Chemistry of Syzygium cumini
K. N. Nair in The Genus Syzygium, 2017
Tannins (vegetable tannin, natural organic tannins, or sometimes tannoid) are a large group of polyphenolic compounds containing sufficient hydroxyl groups and other suitable groups to either bind or precipitate proteins (Lorenz et al. 2014). The tannins are astringent, bitter plant secondary metabolites that cause the dry and puckery feeling in the mouth after the consumption of an unripened fruits (Ashok and Upadhyaya 2012). Tannins are water-soluble phenolic compounds that give the usual phenolic reactions, emphasizing the multiplicity of phenolic groups; the term polyphenolics is used for tannins. Tannin can form complexes with a molecular weight up to 20,000, not only with proteins and alkaloids, but also with some polysaccharides. The tannin compounds are widely distributed in many parts of plants, and play a protective role from predators, and also in plant growth regulation. The destruction or modification of tannins with time plays an important role in the ripening of fruit (Li et al. 2006).
The Journey through the Gene: a Focus on Plant Anti-pathogenic Agents Mining in the Omics Era
Mahendra Rai, Chistiane M. Feitosa in Eco-Friendly Biobased Products Used in Microbial Diseases, 2022
Tannins are a heterogeneous group of water-soluble, astringent polyphenolic compounds, classified into three main categories: hydrolysable, condensed and complex tannins. These SM-PAAs are thought to be partially responsible for the astringent taste of red wines and tea (Vidal et al. 2004; Bandyopadhyay et al. 2012). In plants, tannins were observed in seeds, fruits, flowers, leaves, roots and tree bark samples (Sieniawska and Baj 2017). The role of tannins is associated with plant defense against predation by herbivores and insects, resulting primarily in plant palatability reduction, particularly in young leaves (Barbehenn and Constabel 2011). In roots, tannins are chemical barriers against penetration and colonization by pathogens, while in seeds, they present bactericidal properties (Constabel et al. 2014).
Envisioning Utilization of Super Grains for Healthcare
Megh R. Goyal, Preeti Birwal, Santosh K. Mishra in Phytochemicals and Medicinal Plants in Food Design, 2022
Polyphenols are an indigenous part of our food matrix with some beneficial as well as negative effects on the human body. Tannins are classified under the umbrella of polyphenols. They are widely distributed in the nature and well known for their undesirable effects on the human body. Tannins possess the ability to bind with macromolecules including proteins and starch resulting in the reduced bioavailability of such nutrients. However, such complexes are reversible and dependent on the factors like pH. Similarly, it forms chelate complexes with minerals (calcium and iron) and vitamin B12, which leads to lower absorption and reduced nutritional values (Table 10.5). Furthermore, tannins are considered to be responsible for undesirable sensorial properties of the some food products due to their involvement in the enzymatic browning reactions as well as ability to provide astringency flavor [17, 159].
Health effects, sources, utilization and safety of tannins: a critical review
Published in Toxin Reviews, 2021
Kartik Sharma, Vikas Kumar, Jaspreet Kaur, Beenu Tanwar, Ankit Goyal, Rakesh Sharma, Yogesh Gat, Ashwani Kumar
Tannins are plant based polyphenols which are astringent in nature and are found in different parts of the herbs, plants are consumed as food and feed. These are majorly categorized into two groups, namely, condensed tannins (non hydrolyzable) and hydrolyzable tannins. Hydrolyzable tannins are further sub categorized into gallotannins and ellagitannins, where former are the simplest type among the hydrolyzable tannins (Khanbabaee and van Ree, 2001). A brief explanation of the different types of tannins is given in Figure 1. Condensed tannins, also known as proanthocyanidins, are more complex and therefore not yet determined completely. These are present in amounts greater than condensed tannins which occur only in trace amounts in certain foods (Chung et al.1998). Condensed tannins are the most commonly existing ones that are generally found in stems, legumes, trees, forages, etc. (Hassanpour et al.2011), whereas hydrolyzable tannins are found in seedpod, bark, wood, leaves, fruits, etc.
Protecting HaCaT cells from ionizing radiation using persimmon tannin-Aloe gel composite
Published in Pharmaceutical Biology, 2020
Xi Qian, Zhongmin Wang, Jinliang Ning, Chaoke Qin, Lin Gao, Na He, Dahong Lin, Zhide Zhou, Guiyin Li
Tannin, also known as tannic acid, is widely found in many natural plants such as persimmons (Diospyros kaki L.f [Ebenaceae]), tea leaves, ginkgo leaves, and grape seeds. It has a complex polyphenolic hydroxyl structure that is soluble in water and some organic solutions. Nowadays, Guangxi produces the most persimmons in China (Wang et al. 2017; Li et al. 2019). In order to ensure that most persimmons can mature normally, some green persimmons must be removed. Numerous studies have shown that green persimmons contain large amounts of persimmon tannin (Zhou et al. 2015; Ying et al. 2017). Persimmon tannin has proven useful for the prevention and treatment of ionizing radiation pollution (Wang et al. 2017; Wu et al. 2017; Li et al. 2018). Wu et al. (2015) studied the protective effect of tannin acid on human megakaryocyte injury induced by ionizing radiation. By pretreating human megakaryocytes with different concentrations of tannin, it was shown that tannic acid provided effective protection after 10 Gy 60Co γ-ray irradiation. Recently, our group indicated that persimmon tannin offered a potent radioprotective effect on cell vitality and cell apoptosis of γ-radiation exposure in HEK 293 T cells (Zhou et al. 2016).
Left out in the cold: Serving wines chilled
Published in Temperature, 2019
Christopher T. Simons
Although also perceived in the mouth, astringency and irritation are not tastes. In wine, astringency is the rough or drying sensation that occurs when tannins interact with salivary proteins to reduce lubrication within the oral cavity, whereas irritation is the burning sensation elicited by high concentrations of ethanol. Both astringency and irritation are temperature-dependent. Chilling reduces perceived astringency albeit the effects are fairly small [4]. Suppression of astringency may be due to (a) decreased solution viscosity of the refrigerated solution, (b) a higher salivary flow rate in response to cold solutions, or (c) reduced tannin-protein interactions resulting from colder temperatures. Solution viscosity, salivary flow rate, and the degree of protein-compound interaction have all been shown to affect perceived astringency. When some wines (particularly red varietals) are consumed above optimal serving temperatures, connoisseurs will often characterize them as “hot”. This “hot” sensation is typically evoked in wines with relatively high alcohol content. Ethanol elicits this sensation by activating a temperature-sensitive receptor (TRPV1) normally responsive to hot temperatures [5]. Cooling reduces the likelihood of TRPV1 being activated. Not surprisingly, chilling a wine therefore, will decrease the activation of TRPV1 by ethanol and consequently reduce the “hot”, irritant sensation from the wine.
Related Knowledge Centers
- Alkaloid
- Astringent
- Biomolecule
- Carboxylic Acid
- Macromolecule
- Pesticide
- Polyphenol
- Protein
- Amino Acid
- Hydroxy Group