The key difference between Kojic acid and hydroquinone is that kojic acid has a comparatively slower onset of action and lower efficiency than hydroquinone.
Kojic acid is chemically closely similar to hydroquinone, but they are two different chemical substances. Therefore, they have different properties as well. When used in skincare products as ingredients, both these substances can be effective for hyperpigmentation with different efficiencies.
What is Kojic Acid?
Kojic acid is a chelation agent that forms as a byproduct of the fermentation of malting rice used in Japanese rice wine. This is an acidic compound produced by a fungus named Aspergillus oryzae. This fungus has the Japanese common name “koji.” Kojic acid can act as a mild inhibitor for the formation of pigments in plants and animal tissues. It is also useful in producing some food and cosmetics as an agent to prevent color changes of the product.
The chemical formula of kojic acid is C6H6O4. Its molar mass is 142 g/mol. It appears as a white solid compound that is slightly water-soluble. Kojic acid is formed from the dehydratase enzyme action on glucose. But, pentoses also can act as precursors for this compound.
The applications of kojic acid include the prevention of oxidative browning when cutting fruits, preserving the pink and red color in seafood, lightening the skin when used in cosmetics, and treating skin diseases such as melasma. It has also been used for research purposes to protect Chinese hamster ovary cells from ionizing radiation.
What is Hydroquinone?
Hydroquinone is an aromatic compound having the chemical formula C6H4(OH)2. It is known as benzene-1,4-diol or quinol. This compound is a benzenediol composed of benzene core carrying two hydroxy substituents in para position to each other. It is an aromatic compound and a type of phenol. It is also a derivative of benzene. The average mass of this compound is 110.11 g/mol. It is odorless but slightly bitter tasting in aqueous solutions. The boiling point of hydroquinone is in the range of 285-287 degrees Celsius. The melting point of this compound is in the range of 170-171 degrees Celsius.
Hydroquinone occurs as a white granular solid. There are some substituted derivatives of this compound that are also referred to as hydroquinones. We can produce hydroquinone through two major routes.
The first route is similar to the cumene process involving the dialkylation of benzene with propene to give 1,4-diisopropylbenzene. This compound then reacts with air, resulting in bis(hydroperoxide). This resultant compound is structurally similar to cumene hydroperoxide. It undergoes rearrangement in acid to form acetone and hydroquinone. The other method of production is hydroxylation of phenol over a catalyst.
There are also some natural sources of hydroquinone. It is one of two primary reagents in the defensive glands in bombardier beetles, along with hydrogen peroxide.
There are many important applications of hydroquinone: as an antioxidant, a carcinogenic agent, as an Escherichia coil metabolite, human xenobiotic metabolite, mouse metabolite, a cofactor required for enzyme activity, as a skin lightening agent in skincare products, etc.
What is the Difference Between Kojic Acid and Hydroquinone?
Kojic acid and hydroquinone are important organic compounds that are used as ingredients in skincare products. The key difference between Kojic acid and hydroquinone is that kojic acid has a comparatively slower onset of action and lower efficiency than hydroquinone.
The below infographic presents the differences between Kojic acid and hydroquinone in tabular form for side-by-side comparison.
Summary – Kojic Acid vs Hydroquinone
Kojic acid is a chelation agent that forms as the byproduct of fermentation of malting rice used for Japanese rice wine while hydroquinone is an aromatic compound having the chemical formula C6H4(OH)2. The key difference between Kojic acid and hydroquinone is that kojic acid has a comparatively slower onset of action and lower efficiency than hydroquinone.
1. “Hydroquinone.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.