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.

     

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.     

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.     

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.     

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.     

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.     

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.     

Tannin Content in Vitis Species Red Wines Quantified Using Three Analytical Methods

Tannin content in red wines is positively correlated with astringency perception and wine grade; however, tannin quantification is one of the main challenges. In this study, tannin content was quantified using three analytical methods in commercial red wines from Vitis vinifera and interspecific cold-hardy hybrids including Marquette, Frontenac, and Petite pearl cultivars. Protein (PP) and methylcellulose precipitation (MCP) methods were compared to a HPLC-DAD method, which is based on the interaction between tannins and a hydrophobic surface (RPC). Frontenac wines were the poorest in tannins and Cabernet sauvignon wines were the richest regardless of the method used. In cold-hardy red wines, the tannin content was higher in Marquette with high alcohol content, which suggested that the tannins were extracted from seeds rather than skins. The high limit of quantification of the PP method and the presence of anthocyanin di-glucosides in cold-hardy wines were parameters suggesting that protein and methylcellulose precipitation methods were neither suitable nor reliable for the quantification of tannins in cold-hardy red wines. The tannin content quantified by RPC was positively correlated to tannin quantified by MCP, suggesting that the RPC method would be relevant for the quantification of tannins in red wines.     

UPLC‐ESI‐MS study of the oxidation markers released from tannin depolymerization: toward a better characterization of the tannin evolution over food and beverage processing

Condensed tannins take an important part in the sensory quality of food and beverage. Sensory analyses are usually carried out with various tannin fractions isolated from food or beverage, and their interpretation are limited by the lack of knowledge in the fine and accurate molecular composition of the tannin fractions. Besides, the studies of the chemical reactivity conducted in model solutions with ‘simple’ flavanols allow a better understanding of their evolution pathways, but they cannot take into account their reactivity as polymers, specifically regarding oxidation. In particular, competition between intramolecular and intermolecular reactions may strongly impact on the tannin structures (size, branching and conformation) and consequently on their properties. An ultra‐performance liquid chromatography‐mass spectrometry electrospray ionization mass spectrometer analytical method was thus developed in order to identify oxidized tannins generated by autoxidation. Given the difficulties to separate and detect tannins with high DP, samples were depolymerized by chemical depolymerization prior to analysis. Since the linkages created by oxidation are not cleavable in the usual depolymerization conditions (contrarily to the original interflavanic linkages), specific oxidation residues are released from tannins structures after their autoxidation. Oxidation markers of both intermolecular and intramolecular mechanisms have been identified; these are mainly dimers and trimers, more or less oxidized, and some contain additional hydroxyl groups. Furthermore, the nature of the subunits (extension vs terminal) making up these dimers and trimers was clearly established. Copyright © 2012 John Wiley & Sons, Ltd.     

磷钼钨酸-干酪素法测定丹参药材中鞣质的含量

建立了磷钼钨酸/干酪素法测定丹参药材中鞣质含量的方法。采用室温浸提过夜提取鞣质,在磷钼钨酸与多酚类物质的显色反应进行到90~120min时,于760nm波长处,分别测定供试品溶液中的总酚和不被吸附的多酚的吸光度,以吸光度之差用标准曲线法求得鞣质含量,线性范围为2.00~8.00mg/L,线性关系良好(r=0.9997)。方法具有较高的灵敏度与选择性,精密度和重复性均较好,其RSD分别为0.4%和6.9%,标准加入回收率在80.2%~106%之间,RSD为11.8%。该方法简单、准确,并应用于不同来源的丹参药材的检测,获得了满意的结果。可用于监测丹参药材以及丹参注射液生产过程中鞣质含量的变化。     

Thermal properties of tannin extracted from Anacardium occidentale L. using TGA and FT-IR spectroscopy

The chemical nature of the polyphenols of cashew kernel testa has been determined. Testa contains tannins, which present large molecular complexity and has an ancient use as tanning agents. The use of tannins extracted from cashew testa, considered in many places as a waste, grants an extra value to the cashew. In this work we have analysed through high performance liquid chromatography, infrared spectroscopy (FT-IR) and thermo gravimetric analysis the average molecular weight, main functional groups and thermal properties of tannins extracted from Anacardium occidentale L. The results of these analyses are compared with the commercial grade tannic acid. The FT-IR spectra showed bands characteristic of C = C, C–C and OH bonds. This important bioactive compound present in the cashew nut kernel testa was suggested as an interesting economical source of antioxidants for use in the food and nutraceutical industry.     

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.     

Preliminary extraction of tannins by 1‐butyl‐3‐methylimidazole bromide and its subsequent removal from Galla chinensis extract using macroporous resins

In recent years, ionic liquids have become increasingly attractive as ‘green solvents’ used in the extraction of bioactive compounds from natural plant. However, the separation of ionic liquid from the target compounds was difficult, due to their low vapour pressure and high stabilities. In our study, ionic liquid‐based ultrasonic and microwave‐assisted extraction was used to obtain the crude tannins, then the macroporous resin adsorption technology was further employed to purify the tannins and remove the ionic liquid from crude extract. The results showed that XDA‐6 had higher separation efficiency than other tested resins, and the equilibrium experimental data were well fitted to Langmuir isotherms. Dynamic adsorption and desorption were performed on XDA‐6 packed in glass columns to optimise the separation process. The optimum conditions as follows: the ratio of column height to diameter bed was 1:8, flow rate 1 BV/h (bed volume per hour), 85% ethanol was used as eluant while the elution volume was 2 BV. Under the optimised conditions, the adsorption and desoption rate of tannins in XDA‐6 were 94.81 and 91.63%, respectively. The content of tannins was increased from 70.24% in Galla chinensis extract to 85.12% with a recovery of 99.06%. The result of ultra‐performance liquid chromatography (UPLC)‐MS/MS analysis showed that [bmim]Br could be removed from extract.     

Gel permeation chromatographic study of the molecular weight distribution of tannins in the wood,bark and leaves ofEucalyptus spp.

Summary The molecular weight distribution of tannins from the wood, bark and leaves ofEucalyptus camaldulensis, E. globulus andE. rudis from two different Spanish provenances has been studied by high performance gel permeation chromatography, using the compounds' acetylated derivatives. The MW distribution profiles showed important variability depending on the type of vegetal tissue, the species and, in some cases, on the geographical provenance of the samples. Bark was the vegetal tissue that yielded tannins with the highest molecular weight, followed by wood and leaves. Tannins from wood and bark ofE. camaldulensis were of higher molecular size than those fromE. globulus andE. rudis; those in the leaves ofE. globulus andE. camaldulensis were similar in molecular size and larger than those in the leaves ofE. rudis.     

Rapid determination of tannins in tanning baths by adaptation of BSA method

A rapid and reproducible method for the determination of tannins in vegetable tanning baths is proposed as a modification of the BSA method for grain tannins existing in literature. The protein BSA was used instead of leather powder employed in the Filter Method, which is adopted in Italy and various others countries of Central Europe. In this rapid method the tannin contents is determined by means a spectrophotometric reading and not by means a gravimetric analysis of the Filter Method. The BSA method, which belongs to mixed methods (which use both precipitation and complexation of tannins), consists of selective precipitation of tannin from a solution containing also non tannins by BSA, the dissolution of precipitate and the quantification of free tannin amount by its complexation with Fe(III) in hydrochloric solutions. The absorbance values, read at 522 nm, have been expressed in terms of tannic acid concentration by using a calibration curve made with standard solutions of tannic acid; these have been correlated with the results obtained by using the Filter Method.     

Spectrophotometric determination of tannins in tea and beer samples with iron(III) and 1,10-phenanthroline as reagents

A simple and accurate spectrophotometric method is proposed for the determination of tannins in tea and beer samples based on the reduction of iron(III) to iron(II) by tannins at 80 degrees C for 20 min. The iron(II) was then reacted with 1,10-phenanthroline at pH 4.4 to form a coloured complex. Background correction could be effected by precipitating the tannins in the sample solution twice with gelatin and kaolin. Absorbance measurements were made at 540 nm and the calibration graph was linear from 0 to 5.5 micrograms ml-1 of tannic acid with a slope of 0.213 A p.p.m.-1. The precision for the determination of tannins in a tea sample containing 9.45% of tannins was 1.8%. Most of the ingredients commonly found in tea and beer samples do not interfere with the determination. Several tea and beer samples were analysed for their tannin content using the proposed method.     

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.     

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.     

Thermomechanical analysis of the tannins of <Emphasis Type="Italic">Acacia Nilotica</Emphasis> spp. <Emphasis Type="Italic">Nilotica</Emphasis> as a rapid tool for the evaluation of wood–based adhesives

In this article, autocondensation reactions of Acacia nilotica spp. nilotica (Ann) tannin extracts solutions have been studied at several pH values by thermomechanical analyzer (TMA). TMA has been chosen for this study as it has been shown to give results more rapidly and more precisely than panels. It also tends to exaggerate the differences in results which render it an excellent tool for comparison. Therefore, autocondensation reactions were studied and compared with its polycondensation reactions upon addition of different hardeners such as paraformaldehyde, urea, and PMDI at same pH values. The aim was to evaluate the tannin’s reactivity and therefore its suitability for the production of commercially and technically viable tannin adhesives for wood products. The results of autocondensation showed that the maximum Young’s modulus values (3300 and 3600 MPa) were obtained at pH 4. However, these values have been achieved at high temperature (160 and 208 °C). Results of copolymerization reaction of the tannins with different hardeners revealed that some of these co-reactants were found to depress tannins autocondensations, while others appear to enhance the formation of the final networking. Polycondensation of the Ann tannins with 8% paraformaldehyde and 10% PMDI gave the maximum Young’s modulus values at lower temperature (91–101 °C) and acidic pH5. However, the addition of 20 and 30% PMDI achieved the best Young’s modulus values 2300 and 3300 MPa, respectively, at pH 4. Furthermore, the obtained values were comparable to those obtained by the addition of urea and the self condensation reactions. This is very important for particleboard production from economical and technical point of view. It has been noticed that the addition of hardeners lowered the temperature of hardening, and the obtained values were more consistent with the pH acidity. The study concluded that the tannins of Ann were very reactive, and therefore, it could be a potential precursor for particleboard adhesives. The results also indicated that the tannins can be used alone, and it would possibly produce zero emission environmentally friendly particleboard.     

On the liquid chromatography and identification of the flavonoids,present in the “sumach tannic acid” extracted fromRhus coriaria

Summary The leaves ofRhus coriaria contain about 15–20% polyphenolic compounds. These are mostly hydrolysable tannins, with a central glucose unit, to which several gallic acid rests are bound depsidically. 5 to 10% of the total polyphenolic fraction however, consists of condensed tannins or flavonoids. This work studies the identity and the liquid chromatographic behaviour of these flavonoids. The presence of the dimeric flavonoids agathisflavone, amenthoflavone and hinokiflavone is proved. A new dimeric flavanoid (Sumaflavone) is tentatively identified.