kcal mol−1) and ddT (29.0 kcal mol−1) indicate that the saturated sugar moiety increases the stability of glycosidic bond in contrast to the unsaturated counter parts in d4U and d4T. NBO analysis also shows the kinetic preference of α-path over β-path. Our results provide an exploration for the less antiviral activity of d4U and the influence of saturated ribose on the glycosidic bond stability of pyrimidine d4Ns.

Matrix Assisted Laser Desorption Ionization – Tandem Time-of-Flight – Mass Spectrometry (MALDI-TOF/TOF-MS) Characterization of Oligosaccharides: Structural Identification and Differentiation

Mass spectrometry (MS) has been developed for high-sensitivity structural determination of carbohydrates. Due to the similarity of oligosaccharide structures, there is still insufficient information about the correlation between carbohydrate chemical structure and mass spectra. A series of trisaccharides containing different glycosidic linkages (1→2, 1→3, 1→4, 1→6, 2→1 and 2→6), anomeric configuration (α and β), and monosaccharide (pentose, hexose and hexuronic acid), as well as two cyclodextrins (α- and β-cyclodextrin) were systematically investigated using matrix assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI TOF/TOF MS) in positive and negative ion modes using super-DHB (2,5-dihydroxybenzoic acid) and harmine hydrochloride as matrices, respectively. Cross-ring cleavage generated by A-types ions with neutral losses of 48, 60, 78, 90, or 120 Da were observed in the negative ion MS/MS spectra, and neutral losses of 60, 90, or 120 Da were observed in the positive ion MS/MS spectra. Glycosidic cleavages were observed in both modes. The linkage isomers were unambiguously identified by those diagnostic fragment ions with their relative intensities. Furthermore, the correlation between linkage pattern and characteristic ions successfully allowed the characterization of polysaccharides with different structural features.

Use of group IIB metal ions as charge carriers for collision-induced dissociation of glycopeptide and glycan.

Dissociation of biomolecules by tandem mass spectrometry (MS/MS) generates a variety of fragment ions which provide useful information for the structural characterization of biomolecules. Different fragmentation strategies result in different mass spectra for the same molecule and thus provide distinct features. Charge carriers play important roles in determining the dissociation pathways of the target precursor ions. The use of various transition metals ions as charge carriers of glycopeptide and glycan might provide additional structural information and needs to be investigated. A 9.4T SolariX FTICR mass spectrometer was used for collision-induced dissociation (CID) of glycopeptide and glycan. Group IIB metal ions, including Zn2+ , Cd2+ and Hg2+ , were used as charge carriers. Glycopeptide NLTK-M5 G2 and glycan G1F were used as the model systems. For Zn2+ - and Cd2+ -adducted species, cross-ring cleavages, glycosidic cleavages and cleavages along the peptide backbone could be obtained. There is a high degree of similarity in their CID spectra with that of Mg2+ ion-adducted glycopeptide species. For Hg2+ -adducted species, only glycosidic cleavages were observed in high abundance. The formation of doubly-charged ions (M2+ ) and a series of [f-H]+ fragments indicated unique dissociation pathways for Hg2+ -adducted glycopeptide. Zn2+ and Cd2+ -adducted glycopeptide species produced similar dissociation CID spectra, whereas Hg2+ -adducted species produced significantly different CID spectra. Similar CID dissociation features were also observed for Group IIB metal ions adducted glycan species. These results demonstrated that different metal ions might be used to tune the dissociation behaviors of glycopeptides and glycans.

Tandem Mass Spectrometry for Structural Characterization of Doubly-Charged N-Linked Glycopeptides

Three dissociation methods, including collision-induced dissociation (CID), electron capture dissociation (ECD), and electronic excitation dissociation (EED), were systematically compared for structural characterization of doubly charged glycopeptide. CID produced distinctively different tandem mass spectra for glycopeptide adducted with different charge carriers. Protonated species produced mainly glycosidic cleavages in high abundance. CID of magnesiated glycopeptide formed more cross-ring cleavages, whereas doubly sodiated species produced cleavages at both glycan and peptide moieties. The effect of charge carriers on the fragmentation in ECD and EED was lower than that in CID. ECD produced mainly peptide backbone cleavages but limited cleavages at the glycan moiety, whereas EED of glycopeptide resulted in extensive fragmentation throughout the molecular ion regardless of the charge carriers. Magnesiated species gave, however, more cross-ring cleavages than other charge carriers did. These results demonstrated that EED of magnesiated species could be used as a one-step dissociation method for comprehensive structural analysis of glycopeptides.

Phenolic constituents, antioxidant and α-amylase inhibitory activities of Pulicaria vulgaris growing in Tunisia: an in vitro and in silico study

The present research aimed to establish the polyphenolic profile and to appraise the antioxidant and anti-α-amylase activities of the EtOAc and BuOH extracts from the aerial parts of Pulicaria vulgaris. Total phenolics and flavonoids of both extracts were quantified. A total of 4 and 19 polyphenolic compounds were identified in the EtOAc (major component: methylcatechin: 261.51 ± 0.03 g kg−1) and BuOH extracts (major component: 1,3-O-caffeoylquinic acid:12.95 ± 0.12 g kg−1), respectively, by HPLC-PDA/ESI-MS analysis. P. vulgaris extracts showed interesting in vitro antioxidant properties. The EtOAc and BuOH extracts exhibited an α-amylase inhibitory action (IC50 values of 10.0 and 7.5 μgmL−1, respectively). It has been shown that the EtOAc extract produced an uncompetitive inhibition against α-amylase, while the BuOH extract inhibited this enzyme in mixed manner. The molecular docking analysis of the major constituents of BuOH extract showed a low binding energy, a correct mode of interaction in the active pocket of the enzyme, and an ability to interact with the key residues of glycosidic cleavage (GLU-230 and ASP-206), which can explain the strong inhibitory effect of α-amylase established by the BuOH extract. This is the first report on the polyphenolic composition, antioxidant and anti-α-amylase activities of the extracts from the aerial parts of P. vulgaris.

Production of Prosaikogenin F, Prosaikogenin G, Saikogenin F and Saikogenin G by the Recombinant Enzymatic Hydrolysis of Saikosaponin and their Anti-Cancer Effect.

The saponins of Bupleurum falcatum L., saikosaponins, are the major components responsible for its pharmacological and biological activities. However, the anti-cancer effects of prosaikogenin and saikogenin, which are glycoside hydrolyzed saikosaponins, are still unknown due to its rarity in plants. In this study, we applied two recombinant glycoside hydrolases that exhibit glycoside cleavage activity with saikosaponins. The two enzymes, BglPm and BglLk, were cloned from Paenibacillus mucilaginosus and Lactobacillus koreensis, and exhibited good activity between 30–37 °C and pH 6.5–7.0. Saikosaponin A and D were purified and obtained from the crude B. falcatum L. extract using preparative high performance liquid chromatography technique. Saikosaponin A and D were converted into saikogenin F via prosaikogenin F, and saikogenin G via prosaikogenin G using enzyme transformation with high β-glycosidase activity. The two saikogenin and two prosaikogenin compounds were purified using a silica column to obtain 78.1, 62.4, 8.3, and 7.5 mg of prosaikogenin F, prosaikogenin G, saikogenin F, and saikogenin G, respectively, each with 98% purity. The anti-cancer effect of the six highly purified saikosaponins was investigated in the human colon cancer cell line HCT 116. The results suggested that saikosaponins and prosaikogenins markedly inhibit the growth of the cancer cell line. Thus, this enzymatic technology could significantly improve the production of saponin metabolites of B. falcatum L.

Oxidative Cleavage of Glycosidic Bonds by Synthetic Mimics of Lytic Polysaccharide Monooxygenases.

Lytic polysaccharide monooxygenases (LPMOs) cleave polysaccharides through copper-bound oxyl radicals. We report a synthetic mimic of LPMO that uses micelle-stabilized hydrogen bonds to bind a glycan and two molecularly imprinted hydrophobic pockets to accommodate the alkyl tail of the glycoside and a copper cofactor, respectively. Cleavage of alkyl glycosides and oligosaccharides with hydrogen peroxide occurs at room temperature in aqueous solution, with selectivities for both the glycan and the alkyl aglycon.

Dissociation of Mannose-Rich Glycans Using Collision-Based and Electron-Based Ion Activation Methods.

Three dissociation methods, including collision-induced dissociation (CID), electron capture dissociation (ECD), and electronic excitation dissociation (EED), were evaluated for the dissociation of doubly charged glycans using sodium or magnesium ions as charge carriers. CID produced mainly glycosidic cleavages, although more cross-ring fragment ions could be obtained at higher intensities when magnesium ions were used as charge carriers [M + Mg]2+. The 0,2A3, 0,3A3, and 0,4A3 ions provided structural information on the 3 → 1 and 6 → 1 linkages of the mannoses. Some internal fragment ions, such as 2,4A5_Y3β, were also produced in high abundance, thus providing additional information on the glycan structure. ECD produced limited fragments compared to other dissociation methods when either of the metal ions were used as charge carriers. Cross-ring fragments were obtained in relatively high abundance, with the charge mainly retained on the nonreducing end. EED produced extensive glycosidic and cross-ring cleavages when either metal charge carrier was used. A higher fragmentation efficiency was achieved and more structural-specific fragments were produced when Na+ was used as the charge carrier. Of the 31 possible cross-ring cleavages, including 0,2-, 0,4-, 1,5-, 2,4-, and 3,5-cleavages, 25 were found, thus providing extensive linkage information. A wide range of fragment ions could be obtained in all dissociation methods when Mg2+ was used as the charge carrier. Two specific analytical approaches were found to produce extensively structural-specific information on the glycans studied, namely CID of magnesiated glycans and EED of sodiated glycans. These two methods were selected to further analyze the larger mannose-rich glycans Man6GlcNAc2 and Man8GlcNAc2 and generated extensive structural information.

Oxidation of Lignin-Carbohydrate Complex by Laccase/Co(salen) One-Pot Catalysis

Lignin-carbohydrate complex (LCC) is hybrid structures containing covalently linked moieties of lignin and carbohydrates. The nature and amount of LCC affect both industrial processes and practical applications of lignocellulosic biomass. Herein, the LCC was isolated from bamboo by successive solvent extraction and precipitation. The effects and mechanism of LCC oxidation respectively by laccase, Co(salen), and laccase/Co(salen) in the presence of molecular oxygen have been investigated by composition analysis using the standard of National Renewable Energy Laboratory (NREL) and high-performance anion exchange chromatography (HPAEC), GPC, FTIR, and 2D-HSQC NMR. We can conclude that the laccase/Co(salen) one-pot catalysis modified the LCC in such a way that more carbohydrate was removed from the LCC with lower molecular weight of LCC as shown by GPC; the catalytic treatments produced oxidation at lignin side-chains and cleavage of lignin β-O-4', β-β' and β-5' bonds in LCC, and cleavage of benzyl-sugar ether, phenyl glycoside and γ-ester bonds in LCC, as shown by FTIR and 2D-HSQC NMR, especially after the laccase/Co(salen) one-pot treatment. The further insight of LCC degradation was discussed in light of the results obtained in oxidation of the LCC model compound coniferin.

Preparation of glycosyl carboxylic acids via stereoselective synthesis and oxidative cleavage of C-vinyl glycosides.

We have developed an improved cyanide-free strategy for the synthesis of glycosyl carboxylic acids, employing stereoselective C-vinyl glycosylation and oxidative cleavage of C-vinyl glycosides as key steps. Compared to our previous work, the amount of NaIO4 required for the oxidative cleavage step is reduced significantly from 18 equivalents to 4.5 equivalents. This modification not only is advantageous in terms of operation and costs but also avoids the over-oxidation problem, thus greatly expanding the substrate scope, which is evidenced by the fact that 10 out of 21 glycosyl carboxylic acids synthesized are undocumented. With differently O5-protected furanosyl acids in hand, we demonstrate that an electron-rich protecting group is beneficial for the decarboxylative arylation of furanosyl carboxylic acids. This represents a rare example of protecting groups affecting the reaction efficiency in radical C-glycosylation. As C-vinyl glycosides can be prepared stereoselectively and the oxidative step is stereoretentive, the approach provides an effective means to access 1,2-trans or 1,2-cis glycosyl acids, which would be a valuable alternative to the cyanide-based synthesis of glycosyl carboxylic acids.

The sulfoquinovosyl glycerol binding protein SmoF binds and accommodates plant sulfolipids.

Sulfoquinovose (SQ) is the anionic headgroup of the ubiquitous plant sulfolipid, sulfoquinovosyl diacylglycerol (SQDG). SQDG can undergo delipidation to give sulfoquinovosyl glycerol (SQGro) and further glycoside cleavage to give SQ, which can be metabolized through microbial sulfoglycolytic pathways. Exogenous SQDG metabolites are imported into bacteria through membrane spanning transporter proteins. The recently discovered sulfoglycolytic sulfoquinovose monooxygenase (sulfo-SMO) pathway in Agrobacterium tumefaciens features a periplasmic sulfoquinovosyl glycerol binding protein, SmoF, and an ATP-binding cassette (ABC) transporter. Here, we use X-ray crystallography, differential scanning fluorimetry and isothermal titration calorimetry to study SQ glycoside recognition by SmoF. This work reveals that in addition to SQGro, SmoF can also bind SQ, a simple methyl glycoside and even a short-chain SQDG analogue. Molecular recognition of these substrates is achieved through conserved interactions with the SQ-headgroup together with more plastic interactions with the aglycones. This suggests that the solute binding protein of A. tumefaciens, and related SQ-binding proteins from other sulfoglycolytic pathways, can provide their host organisms direct access to most of the SQ metabolites known to be produced by phototrophs.

Trifluoromethylated Flavonoid-Based Isoxazoles as Antidiabetic and Anti-Obesity Agents: Synthesis, In Vitro α-Amylase Inhibitory Activity, Molecular Docking and Structure-Activity Relationship Analysis.

Diabetes mellitus is a major health problem globally. The management of carbohydrate digestion provides an alternative treatment. Flavonoids constitute the largest group of polyphenolic compounds, produced by plants widely consumed as food and/or used for therapeutic purposes. As such, isoxazoles have attracted the attention of medicinal chemists by dint of their considerable bioactivity. Thus, the main goal of this work was to discover new hybrid molecules with properties of both flavonoids and isoxazoles in order to control carbohydrate digestion. Moreover, the trifluoromethyl group is a key entity in drug development, due to its strong lipophilicity and metabolic stability. Therefore, the present work describes the condensation of a previously synthesized trifluoromethylated flavonol with different aryl nitrile oxides, affording 13 hybrid molecules indicated as trifluoromethylated flavonoid-based isoxazoles. The structures of the obtained compounds were deduced from by 1H NMR, 13C NMR, and HRMS analysis. The 15 newly synthesized compounds inhibited the activity of α-amylase with an efficacy ranging from 64.5 ± 0.7% to 94.7 ± 1.2% at a concentration of 50 μM, and with IC50 values of 12.6 ± 0.2 μM–27.6 ± 1.1 μM. The most effective compounds in terms of efficacy and potency were 3b, 3h, 3j, and 3m. Among the new trifluoromethylated flavonoid-based isoxazoles, the compound 3b was the most effective inhibitor of α-amylase activity (PI = 94.7 ± 1.2% at 50 μM), with a potency (IC50 = 12.6 ± 0.2 μM) similar to that of the positive control acarbose (IC50 = 12.4 ± 0.1 μM). The study of the structure–activity relationship based on the molecular docking analysis showed a low binding energy, a correct mode of interaction in the active pocket of the target enzyme, and an ability to interact with the key residues of glycosidic cleavage (GLU-230 and ASP-206), explaining the inhibitory effects of α-amylase established by several derivatives.

Optimizing acid hydrolysis for monosaccharide compositional analysis of Nostoc cf. linckia acidic exopolysaccharide

The exact estimation of monosaccharide composition is important in the primary structure elucidation of polysaccharides. An acid hydrolysis is usually performed for glycosidic bonds cleavage and releasing of monosaccharides. In this study, optimal conditions of total acid hydrolysis using trifluoroacetic acid (TFA) of acidic lactylated Nostoc cf. linckia exopolysaccharide (EPS) were investigated by NMR spectroscopy. Results of a series of experiments with modified acid concentration, temperature and time of hydrolysis, have shown 2 M TFA, 110 °C, 3 h as the most optimal. The stability of EPS monosaccharide components was also explored. Low stability was found at all tested conditions already during the first hour of hydrolysis; all neutral monosaccharides were degraded from 25% to 40% and glucuronic acid to 75%. NMR, contrary to standard techniques used in monosaccharide compositional analysis (HPLC, HPAEC), allowed simultaneous quantification of all GlcA forms; the free one, that one linked in oligosaccharides, as well as GlcA degradation product γ-lactone. NMR as detection method improves information about uronic acid content in EPS.

Charge transfer dissociation of a branched glycan with alkali and alkaline earth metal adducts.

Alkali and alkaline earth metal adducts of a branched glycan, XXXG, were analyzed with helium charge transfer dissociation (He-CTD) and low-energy collision-induced dissociation (LE-CID) to investigate if metalation would impact the type of fragments generated and the structural characterization of the analyte. The studied adducts included 1+ and 2+ precursors involving one or more of the cations: H+ , Na+ , K+ , Ca2+ , and Mg2+ . Regardless of the metal adduct, He-CTD generated abundant and numerous glycosidic and cross-ring cleavages that were structurally informative and able to identify the 1,4-linkage and 1,6-branching patterns. In contrast, the LE-CID spectra mainly contained glycosidic cleavages, consecutive fragments, and numerous neutral losses, which complicated spectral interpretation. LE-CID of [M + K + H]2+ and [M + Na]+ precursors generated a few cross-ring cleavages, but they were not sufficient to identify the 1,4-linkage and 1,6-branching pattern of the XXXG xyloglucan. He-CTD predominantly generated 1+ fragments from 1+ precursors and 2+ product ions from 2+ precursors, although both LE-CID and He-CTD were able to generate 1+ product ions from 2+ adducts of magnesium and calcium. The singly charged fragments derive from the loss of H+ from the metalated product ions and the formation of a protonated complementary product ion; such observations are similar to previous reports for magnesium and calcium salts undergoing electron capture dissociation (ECD) activation. However, during He-CTD, the [M + Mg]2+ precursor generated more singly charged product ions than [M + Ca]2+ , either because Mg has a higher second ionization potential than Ca or because of conformational differences and the locations of the charging adducts during fragmentation. He-CTD of the [M + 2Na]2+ and the [M + 2K]2+ precursors generated singly charged product ions from the loss of a sodium ion and potassium ion, respectively. In summary, although the metal ions influence the mass and charge state of the observed product ions, the metal ions had a negligible effect on the types of cross-ring cleavages observed.

Characterization of Physico-chemical, Thermal, and Mechanical Properties of Ethiopian Sisal Fibers.

ABSTRACT The objective of this paper was to examine the effectiveness of extraction methods (retting, chemical, and scraping) on physico-chemical, thermal, and mechanical properties of sisal (Agave sisalana) fibers. Thermal analysis (TGA), FT-IR spectroscopy, SEM, XRD, and mechanical strength tests were used to trace back the influence of extraction methods on physico-chemical, thermal, and mechanical properties of sisal fibers. Interestingly, sisal fibers extracted by chemical method (15% NaOH) have shown the highest amount of cellulose (78%) while lignin content (2.5%) is very small compared to the results from other extraction methods, retting, and scraping. The FT-IR peak around 1240 cm−1 confirmed the presence of lignin and hemicellulose which indicates the inefficiency of all extraction methods. Thermal analysis (TGA) showed two degradation peaks representing the evolution of adsorbed moisture and glycosidic cleavage of chemical components of sisal fibers. The chemical method has shown superior tensile strength (387 MPa) relative to similar fibers from retting (278 MPa) and scraping (362 MPa). To sum up, the chemical method can be recommended as a more suitable extraction technique for further engineering applications of sisal fibers.

Understanding Pharmacodynamics of Butyl Isobutyl Phthalate: Where In vitro and In silico Studies Converge

Recent epidemiological studies suggest that postprandial hyperglycemia is an independent risk factor for cardiovascular disease. A human’s high carbohydrate diet majorly consists of a high carbohydrate diet and α-glucosidase is a glucosidase located in the brush border of the small intestine is involved in glycosidic cleavage of starch at α-glycosidic bonds. α-glucosidase inhibitors are a unique class of anti-diabetic drugs particularly useful in individuals with a high carbohydrate diet. α-glucosidase inhibitors works by competitively inhibiting the enzyme α-glucosidase at the brush border of the small intestines, thus delaying the digestion of complex carbohydrate and intestinal absorption of glucose. Hence, in the present study, the α-glucosidase inhibition activity of butyl isobutyl phthalate isolated from chloroform fraction of Rubus steudneri leaves investigated and its possible mechanism of action ascertained in silico. The compound was found to exhibit concentration-dependent inhibition of α-glucosidase with half-maximal inhibitory concentration value of 10.68 g/ml. The results of in vitro α-glucosidase inhibition assay for butyl isobutyl phthalate were promising and substantiated by molecular docking and molecular dynamics studies.