Tannins are large-molecular-weight plant polyphenols that are produced in fruits, berries, leaves, flowers, seeds, stems, and roots of woody and non-woody plants. Hundreds and thousands of individual ...tannin structures are consequently found in many kinds of natural food and feed products. The huge structural variability in tannins is reflected as vast bioactivity differences between them but not in the accuracy of their typical analysis methods. Here, I show how the modern liquid chromatography mass spectrometry methods can be used to obtain new types of two-dimensional tannin fingerprints to better visualize both the tannin content and diversity in plants with just one 10 min analysis per sample.
Eating five servings of fruits and vegetables per day! This is what is highly recommended and heavily advertised nowadays to the general public to stay fit and healthy! Drinking green tea on a ...regular basis, eating chocolate from time to time, as well as savoring a couple of glasses of red wine per day have been claimed to increase life expectancy even further! Why? The answer is in fact still under scientific scrutiny, but a particular class of compounds naturally occurring in fruits and vegetables is considered to be crucial for the expression of such human health benefits: the polyphenols! What are these plant products really? What are their physicochemical properties? How do they express their biological activity? Are they really valuable for disease prevention? Can they be used to develop new pharmaceutical drugs? What recent progress has been made toward their preparation by organic synthesis? This Review gives answers from a chemical perspective, summarizes the state of the art, and highlights the most significant advances in the field of polyphenol research.
Diabetes mellitus is a metabolic disorder characterized by hyperglycemia, which can be counteracted by inhibition of α-glucosidase and α-amylase, both involved in the carbohydrate metabolism. ...Fourteen C-glucosidic ellagitannins and three galloylated glucoses were studied as potential α-glucosidase and α-amylase inhibitors. Most of the compounds were found to be moderate inhibitors of α-amylase, but potent inhibitors of α-glucosidase, showing low-micromolar IC50 values, far lower than that of the antidiabetic drug acarbose. This selectivity can be an advantage for their possible application as functional food ingredients with anti-diabetic properties because strong α-amylase inhibition generally causes undesired side effects. The best inhibitors were selected for further studies. Intrinsic fluorescence measurements confirmed their high affinity towards α-glucosidase, highlighting a static quenching mechanism. Circular dichroism measurements and kinetics of inhibition indicated that the most active C-glucosidic ellagitannin roburin D (RobD) is a competitive inhibitor, whereas α-pentagalloylglucose (α-PGG) acts as a mixed-type inhibitor.
Attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy was used to characterize 40 commercial tannins, including condensed and hydrolyzable chemical classes, provided as powder ...extracts from suppliers. Spectral data were processed to detect typical molecular vibrations of tannins bearing different chemical groups and of varying botanical origin (univariate qualitative analysis). The mid-infrared region between 4000 and 520 cm−1 was analyzed, with a particular emphasis on the vibrational modes in the fingerprint region (1800-520 cm−1), which provide detailed information about skeletal structures and specific substituents. The region 1800–1500 cm−1 contained signals due to hydrolyzable structures, while bands due to condensed tannins appeared at 1300–900 cm−1 and exhibited specific hydroxylation patterns useful to elucidate the structure of the flavonoid monomeric units. The spectra were investigated further using principal component analysis for discriminative purposes, to enhance the ability of infrared spectroscopy in the classification and quality control of commercial dried extracts and to enhance their industrial exploitation.
Tannins (hydrolysable and condensed tannin) are polyphenolic polymers of relatively high molecular weight with the capacity to form complexes mainly with proteins due to the presence of a large ...number of phenolic hydroxyl groups. They are widely distributed in nutritionally important forage trees, shrubs and legumes, cereals and grains, which are considered as anti‐nutritional compounds due to their adverse effects on intake and animal performance. However, tannins have been recognised to modulate rumen fermentation favourably such as reducing protein degradation in the rumen, prevention of bloat, inhibition of methanogenesis and increasing conjugated linoleic acid concentrations in ruminant‐derived foods. The inclusion of tannins in diets has been shown to improve body weight and wool growth, milk yields and reproductive performance. However, the beneficial effects on rumen modulation and animal performance have not been consistently observed. This review discusses the effects of tannins on nitrogen metabolism in the rumen and intestine, and microbial populations (bacteria, protozoa, fungi and archaea), metabolism of tannins, microbial tolerance mechanisms to tannins, inhibition of methanogenesis, ruminal biohydrogenation processes and performance of animals. The discrepancies of responses of tannins among different studies are attributed to the different chemical structures (degree of polymerisation, procyanidins to propdelphinidins, stereochemistry and CC bonding) and concentrations of tannins, and type of diets. An establishment of structure-activity relationship would be required to explain differences among studies and obtain consistent beneficial tannin effects. Copyright
The application of phenol–formaldehyde (PF) resin adhesive has been greatly limited due to its toxicity, non-renewability and high-cost. Tannin, which is mostly extracted from renewable bark, could ...serve as an environmentally friendly bio-based polyphenol material. In this paper, phenol–tannin–urea–formaldehyde (PTUF) resins were prepared by copolymerization of tannin, urea, phenol and formaldehyde. Plywood bonded with those resins was prepared as well. The properties of PTUF resins were characterized by Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). The results showed that the bonding strength of plywood bonded with the optimized PTUF resin could meet the Chinese National Standard (GB/T 17657-2013) for type I plywood. The optimized formula of PTUF resin adhesive was as follows: T/(P+T)=20%, U/(P+T)=30%. The bonding strength of plywood bonded with the optimized PTUF resin was 0.86MPa, and the formaldehyde emission was 0.13mg/L which would meet the requirement of E0 class plywood in accordance with Chinese National Standard (GB/T9846.1-9846.8-2004). TGA results showed that the thermal stability of the PTUF resin was better than that of PF resin in the initial thermal degradation. Therefore, the optimized PTUF resin is a promising substitution of PF resin in some aspects of the wood industry.
Phlorotannins are phloroglucinol-based phenolic compounds, occurring particularly in brown macroalgae, that have been recognized for their promising bioactive properties. In this study, the ...extraction of phlorotannins from
was evaluated with particular emphasis on the influential parameters, including the solvent concentration, solvent-solid ratio, extraction temperature and extraction time, using a single-factor design followed by a Box-Behnken design. The maximum total phlorotannin content, determined using the 2,4-dimethoxybenzaldehyde (DMBA) method, corresponded to 2.92 ± 0.05 mg of phloroglucinol equivalents/g dry seaweed (mg PGE/g DS), and was achieved for extracts carried out with acetone 67% (v/v), a solvent-solid ratio of 70 mL/g and temperature at 25 °C. This crude extract, together with a semi-purified phlorotannin fraction, were further evaluated for their anti-enzymatic capacity against α-glucosidase, α-amylase and pancreatic lipase, both showing promising inhibitory effects, particularly against α-glucosidase for which a greater inhibitory effect was observed compared to the pharmaceutical drug acarbose (IC
= 4.5 ± 0.8 and 0.82 ± 0.3 μg/mL, respectively, against 206.6 ± 25.1 μg/mL). Additionally, the ultra-high-pressure liquid chromatography coupled to mass spectrometry (UHPLC-MS) analysis carried out on the ethyl acetate fraction revealed the presence of fucols, fucophlorethols, fuhalols and several other phlorotannin derivatives. Moreover, possible new phlorotannin compounds, including fucofurodiphlorethol, fucofurotriphlorethol and fucofuropentaphlorethol, have been tentatively identified in this extract. Overall, this study provides evidence that
phlorotannin-rich extracts hold potential for the management of the activity of α-glucosidase, α-amylase and pancreatic lipase, which are well known to be linked to metabolic disorders such as diabetes and obesity.
Retz. forms a key component of traditional folk medicine and is also reported to possess antihepatitis C virus (HCV) and immunomodulatory activities. However, information on the intermolecular ...interactions of phytochemicals from this plant with HCV and human proteins are yet to be established. Thus, by this current study, we investigated the HCV NS3/4A inhibitory and host immune-modulatory activity of phytocompounds from
through in silico strategies involving network pharmacology and structural bioinformatics techniques. To start with, the phytochemical dataset of
was curated from biological databases and the published literature. Further, the target ability of the phytocompounds was predicted using BindingDB for both HCV NS3/4A and other probable host targets involved in the immune system. Further, the identified targets were docked to the phytochemical dataset using AutoDock Vina executed through the POAP pipeline. The resultant docked complexes with significant binding energy were subjected to 50 ns molecular dynamics (MD) simulation in order to infer the stability of complex formation. During network pharmacology analysis, the gene set pathway enrichment of host targets was performed using the STRING and Reactome pathway databases. Further, the biological network among compounds, proteins, and pathways was constructed using Cytoscape 3.6.1. Furthermore, the druglikeness, side effects, and toxicity of the phytocompounds were also predicted using the MolSoft, ADVERpred, and PreADMET methods, respectively. Out of 41 selected compounds, 10 were predicted to target HCV NS3/4A and also to possess druglike and nontoxic properties. Among these 10 molecules, Chebulagic acid and 1,2,3,4,6-Pentagalloyl glucose exhibited potent HCV NS3/4A inhibitory activity, as these scored a lowest binding energy (BE) of -8.6 kcal/mol and -7.7 kcal/mol with 11 and 20 intermolecular interactions with active site residues, respectively. These findings are highly comparable with Asunaprevir (known inhibitor of HCV NS3/4A), which scored a BE of -7.4 kcal/mol with 20 key intermolecular interactions. MD studies also strongly suggest that chebulagic acid and 1,2,3,4,6-Pentagalloyl glucose as promising leads, as these molecules showed stable binding during 50 ns of production run. Further, the gene set enrichment and network analysis of 18 protein targets prioritized 10 compounds and were predicted to potentially modulate the host immune system, hemostasis, cytokine levels, interleukins signaling pathways, and platelet aggregation. On overall analysis, this present study predicts that tannins from
have a potential HCV NS3/4A inhibitory and host immune-modulatory activity. However, further experimental studies are required to confirm the efficacies.
SUMMARY
Plant tannases (TAs) or tannin acyl hydrolases, a class of recently reported carboxylesterases in tannin‐rich plants, are involved in the degalloylation of two important groups of secondary ...metabolites: flavan‐3‐ol gallates and hydrolyzable tannins. In this paper, we have made new progress in studying the function of tea (Camellia sinensis) (Cs) TA—it is a hydrolase with promiscuous acyltransferase activity in vitro and in vivo and promotes the synthesis of simple galloyl glucoses and flavan‐3‐ol gallates in plants. We studied the functions of CsTA through enzyme analysis, protein mass spectrometry, and metabolic analysis of genetically modified plants. Firstly, CsTA was found to be not only a hydrolase but also an acyltransferase. In the two‐step catalytic reaction where CsTA hydrolyzes the galloylated compounds epigallocatechin‐3‐gallate or 1,2,3,4,6‐penta‐O‐galloyl‐β‐d‐glucose into their degalloylated forms, a long‐lived covalently bound Ser159‐linked galloyl–enzyme intermediate is also formed. Under nucleophilic attack, the galloyl group on the intermediate is transferred to the nucleophilic acyl acceptor (such as water, methanol, flavan‐3‐ols, and simple galloyl glucoses). Then, metabolic analysis suggested that transient overexpression of TAs in young strawberry (Fragaria × ananassa) fruits, young leaves of tea plants, and young leaves of Chinese bayberry (Myrica rubra) actually increased the total contents of simple galloyl glucoses and flavan‐3‐ol gallates. Overall, these findings provide new insights into the promiscuous acyltransferase activity of plant TA.
Significance Statement
Here, we have made new progress in the study of the function of tea (Camellia sinensis) tannase—it is a hydrolase with promiscuous acyltransferase activity in vitro and in vivo and promotes the synthesis of simple galloyl glucoses and flavan‐3‐ol gallates in plants. Our results expand our understanding of the real physiological significance of some hydrolases (such as tannases) in plants.
•Pomegranate peel is a juice byproduct and often considered as a waste.•It contains several phenolic compounds.•They mainly include flavonoids (mostly anthocyanins), tannins and phenolic ...acids.•Comprehensive information on characterization of phenolics in peels is provided.•These are desirable in the diet exerting positive effects on the human health.
Pomegranate peel (PoP), a juice byproduct often considered as a waste, comprises nearly around 30–40% portion of the fruit. Phenolic compounds (one class of bioactive phytochemicals) are primarily concentrated in the peel portion of pomegranate fruit. In PoP, the main phenolic compounds reported in the literature include flavonoids (anthocyanins such as pelargonidin, delphinidin, cyanidin along with their derivatives and anthoxanthins such as catechin, epicatechin and quercetin), tannins (ellagitannins and ellagic acid derivatives such as punicalagin, punicalin and pedunculagin) and phenolic acids (such as chlorogenic, caffeic, syringic, sinapic, p-coumaric, ferulic, ellagic, gallic and cinnamic acid). It is generally accepted that phenolic compounds can be more efficiently recovered from PoP by improving the extraction efficiency. The curative relevance of these compounds has been mainly assessed by in vitro experimentation. Therefore, conclusive clinical trials of the phenolic compounds present in PoP are essential for correct validation of their health benefits.
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