“…In the last years several studies have been directed to the development of novel tyrosinase inhibitors inspired by natural scaffolds, which should overcome stability, efficacy, and isolation yield issues. One of the main exploited scaffolds is hydroxycinnamic acid: indeed several hydroxycinnamic acid analogues have been synthesized through the most disparate approaches [123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141], leading in some cases to very potent mushroom tyrosinase inhibitors (Figure 17), such as 2,4-dihydroxycinnamides (IC 50 = 0.0112-0.16 µM) [132,133]. A thiophenyl derivative of 2,4-dihydroxycinnamic acid has also exhibited a very low IC 50 value (0.013 µM) against the monophenolase activity of the enzyme [134].…”
Section: Synthetic Phenolic Inhibitors Of Mushroom Tyrosinasementioning
confidence: 99%
“…In the last five years, several natural and synthetic phenolic compounds have been described also as inhibitors of tyrosinase from animal and human sources. Most of these studies used B16 murine melanoma cell lines as a model [52,55,75,85,95,96,99,114,122,123,[127][128][129][132][133][134][135]138,139,151,153,155,163,, although some papers using zebrafish as an in vivo whole animal model have also been published [55,116,206]. As to the human sources, data on inhibition of human recombinant or purified tyrosinase [9,207], human melanoma cells [130,136], normal human melanocytes [208][209][210][211], or human skin models consisting of reconstructed three-dimensional human epidermis [212][213][214][215] have been published (Figure 21).…”
Section: Human and Animal Tyrosinase Phenolic Inhibitorsmentioning
One of the most common approaches for control of skin pigmentation involves the inhibition of tyrosinase, a copper-containing enzyme which catalyzes the key steps of melanogenesis. This review focuses on the tyrosinase inhibition properties of a series of natural and synthetic, bioinspired phenolic compounds that have appeared in the literature in the last five years. Both mushroom and human tyrosinase inhibitors have been considered. Among the first class, flavonoids, in particular chalcones, occupy a prominent role as natural inhibitors, followed by hydroxystilbenes (mainly resveratrol derivatives). A series of more complex phenolic compounds from a variety of sources, first of all belonging to the Moraceae family, have also been described as potent tyrosinase inhibitors. As to the synthetic compounds, hydroxycinnamic acids and chalcones again appear as the most exploited scaffolds. Several inhibition mechanisms have been reported for the described inhibitors, pointing to copper chelating and/or hydrophobic moieties as key structural requirements to achieve good inhibition properties. Emerging trends in the search for novel skin depigmenting agents, including the development of assays that could distinguish between inhibitors and potentially toxic substrates of the enzyme as well as of formulations aimed at improving the bioavailability and hence the effectiveness of well-known inhibitors, have also been addressed.
“…In the last years several studies have been directed to the development of novel tyrosinase inhibitors inspired by natural scaffolds, which should overcome stability, efficacy, and isolation yield issues. One of the main exploited scaffolds is hydroxycinnamic acid: indeed several hydroxycinnamic acid analogues have been synthesized through the most disparate approaches [123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141], leading in some cases to very potent mushroom tyrosinase inhibitors (Figure 17), such as 2,4-dihydroxycinnamides (IC 50 = 0.0112-0.16 µM) [132,133]. A thiophenyl derivative of 2,4-dihydroxycinnamic acid has also exhibited a very low IC 50 value (0.013 µM) against the monophenolase activity of the enzyme [134].…”
Section: Synthetic Phenolic Inhibitors Of Mushroom Tyrosinasementioning
confidence: 99%
“…In the last five years, several natural and synthetic phenolic compounds have been described also as inhibitors of tyrosinase from animal and human sources. Most of these studies used B16 murine melanoma cell lines as a model [52,55,75,85,95,96,99,114,122,123,[127][128][129][132][133][134][135]138,139,151,153,155,163,, although some papers using zebrafish as an in vivo whole animal model have also been published [55,116,206]. As to the human sources, data on inhibition of human recombinant or purified tyrosinase [9,207], human melanoma cells [130,136], normal human melanocytes [208][209][210][211], or human skin models consisting of reconstructed three-dimensional human epidermis [212][213][214][215] have been published (Figure 21).…”
Section: Human and Animal Tyrosinase Phenolic Inhibitorsmentioning
One of the most common approaches for control of skin pigmentation involves the inhibition of tyrosinase, a copper-containing enzyme which catalyzes the key steps of melanogenesis. This review focuses on the tyrosinase inhibition properties of a series of natural and synthetic, bioinspired phenolic compounds that have appeared in the literature in the last five years. Both mushroom and human tyrosinase inhibitors have been considered. Among the first class, flavonoids, in particular chalcones, occupy a prominent role as natural inhibitors, followed by hydroxystilbenes (mainly resveratrol derivatives). A series of more complex phenolic compounds from a variety of sources, first of all belonging to the Moraceae family, have also been described as potent tyrosinase inhibitors. As to the synthetic compounds, hydroxycinnamic acids and chalcones again appear as the most exploited scaffolds. Several inhibition mechanisms have been reported for the described inhibitors, pointing to copper chelating and/or hydrophobic moieties as key structural requirements to achieve good inhibition properties. Emerging trends in the search for novel skin depigmenting agents, including the development of assays that could distinguish between inhibitors and potentially toxic substrates of the enzyme as well as of formulations aimed at improving the bioavailability and hence the effectiveness of well-known inhibitors, have also been addressed.
“…To catch up with the recent advancement in human tyrosinase inhibitors [ 56 , 57 , 58 ], over the past decade, we have identified many tyrosinase inhibitors and have accumulated much structure–activity relationship data [ 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. Based on these data, we concluded the ( E )-β-phenyl-α,β-unsaturated carbonyl scaffold plays an essential role in tyrosinase inhibitory activity and that when the β-phenyl of the scaffold is a 4-substituted resorcinol (2,4-dihydroxyphenyl), derivatives with such scaffolds exhibit potent tyrosinase inhibitory activities ( Figure 1 ).…”
We previously reported (E)-β-phenyl-α,β-unsaturated carbonyl scaffold ((E)-PUSC) played an important role in showing high tyrosinase inhibitory activity and that derivatives with a 4-substituted resorcinol moiety as the β-phenyl group of the scaffold resulted in the greatest tyrosinase inhibitory activity. To examine whether the 4-substituted resorcinol moiety could impart tyrosinase inhibitory activity in the absence of the α,β-unsaturated carbonyl moiety of the (E)-PUSC scaffold, 10 urolithin derivatives were synthesized. To obtain more candidate samples, the lactone ring in synthesized urolithins was reduced to produce nine reduced urolithins. Compounds 1c (IC50 = 18.09 ± 0.25 μM), 1h (IC50 = 4.14 ± 0.10 μM), and 2a (IC50 = 15.69 ± 0.40 μM) had greater mushroom tyrosinase-inhibitory activities than kojic acid (KA) (IC50 = 48.62 ± 3.38 μM). The SAR results suggest that the 4-substituted resorcinol motif makes an important contribution to tyrosinase inhibition. To investigate whether these compounds bind to human tyrosinase, a human tyrosinase homology model was developed. Docking simulations with mushroom and human tyrosinases showed that 1c, 1h, and 2a bind to the active site of both tyrosinases with higher binding affinities than KA. Pharmacophore analyses showed that two hydroxyl groups of the 4-substituted resorcinol entity act as hydrogen bond donors in both mushroom and human tyrosinases. Kinetic analyses indicated that these compounds were all competitive inhibitors. Compound 2a inhibited cellular tyrosinase activity and melanogenesis in α-MSH plus IBMX-stimulated B16F10 melanoma cells more strongly than KA. These results suggest that 2a is a promising candidate for the treatment of skin pigment disorders, and show the 4-substituted resorcinol entity importantly contributes to tyrosinase inhibition.
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