Microbial degradation of tannins – A current perspective

Tannins are water-soluble polyphenolic compounds having wide prevalence in plants. Hydrolysable and condensed tannins are the two major classes of tannins. These compounds have a range of effects on various organisms – from toxic effects on animals to growth inhibition of microorganisms. Some microbes are, however, resistant to tannins, and have developed various mechanisms and pathways for tannin degradation in their natural milieu. The microbial degradation of condensed tannins is, however, less than hydrolysable tannins in both aerobic and anaerobic environments. A number of microbes have also been isolated from the gastrointestinal tract of animals, which have the ability to break tannin-protein complexes and degrade tannins, especially hydrolysable tannins. Tannase, a key enzyme in the degradation of hydrolysable tannins, is present in a diverse group of microorganisms, including rumen bacteria. This enzyme is being increasingly used in a number of processes. Presently, there is a need for increased understanding of the biodegradation of condensed tannins, particularly in ruminants.     

Paeonia emodi Royle: Ethnomedicinal uses,phytochemistry and pharmacology

Paeonia emodi (Peony) is a well known Himalayan medicinal plant used in the treatment of hypertension, palpitations, asthma, uterine diseases, colic, bilious obstructions and has also been used as an anticoagulant. Many of these ethnomedicinal properties have been experimentally proven in different animal models. The present work reviews the ethnopharmacology, therapeutic potential and phytochemistry of P. emodi. Different classes of natural products like triterpenoids, monoterpenoids, phenolics and tannins have been isolated from the species. These compounds possess wide therapeutic profile like cardiovascular and airway relaxant, lipoxygenase and β-Glucuronidase inhibitory and free radical scavenging properties.     

Metabolic diversity and bioactivity screening of mangrove plants: a review

Mangrove forests are salt tolerant plants confined to the coastal areas and occupy only 5% of the total forest areas of the world. These are the most hostile environment with fluctuating tidal and saline regime and a limited plant species can survive under such condition. Nevertheless, these plants are most valuable resources and provide economic and ecological benefits to the coastal people. Several mangrove species have been used in traditional medicine or have few applications as insecticide and pesticide. Mangroves are biochemically unique, producing wide array of natural products with unique bioactivity. They possess active metabolites with some novel chemical structures which belong to diverse chemical classes such as alkaloids, phenol, steroids, terpenoids, tannins, etc. The present review examines recent investigations on the biological activities of extracts and phytochemicals identified from mangroves and their associates as antimicrobial, antiviral, antioxidant, anticancer and many other properties like antiproliferative, insecticidal, antimalarial, antifeedant, central nervous system depressant and anti-plasmodial etc. The present article also emphasizes and creates an awareness of potential mangroves and their associates as a source of novel medicines, agrochemicals and source of many biologically active compounds.     

Effects of chemically defined tannins on poly (ADP-ribose) glycohydrolase activity.

Three classes of chemically defined tannins, gallotannins, ellagitannins and condensed tannins were examined for their inhibitory activities against purified poly (ADP-ribose) glycohydrolase. Ellagitannins showed higher inhibitory activities than gallotannins. In contrast, condensed tannins, which consist of an epicathechin gallate (ECG) oligomer without a glucose core were not appreciably inhibitory. Kinetic analysis revealed that the inhibition of ellagitannins was competitive with respect to the substrate poly(ADP-ribose), whereas gallotannins exhibited mixed-type inhibition. These results suggest that conjugation with glucose of hexahydroxy-diphenoyl (HHDP) group, which is a unique component of ellagitannins, potentiated the inhibitory activity, and that the structure of ellagitannins may have a functional domain which competes with poly(ADP-ribose) on the poly(ADP-ribose) glycohydrolase molecule.     

Haemanalysis of tannins: The concept of relative astringency

The astringency of tannins, that is their efficiency as precipitants of proteins, is determined by their reaction with the proteins of haemolysed blood and calorimetric determination of residual haemoglobin. The method is accurate and sensitive because of the narrow range of concentration of tannin between that required to initiate precipitation (the threshold concentration) and that for complete precipitation. ‘Relative astringency’ (RA) is the ratio of the concentration of the tannic acid to that of the tannin which effects the same degree of precipitation. The RA of certain esters of hexahydroxydiphenic acid and of certain procyanidins of known constitution has been determined and the results applied to the ellagitannins and/or leucoanthocyanins present in species of Shorea, Geranium and other plants. The homology of each of these classes of tannins is discussed in the light of the results.     

Invited review: Tannins as a potential alternative to antibiotics to prevent coliform diarrhea in weaned pigs

In addition to a multifactorial etiology of nutritional, social and environmental stressors, post-weaning diarrhea (PWD) in pigs is often related to infection with specific pathogens such as enterotoxigenic Escherichia coli (ETEC). In swine farming operations, the incidence of PWD is a global concern and is associated with an unbalanced gut status, resulting in poor performance and high antimicrobial consumption via prophylaxis and metaphylaxis. Increases in antimicrobial resistance are reinforcing an already-urgent need for sustainable, alternative solutions for maintaining optimal gut health in livestock. Tannin-rich plants and extracts contain bioactive compounds that could be of great interest in this respect. This review describes how the use of tannins around weaning could be beneficial for pigs, with special emphasis on the reduction of ETEC-related PWD. An overview of the broad chemical diversity of tannins is presented together with their physicochemical and biological properties, as well as how they may be metabolized in the digestive tract. The pharmacological effects exerted by tannins are summarized; more precisely, the possible mechanisms by which tannins can disrupt the different steps of the pathogenesis of ETEC-related PWD are highlighted. The factors affecting the bioactivity of tannins are also discussed, shedding light on the importance of chemical structure among different tannins.     

额济纳绿洲胡杨（Populus euphratica）酚类物质含量和分布及其与土壤水分的关系

采用分光光度法测定了额济纳绿洲胡杨(Populus euphratica)的披针形叶、卵圆形叶、嫩枝、枝(D《5 mm)、枝(5～10 mm)、主干树皮、根(D《2 mm)、根(2～5 mm)和根(5～10 mm)9类器官中的总酚、黄酮和缩合单宁含量.结果表明,总酚含量较高的器官为皮(27.93 mg/s),叶、根、枝中总酚含量分别为17.64 mg/g(两类叶均值)、16.72mg/g(三类根均值)、12.19 mg/g(三类枝均值);黄酮含量较高的器官为皮(51.30 mg/g),叶、根、枝中黄酮含量分别为28.45 mg/g(两类叶均值)、39.99 mg/g(三类根均值)、23.67 mg/g(三类枝均值);根中缩合单宁含量较高,三类根均值为22.10 mg/g,皮、叶、枝中缩合单宁含量分别为8.41 mg/g、4.03 mg/g(两类叶均值)、4.47 mg/g(三类枝均值).披针形叶和卵圆形叶中酚类物质含量没有显著性差异(P》0.05);随着枝不断成熟,嫩枝、枝(D《5mm)、枝(5～10mm)中酚类物质逐渐减少;随着根直径减少,根中缩合单宁逐渐增加,细根(D《2mm)中的缩合单宁含量最高(25.95 mg/g).分析胡杨各器官中酚类物质含量与土壤水分的关系,结果表明卵圆形叶中酚类物质含量与土壤水分含量成显著负相关关系(P《0.05,总酚:r=-0.949;黄酮:r=-0.923;缩合单宁:r=-0.944).研究揭示了极端干旱地区胡杨各器官中酚类物质的变化规律,及其与环境因子的相互作用关系.     

Polyphenol contents and antioxidant activity of soybean seed extracts

The antioxidant activity and contents of various polyphenol classes in the seeds of 20 soybean hybrids were evaluated. Total polyphenols, tannins and proanthocyanidins were determined after extraction of plant material with 70% aqueous acetone. In addition, flavonoid content was determined. Antioxidant activity of seed extracts was evaluated by DPPH free radical scavenging activity assay. A positive linear correlation between antioxidant activity and contents of total phenols, tannins and proanthocyanidins was established. The highest antioxidant activity was observed in the extracts of hybrids which have higher levels of all polyphenol classes examined. The most of the single-cross hybrids were poor in tannins which recommend them as good source for ensiled livestock feed. Results suggested that polyphenol content should be considered as an important feature of the soybean seed.     

Molecular weight profiles of proanthocyanidin polymers

The MW profiles of proanthocyanidin polymers (condensed tannins) from 32 samples representing a wide range of plant tissues of many different species have been obtained by gel permeation chromatography of the peracetate derivatives. The tannins vary widely in MW, with M?_n values for the peracetates in the range 1600–5500. The MW profiles vary greatly from those with narrow, rather smooth distributions, to those which are discontinuous.     

Bioactive compounds in legumes: pronutritive and antinutritive actions. Implications for nutrition and health

Legume seeds are employed as a protein source for animal and human nutrition not only for their nutritional value (high in protein, lipids and dietary fibre), but also their adaptability to marginal soils and climates. Human consumption of legumes has been increased in recent years, being regarded as beneficial food ingredients. Legume seeds contain a great number of compounds which qualify as bioactive compounds with significant potentials benefits to human health. These compounds vary considerably in their biochemistry and they can be proteins, glycosides, tannins, saponins, alkaloids, etc. Hence, methods for their extraction, determination and quantification are specific of each compound. They do not appear equally distributed in all legumes, and their physiological effects are diverse. Some of these compounds are important in plant defence mechanisms against predators or environmental conditions. Others are reserve compounds, accumulated in seeds as energy stores in readiness for germination. Processing generally improves the nutrient profile of legume seed by increasing in vitro digestibility of proteins and carbohydrates and at the same time there are reductions in some antinutritional compounds. Most antinutritional factors are heat-labile, such as protease inhibitors and lectins, so thermal treatment would remove any potential negative effects from consumption. On the other hand tannins, saponins and phytic acid are heat stable but can be reduced by dehulling, soaking, germination and/or fermentation. New directions in bioactive compounds research in the last decade have led to major developments in our understanding of their role in nutrition. The scientific interest in these compounds is now also turning to studies of their possible useful and beneficial applications as gut, metabolic and hormonal regulators and as probiotic/prebiotic agents.     

Metabolite profiling and quantification of phenolic compounds in methanol extracts of tomato fruit

The consumption of tomatoes and tomato products has been associated with a reduction in the risk of contracting some types of cancer and other chronic diseases. These beneficial properties may be attributed to the presence of key metabolites and the interactions among them. We have developed and validated an analytical method for the comprehensive profiling of semi-polar metabolites in the methanol extract of three cultivars of raw tomatoes (Daniela, Raf and Rambo) grown in Almería, in south-east Spain. Diode-array and time-of-flight/ion-trap mass spectrometry detectors were used to ensure the wide detection of metabolites with highly divergent properties. The masses thus detected were assigned by matching their accurate mass-signals with tomato compounds reported in the literature, and supplemented by UV and MS/MS information, reference compounds and existing metabolite databases. In this way we were able to identify tentatively 135 compounds belonging to various structural classes, 21 of which are to our knowledge reported for the first time in the tomato fruit. Among the metabolites identified, the most abundant were phenolic compounds. This class of secondary metabolites is attracting considerable attention from producers and consumers due to their antioxidant activity and nutritional properties. Their quantitative analysis was achieved by using closely related derivatives for each family.     

Highly consistent patterns for inherited human diseases at the molecular level

Over 1600 mammalian genes are known to cause an inherited disorder, when subjected to one or more mutations. These disease genes represent a unique resource for the identification and quantification of relationships between phenotypic attributes of a disease and the molecular features of the associated disease genes, including their ascribed annotated functional classes and expression patterns. Such analyses can provide a more global perspective and a deeper understanding of the probable causes underlying human hereditary diseases. In this perspective and critical view of disease genomics, we present a comparative analysis of genes reported to cause inherited diseases in humans in terms of their causative effects on physiology, their genetics and inheritance modes, the functional processes they are involved in and their expression profiles across a wide spectrum of tissues. Our analysis reveals that there are more extensive correlations between these attributes of genetic disease genes than previously appreciated. For instance, the functional pattern of genes causing dominant and recessive diseases is markedly different. Also, the function of the genes and their expression correlate with the type of disease they cause when mutated. The results further indicate that a comparative genomics approach for the analysis of genes linked to human genetic diseases will facilitate the elucidation of the underlying molecular and cellular mechanisms.     

Effect of different dietary tannin extracts on lamb growth performances and meat oxidative stability: comparison between mimosa,chestnut and tara

Little information is available on the effects of different sources of tannins on ruminant product quality. Nowadays several tannin-rich extracts, produced from different plants, are available and contain tannins belonging to different chemical groups, but most of these have not been used so far as feed supplements. The present study aimed at comparing the effects of feeding three tannin extracts (one containing condensed tannins and two containing hydrolysable tannins) to lambs on growth performances and meat oxidative stability. Comisana male lambs were divided into four groups (n=9 each) and were fed for 75 days: a concentrate-based diet (CON), or CON supplemented with 4% tannin extracts from either mimosa (MI; Acacia mearnsii, De Wild; condensed tannins), chestnut (CH; Castanea sativa, Mill; hydrolysable ellagitannins) or tara (TA; Cesalpinia spinosa, (Molina) Kuntze; hydrolysable gallotannins). Only CH reduced growth rate, final weight, carcass weight and feed intake (P<0.05). Tannins did not affect the concentration of the main fatty acid classes and the peroxidability of the intramuscular fat (P>0.05). The TA diet increased (P<0.001) the concentration of γ-tocopherol in muscle and tended to increase that of α-tocopherol (P=0.058). Oxidative stability of raw and cooked meat, or of meat homogenates incubated with pro-oxidants, was not affected by the extracts. These results, compared with those reported in the literature, highlight that some effects of tannins cannot be easily generalized, but may strictly depend on their specific characteristics and on conditions inherent to the basal diet and the metabolic status of the animals.     

Dietary phytochemicals as rumen modifiers: a review of the effects on microbial populations

In the recent years, the exploration of bioactive phytochemicals as natural feed additives has been of great interest among nutritionists and rumen microbiologists to modify the rumen fermentation favorably such as defaunation, inhibition of methanogenesis, improvement in protein metabolism, and increasing conjugated linoleic acid content in ruminant derived foods. Many phytochemicals such as saponins, essential oils, tannins and flavonoids from a wide range of plants have been identified, which have potential values for rumen manipulation and enhancing animal productivity as alternatives to chemical feed additives. However, their effectiveness in ruminant production has not been proved to be consistent and conclusive. This review discusses the effects of phytochemicals such as saponins, tannins and essential oils on the rumen microbial populations, i.e., bacteria, protozoa, fungi and archaea with highlighting molecular diversity of microbial community in the rumen. There are contrasting reports of the effects of these phytoadditives on the rumen fermentation and rumen microbes probably depending upon the interactions among the chemical structures and levels of phytochemicals used, nutrient composition of diets and microbial components in the rumen. The study of chemical structure–activity relationships is required to exploit the phytochemicals for obtaining target responses without adversely affecting beneficial microbial populations. A greater understanding of the modulatory effects of phytochemicals on the rumen microbial populations together with fermentation will allow a better management of the rumen ecosystem and a practical application of this feed additive technology in livestock production.     

Proteomic approaches for studying human parenchymal lung diseases

Parenchymal lung diseases comprise a wide variety of diseases, with different etiologies, pathogeneses and prognoses. This perspective provides an overview of two different disease types: chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. Chronic obstructive pulmonary disease, which is related to smoking, is one of the leading causes of chronic morbidity and mortality around the world, being characterized by airway obstruction and parenchymal lung damage (emphysema). Idiopathic pulmonary fibrosis of unknown etiology is classified as one of the most important idiopathic interstitial pneumonias and is connected to patchy but progressive lung fibrosis. Both diseases are generally diagnosed late and respond poorly to medical therapies. Although numerous biomarkers have been proposed for these diseases, they have not been validated or implemented into clinical practice. This perspective emphasizes some typical features of these diseases with different types of lung damage, how they are reflected in different samples, as well as potential advances and problems of current and future nonbiased proteomic approaches.     

Exploring in silico affinity of flavonoids and tannins to human fibroblast growth factorinducible14 (Fn14), a member of TNF receptor super family

The Fn14 and TWEAK are the receptor and ligand respectively and their mutual recognition and binding was reported to induce pathogenesis of cancer and chronic autoimmune diseases. We had identified Fn14 as a novel target of low linear energy transfer (LET) ionizing radiation in mice population. In the present study we generated the novel homology model of human Fn14, optimized its energy and validated for authenticity by checking Ramachandran plot and also by calculating the RMSD. Based on our earlier findings with Hippophae rhamnoides, a group of flavonoids and tannins were screened for their docking potential with Fn14 at the site where its natural ligand TWEAK was binding. The comparative docking analysis showed that the order of docking, from best to least, was Genistein, Rutin, Gallic acid ethyl ester and Quercetin, respectively. The findings predicted the radiomodifying action of flavonoids and tannins. The study has immediate applications in development of non-toxic drugs/ nutraceuticals that may protect human population from harmful effects of radiation in various situations, such as nuclear accidents, occupational exposure, diagnosis or radiotherapy.     

A seasonal census of phenolics, fibre and alkaloids in foliage of forest trees in Costa Rica: some factors influencing their distribution and relation to host selection by Sphingidae and Saturniidae

The foliage of 80 species common in the Santa Rosa National Park, Costa Rica, has been analysed for content of total phenolics, condensed tannins, acid detergent fibre and water. Wherever possible analyses were performed at three stages in the life cycle of the leaf: young but fully expanded (coinciding with the beginning of the rainy season); middle-aged (two months later); and old (six months later). A comparison of the three age classes showed no significant change in the levels of phenolics or fibre as leaves aged but water content decreased significantly. A comparison of deciduous and evergreen species in the sample showed that the latter group had leaves with a significantly higher fibre content at all three sampling times, most particularly at the beginning of the rainy season, but other measures were not significantly different. Alkaloids were much more common in the foliage of deciduous species and it was observed that their distribution differed significantly from that of total phenolics and condensed tannins. It is suggested that the interaction that occurs between many tannins and alkaloids would be liable to reduce the defence capability of both classes of compounds if they occurred together.
High levels of defoliation occur in the early rainy season (third to tenth weeks) due to larvae of moths of the Sphingidae and Saturniidae. A comparison of investigated tree species that host larvae of these two taxa shows a striking dichotomy. Species that are selected by Sphingidae tend to be relatively deficient in levels of phenolics but are more likely to contain alkaloids, and probably other small toxic molecules. Saturniidae, on the other hand, appear to prefer host-species rich in phenolics but poor in alkaloids.     

A tripartite clustering analysis on microrna, gene and disease model

Alteration of gene expression in response to regulatory molecules or mutations could lead to different diseases. MicroRNAs (miRNAs) have been discovered to be involved in regulation of gene expression and a wide variety of diseases. In a tripartite biological network of human miRNAs, their predicted target genes and the diseases caused by altered expressions of these genes, valuable knowledge about the pathogenicity of miRNAs, involved genes and related disease classes can be revealed by co-clustering miRNAs, target genes and diseases simultaneously. Tripartite co-clustering can lead to more informative results than traditional co-clustering with only two kinds of members and pass the hidden relational information along the relation chain by considering multi-type members. Here we report a spectral co-clustering algorithm for k-partite graph to find clusters with heterogeneous members. We use the method to explore the potential relationships among miRNAs, genes and diseases. The clusters obtained from the algorithm have significantly higher density than randomly selected clusters, which means members in the same cluster are more likely to have common connections. Results also show that miRNAs in the same family based on the hairpin sequences tend to belong to the same cluster. We also validate the clustering results by checking the correlation of enriched gene functions and disease classes in the same cluster. Finally, widely studied miR-17-92 and its paralogs are analyzed as a case study to reveal that genes and diseases co-clustered with the miRNAs are in accordance with current research findings.     

Aerosol gene therapy

Gene therapy is a novel field of medicine that holds tremendous therapeutic potential for a variety of human diseases. Targeting of therapeutic gene delivery vectors to the lungs can be beneficial for treatment of various pulmonary diseases such as lung cancer, cystic fibrosis, pulmonary hypertension, alpha-1 antitrypsin deficiency, and asthma. Inhalation therapy using formulations delivered as aerosols targets the lungs through the pulmonary airways. The instant access and the high ratio of the drug deposited within the lungs noninvasively are the major advantages of aerosol delivery over other routes of administration. Delivery of gene formulations via aerosols is a relatively new field, which is less than a decade old. However, in this short period of time significant developments in aerosol delivery systems and vectors have resulted in major advances toward potential applications for various pulmonary diseases. This article will review these advances and the potential future applications of aerosol gene therapy technology.     

Phytochemicals and their effective role in the treatment of diabetes mellitus: a short review

There is a global increase in the incidence of diabetes mellitus (DM). Hyperglycemia is one of the prevailing conditions which gives rise to various diabetic complications. The major complications include diabetic nephropathy, retinopathy, neuropathy, delayed wound healing, heart attack, peripheral vascular disturbances and diabetic ketoacidosis. Treatment of complications due to DM always poses a challenge to the attending clinician. Alongsideallopathic medicines, DM and its complications were reported to be effectively treated with various natural products. In the present review, we discuss the role of different phytochemicals which were reported to be beneficial in the treatment of hyperglycemic conditions in DM. Most medicinal plants contain micronutrients, amino acids and proteins, mucilages, essential oils, sterols and triterpenoids, saponins, carotenoids, alkaloids, flavonoids, phenolic acids, tannins, bitter principles and coumarins. We discuss the effective role of these phytochemicals with an emphasis on secondary metabolites which mimic the action of insulin, and highlight their importance as future antidiabetic agents.