Discovery of 'Tachibana peel extract' effectively preventing melanin production and transfer
Kosé discovered that 'tachibana peel extract' inhibits melanin production and transfer by acting on epidermal cells to suppress SCF and PAR2. Presented at the Pharmaceutical Society of Japan.
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- 📰 Published: April 14, 2026 at 19:10
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Kosé Corporation (Headquarters: Chuo-ku, Tokyo; President and CEO: Shinji Tanaka) has discovered that 'tachibana peel extract,' obtained from the mature peel of tachibana (a type of citrus), has the effect of suppressing the production and transfer of melanin. Specifically, it confirmed the existence of mechanisms that suppress melanocyte activation mediated by epidermal cells and suppress the uptake of melanin transferred from melanocytes to epidermal cells. Part of the results of this research was presented at the 146th Annual Meeting of the Pharmaceutical Society of Japan (March 26-29, 2026).
Figure 1: Mechanism of spot suppression and melanin uptake suppression effect of 'Tachibana peel extract'
Background of the Research
Age spots that appear on the skin as we age are one of the typical skin concerns many people have. Spots occur when melanocytes activated by stimuli such as UV rays produce excess melanin, which is then taken up and accumulated by epidermal cells closer to the skin's surface. In other words, the interaction between melanocytes that produce melanin and the epidermal cells that receive it is crucial for spot formation.
Tachibana peel (Chenpi), dried mature peel of rutaceous citrus, is known as an ingredient that suppresses spot formation, and its direct action to suppress melanocyte activation had been confirmed. However, how tachibana peel acts within the 'interaction between melanocytes and epidermal cells,' which is important for spot formation, had not been confirmed. Therefore, in this study, we attempted to clarify the entire mechanism of spot suppression by tachibana peel.
Confirmed the effect of 'Tachibana peel extract' in suppressing melanocyte activation via epidermal cells
Melanin, which causes spots, is formed in melanocytes deep within the skin. When epidermal cells enter an inflammatory state, the production of SCF, a protein that acts as a command for melanocytes to produce melanin, increases, and melanin is generated. Since 'tachibana peel extract' has been confirmed to have anti-inflammatory effects, we verified changes in the amount of SCF produced by adding it to epidermal cells. First, as a result of adding 'tachibana peel extract' to epidermal cells, it was revealed that not only the amount of SCF produced intracellularly but also the amount of SCF released extracellularly decreased. Next, to verify the effect from epidermal cells to melanocytes, we added a culture medium containing the components released from the epidermal cells to melanocytes. As a result, it was confirmed that the activity of tyrosinase, an enzyme involved in melanin production, decreased compared to those without the addition of 'tachibana peel extract' (Figure 2). From these results, it was found that 'tachibana peel extract' can approach the suppression of spot formation by acting on epidermal cells and suppressing the release of melanocyte-stimulating factors.
Figure 2: Amount of SCF released by the addition of 'Tachibana peel extract' and tyrosinase activity by the addition of culture medium
Confirmed the effect of 'Tachibana peel extract' in suppressing melanin uptake by epidermal cells
One of the mechanisms of spot formation is that epidermal cells receive and take up melanin produced by melanocytes into their cells. This uptake of melanin is known to be promoted by a protein called PAR2 produced by epidermal cells. This PAR2 also exists in the periphery of spots and can be a factor that spreads existing spots. Therefore, we verified how the amount of PAR2 produced and the amount of melanin uptake by epidermal cells change by adding 'tachibana peel extract.'
First, when we measured the amount of PAR2 produced after adding 'tachibana peel extract' to epidermal cells, we confirmed that its production was suppressed. Next, we verified whether the amount of melanin actually taken up by epidermal cells decreased by adding the same ingredient. As a result of adding melanin and 'tachibana peel extract' to epidermal cells, the amount of melanin taken up decreased compared to epidermal cells that did not receive the addition (Figures 1 and 3). From these results, it was found that the addition of 'tachibana peel extract' has the effect of suppressing PAR2 production and decreasing the melanin uptake of epidermal cells, which is a factor that spreads spots.
Figure 3: Amount of melanin uptake by epidermal cells due to the addition of 'Tachibana peel extract'
From the above results, we discovered that 'tachibana peel extract' has the effect of suppressing melanocyte activation by decreasing SCF release from epidermal cells, and the effect of preventing melanin uptake by epidermal cells by suppressing PAR2 production, in addition to its previously known direct action on melanocytes.
Future Prospects
Through this research, it has been shown that 'tachibana peel extract' acts not only directly on melanocytes, which was previously known, but also on epidermal cells, preventing the accumulation of melanin in epidermal cells through production and transfer...
Figure 1: Mechanism of spot suppression and melanin uptake suppression effect of 'Tachibana peel extract'
Background of the Research
Age spots that appear on the skin as we age are one of the typical skin concerns many people have. Spots occur when melanocytes activated by stimuli such as UV rays produce excess melanin, which is then taken up and accumulated by epidermal cells closer to the skin's surface. In other words, the interaction between melanocytes that produce melanin and the epidermal cells that receive it is crucial for spot formation.
Tachibana peel (Chenpi), dried mature peel of rutaceous citrus, is known as an ingredient that suppresses spot formation, and its direct action to suppress melanocyte activation had been confirmed. However, how tachibana peel acts within the 'interaction between melanocytes and epidermal cells,' which is important for spot formation, had not been confirmed. Therefore, in this study, we attempted to clarify the entire mechanism of spot suppression by tachibana peel.
Confirmed the effect of 'Tachibana peel extract' in suppressing melanocyte activation via epidermal cells
Melanin, which causes spots, is formed in melanocytes deep within the skin. When epidermal cells enter an inflammatory state, the production of SCF, a protein that acts as a command for melanocytes to produce melanin, increases, and melanin is generated. Since 'tachibana peel extract' has been confirmed to have anti-inflammatory effects, we verified changes in the amount of SCF produced by adding it to epidermal cells. First, as a result of adding 'tachibana peel extract' to epidermal cells, it was revealed that not only the amount of SCF produced intracellularly but also the amount of SCF released extracellularly decreased. Next, to verify the effect from epidermal cells to melanocytes, we added a culture medium containing the components released from the epidermal cells to melanocytes. As a result, it was confirmed that the activity of tyrosinase, an enzyme involved in melanin production, decreased compared to those without the addition of 'tachibana peel extract' (Figure 2). From these results, it was found that 'tachibana peel extract' can approach the suppression of spot formation by acting on epidermal cells and suppressing the release of melanocyte-stimulating factors.
Figure 2: Amount of SCF released by the addition of 'Tachibana peel extract' and tyrosinase activity by the addition of culture medium
Confirmed the effect of 'Tachibana peel extract' in suppressing melanin uptake by epidermal cells
One of the mechanisms of spot formation is that epidermal cells receive and take up melanin produced by melanocytes into their cells. This uptake of melanin is known to be promoted by a protein called PAR2 produced by epidermal cells. This PAR2 also exists in the periphery of spots and can be a factor that spreads existing spots. Therefore, we verified how the amount of PAR2 produced and the amount of melanin uptake by epidermal cells change by adding 'tachibana peel extract.'
First, when we measured the amount of PAR2 produced after adding 'tachibana peel extract' to epidermal cells, we confirmed that its production was suppressed. Next, we verified whether the amount of melanin actually taken up by epidermal cells decreased by adding the same ingredient. As a result of adding melanin and 'tachibana peel extract' to epidermal cells, the amount of melanin taken up decreased compared to epidermal cells that did not receive the addition (Figures 1 and 3). From these results, it was found that the addition of 'tachibana peel extract' has the effect of suppressing PAR2 production and decreasing the melanin uptake of epidermal cells, which is a factor that spreads spots.
Figure 3: Amount of melanin uptake by epidermal cells due to the addition of 'Tachibana peel extract'
From the above results, we discovered that 'tachibana peel extract' has the effect of suppressing melanocyte activation by decreasing SCF release from epidermal cells, and the effect of preventing melanin uptake by epidermal cells by suppressing PAR2 production, in addition to its previously known direct action on melanocytes.
Future Prospects
Through this research, it has been shown that 'tachibana peel extract' acts not only directly on melanocytes, which was previously known, but also on epidermal cells, preventing the accumulation of melanin in epidermal cells through production and transfer...