posted on 2022-01-20, 21:33authored byWei Wang, Lin Chen, Weiwei Wang, Jianyong Zhang, Ulrich H. Engelhardt, Heyuan Jiang
Some
catechins and their dimeric oxidation products are well known
to possess antimelanogenic activity, which could be influenced by
their structures and oxidative dimerization. This study compared the
antimelanogenic activity of different catechins and dimeric oxidation
products and clarified the mechanism using an α-MSH-stimulated
B16F10 cell model. It was found that 100 μg/mL (−)-gallocatechin
gallate, (−)-epigallocatechin gallate, theasinensin A, and
theaflavine-3,3′-digallate could significantly inhibit melanin
synthesis without cytotoxicity. The tyrosinase (TYR) activities were
26.24 ± 4.97, 31.57 ± 5.37, 66.10 ± 9.62, and 78.19
± 5.14%, respectively, and the melanin contents were 38.29 ±
3.50, 41.21 ± 7.62, 62.13 ± 9.80, and 68.82 ± 11.62%,
respectively. These compounds inhibit melanin production by attenuating
the mRNA levels of TYR, TRP1, and TRP2 gene. The structure–activity
relationship showed that geometrical isomerism was not the key factor
affecting catechins’ antimelanogenic activity. Compared with
the catechol, catechins with B-ring pyrogallol inhibited melanin synthesis
more effectively. The number of galloyl groups was positively correlated
with antimelanogenic activity. Compared with 3-galloyl, 3′-galloyl
was a stronger active group in antimelanogenesis. Interestingly, the
contribution of B-ring pyrogallol to the antimelanogenic activity
was significantly stronger than that of 3-galloyl in catechins. Additionally,
the antimelanogenic activity of the dimeric oxidation product at 100
μM was more than or equal to that of individual substrate–catechin,
while being significantly less than that of the substrate–catechin
mixture. Results indicated that pyrogallol and galloyl were the active
groups inhibiting melanin synthesis. The oxidative dimerization weakened
the antimelanogenic activity of the substrate–catechin mixture.