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Arbutine

Arbutin is found in the dried leaves of a number of different plant species including bearberry  (Arctostaphylos uva-ursi).  The leaves and leaf extracts from uva ursi are used in non-prescription medicinal products mainly to treat urinary tract infection, cystitis, kidney stones, and as a diuretic.  The  active component, arbutin, is converted to hydroquinone (HQ) which has antimicrobial, astringent, and  desinfectant properties.  

Arbutin is also an inhibitor of melanin formation and is use in some skinlightening products.  It is rapidly metabolized and excreted in rats as unchanged arbutin and in humans as HQ, HQ glucuronide, and HQ sulfate.  HQ induced  renal tubule adenomas in  male rats and liver  adenomas and thyroid gland follicular cell hyperplasia in mice.  It was negative in the Ames assay but  induced mutations and micronuclei in mouse L5178Y lymphoma and chromosome aberrations and sisterchromatid exchange in Chinese hamster ovary cells.  Side effects reported from the ingestion of dried uva ursi leaves included nausea and vomiting, irritability, insomnia, and an increased heart rate.  Extremely  high doses can cause ringing in the ears, shortness of breath, convulsions, collapse, and delirium.  
Uva ursi has also  been linked with albuminuria, hematuria, and urine cast; liver damage is  also a risk with long-term use.  In vitro studies of human melanocytes exposed to arbutin at concentrations below 300  µg/mL reported decreased tyrosinase activity and melanin content with little evidence of cytotoxicity.  Arbutin did  not induce mutations in hamster V79 cells, except after preincubation with β-glycosidase.   Bone marrow micronuclei were not induced in mice after oral treatment with arbutin, and a mixture of  uva ursi extracts did not induce micronuclei in cultured human lymphocytes

Bearberry extract is used in skin lightening treatments designed for long term and regular use. An active agent in brands of skin lightening preparations, it is more expensive than traditional skin lightening ingredients like hydroquinone, which is now banned in many countries. In vitro studies of human melanocytes exposed to arbutin at concentrations below 300 μg/mL reported decreased tyrosinase activity and melanin content with little evidence of cytotoxicity.[1]

Risks
Arbutin is glucosylated hydroquinone,[2] and may carry similar cancer risks,[7] although there are also claims that arbutin reduces cancer risk.[4] The German Institute of Food Research in Potsdam found that intestinal bacteria can transform arbutin into hydroquinone, which creates an environment favorable for intestinal cancer.[5]

  1. Arbutin Archived May 27, 2010, at the Wayback Machine., Supporting Nomination for Toxicological Evaluation by the National Toxicology Program
  2. Jump up^ O'Donoghue, J L (September 2006). "Hydroquinone and its analogues in dermatology – a risk-benefit viewpoint". Journal of Cosmetic Dermatology. 5 (3): 196–203. doi:10.1111/j.1473-2165.2006.00253.x. PMID 17177740. The potential toxicity of HQ (hydroquinone) is dependent on the route of exposure
  3. Jump up^ Treatment of hyperpigmentation problems / skin lightening[unreliable source?]
  4. Jump up^ Bowman, Lee. July 25, 2005. Scripps Howard News Service. High yuck factor not necessarily good for us anymore Archived September 28, 2007, at the Wayback Machine.
  5. Jump up^ Blaut M, Braune A, Wunderlich S, Sauer P, Schneider H, Glatt H (2006). "Mutagenicity of arbutin in mammalian cells after activation by human intestinal bacteria". Food Chem. Toxicol. 44 (11): 1940–7. doi:10.1016/j.fct.2006.06.015. PMID 16904805.

Hydroquinone O-β-D-glucoside, also called arbutin, isspread in more superior plants such as: Arctostaphylos uva-ursi (L) Spreng., Vaccinium vitis-idea L., Pyrus communis L., Lathyrus sp. From the pharmacologic point of view arbutin is of interest due to two therapeutic applications. The
antibacterial properties recommend the use of the leaves of Arctostaphylos uva-ursi in the form of infusions for the treatment of the urogenital tract infections (cystitis, nephritis, gonorrhoea, endometriosis, etc.). It also shows the property of suppressing melanin biosynthesis in the human 
skin. The pharmacological active compound is hydroquinone which originates from arbutin by in vivo glucoside cleavage.

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