Astringency phenolic acid

N.A. Silicic acid, silicates, flavonoids, phenolic acid, nicotine, sterols.100 Regeneration of connective tissue, clotting agent, astringent effect on genitourinary system. 

N.A. Lycopus virginicus L. Phenolic acids, caffeic derivatives, chlorogenic derivatives, ellagic acids." Treat overactive thyroid gland, an astringent to reduce the production of mucus. 

Among polyphenolic compounds, two types of flavonoids, the anthocyanins and flavanols (i.e., catechins, proanthocyanidins, condensed tannins), are particularly relevant to the quality of red wines, as they are key compounds for color definition and astringency. Other flavonoids such as flavonols may have some influence on color and bitterness, although they are present in red wines in much lower amounts. Phenolic acids and hydrolysable tannins, released from barrel wood, may also have an influence on wine taste and color, and hydroxycinnamoyl derivatives from grape must are involved in the oxidative browning of white wines together with flavanols. Besides, some of these perceptions may be modified by other sensory characteristics (e.g. sourness, sweetness) related to other wine components (Preys et al. 2006). 

Anthocyanins, flavanols and phenolic acids are the main polyphenols of grapes and grape-derived foods, responsible for their major organoleptic properties. Anthocyanins are directly involved in the color of most red fruits including grapes (7) while flavanols are thought to make an important contribution to the astringency and bitterness of plant derived foods (2,3). 

The plant contains iridoid glycosides asperuloside (120) monotropein and aucubin (19), phenolic acids caffeine, gallic acid, anthraquinone derivatives, flavonoids, coumarins, citric acid and red dye. It has been employed in the form of an infusion, as aperient, diuretic, refrigerant, alternative and antiscorbutic. Extract of leaves used as astringent, plant paste applied on skin disease [69,153]. 

Phenolic acids occur naturally in higher plants, usually as free adds, glycosides, esters, or in insoluble-bound form in a complex mixture of other phenolic compounds. The presence of phenolic acids in food products has been associated with astringency, discoloration, inhibition of enzyme activity, and antioxidant properties, among others [15]. A major portion of phenohc acids present in almond was found in the form of soluble esters. Wijeratne et al. [16] reported that the total amounts of identified free phenolic acids were 16.3, 14[ig/g and a trace amount in skin, shell, and whole seed extracts, respectively, whereas the amounts for total esterified phenolic acids were 279.6,967.1, and 40.3 [ig/g, respectively. 

Phenolic acids contribute to the sensory and nutritional qualities of fruits, vegetables, and derived foods. Directly or indirectly, they play a role in color, astringency, bitterness, and aroma, and they also are of great interest to humans, because of their antioxidant capacity [2,4]. 

Sinapoyl esters are considered antinutritional compounds because they have a bitter and astringent taste, thus contributing to the bitter taste of rapeseed meal. The intensity of the bitter taste is comparable to the intensity of the bitter taste of caffeine. In the refining of rapeseed oil, sinapines form complexes with proteins. They show lower antioxidant activity than the corresponding phenolic acids and do not have antimicrobial effects. Sinapines present in the feed of some breeds of laying hens cause an off-flavour and fish-like odour of yolks. 

The phenolic composition of apple consists of cinnamic acids, flavonols, dihydrochalcones, and flavan-3-ols (50,56). In the apple fruit processing industry, hydroxycinnamic acid derivatives and flavan-3-ols are important due to their contribution to the astringency, haze, and browning in apple juice and cider. Chlorogenic acid represents the major hydroxycinnamic acid derivative. The flavan-3-ols (catechins) are present in the monomeric form as well as in oligomeric and polymeric forms (procyanidins) in apple and apple products (56). 

Phenylpropanoids have an aromatic ring with a three-carbon substituent. Caffeic acid (308) and eugenol (309) are known examples of this class of compounds. Phenylpropanoids are formed via the shikimic acid biosynthetic pathway via phenylalanine or tyrosine with cinnamic acid as an important intermediate. Phenylpropanoids are a diverse group of secondary plant compounds and include the flavonoids (plant-derived dyes), lignin, coumarins, and many small phenolic molecules. They are known to act as feeding deterrents, contributing bitter or astringent properties to plants such as lemons and tea. 

MPs are constituted by 90% of mannose, protein and phosphoric acids and represent the 35% of total polysaccharides in wine (Vidal et al. 2003). MPs combined with phenolic compounds have shown an indirect effect on astringency, although their stabilizing effect on protein precipitation in white wine and tartrate crystallization in both red and white wines are their main function (Ribereau-Gayon et al. 2006). Glucomannoproteinshscve been also detected in wines in lower amount than MPs (Ribereau-Gayon et al. 2006). 

Grape phenolics compounds are important to wine colour, flavour, astringency and bitterness, with red wines generally containing 1200-1800 mg gallic acid equiv-alents/L of total phenolics, six- to ninefold more than present in white wines (Kennedy et al. 2006). Hydroxycinnamic acids (non-flavonoid phenolics) are major phenolic compounds of white wines and are responsible for their colour. Other non-flavonoid phenolics contribute flavour, such as vanillin, vinyl phenols and gallic acid. Vinyl and ethyl phenols, which can be present to variable extents, elicit phenolics, medical, Bandaid , barnyard and spicy characters in wine, which are generally... 

More recently benzoic acid derivatives (MW 122-170) have also been shown to be astringent (17). The most astringent compounds, salicylic (2-hydroxy benzoic acid) and gentisic (2,5 dihydroxy benzoic acid) acids, were ortho substituted, but neither had vicinal hydroxyl groups. Both derivatives had lower pHs than the non-ortho substituted ones, which may have contributed not only to sourness but also to astringency. McManus et al (1981) (18) proposed previously that simple phenols which contain 1,2 dihydroxy or 1,2,3 trihydroxy groups (such as epicatechin or catechin) may cross link and thereby precipitate proteins. It could be speculated that ortho substitution conveys some kind of binding capability similar to that of flavan-3-ols or polyphenolics of hi er MW. 

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