Arbutin is still active in the whitening market. However, because of the similar structure to hydroquinone, whether arbutin is stable has also been discussed. 
Stability of Arbutin
1. Stability of β-arbutin
The stability of β-arbutin was evaluated by high performance liquid chromatography, and it was found that the aqueous solution of β-arbutin was relatively stable at pH=5 and temperature of 40°C. Relatively unstable at pH=3. And the content of hydroquinone was positively correlated with the placing time. Epidermal cells promote the breakdown of β-arbutin. And the compounding of β-arbutin with vitamin C and pearl powder will reduce its stability.
In addition, nearly half of β-arbutin can be converted into hydroquinone after 24 hours of action with β-glucosidase. About 90.7% of β-arbutin could be hydrolyzed to hydroquinone after co-culturing with mixed microorganisms obtained from human skin surface for 48 hours.
The results of human trials showed that after 4 days of continuous use of cosmetics containing 6.3% arbutin, hydroquinone could be detected on the skin.
2. Stability of α-Arbutin
The stability of α-arbutin is better than that of β-arbutin. Studies have found that α-arbutin is stable under the action of surfactants and metal ions, and is also relatively stable under the action of high temperature. However, it is slightly less stable in methylparaben, and is less stable under extremely acid, extremely alkaline and ultraviolet irradiation. Therefore, care should be taken to avoid the above instability during the formulation process.
The effect of light on the stability of α-arbutin was explored. The results showed that the α-arbutin in the cream state was more stable than the α-arbutin in the solution state after sunlight and UV irradiation.
3. Stability of deoxyarbutin
Deoxyarbutin can be stored at a low temperature of 8°C for two years, with good microbial stability. But at room temperature and weak acid conditions, it can be hydrolyzed to generate hydroquinone after being placed for 3 months. In addition, deoxyarbutin is unstable to heat, light and UV irradiation in aqueous solution, and water may promote the hydrolysis of deoxyarbutin to hydroquinone. Therefore, it is recommended to use deoxyarbutin in an anhydrous emulsification system.
Market Application Of Arbutin
1. Dosage
In 2015, SCCS issued a safety assessment opinion on α-arbutin, β-arbutin and deoxyarbutin: 2% α-arbutin in face cream and 0.5% in body lotion is safe. Creams containing 7% beta-arbutin are safe. Creams containing 3% deoxyarbutin may be unstable due to storage conditions, etc., resulting in the formation of hydroquinone.
2. Security
In addition, the safety of α-arbutin is higher than that of β-arbutin. Arbutin should be avoided as much as possible with VC, pearl powder and methylparaben in the formula. It is best to use a brown bottle to avoid UV exposure and avoid risks.
Although arbutin was once very popular as a whitening product, with the development of society, people's concept of safe and healthy skin care has gradually deepened. Although arbutin is safe to a certain extent, its potential danger cannot be ignored.