L-arbutin (also referred to simply as arbutin), naturally occurs in a variety of plants. Most commonly, it is extracted from the bearberry plant, which has been used in herbal medicine as far back as the 13th century. Bearberry was listed in the London Pharmacopoeia in 1788 and is often referred to using its Latin name, uva ursi. L-arbutin is also found in wheat, cranberries, blueberries, and the skins of pears.
When applied to the skin, L-arbutin inhibits the action of the enzyme tyrosinase, which is the precursor to melanin. Melanin is the pigment that forms when human skin is exposed to UVB radiation, primarily from the sun. The darkening of the skin caused by the release of melanin is commonly referred to as a sun tan. The body releases melanin in response to the action of UVB radiation on the skin because melanin is a photoprotectant. Melanin absorbs harmful UV rays and converts them into harmless heat. Melanin is responsible for protecting the skin from DNA damage that is the root cause of skin cancers, such as malignant melanoma.
Although the action of melanin is generally beneficial, some individuals produce melanin unevenly. People with fair skin can find that melanin is concentrated in localized areas of the skin, causing freckles and moles. As skin ages, excessive sun exposure can result in clumping of melanin in the form of age spots. The skin condition known as chloasma or melasma is the result of over-stimulation of the melanocytes that produce melanin pigment. Dark, hyperpigmented areas form on the surface of the skin, most commonly on the cheeks, lips, nose, and forehead.
Individuals who are self-conscious about hyperpigmentation may turn to skin lighteners, such as L-arbutin and hydroquinone. Hydroquinone has been the subject of debate in many countries. Clinical tests on hydroquinone have revealed some serious side effects, including ochronosis, skin irritation, and skin cancer. These test results have led to hydroquinone being banned in Japan and the European Union. The U.S. Food and Drug Administration (FDA) have classified hydroquinone as safe for topical use. However, some individuals may prefer to avoid using hydroquinone, given the negative test results.
L-arbutin is a glycosylated hydroquinone. It produces very similar effects to hydroquinone in terms of blocking the production of melanin. However, clinical tests have revealed that L-arbutin appears to have a gentler action, meaning that it is less likely to cause skin irritation. In addition, L-arbutin is non-systemic, which means that it does not penetrate the skin and enter the bloodstream. This suggests that L-arbutin does not have the same potential for toxic side effects as hydroquinone. However, care should be taken not to use L-arbutin excessively as some studies have suggested that long-term use of L-arbutin may have negative health implications.
L-arbutin is considered a useful ingredient in anti-aging skin creams, lotions and serums. The reason for this is that L-arbutin addresses the discolored areas of the skin known as age spots. These hyperpigmented areas of the skin are a visible sign of the premature aging effects of the harmful UVA and UVB rays that radiate from the sun. Sun exposure is unavoidable. Even on overcast days, powerful UVA and UVB rays emanating from the sun reach the earth's surface. For this reason, it is essential to wear a high factor sunscreen every day to protect the skin from sun damage.
L-arbutin is currently the only chirally-correct skin lightener on the market. Molecules exist in two forms, which are mirror images of each other. The body will recognize one version of the molecule and use it as intended. Meanwhile, the molecule that is the mirror image is not recognized by the body. At best, the body disposes of the mirror image molecule as waste. At worst, the body may regard it as a toxin, leading to irritation, inflammation, and free radical damage.
The leaves of the bearberry plant, which contain L-arbutin, were traditionally harvested, dried, and ingested as a remedy for bladder and urinary tract infections. L-arbutin has an antibacterial action, which contributes to this healing effect. Dried, powered bearberry plant leaves, known as uva ursi, can be taken in capsule form. Alternatively, the capsules can be broken open and made in to a hot, herbal infusion. Care should be taken to follow dosage guidelines as excessively high levels of uva ursi can cause liver damage.