Quantification Of Tannins Research Articles

In vitro activity of neem (Azadirachta indica) and cassava (Manihot esculenta) on three pre-parasitic stages of susceptible and resistant strains of Teladorsagia (Ostertagia) circumcincta

Anthelmintic resistance of gastrointestinal nematodes is considered as one of the main limiting factors causing significant economic losses to the small ruminant industry. The anthelmintic properties of some plants are among the suggested alternative solutions to control these parasitic worms. The present study investigated the anthelmintic activity of neem (Azadirachta indica) and cassava (Manihot esculenta) leaf extracts against the susceptible and resistant strains of one of the most important nematodes in small ruminants, Teladorsagia (Ostertagia) circumcincta. Three different in vitro tests: egg hatch test, larval development assay, and larval paralysis assay were used to determine the efficiency of neem and cassava extracts on three pre-parasitic stages of T. circumcincta. The LC50 was determined for the most potent extract in each plant as well as the phytochemical tests, total tannin quantification and cytotoxicity on peripheral blood mononuclear cells of goats. The results revealed a high anthelmintic activity of neem methanol extract (NME) and cassava methanol extract (CME) on both strains of T. circumcincta without significant differences between the strains. The first stage larvae were more sensitive with the lowest LC50 at 7.15mg/ml and 10.72mg/ml for NME and CME, respectively, compared with 44.20mg/ml and 56.68mg/ml on eggs and 24.91mg/ml and 71.96mg/ml on infective stage larvae.

Chemical Profiling and Quantification of Tannins in Phyllanthus niruri Linn. Fractionated by SFE Method

Chemical profiles or fingerprints of polyphenolic compounds (condensed and hydrolyzable tannins) in various fractions of Phyllanthus niruri Linn extracted using supercritical carbon dioxide and various polar cosolvents, namely water, methanol, and ethanol are presented. Chemical analysis of the extracted fractions was undertaken using High Performance Liquid Chromatography (HPLC) with the in-house method. Good peak reproducibility of intra-day (R.S.D range 0.01–0.21 min) and inter-day (R.S.D range 0.5–0.8 min) was obtained for the detection of ellagitannins (hydrolyzable tannins) and flavonoids (condensed tannins). Fractions extracted using ethanol-water mixtures as cosolvent at 200 bar and 60°C exhibited an appealing behavior whereby non-polar compounds and flavonoids were able to be fractionated before the extraction of ellagitannins. Contents of three major ellagitannins, namely gallic acid (0.39–0.48% g/g), corilagin (2.42–3.00% g/g), and ellagic acid (5.94–6.48% g/g), were relatively higher compared to the commercial HEPAR-P™ standardized extract (0.21, 2.64, and 4.17% g/g, respectively). The study shows that the supercritical fluid extraction (SFE) method with the use of appropriate cosolvents is able to produce P. niruri fractions with improved yields and different chemical characteristic, which thus can be used as a rapid preparative tool for further downstream processing of plant samples.

Radical scavenging and antioxidant activities of methanolic extracts fromHypericumspecies growing in Bulgaria

Thirteen Hypericum species growing in Bulgaria were investigated for free radical-scavenging activity, antioxidant activity, total tannins and total flavonoids contents. Methanolic extracts from the Hypericum species were analyzed for radical scavenging and antioxidant activities using DPPH-, ABTS- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC) method. Butylated hydroxytoluene and ascorbic acid were used as positive controls. Methanolic extracts from H. cerastoides, H. perforatum and H. maculatum demonstrate the highest antioxidant activities and are potential sources of natural antioxidant compounds. The quantification of tannins and flavanoids were determined in Hypericum species using Folin-Chiocalteu reagent and AlCl3, respectively. The amounts of the tannins ranged from 1.30 ± 0.01 mg/100 g dw in H. elegans to 8.67 ± 0.02 g/100 g dw in H. perforatum. The highest concentration of flavonoids was found in H. cerastoides (1.22 ± 0.02 g/100g dw), and the lowest amount was established in H. olympicum (0.20 ± 0.03 g/100g dw).

Tannin Quantification in Red Grapes and Wine: Comparison of Polysaccharide- and Protein-Based Tannin Precipitation Techniques and Their Ability to Model Wine Astringency

Quantification of red grape tannin and red wine tannin using the methyl cellulose precipitable (MCP) tannin assay and the Adams-Harbertson (A-H) tannin assay were investigated. The study allowed for direct comparison between the repeatability of the assays and for the assessment of other practical considerations such as time efficiency, ease of practice, and throughput, and assessed the relationships between tannin quantification by both analytical techniques. A strong correlation between the two analytical techniques was observed when quantifying grape tannin (r(2) = 0.96), and a good correlation was observed for wine tannins (r(2) = 0.80). However, significant differences in the reported tannin values for the analytical techniques were observed (approximately 3-fold). To explore potential reasons for the difference, investigations were undertaken to determine how several variables influenced the final tannin quantification for both assays. These variables included differences in the amount of tannin precipitated (monitored by HPLC), assay matrix variables, and the monomers used to report the final values. The relationship between tannin quantification and wine astringency was assessed for the MCP and A-H tannin assays, and both showed strong correlations with perceived wine astringency (r(2) = 0.83 and r(2) = 0.90, respectively). The work described here gives guidance to those wanting to understand how the values between the two assays relate; however, a conclusive explanation for the differences in values between the MCP and A-H tannin assays remains unclear, and further work in this area is required.

Identification of Spectral Regions for the Quantification of Red Wine Tannins with Fourier Transform Mid-Infrared Spectroscopy

Accomplishment of fast tannin measurements is receiving increased interest as tannins are important for the mouthfeel and color properties of red wines. Fourier transform mid-infrared spectroscopy allows fast measurement of different wine components, but quantification of tannins is difficult due to interferences from spectral responses of other wine components. Four different variable selection tools were investigated for the identification of the most important spectral regions which would allow quantification of tannins from the spectra using partial least-squares regression. The study included the development of a new variable selection tool, iterative backward elimination of changeable size intervals PLS. The spectral regions identified by the different variable selection methods were not identical, but all included two regions (1485-1425 and 1060-995 cm(-1)), which therefore were concluded to be particularly important for tannin quantification. The spectral regions identified from the variable selection methods were used to develop calibration models. All four variable selection methods identified regions that allowed an improved quantitative prediction of tannins (RMSEP = 69-79 mg of CE/L; r = 0.93-0.94) as compared to a calibration model developed using all variables (RMSEP = 115 mg of CE/L; r = 0.87). Only minor differences in the performance of the variable selection methods were observed.

Effect of Wine Dilution on the Reliability of Tannin Analysis by Protein Precipitation

A reported analytical method for tannin quantification relies on selective precipitation of tannins with bovine serum albumin. The reliability of tannin analysis by protein precipitation on wines having variable tannin levels was evaluated by measuring the tannin concentration of various dilutions of five commercial red wines. Tannin concentrations of both very diluted and concentrated samples were systematically underestimated, which could be explained by a precipitation threshold and insufficient protein for precipitation, respectively. Based on these findings, we have defined a valid range of the tannin response in the protein precipitation-tannin assay, which suffers minimally from these problems.

A High-throughput Method for the Quantification of Proanthocyanidins in Forage Crops and its Application in Assessing Variation in Condensed Tannin Content in Breeding Programmes for Lotus corniculatus and Lotus uliginosus

Lotus corniculatus and Lotus uliginosus are agronomically important forage crops used in ruminant livestock production. The condensed tannin (CT) content, dry matter (DM) production, and persistence of these species are key characteristics of interest for future exploitation of these crops. Here we present field data on 19 varieties of L. corniculatus, 2 varieties of L. uliginosus and, additionally, a glasshouse experiment using 6 varieties of L. corniculatus and 2 varieties of L. uliginosus. Current methods for the quantification of condensed tannins in crop species are slow and labor intensive and are generally based upon polymer hydrolysis following the extraction of chlorophyll in a liquid phase. Presented here is a high-throughput protocol for condensed tannin quantification suitable for microtiter plates based upon the precipitation of condensed tannin polymers in complex with bovine serum albumin (BSA) with subsequent hydrolysis of precipates using butan 1-ol/ hydrochloric acid.

Analysis of Tannins in Red Wine Using Multiple Methods: Correlation with Perceived Astringency

The purpose of this study was to assess the relationship between astringency and tannin concentration in red wine using various analytical methods. Forty red wines were selected from a large commercial producer based on preliminary assessment of tannin variation and with selection intended to reflect potential variation in tannin amount. Tannin concentration was determined using previously published analytical methods, including absorption of light at 280 nm, reaction with 4-dimethylaminocinnamaldehyde, protein precipitation, phloroglucinolysis, and gel permeation chromatography. Results indicated that clear differences in tannin quantification existed in terms of the actual amount reported and in the relationship with perceived astringency in red wine. The analytical methods having the strongest correlations with perceived astringency were protein precipitation (r² = 0.82), phloroglucinolysis (r² = 0.73), and gel permeation chromatography (r² = 0.74). Given the equipment availability of most wineries, it was determined that protein precipitation was the most useful analytical method for astringency assessment. Because the protein precipitation method is similar to the physiological response to astringents, it could become an important in vitro tool for understanding how tannin structure modification leads to modification in astringency perception.

Extraction of Condensed Tannins from Cervid Feed and feces and Quantification using a Radial Diffusion Assay

A radial diffusion assay was employed to quantify condensed tannins (CT) in feed and feces of mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus). This biological assay measures the precipitation of bovine serum albumin (BSA), with the area of the precipitation ring being proportional to the amount of extracted CT applied to the well. CT extracted from the bark of white spruce (Picea glauca) was used as the standard. CT were extracted with 70% (v/v) aqueous acetone and precipitated with 50% (v/v) aqueous methanol or 70% (v/v) aqueous acetone. Functional range of CT weights for suitable ring measurement was 0.5-4.0 mg, and equilibrium was achieved within an incubation period of 24 hr. Methanol (50%) was a more effective precipitation solvent than acetone (70%) having 13 +/- 4% greater specific activity (P < 0.05) and superior capabilities for predicting CT content. Precipitation rings were evaluated on images magnified on a photocopier. Ring diameters measured on a 200% enlarged photocopy provided the most precise estimate of ring area (R2 = 0.98). This convenient method reduced analysis times and enhanced accuracy and precision of tannin quantification. Analytical consequences and future research requirements are considered.

Analysis of grape and wine tannins: Methods, applications and challenges

Tannins are polyphenolic secondary metabolites, which can be found in many higher plants and are identified by their ability to complex with and precipitate proteins. This key property is believed to be responsible for the mouth-feel and astringency caused by wine tannins. The analysis of tannins is of interest to practitioners in a diverse range of fields, including chemistry, pharmacology, food science, animal nutrition, ecology and plant physiology. There is a desire within the Australian wine industry to exploit objective tannin measures to complement human sensory assessment for style and quality specifications. This review, therefore, concentrates on grape-derived condensed tannins, also known as proanthocyanidins, and wine tannins formed from grape tannins. We summarise recent advances with the development of analytical methods for the quantification of tannins, review techniques for the structural characterisation of tannin molecules and emphasise the need to refine these techniques.

Effect of drying method and length of storage on tannin and total phenol concentrations in Pigeon pea seeds

Total phenols and condensed tannins in Pigeon pea seeds were determined by flow injection spectrophotometry. Folin-Denis and vanillin assays were used for total phenol and condensed tannin, respectively. Three Pigeon pea accessions were cultivated in a greenhouse. After harvesting, one access was separated into two aliquots. One aliquot was freeze-dried (−196 °C), and the other was dried in a forced air oven at 50 °C, like the other access samples, to evaluate drying temperature interference. The seeds were initially analyzed and then stored at around −10 °C, 16 °C or at ambient temperature (25 ± 10 °C). The stored samples were analysed every 30 days, for a 90 day period. A significant difference ( P<0.05) occurred between the drying methods for condensed tannin as well as for total phenols, regardless of the storage conditions. The experiments for comparing total phenols, obtained at different storage times, showed significant differences ( P<0.05) for total phenols, indicating that tannin quantification has to be done immediately after harvesting to avoid formation of protein complexes or polymerisation, which lead to erroneous results. In accordance with results, freeze-drying proved to be best for preserving the characteristics of the sample. In order to compare the tannin and phenol contents within accessions, fresh seeds should be used.

An assay to estimate tannins added to postmortem Turkey meat.

A method for quantification of tannins in wine was adapted to determine tannins added to turkey meat. Standard curves containing varying amounts of GSE [0, 0.5, 1.0, 1.5, 2.0, 2.5, and 5.0%, (w/w)] as a source of tannins were developed. The R(2) value of the mean standard curve was 0.9992. The overall percent recovery of GSE in meat was determined to be 54.78%. Results showed that estimation of GSE in four out of five of the spiked samples was less than or equal to 10%. It is unclear as to why spiked samples at 0.048 mg of GSE were always underestimated (25.0%). Overall, the method seems applicable for estimation of tannins in poultry meat and is probably applicable to estimation of tannins in other meat products.

HPLC isolation, identification and quantification of tannins from Guiera senegalensis

Nine galloylquinic acids, namely, 3-O-, 5-O-, 1,3-di-O-, 3,4-di-O-, 3,5-di-O-, 4,5-di-O-, 1,3,4-tri-O-, 3,4,5-tri-O- and 1,3,4,5-tetra-O-galloylquinic acid, were isolated by column chromatography and preparative HPLC from different parts of Guiera senegalensis. HPLC methods for the identification and quantification of gallotannins were perfected for the different plant parts. Isolation methods were performed using a solvent gradient dependent on the tannin composition. An isocratic method was used to quantify the main tannin (3,4,5-tri-O-galloylquinic acid) and 1,3,4,5-tetra-O-galloylquinic acid, which has already been studied with respect to its pharmacological activities, as well as 3,5-di-O- and 4,5-di-O-galloylquinic acids. The leaves, galls, stems and roots showed quantitative and qualitative differences with respect to the chemical composition of their tannins. Copyright © 2000 John Wiley & Sons, Ltd.

Effect of pH, Temperature, and Time on Inactivation of Tannins and Possible Implications in Detannification Studies

The tannins from quebracho and leaves of Acioa barteri after purification, and commercially available tannic acid, were stored in buffers of different pH values (6−11) at 0, 20, and 37 °C. The recovery of tannins was monitored at different time intervals (up to 18 h) using Folin−Ciocalteu and butanol−HCl−Fe3+ reagents. The recovery of tannins decreased with increase in time of storage, increase in pH, and increase in temperature. The decrease in the recovery of tannins was accompanied by a decrease in their protein precipitation capacity, and also there was no defined peak for the assay medium following the butanol−HCl−Fe3+ method for the purified quebracho and A. barteri tannins when stored at pH 11. These observations suggested that the decrease in recovery of tannins was due to inactivation of tannins. A. barteri tannins were found to be most susceptible to pH-mediated inactivation. The stirring of quebracho tannins increased the rate of inactivation at pH 11. The results suggested that alkaline pH inactivates the tannins. The rate of inactivation is higher at higher temperatures, and it can be further increased by oxygen present in the air or possibly by any other oxidizing agent. These observations were exploited to detannify tannins in some agroindustrial byproducts by using hydrogen peroxide (a strong oxidizing agent) in the presence of sodium hydroxide. This treatment was found to be very effective; the decrease in tannins reached as high as 99% in some cases. The results of the present study also highlighted a problem related to quantification of tannins in samples treated with alkalis. During extraction of tannins from such materials, tannins were inactivated due to alkalinity in the extraction medium, thereby giving an underestimate of the actual tannin levels. The alkalinity in the extraction medium results from the residual alkali present in the treated materials. This problem was overcome by addition of hydrochloric acid in the extraction medium so that the pH during extraction did not rise above 7. The results of the present study also suggest that for studying the nutritional, physiological, and biological effects of tannins (i) the pH of the tannin-containing solution should never at any stage be alkaline, (ii) the solution should be kept at low temperature, and (iii) the exposure to oxygen or to any other oxidizing agent should be avoided. Keywords: Inactivation of tannins; pH; temperature; detannification; quantification of tannins