LC Determination of Gallic Acid in Preparations Derived from Schinus terebinthifolius Raddi

The aim of the present paper was to develop and validate a method to determine gallic acid and tannins by LC. Validation was carried out in accordance with Brazilian Resolution 899/2003. The method showed satisfactory results for precision, accuracy, specificity and linearity. Variations on the composition and flow rate of the mobile phase influenced the peak area and retention time. The method was applied to determine the amount of hydrolysable tannins in preparations containing Schinus terebinthifolius Raddi.     

Influence of Phytochemical Reductive Capacity on Ultraviolet–visible Spectroscopic Behavior of Silver Nanoparticles

ABSTRACT

A widely used method for obtaining silver nanoparticles uses plant extracts for reduction because of the presence of phytochemicals such as terpenoids, tannins, and flavonoids. Extracts of Flores sambuci, Hypericum perforatum, Lavandula angustifolia, Origanum vulgare, Rosmarinus officinalis, and Salvia officinalis were used for generating silver nanoparticles. The ultraviolet–visible spectra of silver nanoparticle solutions were correlated with variations of phytochemical characteristics to evaluate the plant extracts. These parameters were the antioxidant activity, total flavonoids, total tannins, total terpenoids, and total phenolics. Correlations between measurements of extracts’ phytoreductive characteristics were explained using Pearson coefficients. The results showed medium linear positive correlations for total tannins with the spectra of silver nanoparticle solutions. The antioxidant activity and total terpenoids presented medium linear negative correlations. Pearson coefficients between total phenolics and relative areas from ultraviolet–visible spectra from 350 to 600?nm were close to zero indicating no linear correlation.     

Enhancement of antibiotic activity by phytocompounds of Turnera subulata

Abstract

The present study aimed to evaluate the antibacterial and modulatory activity of the Turnera subulate methyl extract in isolation or in combination with aminoglycoside antibiotics, using the microdilution method. The Turnera subulata methyl extract was used in isolation in the antibacterial assays and in combination with antibiotics in the modulation assays. All tests were performed in triplicates. The Turnera subulata methyl extract presented both antibacterial and antibiotic-modulatory effects in vitro, in isolation and in association with aminoglycosides. The extract activity depends on the bacterial strain and may be associated with the presence of tannins and flavonols. However, further studies are required to characterize the Turnera subulata potential for the development of new drugs against multiresistant bacteria.     

Formaldehyde Condensation Products of Model Phenols for Conifer Bark Tannins

Abstract

Gel permeation chromatography of the condensation products of phenols and formaldehyde proved effective in understanding the reactions of condensed tannins with formaldehyde. Rates of condensation of phloroglucinols, resorcinols, catechols, (+)catechin, and (-)epicatechin were examined to determine if methylol-tannins from southern pine bark could be prepared as resin intermediates. The phloroglucinols (models for the A-ring of pine bark tannins) were so much more reactive than were the resorcinols (models for the A-ring of wattle tannins), that preparation of methylol-tannins from pine bark tannins seems unlikely even though this approach has been applied successfully to synthesis of resins from wattle tannins. The methylol content of catechin-formaldehyde condensation products was very low. The catechol B-ring was unreactive under conditions in which condensations of pine bark tannins could be controlled. Although there is much less steric hindrance of the A-ring of (-)epicatechin than of (+)catechin, differences in the rates of condensation of these isomers were not detected. GPC and H-NMR spectra of (+)catechin condensation products showed that a dimer formed rapidly and that further condensation occurred more slowly.     

Modulation of antibiotic activity by the hydroalcoholic extract from leaves of Caryocar coriaceum WITTM

The aim of this study was to identify the presence of tannins, phenols and flavonoids on the hydroalcoholic extract of Caryocar coriaceum leaves (HECCL) and to determine the antioxidant and antibacterial activity of this extract. The extract was tested alone (1024–1 μg/mL) or associated (MIC/8) with several antibiotics in order to identify any antibacterial activity against multiresistant bacterial strains (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa). The existence of tannins, total phenols (901.31 mg/g) and flavonoids (89.68 mg/g) was confirmed in the HECCL. The presence of rutin and quercetin were confirmed by Thin-layer chromatography (TLC). Using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, the antioxidant activity of the extract (9 μg/mL) was determined. Moreover, the Minimum Inhibitory Concentration (MIC) value found for HECCL was 1024 μg/mL and the association between HECCL (MIC/8) with benzylpenicillin significantly changed its minimum inhibitory concentration from 2500 to 625 μg/mL against E. coli.     

Spectrofluorimetric determination of tannins based on their activative effect on the Cu(II) catalytic oxidation of rhodamine 6G by hydrogen peroxide

A simple and highly sensitive kinetic fluorimetric method is proposed for the determination of trace tannins, based on the activation of tannins on the oxidation of rhodamine 6G (Rh 6G) by hydrogen peroxide catalyzed by Cu(II) ion. The calibration graph was rectilinear in the range 0.08-1.28 mg l⁻¹ for tannin, the 3σ detection limit for tannin is 0.0455 mg l⁻¹. The relative standard deviation for 11 determinations of 0.4 mg l⁻¹ tannin is 0.96%. The proposed method has been successfully used to determine tannins in tea and Chinese gall. The results obtained were compared with those provided by the Folin-Ciocalteu method. This is the first procedure to be reported for the determination of tannins based on fluorimetric measurements.     

Evaluation of the antioxidant and anti-inflammatory activities of solvent extracts of Tricholepis chaetolepis (Boiss) Rech. f. whole plant

Abstract

The whole plant, Tricholepis chaetolepis, powder was investigated using proximate and fluorescence analysis along with determining the extractive values. Total phenolics, flavonoids and total protein contents of n-hexane, chloroform and methanolic extracts of the whole plant were also determined. The anti-diabetic activity of all the three extracts of the plant was determined by in vitro alpha-amylase inhibition assay. The anti-oxidant potential was evaluated using Phosophomolybdenum and DPPH methods. The anti-inflammatory potential of all extracts were determined by carrageenan-induced rat paw oedema model. The evaluation of the plant extracts exhibited the anti-diabetic, anti-oxidant, and anti-inflammatory activities in dose dependent fashion. The research concludes that Tricholepis chaetolepis extracts contain phenol, flavonoids, and tannins that show observable anti-oxidant and anti-diabetic potential. It is also concluded that the methanol extract of the plant showed the maximum effect against inflammation induced by carrageenan in rat paw oedema as compared with n-hexane and chloroform extracts.     

Fractionation of Pharmacologically Active Plant Polyphenols by Centrifugal Partition Chromatography

Abstract

Centrifugal partition chromatography (CPC) has been applied to the preparative fractionation of pharmacologically active polyphenols contained in the crude extracts from three medicinal plants. 1) (-)-Epigallocatechin gallate, the main component of tea polyphenols, which inhibits tumor promotion, 2) oligomeric hydrolyzable tannins, having host-mediated anti-tumor activity and antiviral activity, contained in Woodfordia fruticosa flower, 3) polyphenolic components of licorice, having anti-HIV activity. The results obtained with cartridges of medium volume and of small volume were compared during the fractionation of tea polyphenols.     

Tannin and Related Compounds from Terminalia catappa and Terminalia parviflora

Continuing chemical examination on tannins and related compounds of Combretaceous plants has led to the isolation of one novel complex type tannin, catappanin A, together with two phenolcarboxylic acids, two phenol glucoside gallates, seven ellagic tannins, one other hydrolyzable tannin, four flavan-3-ols and two complex type tannins from the bark of Terminalia catappa. In addition, from the bark of Terminalia parviflora one new methyl glucoside gallate, methyl 3,6-di-O-galloyl-β-D-glucoside, three phenolcarboxylic acids, three gallotannins, six ellagitannins and three other hydrolyzable tannins were isolated. Their structures were elucidated on the basis of chemical and spectroscopic evidence.     

Simultaneous LC–UV Determination of 5-Methyl-1-(3-fluorophenyl)-2-(1H)- pyridone and Its Two Metabolites in Rat Plasma

A simple, rapid, and reproducible isocratic reverse-phase HPLC method was developed to simultaneously determine AKF-PD and its two oxidized metabolites in rat plasma. 5-Carboxyl-1-phenyl-2-(1H)-pyridone and phenacetin were used as internal standards to ensure the precision and accuracy of the method. The analytes were separated on a C₁₈ reversed-phase column with methanol—phosphate buffer (20 mM, pH 2.5) as mobile phase. The limits of detection for AKF-PD and its two oxidized metabolites was 0.1 μg mL⁻¹. The method is applicable for the pharmacokinetic studies of AKF-PD and its metabolites in rats.

     

LC Determination of Five Flavonoid Aglycones in the Tibetan Medicinal Plant Oxytropis falcata Bunge

A simple, efficient and accurate liquid chromatographic method was established to determine five flavonoid aglycones, 7-hydroxy flavonone, pinocembrin, 2′,4′-dihydroxy chalcone, 2′-hydroxy-4′-methoxy chalcone and pinostrobin in the whole plant powder of Oxytropis falcata Bunge. These five compounds were separated on an Agilent Zorbax Eclipse XDB-C₈ column (150 × 4.6 mm, 5 μm). Mobile phases were composed of water containing 0.1% v/v formic acid and acetonitrile using gradient elution. The established method was validated for linearity, accuracy, precision, limit of detection and quantitation, repeatability and stability.

     

Microbial Sensor for Determination of Tannic Acid

A fungus biosensor based on an oxygen electrode andAspergillus ustusimmobilized in poly(vinyl alcohol) was developed to determine tannic acid in a batch system. The optimum temperature was 30.0°C and the optimum pH was 7.0 in 0.10 M phosphate buffer. The regression equation of the calibration curve between 0.0250 and 1.025 mM was (x lny)^{(−0.72724−x0.53/54)}+C(xlny)^{(−0.21891−x0.08/2)}=A+B/x(r≥ 0.99985). The sensor had a life of at least 2 weeks; it yielded a negligible response to the compounds commonly coexisting with vegetable tannins.     

Transport behavior of ellagic acid of pomegranate leaf tannins and its correlation with total cholesterol alteration in HepG2 cells

The aim of this study was to investigate whether ellagic acid in pomegranate leaf tannins could be transported into HepG2 cells and its transport behavior. High‐performance liquid chromatography coupled with a 996 photodiode array detector at 254 nm was applied. The mobile phase was an acetonitrile–water solution (containing 0.1% triethylamine, pH 3.0; 16:64, v/v, for determining ellagic acid in cells). The flow rate was 0.8 mL/min. Cells were incubated with pomegranate leaf tannins with 100 and 50 µg/mL (containing 1.71 and 0.85 µg/mL of ellagic acid, respectively) for a specific time, then lysed and sonicated in methanol to extract intracellular ellagic acid. A 10 µL aliquot of sample was injected into the HPLC system to determine ellagic acid concentration. The results showed that ellagic acid in pomegranate leaf tannins could be transported into the cells, which was in correlation with total cholesterol alteration in the cells. This is the first time that the transport behavior of ellagic acid through HepG2 cells in vitro has been comprehensively demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.     

Determination of Pesticides in Carrots by Gas Chromatography–Mass Spectrometry

ABSTRACT

A sensitive and selective method was developed to determine pesticides in carrots by gas chromatography–mass spectrometry following the development of an optimized extraction procedure. The method was validated for 30 organochlorine pesticides for gas chromatography with electron capture detection obtaining limit of detection from 0.18 to 0.92?µg/kg except for cis- and trans-permenthrin. Twenty-six carrot samples were analyzed and six pesticides were detected. The results compared with the accepted maximum residue levels in correlation to crop origin.     

The kinetics of condensation of phenolic polyflavonoid tannins with aldehydes

The rate constants and free energies of activation of the acid-and base-catalyzed reactions of floroglucinolic and resorcinolic flavonoid A rings of pine and wattle tannins, respectively, as well as the model compounds resorcinol, floroglucinol, and catechol, with formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, and furfural, were obtained. Second-order kinetics were found to fit these reactions. Indication and proof of the existence of unstable aldehyde ether bridges and their fast rearrangement at ambient temperature to alkyl bridges for fast-reacting phenols or phenolic compounds, such as tannins, were obtained for the first time. The dependence of the reaction kinetics on the concentration of OH- catalyst was investigated. Anomalies in the behavior of wattle tannin with aldehydes and n-butyraldehyde with phenols were observed and partially explained. The results led to a slightly different interpretation of the wattle tannin flavonoid structure.     

Phenolics from Acalypha indica

Two novel hydrolysable tannins, potassium brevifolincarboxylate and acaindinin, together with eight known tannins—1-O-galloyl-β-D -glucose, 1,2,3,6-tetra-D -galloyl-β-D -glucose, corilagin, geraniin, acetonylgeraniin A, euphormisin M₂, repandusinic acid A, and chebulagic acid, as well as two flavonoid glycosides — quercetin 3-O-β-D -glucoside and rutin, were isolated from Acalypha indica. Their structures were elucidated on the basis of chemical and spectroscopic evidence.     

Stereoselective Determination of Ornidazole Enantiomers in Human Plasma and Urine Samples by Chiral LC: Application to Pharmacokinetic Study

A stereoselective liquid chromatographic method to determine the enantiomers of ornidazole in human plasma and urine has been developed and validated. After addition of the internal standard (naproxen), samples were acidified and extracted with diethyl ether. The separation was performed on a Chiralcel OB-H column, using hexane-ethanol- glacial acetic acid (94:6:0.08, v/v) as the mobile phase. The method was validated for specificity, linearity, sensitivity, precision, accuracy and stability. For each enantiomer of ornidazole, linear calibration curves were obtained over the concentration range of 0.16–20 μg mL⁻¹ in plasma and 0.32–20 μg mL⁻¹ in urine. For both enantiomers of ornidazole in plasma and urine, the coefficient of variation for precision were consistently less than 12% and accuracy were within ±14% in terms of relative error. Application of the method to a preliminary pharmacokinetic study showed that this validated method was qualified for the direct determination of ornidazole enantiomers in human plasma and urine.

     

Stimulation quantification of four natural lipase inhibitors from Alismatis Rhizoma by high-performance thin-layer chromatography method

The lipase inhibitory activities of four main components from the rhizomes of Alisma orientale (Sam.) Juz. were evaluated by an in situ high-performance thin-layer chromatography (HPTLC)‒bioautographic assay taking orlistat as control standard. The order of relative activity was alisol B 23-acetate > alisol B > alisol A > alisol C 23-acetate. With that, an accurate, efficient and sustainable HPTLC method was developed to simultaneously determine the four lipase inhibitors from the methanolic extracts of Alismatis Rhizoma (AR). The method was carried out on HPTLC glassed plates (20 × 10 cm) coated with silica gel 60 F₂₅₄ (0.2 mm thickness) using a mixture of cyclohexane and ethyl acetate (1:1, V/V) as the mobile phase. The R_F values found for alisol B 23-acetate, alisol C 23-acetate, alisol B and alisol A were 0.62, 0.42, 0.28 and 0.09, respectively. The method was validated for specificity, linear range, precision, stability, and recovery. The results determined by scanning densitometry showed no significant difference to the results obtained by HPLC. The developed method was verified to be trustworthy for the evaluation of quality markers in AR.

     

Electrochemical Determination of Tannins Using Multiwall Carbon Nanotubes Modified Glassy Carbon Electrode

A novel chemically modified electrode is prepared on the basis of the attachment of multiwall carbon nanotubes (MWNTs) to the surface of a glassy carbon electrode (GCE) in the presence of a hydrophobic surfactant. The electrochemical behavior of tannins at the MWNTs-modified GCE is investigated. Tannins yield a well-defined oxidation at about 0.30 V (SCE) at the MWNTs-modified GCE. MWNT-film shows remarkable enhancement effect on the oxidation peak current of tannins. The experimental parameters are optimized, and a direct electrochemical method to detect tannins is proposed. The oxidation peak current is proportional to the concentration of tannins over the range from 4 × 10^–7 to 2 × 10^–4 M, and the detection limit is 1 × 10^–7 mol/l after 5 min of accumulation. The relative standard deviation of 6% for determination of 2 × 10^–6 mol/l tannins indicates excellent reproducibility. The analysis method is demonstrated by using tea and Chinese gall samples.     

Design,Synthesis, and Antiviral Activity of α-Aminophosphonates Bearing a Benzothiophene Moiety

Abstract

A series of α-aminophosphonates containing a benzothiophene moiety was designed and synthesized. All synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, ³¹P NMR, infrared spectroscopy, and elemental analysis. The half-leaf method was used to determine the in vivo efficacy of α-aminophosphonates bearing a benzothiophene moiety against the tobacco mosaic virus (TMV). Bioassay results showed that all compounds exhibited certain anti-TMV activity at 500 μg/mL concentration. Compound 2f exhibited a curative effect of up to 48.1% against TMV, which was almost similar to that obtained from the standard ningnanmycin (51.9%).

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures, and tables.]