Arbutin
| Structural formula | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||||||||||||
| General | ||||||||||||||||||||||
| Surname | Arbutin | |||||||||||||||||||||
| Molecular formula | C 12 H 16 O 7 | |||||||||||||||||||||
| Brief description |
yellowish needle-shaped crystals with a bitter taste |
|||||||||||||||||||||
| External identifiers / databases | ||||||||||||||||||||||
|
||||||||||||||||||||||
| properties | ||||||||||||||||||||||
| Molar mass | 272.26 g mol −1 | |||||||||||||||||||||
| Physical state |
firmly |
|||||||||||||||||||||
| Melting point |
199.5 ° C |
|||||||||||||||||||||
| Vapor pressure |
practically 0 at 25 ° C |
|||||||||||||||||||||
| solubility |
moderate in water (50 g l −1 ) |
|||||||||||||||||||||
| safety instructions | ||||||||||||||||||||||
|
||||||||||||||||||||||
| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||||||||
Arbutin (hydroquinone-β- D -glucopyranoside) is a chemical compound from the group of aryl-β- glucosides and hydroquinones .
Occurrence
Arbutin occurs in damiana , lingonberries , blueberries , raspberries , wheat germ , porst , round- leaf wintergreen , bearberry (minimum requirement according to the European Pharmacopoeia 7%), coffee , tea , red wine as well as pears and pear leaves (with more or less content). It is converted into glucose and hydroquinone in the intestine by bacteria .
biosynthesis
The precursor of arbutin is the coumaric acid formed via the shikimate pathway . By a β-oxidation of the propylene-side chain is formed of p -hydroxybenzoic acid , from which, finally, by oxidative decarboxylation of the benzohydroquinone is formed. The latter is now O - glycosylated to give arbutin.
pharmacology
As a hydroquinone glucoside, arbutin is a prodrug . In its original form it is poorly absorbable and in this form cannot reach its place of action. Before it can be absorbed, it must first be hydrolyzed in the stomach and upper small intestine to form well-absorbable hydroquinones. The "detoxification" takes place in the liver by conjugating hydroquinone with glucuronic acid or sulfuric acid, which improves the water solubility and thus the transport in the blood. In this way, 70% to 75% of the amount absorbed reaches the kidneys within 6 hours and is excreted there with the urine. Bacteria in the bladder can break down the hydroquinone complex again and thus release hydroquinone. Hydroquinone has an antibacterial effect. Arbutin-containing drugs (e.g. bearberry leaves) and their extracts are therefore used medicinally for bacterial infections of the urinary tract.
Application restrictions
The hydroquinone produced from arbutin has a liver-damaging effect in higher doses and is suspected of having mutagenic or possibly even carcinogenic effects. This results in the restrictions in use:
- Not more than 5 times a year and only for 1 week
- Not during pregnancy or breastfeeding
- Not in children
Due to the high tannin content of arbutin-containing drugs, nausea and vomiting are possible when brewed as tea. It should therefore be prepared as a cold macerate , as hardly any tannins are extracted from the plant material.
Individual evidence
- ^ Entry on Arbutin. In: Römpp Online . Georg Thieme Verlag, accessed on November 18, 2014.
- ↑ a b c d data sheet Arbutin at Sigma-Aldrich , accessed on November 7, 2016 ( PDF ).
- ↑ a b Entry on Arbutin in the Hazardous Substances Data Bank , accessed November 18, 2014.