Generality
Kojic acid (or kojic acid, if you prefer) is a substance known for its extraordinary lightening virtues: not surprisingly, it is widely used in cosmetics to prepare creams or gels with depigmenting action.
If until a few years ago kojic acid was extracted from rice bran, today the lightening molecule par excellence is produced biotechnologically starting from numerous species belonging to the genus Aspergillus And Penicillium.
Curiosity
Kojic acid (also known as Kojic acid) owes its name to the main fungus that produces it: Aspergillus oryzae, a mushroom which - in Japanese language - is renamed "Koji".
Characteristics and Properties
Kojic acid is well known for its lightening properties when applied to the skin.
At the same time, kojic acid is able to inhibit the formation of pigments also in plant tissues and not only in animal ones.
Besides the well-known depigmenting properties, kojic acid boasts antioxidant, antibacterial and antifungal virtues.
Furthermore, from some studies conducted on animals, it emerged that kojic acid could prove to be a potential ally in protecting the organism from damage caused by ionizing radiation (such as, for example, gamma rays).
Finally, other studies conducted in vitro have shown that co-crystals of kojic acid and quercetin (a flavonoid present in many types of fruit and vegetables) exert a better "cytostatic action than that of the single quercetin against malignant cells of human tumors. such as ovarian cancer and colon cancer. Kojic acid - in association with quercetin - could be a future and potential therapeutic adjuvant in the treatment of these cancers.
Uses
Despite the different and potential properties of kojic acid, its use is mostly limited to the food and cosmetic fields.
In the food sector, kojic acid can be used on fruit that has already been peeled and cut in order to prevent the onset of brownish color, an indication of oxidation. In addition to this, kojic acid is used to preserve the pink or red color typical of seafood.
In the cosmetic field, however, this molecule is used as a depigmenting agent inside lightening masks and creams.
Mechanism of action
As mentioned, kojic acid is used in cosmetics in the treatment of skin spots of various origins (solar and senile lentigo), melasma, chloasma and other disorders characterized by skin hyperpigmentation, thanks to its depigmenting action.
The mechanism of action by which kojic acid exerts this action is rather complex: the substance acts by inhibiting the biosynthesis of melanin, the main pigment that defines the color of the skin. More precisely, kojic acid performs its function by deactivating the tyrosinase enzyme, responsible for the transformation of tyrosine into intermediates useful for synthesizing melanin.
Cosmetics with Kojic Acid
The skin has an iron memory about the solar or artificial radiation suffered: UV radiation can create devastating effects on the skin in the long term, causing noticeable, pronounced and premature skin aging. The most immediate side effects of solar radiation are skin hyperchromias, or dark spots, if you prefer.
So here is that the lightening creams with kojic acid can attenuate - if not completely remove - the chromatic alterations suffered.
But the uses of kojic acid do not stop at the spots caused by the sun. Kojic acid products, in fact, are also effective in reducing other types of skin discoloration, in particular:
- Freckles;
- Melasma, chloasma or other pregnancy spots
- Senile lentigo;
- Rings under the eyes;
- Other acquired hyperpigmentation disorders.
Kojic acid cosmetics, of course, must be applied topically, then spread directly on the skin with altered colors.
Most of the time, this lightening substance is formulated in creams, but it is also possible to find it in the form of lotions, gels or serums at rather low concentrations (less than or equal to 1%). To minimize the risk of skin side effects, the Kojic acid is often used at an even lower concentration of 0.2%.
The frequency of application of kojic acid-based cosmetics depends on the problem to be treated and the type of skin: for example, hypersensitive skin does not like frequent use of the product. In such circumstances, it is necessary to re-evaluate the product.
Recommendations
After applying a kojic acid cream on the skin, it is recommended to apply a generous layer of sun protection (especially in summer), to preserve the skin as much as possible from the production of new melanin induced by the stimulation of ultraviolet rays.
Other lightening agents
To make a lightening cosmetic more natural and to minimize the risk of adverse reactions to the product, kojic acid can be replaced with natural molecules with similar action. Among these substances, a leading role is played by polyphenols, in particular flavonols, isoflavonoids, stilbenes and coumarins. Just to give some examples, pomegranate juice is a source of ellagic acid, a compound with a significant inhibitory activity on tyrosinase.
Other "whitening" substances with an activity similar to that of kojic acid are Mulberroside F, a flavonol extracted from the leaves of Morus alba, a plant used in herbal medicine for its hypoglycemic properties.
Similarly, liquorice extracts too, thanks to the presence of isoflavonoids, exert an "excellent lightening action comparable to that of kojic acid."
In an "unnatural" lightening product, kojic acid can be replaced by hydroquinone, a powerful bleaching agent capable of degrading and destroying melanosomes and melanocytes. However, given its evident side effects (erythema, desquamation, irritation, contact dermatitis, etc.), the use of hydroquinone in cosmetics is prohibited: the use of this molecule requires a medical prescription.
Kojic Acid and Exfoliants
Kojic acid is often formulated in association with exfoliating substances. In fact, an excellent positive effect has been observed from the association of lightening substances with chemical exfoliants such as mandelic acid, salicylic acid and tartaric acid. Even creams with glycolic acid (with known exfoliating properties) are often prepared in association with kojic acid or other depigmenting substances.
The embrace of lightening molecules with exfoliating substances, acting in synergy, effectively promotes the elimination of surface horny cells - richer in melanin and responsible for dark spots on the skin - while encouraging cell turnover.
Side effects
It is not uncommon that after one or more cosmetic treatments with kojic acid, the skin reacts negatively. Among the most common side effects related to the application of kojic acid, we remember:
- Contact allergies;
- Skin sensitization;
- Dermatitis;
- Itching.
