Characterization of Acacia mangium polyflavonoid tannins by MALDI-TOF mass spectrometry and CP-MAS 13C NMR

Comparative evaluation of tannin from banana bunch and stem syrup for leather processing

Utilization of vegetable tannins in leather processing is one of the convenient solutions to protect the environment pollution. Herein, the banana bunch and syrup of banana stem are utilized to prepare an ecofriendly tanning agent. The yield of banana bunch extraction efficiency is found 69.80 %. FT-IR analysis confirmed the presence of condensed type tanning component owing to the bearing of different polyphenolic groups. The content of tannins in extracted banana bunch and stem syrup is 3.13 % and 2.6 %, respectively. The phenolic content in the banana bunch extract is determined to be 1332.37 mg GAE/100g of dried weight and in syrup was 873.92 mg GAE/100g of dried weight. This makes it possible to be used as vegetable tanners. The extracted bunch and syrup are applied to re-tan leather and compared with conventionally used vegetable tanning agent (quebracho) in parallel. Tensile strength, tear strength and elongation percentage for the extracted banana bunch and syrup are obtained at 23.84 N/mm2, 68.26 N/mm, 47.07 %, and 22.97 N/mm2, 68.38 N/mm, 40.70 %, respectively. The softness is found 1.41 for the extracted bunch and 2.01 for the syrup. The grain crack load, distension at grain crack, strength at ball burst, distension at ball burst are 246.86 N, 13.24 mm, 530.77 N, 24.54 mm for banana stem syrup and 338.77 N, 13.42 mm, 460.65 N, 29.08 mm for bunch extract, respectively. The shrinkage temperatures recorded for banana bunch extract, syrup and Quebracho (control trial) tannins tanned leather samples are 76.5 °C, 75 °C and 84 °C subsequently. The flexing endurance of the bunch extract and syrup revealed acceptable values that are less than 4. Moreover, the bunch extract tanned leather shows greater thermal stability and for syrup it is similar with the quebracho tanned leather. All the results are satisfactory compared to the control trial. Finally, tanned leather is evaluated to assess the possibility of the newly developed tannin which proves its efficiency as a potential source of tanning material for the leather industry.

Component and Structure of Aspergillus flavipes sp.-Biodegraded Bayberry Tannins: A Potential Routine for Condensed Tannin Cleaner Degradation and Disposal

Chemical degradation is widely used for producing lower-molecular-weight tannin compounds and tannin disposal, but it has negative effects on the environment, such as causing secondary pollution and consuming energy. For overcoming these disadvantages, a cleaner and sustainable degradation and disposal method for condensed tannins was developed through biodegradation. In this study, bayberry tannin solution, one kind of condensed tannin, was biodegraded by Aspergillus flavipes sp. at first; then, gel permeation chromatography and high-performance liquid chromatography were used for separating the biodegraded and original tannins to analyze the differences in components; finally, the changes in the tannin structure after biodegradation were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance. The results showed that the high-molecular-weight components decreased while the low-molecular-weight components increased when bayberry was subjected to A. flavipes sp. biodegradation; furthermore, the molecular weight of the biodegraded bayberry tannin decreased from 3371 to 2658 Da. Meanwhile, the structure of bayberry tannin polyflavonoids, especially A ring and C ring together with the galloyl group, was destroyed and some small fragments were generated during biodegradation. These structural changes resulted in the increase of low-molecular-weight phenols but the decrease of polyflavonoids after bayberry biodegradation. These would be the pieces of evidence showing that A. flavipes sp. consumed simple phenols as nourishment for growth and converted polyflavonoids into low-molecular-weight substances at the same time. To sum up, biodegradation can be used in every field where condensed tannins should be degraded or removed for a cleaner and ecofriendly routine.

Flavanols from Nature: A Phytochemistry and Biological Activity Review

Flavanols, a common class of secondary plant metabolites, exhibit several beneficial health properties by acting as antioxidant, anticarcinogen, cardioprotective, anti-microbial, anti-viral, and neuroprotective agents. Furthermore, some flavanols are considered functional ingredients in dairy products. Based on their structural features and health-promoting functions, flavanols have gained the attention of pharmacologists and botanists worldwide. This review collects and summarizes 121 flavanols comprising four categories: flavan-3-ols, flavan-4-ols, isoflavan-4-ols, and flavan-3,4-ols. The research of the various structural features and pharmacological activities of flavanols and their derivatives aims to lay the groundwork for subsequent research and expect to provide mentality and inspiration for the research. The current study provides a starting point for further research and development.

Analysis of the Structural Aspects of Tannin-Based Adhesives by 2D-NMR

We developed non-toxic, harmless adhesives composed of all-natural and renewable resources, of which one was composed of tannin and gelatin, which unfortunately was lacking water resistance, and the other of tannin and ε-poly-l-lysine. In this study, we analyzed the chemical structures of these adhesives by two-dimensional nuclear magnetic resonance (2D-NMR) to explain the difference in water-resistance of the two glues. The results showed that only one proton was left in the benzene ring of tannin after mixing. This suggests that the amino group of the protein was directly attached to the benzene ring by a Michael addition-type reaction, and not to the hydroxyl group. In addition, the heteronuclear multiple bond correlation spectrum of the tannin-poly-l-lysine compound indicated that the hydroxyl groups of the tannin oxidized, suggesting the improvement of its water resistance.

Mass spectrometry as a tool to advance polymer science

In contrast to natural polymers, which have existed for billions of years, the first well-understood synthetic polymers date back to just over one century ago. Nevertheless, this relatively short period has seen vast progress in synthetic polymer chemistry, which can now afford diverse macromolecules with varying structural complexities. To keep pace with this synthetic progress, there have been commensurate developments in analytical chemistry, where mass spectrometry has emerged as the pre-eminent technique for polymer analysis. This Perspective describes present challenges associated with the mass-spectrometric analysis of synthetic polymers, in particular the desorption, ionization and structural interrogation of high-molar-mass macromolecules, as well as strategies to lower spectral complexity. We critically evaluate recent advances in technology in the context of these challenges and suggest how to push the field beyond its current limitations. In this context, the increasingly important role of high-resolution mass spectrometry is emphasized because of its unrivalled ability to describe unique species within polymer ensembles, rather than to report the average properties of the ensemble.

Copigmentation of Malvidin-3-O-Monoglucoside by Oenological Tannins: Incidence on Wine Model Color in Function of Botanical Origin, pH and Ethanol Content

The effect of the botanical origin, pH level and ethanol content of different oenological tannins on the color of malvidin-3-O-monoglucoside solution, including their effectiveness as copigments, was studied. Briefly, a model wine solution (4 g/L of tartaric acid, pH 3.5 and 12% ethanol) containing 50 mg/L of malvidin-3-O-monoglucoside was prepared and supplemented with 0.1, 0.2 and 0.4 g/L of commercial tannins using (−)-epicatechin as reference control copigment. Six additional model wine solutions (12% ethanol at pH 3.1, 3.5 or 3.9, and 10%, 12% or 14% ethanol at pH 3.5) were prepared as previously described. Samples were stored under airtight conditions. After a week the full absorbance spectrum in the visible range (400–800 nm) was measured and CIELAB color space was determined. These measurements, including an increase in a* (redness), a decrease in b* (yellowness) and a decrease in L* (lightness), indicated that all oenological tannins had a clear positive effect on color copigmentation. Moreover, hydrolysable tannins appeared to be better copigments than condensed tannins as the copigmentation effectiveness (Cp) was found to be between two to four times higher. The effects of these tannins were dose-dependent because a higher addition resulted in a greater impact on copigmentation. In general, an increase in pH and ethanol content resulted in a decrease of the effect of tannins on color. Independent of intrinsic wine conditions, hydrolysable tannins, more specifically gallotannin, remain the most effective in increasing red wine color. These results prove that supplementation with oenological tannins, especially hydrolysable tannins, could be an interesting tool for the improvement of the red wine color.

Characterization and Potential Antidiabetic Activity of Proanthocyanidins from the Barks of Acacia mangium and Larix gmelinii

Proanthocyanidins in ethanol extracts from the barks of Acacia mangium and Larix gmelinii were analyzed by gel permeation chromatography, MALDI-TOF/TOF MS, and HPLC/MS. The inhibitory effects of proanthocyanidins and acid-catalyzed hydrolysis of proanthocyanidins against carbolytic enzymes were also tested. A significant relationship between carbolytic enzymes inhibition and degree of polymerization was established, showing that the degree of polymerization is a major contributor to the biological activity of the proanthocyanidins from both types of woody plant bark. The results indicate that proanthocyanidins from the barks of A. mangium and L. gmelinii have potential antidiabetic properties.

Complementarity of Matrix- and Nanostructure-Assisted Laser Desorption/Ionization Approaches

In recent years, matrix-assisted laser desorption/ionization (MALDI) has become the main tool for the study of biological macromolecules, such as protein nano-machines, especially in the determination of their molecular masses, structure, and post-translational modifications. A key role in the classical process of desorption and ionization of the sample is played by a matrix, usually a low-molecular weight weak organic acid. Unfortunately, the interpretation of mass spectra in the mass range of below m/z 500 is difficult, and hence the analysis of low molecular weight compounds in a matrix-assisted system is an analytical challenge. Replacing the classical matrix with nanomaterials, e.g., silver nanoparticles, allows improvement of the selectivity and sensitivity of spectrometric measurement of biologically important small molecules. Nowadays, the nanostructure-assisted laser desorption/ionization (NALDI) approach complements the classic MALDI in the field of modern bioanalytics. In particular, the aim of this work is to review the recent advances in MALDI and NALDI approaches.

Analytical Profiling of Proanthocyanidins from Acacia mearnsii Bark and In Vitro Assessment of Antioxidant and Antidiabetic Potential

The proanthocyanidins from ethanol extracts (80%, v/v) of Acacia mearnsii (A. mearnsii) bark on chemical-based and cellular antioxidant activity assays as well as carbolytic enzyme inhibitory activities were studied. About 77% of oligomeric proanthocyanidins in ethanol extracts of A. mearnsii bark were found by using normal-phase HPLC. In addition, HPLC-ESI-TOF/MS and MALDI-TOF/TOF MS analyses indicated that proanthocyanidins from A. mearnsii bark exhibited with a degree of polymerization ranging from 1 to 11. These results of combined antioxidant activity assays, as well as carbolytic enzyme inhibitory activities of proanthocyanidins from A. mearnsii bark, indicated an encouraging antioxidant capacity for the high polyphenol content and a potential for use as alternative drugs for lowering the glycemic response.

New approach for fast identification of cyclitols by MALDI-TOF mass spectrometry

INTRODUCTION

Alfalfa (Medicago sativa L.) is the subject of many studies due to its numerous chemical constituents and beneficial properties. Among these constituents are cyclitols, which have attracted attention due to the variety of biological properties they have.

OBJECTIVE

A rapid and sensitive analytical procedure based on matrix-assisted laser desorption ionisation technique with time-of-flight and mass spectrometry (MALDI-TOF-MS) analysis was used for the first time for the identification of three cyclitols from different parts of alfalfa.

METHODOLOGY

Plant extracts were prepared and purified using Soxhlet extraction and solid-phase extraction (SPE). Then, samples were dissolved in α-cyano-4-hydroxycinnamic acid (HCCA) matrix, and subjected to MALDI-TOF-MS analysis.

RESULTS

The ion at m/z 524.0 was distributed in all standards and in leaves and stem extracts. In turn, the signal at m/z 335.1 was found in all standards and all alfalfa extracts. The ion at m/z144.1 was found just for d-chiro-inositol and distributed in all extracts. Both signals at m/z 265.9 and 250.0 were found only in l-chiro-inositol standard and the extract of stem. However, the ion at m/z 177.1 was found in d-pinitol standard and the extract of leaves. Based on molecular weights, information on fragment ions obtained by MALDI-TOF-MS, and the chemistry of cyclitols, we successfully identified three cyclitols (d-chiro-inositol, l-chiro-inositol, d-pinitol) in different parts of alfalfa (leaves, stem, flowers).

CONCLUSION

The obtained results in this study proved that MALDI-TOF-MS is a rapid, sensitive and very powerful tool for identification of cyclitols within plants and has the potential to differentiate between enantiomers.

Relationships between Structures of Condensed Tannins from Texas Legumes and Methane Production During In Vitro Rumen Digestion

Previous studies showed that a series of purified condensed tannins (CTs) from warm-season perennial legumes exhibited high variability in their modulation of methane production during in vitro rumen digestion. The molecular weight differences between these CTs did not provide correlation with either the in vitro CH₄ production or the ability to precipitate bovine serum albumin. In an effort to delineate other structure-activity relationships from these methane abatement experiments, the structures of purified CTs from these legumes were assessed with a combination of methanolysis, quantitative thiolysis, ¹H-13C HSQC NMR spectroscopy and ultrahigh-resolution MALDI-TOF MS. The composition of these CTs is very diverse: procyanidin/prodelphinidin (PC/PD) ratios ranged from 98/2 to 2/98; cis/trans ratios ranged from 98/2 to 34/66; mean degrees of polymerization ranged from 6 to 39; and % galloylation ranged from 0 to 75%. No strong correlation was observed between methane production and the protein precipitation capabilities of the CT towards three different proteins (BSA, lysozyme, and alfalfa leaf protein) at ruminal pH. However, a strong non-linear correlation was observed for the inhibition of methane production versus the antioxidant activity in plant sample containing typical PC- and PD-type CTs. The modulation of methane production could not be correlated to the CT structure (PC/PD or cis/trans ratios and extent of galloylation). The most active plant in methane abatement was Acacia angustissima, which contained CT, presenting an unusual challenge as it was resistant to standard thiolytic degradation conditions and exhibited an atypical set of cross-peak signals in the 2D NMR. The MALDI analysis supported a 5-deoxy flavan-3-ol-based structure for the CT from this plant.

Chemical characterization, antioxidant properties and oxygen consumption rate of 36 commercial oenological tannins in a model wine solution

The chemical composition (CC), antioxidant capacity (AC) and oxygen consumption rate (OCR) of 36 different commercial tannins were measured. The CC was analyzed by total polyphenol index, Bate-Smith, methyl-cellulose, Folin-Ciocalteu, OIV official method and phloroglucinolisis. The AC was measured by different methods (ABTS, CUPRAC, DPPH, FRAP, ORAC) using Trolox as standard. The OCR was measured using a non-invasive method based on luminescence. The results indicate that it is possible to obtain differentiation between procyanidins/prodelphinidins, profisetinidins/prorobinetidins, gallotannins and ellagitannins by PCA based on their CC data. It is also possible to separate condensed from hydrolysable tannins by PCA based on their AC data. The results show that ellagitannins are the fastest oxygen consumers of the various oenological tannins, followed in descending order by condensed tannins and finally gallotannins. The combination of CC, AC and OCR analyses enable to classify tannins according to their effectiveness in protecting wines against oxidation.

Extraction approaches used for the determination of biologically active compounds (cyclitols, polyphenols and saponins) isolated from plant material

Based on the bioactive properties of certain compounds, such as antioxidant and anti-inflammatory activities, an interesting subject of research are natural substances present in various parts of plants. The choice of the most appropriate method for separation and quantification of biologically active compounds from plants and natural products is a crucial step of any analytical procedure. The aim of this review article is to present an overview of a comprehensive literature study from the last 10 years (2007-2017), where relevant articles exposed the latest trends and the most appropriate methods applicable for separation and quantification of biologically active compounds from plant material and natural products. Consequently, various extraction methods have been discussed, together with the available procedures for purification and pre-concentration and dedicated methods used for analysis.

Detailed Chemical Composition of Condensed Tannins via Quantitative (31)P NMR and HSQC Analyses: Acacia catechu, Schinopsis balansae, and Acacia mearnsii

The chemical composition of Acacia catechu, Schinopsis balansae, and Acacia mearnsii proanthocyanidins has been determined using a novel analytical approach that rests on the concerted use of quantitative (31)P NMR and two-dimensional heteronuclear NMR spectroscopy. This approach has offered significant detailed information regarding the structure and purity of these complex and often elusive proanthocyanidins. More specifically, rings A, B, and C of their flavan-3-ol units show well-defined and resolved absorbance regions in both the quantitative (31)P NMR and HSQC spectra. By integrating each of these regions in the (31)P NMR spectra, it is possible to identify the oxygenation patterns of the flavan-3-ol units. At the same time it is possible to acquire a fingerprint of the proanthocyanidin sample and evaluate its purity via the HSQC information. This analytical approach is suitable for both the purified natural product proanthocyanidins and their commercial analogues. Overall, this effort demonstrates the power of the concerted use of these two NMR techniques for the structural elucidation of natural products containing labile hydroxy protons and a carbon framework that can be traced out via HSQC.

Characterization and Physicochemical Properties of Condensed Tannins from Acacia catechu

Condensed tannins from Acacia catechu were carefully studied to determine their chemical structure and physicochemical properties. The combined use of MALDI-TOF-MS and (13)C NMR revealed that catechin and epicatechin are the predominant monomers. Most of the compounds were dimers, as confirmed by size exclusion chromatography measurements. To evaluate their potential as aromatic building block in polymer synthesis, special care was given to the characterization and quantification of the different OH groups. A detailed (31)P NMR analysis showed the predominance of catechin, with a catechin/epicatechin ratio of 4.2:1. Two distinct (1)H NMR measurements confirmed the quantification. The thermal properties were also determined: the tannins showed a high temperature of degradation (ca. 190 °C) and a high glass transition temperature (ca. 140 °C), allowing for thermal processing or chemical reactions at relatively high temperature. A. catechu tannins thus present interesting features to be used as aromatic building blocks in polymer materials.

Development of methodology for identification the nature of the polyphenolic extracts by FTIR associated with multivariate analysis

Tannins are polyphenolic compounds of complex structures formed by secondary metabolism in several plants. These polyphenolic compounds have different applications, such as drugs, anti-corrosion agents, flocculants, and tanning agents. This study analyses six different type of polyphenolic extracts by Fourier transform infrared spectroscopy (FTIR) combined with multivariate analysis. Through both principal component analysis (PCA) and hierarchical cluster analysis (HCA), we observed well-defined separation between condensed (quebracho and black wattle) and hydrolysable (valonea, chestnut, myrobalan, and tara) tannins. For hydrolysable tannins, it was also possible to observe the formation of two different subgroups between samples of chestnut and valonea and between samples of tara and myrobalan. Among all samples analysed, the chestnut and valonea showed the greatest similarity, indicating that these extracts contain equivalent chemical compositions and structure and, therefore, similar properties.

¹H-¹³C HSQC NMR spectroscopy for estimating procyanidin/prodelphinidin and cis/trans-flavan-3-ol ratios of condensed tannin samples: correlation with thiolysis

Studies with a diverse array of 22 purified condensed tannin (CT) samples from nine plant species demonstrated that procyanidin/prodelphinidin (PC/PD) and cis/trans-flavan-3-ol ratios can be appraised by (1)H-(13)C HSQC NMR spectroscopy. The method was developed from samples containing 44-∼100% CT, PC/PD ratios ranging from 0/100 to 99/1, and cis/trans ratios ranging from 58/42 to 95/5 as determined by thiolysis with benzyl mercaptan. Integration of cross-peak contours of H/C-6' signals from PC and of H/C-2',6' signals from PD yielded nuclei-adjusted estimates that were highly correlated with PC/PD ratios obtained by thiolysis (R(2) = 0.99). cis/trans-Flavan-3-ol ratios, obtained by integration of the respective H/C-4 cross-peak contours, were also related to determinations made by thiolysis (R(2) = 0.89). Overall, (1)H-(13)C HSQC NMR spectroscopy appears to be a viable alternative to thiolysis for estimating PC/PD and cis/trans ratios of CT if precautions are taken to avoid integration of cross-peak contours of contaminants.

α-Amylase and lipase inhibitory activity and structural characterization of acacia bark proanthocyanidins

The bark extract of Acacia mearnsii showed strong lipase and α-amylase inhibition activities. Fractionation of the extract by column chromatography and subsequent (13)C NMR and MALDI-TOF-MS analysis revealed that the active substances are proanthocyanidin oligomers mainly composed of 5-deoxyflavan-3-ol units. In addition, 4'-O-methylrobinetinidol 3'-O-β-D-glucopyranoside, fisetinidol-(4α,6)-gallocatechin, and epirobinetinidol-(4β,8)-catechin were isolated as new compounds, and their structures were determined from spectroscopic data. Furthermore, a modified thiol degradation method using strongly acidic conditions was applied to the extract to yield three thiol degradation products derived from robinetinidol units. This method is useful for characterizing acacia proanthocyanidins (wattle tannins).

Tannin fingerprinting in vegetable tanned leather by solid state NMR spectroscopy and comparison with leathers tanned by other processes

Solid state ¹³C-NMR spectra of pure tannin powders from four different sources – mimosa, quebracho, chestnut and tara – are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The ²⁷Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance.

Extraction and analysis of polyphenols: recent trends

In recent years, there has been an increasing interest in diets rich in fruits and vegetables and this is mostly due to their presumed role in the prevention of various degenerative diseases, such as cancer and cardiovascular diseases. This is mainly due to the presence of bioactive compounds, such as polyphenols, carotenoids, among others. Polyphenols are one of the main classes of secondary metabolites derived from plants offering several health benefits resulting in their use as functional foods. Prior to the use of these polyphenols in specific applications, such as food, pharmaceutical, and the cosmetic industries, they need to be extracted from the natural matrices, then analyzed and characterized. The development of an efficient procedure for the extraction, proper analysis, and characterization of phenolic compounds from different sources is a challenging task due to the structural diversity of phenolic compounds, a complex matrix, and their interaction with other cellular components. In this light, this review discusses different methods of extraction, analysis, and the structural characterization of polyphenolic compounds.