Flavonoid compounds and antibacterial mechanisms of different parts of white guava (Psidium guajava L. cv. Pearl)

Abstract

The flavonoid compositions, extracted from leaves, peel and flesh of white guava (Psidium guajava L. cv. Pearl), were identified and quantified by UPLC-ESI-QTOF-MS, HPLC-ESI-MS/MS and HPLC. The main components of three extracts all were quercetin-glycosides, but the proportion and content of quercetin-hexoside and quercetin-pentoside in each extract were different. Based on the measurements of MIC, MBC value and time killing curve, it emerged that 3 flavonoid extracts of white guava had good antibacterial effects on four pathogenic bacteria. White guava leaves flavonoids (WGLF) concentrations of 5.00?mg/mL and 0.625?mg/mL could change the micro-morphology of Escherichia coli and Staphylococcus aureus. It suggested that the antibacterial mechanism of WGLF on gram-positive and gram-negative bacteria was to destroy the structure and function of the cell membrane. It is indicated that the flavonoid extracts from white guava is a potential natural antimicrobial agent.     

Synthesis,structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me₂Sn(L)] (2), [Bu₂Sn(L)] (3), and [Ph₂Sn(L)] (4) [where H₂L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H₂L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. The molecular structures of H₂L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H₂L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H₂L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-C angles determined from ¹J(¹¹⁹Sn, ¹³C) for 2, 3, and 4 are 124.35°, 123.11°, and 123.82°, respectively. The values of δ(¹¹⁹Sn) for 2, 3, and 4 are ?153.4, ?180.59, and ?158.3 ppm, respectively, indicating five-coordinate tin(IV). From NMR data a distorted trigonal-bipyramidal configuration at each tin is proposed.     

The Use of HPLC/Thermospray Ms for the Confirmation of Aflatoxins in Peanuts

Abstract

An HPLC/Thermospray MS method is described for the determination of aflatoxins B₁, B₂, G₁ and G₂ in peanut extracts. Samples are extracted and prepared for analysis using an SPE method. The final determination utilizes reversed phase HPLC with a thermospray MS detector. The use of the MS allowed for unequivocal identification of aflatoxins in the extracts.     

Ionic liquids from the cationic cobalt(III) Schiff base complex, [Co(acacen)L2][Tf2N] (acacen = N,N′-bis(acetylacetone)ethylenediamine,Tf2N = bis(trifluoromethanesulfonyl)amide)

Ionic liquids comprising cationic cobalt(III) complexes [Co(acacen)L₂][Tf₂N] (L?=?3-butylpyridine (1), 1-butylimidazole (2); acacen?=?N,N′-bis(acetylacetone)ethylenediamine, Tf₂N?=?bis(trifluoromethanesulfonyl)amide) were prepared. 1 is a liquid at room temperature and exhibits a glass transition at ?12?°C, whereas 2 is a solid at room temperature with a melting point of 74.6?°C and glass transition temperature of ?15?°C upon cooling from the melt. These salts are reddish brown diamagnetic materials that are stable against air and water; these properties differ from those of the corresponding iron(III) salt. Desorption of the axial ligands of 1 and 2 occurs at 180 and 207?°C, respectively.     

Simultaneous quantification of metformin and glipizide in human plasma by high‐performance liquid chromatography–tandem mass spectrometry and its application to a pharmacokinetic study

A selective, sensitive and rapid high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) method was developed and validated to determine metformin and glipizide simultaneously in human plasma using phenacetin as internal standard (IS). After one‐step protein precipitation of 200 μL plasma with methanol, metformin, glipizide and IS were separated on a Kromasil Phenyl column (4.6 × 150 mm, 5 µm) at 40°C with an isocratic mobile phase consisting of methanol–10 mmol/L ammonium acetate (75:25, v/v) at a flow rate of 0.35 mL/min. Electrospray ionization source was applied and operated in the positive mode. Multiple reaction monitoring using the precursor → product ion combinations of m/z 130 → m/z 71, m/z 446 → m/z 321 and m/z 180 → m/z 110 were used to quantify metformin, glipizide and IS, respectively. The linear calibration curves were obtained over the concentration ranges 4.10–656 ng/mL for metformin and 2.55–408 ng/mL for glipizide. The relative standard deviation of intra‐day and inter‐day precision was below 10% and the relative error of accuracy was between ?7.0 and 4.6%. The presented HPLC‐MS/MS method was proved to be suitable for the pharmacokinetic study of metformin hydrochloride and glipizide tablets in healthy volunteers after oral administration. Copyright © 2012 John Wiley & Sons, Ltd.     

Screening and analysis of metabolites in rat urine after oral administration of Apocynum venetum L. extracts using HPLC–TOF‐MS

HPLC with diode array detection and ESI‐TOF‐MS was used for the study of the constituents in Apocynum venetum L. extracts and the metabolites in rat urine after oral administration of A. venetum L. extracts. A formula database of the known constituents in A. venetum L. was established, and 21 constituents were rapidly identified by accurately matching their molecular masses with the formulae of the compounds in the database. Furthermore, 34 metabolites were detected and elucidated in the rat urine. The scientific and plausible biotransformation pathways of the flavonoid components in A. venetum L. were also proposed together with the presentation of clues for potential mechanisms of bioactivity. This specific and sensitive HPLC–ESI‐TOF‐MS method can be used to identify the chemical components in the extracts of A. venetum L. and their metabolites in rat urine. This method can also be used to reveal the possible metabolic mechanisms of action of the extract components in vivo.     

Synthesis and investigation of surface active properties of green glucosyl esters

We here reported on the regioselective biosynthesis of green glucosyl monoesters surfactants which were confirmed by chemical analysis methods using immobilized enzyme catalysis with N-fatty acyl amino acid and D-glucose as substrate. Lipozyme 435 was the most efficient lipase to catalyze the transesterification reaction in t-butanol at 50?°C. The target compounds showed good surface properties. The CMC values of glucosyl esters 15-22 were 4.97, 3.96, 1.87, 0.48?mmol/L, and 4.70, 3.53, 1.58 and 0.42?mmol/L at 25?°C, respectively. It was noteworthy that the micellization physiochemical parameters were calculated and the micellization was exothermic process. Meanwhile, it was entropy driven in the formation of micelles related to the structure of glucosyl esters at different temperature.     

Two new aromatic polyketides from a deep-sea fungus Penicillium sp. SCSIO 06720

Abstract

Two new compounds, 5-[2-hydroxypropane-1-yl]-2,6-dimethlbenzene-1,3-diol (1) and coniochaetone L (2), together with 19 known compounds (3–21), were isolated from a deep-sea fungus, Penicillium sp. SCSIO 06720. Their structures and absolute configurations were elucidated by detailed NMR, MS spectroscopic analyses, chiral-phase HPLC analysis, and electronic circular dichroism spectra. All the isolated compounds (1–21) were tested for their antibacterial and HIV latency-reversal activities. Among these compounds, compound 16 showed moderate antibacterial activities against Staphylococcus aureus ATCC 29213 and Methicillin-Resistant Staphylococcus Aureus-shh-1 with MIC values of 10.4?±?3.7?μg/mL and 46.9?±?29.7?μg/mL, respectively, which were comparable to that of the positive control ampicillin with MIC values of 0.5?±?0.4?μg/mL and 2.7?±?0.9?μg/mL, respectively.     

New π ligand N,N,N,N′,N′,N′-hexaallylethylenediaminium (L2+): Synthesis and crystal structures of LBr2 · 2H2O and its cuprocomplexes L[CuII(Br0.45Cl3.55)], L[Cu 4I (Br4.55Cl1.45)], and L[Cu 4I Br6]

The alkylation of ethylenediamine with allyl bromide in the presence of a fourfold (with respect to ethylenediamine) molar amount of NaHCO₃ in acetone with an ethanol admixture (15: 1) affords LBr₂ · 2H₂O (I), where L²⁺ is the N,N,N,N′,N′,N′-hexaallylethylenediaminium cation. Single crystals of complexes L[Cu^II(Br_0.45Cl_3.55)] (II), L[Cu₄^I(Br_4.55Cl_1.45)] (III), and L[Cu₄^IBr₆] (IV) are prepared by ac electrochemical synthesis from an ethanolic solution of LBr₂ · 2H₂O, CuCl₂ · 2H₂O (or CuBr₂) at copper wire electrodes. The crystal structures of compounds I–IV are determined by X-ray diffraction analysis. The crystals of complex I are monoclinic: space group P2₁/n, a = 8.544(3), b = 10.404(3), c = 13.350(4) ?, β = 97.29(3)°, V = 1177.2(6) ?³, Z = 2. The bromine anions in compound I are bonded to the L²⁺ cations and water molecules through hydrogen contacts (E)H…Br (E = O, C) of 2.57(3)–2.86(3) ?. The crystals of compounds II–IV are triclinic: space group P . For II: a = 8.762(4), b = 9.163(4), c = 16.500(6) ?, α = 95.62(4)°, β = 96.39(4)°, γ = 111.46(4)°, V = 1211.4(9) ?³, Z = 2; for III: a = 9.074(4), b = 9.435(4), c = 9.829(5) ?, α = 116.12(4)°, β = 104.14(4)°, γ = 100.22(4)°, V = 692.3(6) ?³, Z = 1; for IV isostructural III: a = 9.084(4), b = 9.404(4), c = 9.869(4) ?, α = 116.31(3)°, β = 104.00(3)°, γ = 100.37(3)°, V = 692.1(5) ?³, Z = 1. Unlike the isolated tetrahedral CuX₄²⁻ anion in structure II, an original chain anion (Cu₄X₆²⁻) _n is observed in the structures of π complexes III and IV. Original Russian Text ? M.M. Monchak, A.V. Pavlyuk, V.V. Kinzhibalo, M.G. Mys’kiv, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 6, pp. 414–419.     

Isolation and identification of a new neo-clerodane diterpenoid from Teucrium chamaedrys L.

Teucrium chamaedrys L. is an aromatic and medicinal plant used as traditional medicine. Aerial parts of the plant material were dried and extracted with hexane–dichloromethane (extract 1), ethyl acetate–dichloromethane (extract 2) and methanol–dichloromethane (extract 3) in a ratio of 1:1 at rt successively. The solvents were evaporated to give crude extracts. Extract 1 was suspended in water at 60°C then partitioned successively with hexane and ethyl acetate to give hexane and ethyl acetate portions. After the column chromatography (silica gel) of ethyl acetate extract, one new and four known compounds were isolated. The new compound was named as 1(12S,18R)-15,16-epoxy-2β,6β-dihydroxy-neo-cleroda-13(16),14-dien-20,l2-olide-l8,l9-hemiacetal (teuchamaedryn D) (4). The known compounds were teucrin A (1), dihydroteugin (2), teucroxide (3), syspirensin A (5). The chromatographic methods were also applied for extract 3 to isolate verbascoside (6) and teucrioside (7). The structure of isolated compounds was elucidated by spectroscopic methods including LC-TOF/MS, 1D NMR and 2D NMR.     

Dynamic Modelling of Nickel Complexation in Xylem Sap of Quercus ilex: A Voltammetric Study

Holm oak (Quercus ilex) is the dominant tree growing on serpentine soils of northeast Portugal, characterized by elevated soil concentrations of Ni and Mg, combined with low Ca concentrations. Apparently Q. ilex does not suffer from excessive concentrations of Ni in the soil. In this work we report a complexation study of nickel by the relevant ligands present in xylem sap: histidine, aspartic acid, oxalic and citric acids, at 0.10 M ionic strength and pH 5.5. Single and mixed complexes were characterized. To validate the proposed complexation model, diluted solutions of Q. ilex xylem sap were titrated with nickel. All studies were done using square‐wave voltammetry (SWV) at a hanging mercury drop electrode. Due to the dynamic nature of SWV, it is possible to obtain the conditional stability constants of the complexes formed but also to have knowledge on the kinetics of the interconversion of the species present.     

Chemically characterised Pimenta dioica (L.) Merr. essential oil as a novel plant based antimicrobial against fungal and aflatoxin B1 contamination of stored maize and its possible mode of action

Abstract

The chemical characterisation of Pimenta dioica essential oil (PDEO) revealed the presence of 50 components, amongst which α-Terpineol (30.31%) was the major component followed by β-Linalool (6.75%) and γ-Terpinene (4.64%). The oil completely inhibited the growth of aflatoxin B₁ secreting strain Aspergillus flavus LHP-VS-8 and aflatoxin B₁ production at 2.5?µL/mL and 1.5?µL/mL, respectively. The oil caused dose dependent reduction of methylglyoxal (an AFB₁ inducer), enhanced leakage of Ca²⁺, Mg²⁺ and K⁺ ions and significantly reduced ergosterol content of fungal plasma membrane. During in situ experiments, PDEO exhibited complete protection of fumigated maize cob slices from fungal infestation without affecting seed germination. The chemically characterised PDEO is recommended as a plant based preservative and shelf life enhancer of food commodities by preventing fungal growth, AFB₁ production and lipid peroxidation. This is the first report on PDEO as inhibitor of AFB₁ secretion and methylglyoxal biosynthesis.     

Linking traditional anti-ulcer use of rhizomes of Bergenia ciliata (Haw.) to its anti-Helicobacter pylori constituents

Abstract

The rhizomes of Bergenia ciliata (B. ciliata, Family: Saxifragaceae) are widely used for treating gastric ulcers in folk medicine in Asia. It was hypothesized that anti-ulcer activity of B. ciliata is due to its anti-Helicobacter pylori (H. pylori) activity. The anti-H. pylori activity was investigated on six clinical bacterial isolates using agar well-diffusion and broth micro-dilution methods. The anti-H. pylori activity of amoxicillin (standard) was the highest (Zone of inhibition; ZI?=?25?mm, minimum inhibitory concentration; MIC=0.125?µg/µL) whereas among all the extracts of the rhizomes, methanol extract showed the highest activity (ZI?=?16?mm, MIC?=?12.50?µg/µL). Bioassay guided isolation of methanol extract using chromatographic and crystallization techniques isolated bergenin (ZI?=?21mm, MIC?=?0.391µg/µL) as constituent responsible for anti-H. pylori activity. The present study describes for the first time anti-H. pylori activity and possible mechanism of anti-ulcer properties of rhizomes of B. ciliata.     

Identification of coumarins in traditional Chinese medicine by direct-injection electrospray ionisation tandem mass spectrometry and high-performance liquid chromatography-mass spectrometry

A simple and rapid method has been developed for the identification of coumarins in the crude extract of traditional Chinese medicine by direct-injection electrospray ionisation (ESI) and tandem mass spectrometry (MS/MS). In this study, osthole (OS) were evaluated directly in the extract of Angelica dahurica Benth, Radix Angelicae pubescentis, and Fructus cnidii using this method. Imperatorin (IM) and its isomers isoimperatorins (IO) were detected in the three traditional Chinese medicines by direct injection ESI/MS/MS and confirmed by HPLC-ESI/MS. Our experimental data reveal that ESI/MS/MS is a sensitive, rapid and convenient technique to identify some constituents in complex and mixed plant extracts.     

One new 19-nor cucurbitane-type triterpenoid from the stems of Momordica charantia

One new 19-nor cucurbitane-type triterpenoid (3β,9β,25-trihydroxy-7β-methoxy-19-nor-cucurbita-5,23(E)-diene) (1), together with other six known cucurbitane-type triterpenoids (2–7), were isolated from the stems of Momordica charantia L. The chemical structure of 1 was elucidated by extensive 1D NMR and 2D NMR (HSQC, HMBC, COSY and ROESY), MS experiments. Using MTT assay, compound 1 exhibited weak cytotoxicity against HL-60, A-549, and SK-BR-3 cell lines with the IC₅₀ values at 27.3, 32.7 and 26.6 μM, respectively.     

Inula viscosa (L.) Aiton leaves and flower buds: Effect of extraction solvent/technique on their antioxidant ability,antimicrobial properties and phenolic profile

Abstract

This study was designed to establish the most effective solvent/technique for extracting antioxidant phytoconstituents from leaves and flower buds of Inula viscosa (L.) Aiton (Asteraceae) grown wild in Morocco. Maceration and hot extraction with methanol or water and Soxhlet ethanol extraction were utilized. The antioxidant potential was evaluated in vitro by DPPH, reducing power, and ferrous ions chelating activity assays. I. viscosa leaf and flower bud extracts displayed the strongest effect in the DPPH test, being the Soxhlet ethanol the most active ones (IC₅₀ = 54.24?±?0.21?μg/mL and 39.77?±?0.23?μg/mL); thus, they were selected for further investigations. The antimicrobial efficacy of the Soxhlet ethanol extracts against ATCC and food isolates strains was assayed; the leaf extract showed the best activity, and Candida albicans was the most sensitive strain (MIC = 125?µg/mL). The extracts resulted non-toxic against Artemia salina. Among the phenolics characterised by HPLC-PDA-ESI-MS, hispidulin hexoside, patuletin and spinacetin were identified for the first time.     

Dinuclear Zn(II) and Hg(II) complexes of an angular dipyridyl ligand: syntheses,crystal structures,and properties

The angular polytopic dipyridyl ligand 2,6-bis(quinoline-2-carboxamido)pyridine (H₂L) was prepared. Assemblies of H₂L with ZnAc₂ and HgAc₂ resulted in two new dinuclear complexes [Zn₂(L)(Ac)₂]?·?1.5H₂O?·?0.5CH₃OH (1) and [Hg₂(L)(Ac)₂]?·?5H₂O?·?CH₃OH (2) where the doubly deprotonated L^2? bi-chelate as μ-kN,N′?:?kN″,N″′, bridging the two metal centers (Ac?=?acetate). In 1, the two Zn(II) ions are also doubly bridged by two Ac ions in a μ-kO?:?kO′ coordination, and thus each metal center adopts a distorted tetrahedral geometry. In 2, each Ac ion is only terminal to Hg(II), in a rare distorted triangular or T-shaped coordination geometry. Free H₂L, 1, and 2 emit interesting bluish-green fluorescence with strong intensities. Thermogravimetric analysis of 1 shows that the dinuclear structure of 1 is stable to 382°C.     

Development and validation of a HPLC-MS/MS method for the determination of venlafaxine enantiomers and application to a pharmacokinetic study in healthy Chinese volunteers

An HPLC‐MS/MS method has been developed and validated for the determination of venlafaxine enantiomers in human plasma and applied to a pharmacokinetic study in healthy Chinese volunteers. The method was carried out on a vancomycin chiral column (5 µm, 250 × 4.6 mm) maintained at 25°C. The mobile phase was methanol–water containing 30 mmol/L ammonium acetate, pH 3.3 adjusted with aqueous ammonia (8:92, v/v) at the flow rate 1.0 mL/min. A tandem mass spectrometer with an electrospray interface was operated in the multiple reaction monitoring mode to detect the selected ions pair at m/z 278.0 → 120.8 for venlafaxine enantiomers and m/z 294.8 → 266.7 for estazolanm (internal standard). The method was linear in the concentration range of 0.28–423.0 ng/mL. The lower limit of quantification was 0.28 ng/mL. The intra‐and inter‐day relative standard deviations were less than 9.7%. The method was successfully applied for the evaluation of pharmacokinetic profiles of venlafaxine enantiomers in 18 healthy volnteers. Validation parameters such as the specificity, linearity, precision, accuracy and stability were evaluated, giving results within the acceptable range. Pharmacokinetic parameters of the venlafaxine enantiomers were measured in the 18 healthy Chinese volunteers who received a single regimen with venlafaxine hydrochloride capsules. The results show that AUC_(0–∞), C_max and t_1/2 between S‐venlafaxine and R‐venlafaxine are significantly different (p < 0.05). Copyright © 2010 John Wiley & Sons, Ltd.     

LC-ESI-MS/MS and cytotoxic activity of three Pistacia species

LC-ESI-MS/MS was used for a comprehensive characterisation of ethanol extract from the leaves of three Pistacia species. After optimisation of the method and the use of the negative ionisation mode, a total of 42 different compounds were identified, of which 22 were tentatively characterised in P. chinensis Bunge, 33 in P. khinjuk stocks and 25 in P. lentiscus L. leaves. Flavonoids, phenolic acids, and their derivatives were the most abundant identified compounds. LC-ESI-MS/MS revealed identification of 15, 18 and 6 not previously detected compounds in P. chinensis Bunge, P. khinjuk Stocks and P. lentiscus L., respectively. The three extracts were also tested for their cytotoxic activities against human PC3 prostate cancer, A549 lung cancer, MCF7 breast cancer and HepG2 liver cancer. Generally, all the extracts have a moderate cytotoxic activity against lung, breast and prostate cancer, with different IC₅₀. However, only P. lentiscus L. showed moderate activity against liver cancer.     

Molecular weight distribution and thermal characterization of polydimethylsilmethylene

1,1,3,3-Tetramethyl-1,3-disilacyclobutane (I) was polymerized under the following conditions with H₂PtCl₆·6H₂O as catalyst: (a) addition of I dropwise to a large excess of catalyst at room temperature, producing [(CH₃)₃SiCH₂(CH₃)₂Si]₂O in 90% yield; (b) polymerization at room temperature in the presence of 10% water with 23 ppm Pt, yielding 9% conversion to low molecular weight polymer after 4 weeks; (c) polymerization in an open vessel (25°C., 7 ppm Pt, M?_n = 1.2 × 10⁵), a closed vessel (100°C., 28 ppm Pt, M?_n = 1.7 × 10⁵), in a closed tube after twice freezing and evacuating (25°C., 23 ppm Pt, M?_n = 2.9 × 10⁵); (d) polymerization in an oxygen atmosphere (25°C., 17 ppm Pt, M?_n = 2.7 × 10⁵). The molecular weight distributions of the polymers with M?_n = 1.2 × 10⁵ and 1.7 × 10⁵ was studied by gel-permeation chromatography. Ratios of M?_w/M?_n are 3.1 and 2.7, respectively. In both cases a long tail of high molecular weight polymer is evident. Interpretation of the molecular weight distributions is qualitatively discussed on the basis of a postulated seven-step mechanism. Water is shown to be a source of chain termination. Evidence is presented for the existance of ?SiOSi? and ?SiOH in the silmethylene polymers. Negligible cyclization occurs. Orders of thermal stability measured by DTA and TGA for polydimethylsilmethylene (A), polydimethylsiloxane (B), and polysiobutylene (C) are: in He, A > B > C; in air, in air, B > C ? A. A fractionally precipitated polydimethylsilmethylene had a weight loss of less than 5% by 600°C. by TGA analysis at 10°C./min. in He.