Polyphenols

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Quercetin , a polyphenol found in apples and onions

Polyphenols are aromatic compounds that contain two or more hydroxyl groups directly attached to an aromatic ring ; the name is derived from phenol , with the prefix poly- for 'a lot'.

Natural polyphenols occur in plants as secondary plant substances. They represent bioactive substances such as colorings , flavorings and tannins and are supposed to protect the plant from predators or to attract insects to pollinate with their color. Some plants also use polyphenols as protection for the photosynthesis apparatus due to their antioxidant effects and the filtering of high- energy UV-B radiation . Polyphenols are also the basic building blocks of important biopolymers such as lignin and suberin .

Among the polyphenols are numerous different plant substances, such as dyes of flavonoids and anthocyanins , procyanidins , benzoic acid derivatives (eg. As the hydroxy benzoic acids such as vanillin , the trihydroxybenzoic as gallic acid and dihydroxybenzoic as protocatechuic ), cinnamic acid derivatives (the hydroxycinnamic acids such as caffeic acid and p -Cumaric acid ) and stilbene derivatives (such as resveratrol ).

origin

Plants with a high polyphenol content are, for example, the chokeberry , the real walnut , the leaves and grapes of the grapevine , also in red wine , the peel and pulp of the mangosteen fruit ( Garcinia mangostana ), the juice of the pomegranate ( Punica granatum ), which among other things contains punicalagin, Contains ellagic acid and gallic acid , ginkgo , tea , rock roses and the seeds of perilla ( Perilla frutescens , also known as "black nettle" or, misleadingly, "wild sesame"). In addition, polyphenols (are flavonoids ) from the bark of pine trees and from larch wood for use in medicine extracted .

effect

Many polyphenols are considered to be beneficial to health. Some polyphenols, like other antioxidants , have anti-inflammatory and cancer preventive effects, among other things . In various studies with pomegranate polyphenols, inhibited growth of cancer cells in the mammary gland, lungs, skin, intestines and prostate has been observed. Flavonoids and anthocyanins protect body cells from free radicals and slow down cell oxidation . They reduce the fat deposits ( plaques ) in the blood vessels and thus prevent arteriosclerosis . For example, the thickness of the inner vascular wall of the carotid artery was reduced by up to 30% in patients with arteriosclerosis after consuming pomegranate juice for a year, while it increased by up to 9% in the control group.

Other polyphenols, such as the larch extract taxifolin, are used in addition to cancer prevention in many cases for the treatment of cerebral infarction ( ischemic stroke ) and its sequelae, cerebral thrombosis , coronary heart disease and angina pectoris .

An in vivo study with female mice who had developed spontaneous hair loss on the head, neck and back found that 33% of the mice in Group A who received polyphenol extract from green tea with their drinking water had a significant one Hair regrowth was observed during the six month treatment. No hair growth was observed among the mice of control group B that received only water.

Polyphenols from grapes inhibit the type of bacteria Streptococcus mutans , which contributes to the build-up of plaque and so-called biofilms on the teeth. With their bactericidal effect, polyphenols inhibit the harmful effects of bacteria and thus also have a preventive effect against dental caries .

At the same time, polyphenols from plant foods can bind to digestive enzymes and thus reduce the absorption of nutrients in the intestine. In healthy people, the proline-rich proteins contained in saliva prevent this effect by forming a stable complex with the polyphenols in the digestive tract.

The effects of the polyphenols from tea and cocoa can be hindered by the addition of milk , because the casein in milk is also rich in proline.

Polyphenols can be detected with iron (III) chloride solutions. They react with iron (III) ions to form green to blue colored complex compounds.

toxicology

Many polyphenols have positive biological properties in low doses, such as those found in plants, but can also show toxic effects in in-vitro studies and in high doses. If they are used in high doses or long-term, such effects are also possible in the organism, which is why such doses and / or long-term applications are rather unusual. Apigenin , quercetin , taxifolin and kaempferol, for example, are cytostatic , which is why they and some other polyphenols, e.g. B. catechol , genistein and gossypol , are classified as harmful , quercetin even as toxic. Polyphenols are usually not absorbed unchanged in the human body and therefore show very different pharmacokinetic behavior depending on the chemical structure, which is why the results of in vitro experiments with polyphenols can only be transferred to humans to a limited extent. In addition, their effect is modulated by the so-called matrix effect of other secondary plant substances. Quercetin, for example, has been shown to have a mutagenic effect, but if it is present in a plant matrix that contains other polyphenols such as tannins , the overall antimutagenic effect of the plant extract predominates.

Literature and further sources

Individual evidence

  1. ↑ EP Lansky, RA Newman: Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. In: J Ethnopharmacol . 109 (2), January 19, 2007, pp. 177-206. PMID 17157465 .
  2. ↑ M. Aviram et al .: Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation. In: Clinical Nutrition. 23, 2004, pp. 423-433. PMID 15158307 .
  3. ↑ ON Pozharitskaya et al .: Determination and pharmacokinetic study of taxifolin in rabbit plasma by high-performance liquid chromatography. In: Phytomedicine . 16, 2009, pp. 244-251. PMID 19110406 .
  4. ↑ Adeleh Esfandiari, A. Paul Kelly: The effects of tea polyphenolic compounds on hair loss among rodents. In: Journal of the National Medical Association. 97 (8), August 2005. PMID 16173333 .
  5. ^ Hyun Koo et al: Chemical Characterization of Red Wine Grape ("Vitis vinifera" and "Vitis Interspecific Hybrids") and Pomace Phenolic Extracts and Their Biological Activity against "Streptococcus mutans". In: Journal of Agricultural and Food Chemistry . Volume 55 (25), 2007, pp. 10200-10207. PMID 17999462 .
  6. ↑ The power of wine. Polyphenols from grapes work against bacteria that can cause tooth decay. In: Wissenschaft.de. January 4, 2008, accessed September 8, 2019 .
  7. ↑ J. Heilmann, I. Merford: Current knowledge on the metabolism of flavonoids. I. Absorption and metabolism of flavonols. In: Pharmacy in our time . 27 (2), 1998, pp. 58-65.
  8. ↑ J. Heilmann, I. Merford: Current state of knowledge on the metabolism of flavonoids. II . Resorption and metabolism of flavones, flavanones, flavans, proanthocyanidins and isoflavonoids. In: Pharmacy in our time. 27 (4), 1998, pp. 173-183.
  9. ↑ JT MacGregor, L. Jurd: Mutagenicity of plant flavonoids: Structural requirements for mutagenic activity. In: Mutation Res. 54, 1978, pp. 297-309.
  10. ^ A. Duration, P. Metzner, O. Schimmer: Proanthocyanins from the bark of Hammamelis virginiana exhibit antimutagenic properties against nitroaromatic compounds. In: Planta Med. 64, 1998, pp. 324-327.
  11. ↑ O. Schimmer: Vegetable Antimutagens. In: Dtsch. Apoth. Ztg. 139, 1999, pp. 51-62.