Laboratory of Medicinal Chemistry, College of Pharmacy, Pusan National University, Busan 46241, South Korea.
Department of Anatomy, Pusan National University School of Medicine, 49 Busandaehak-ro, Mulgeum-eup, Yangsan-si, Gyeongsangnam-do 50612, South Korea; Department of Pharmacy, Comsats University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
Bioorg Chem. 2019 Jun;87:43-55. doi: 10.1016/j.bioorg.2019.03.001. Epub 2019 Mar 4.
Abnormal melanogenesis results in excessive production of melanin, leading to pigmentation disorders. As a key and rate-limiting enzyme for melanogenesis, tyrosinase has been considered an important target for developing therapeutic agents of pigment disorders. Despite having an (E)-β-phenyl-α,β-unsaturated carbonyl scaffold, which plays an important role in the potent inhibition of tyrosinase activity, cinnamic acids have not attracted attention as potential tyrosinase inhibitors, due to their low tyrosinase inhibitory activity and relatively high hydrophilicity. Given that cinnamic acids' structure intrinsically features this (E)-scaffold and following our experience that minute changes in the chemical structure can powerfully affect tyrosinase activity, twenty less hydrophilic cinnamamide derivatives were designed as potential tyrosinase inhibitors and synthesised using a Horner-Wadsworth-Emmons reaction. Four of these cinnmamides (4, 9, 14, and 19) exhibited much stronger mushroom tyrosinase inhibition (over 90% inhibition) at 25 µM compared to kojic acid (20.57% inhibition); crucially, all four have a 2,4-dihydroxy group on the β-phenyl ring of the scaffold. A docking simulation using tyrosinase indicated that the four cinnamamides exceeded the binding affinity of kojic acid, and bound more strongly to the active site of tyrosinase. Based on the strength of their tyrosinase inhibition, these four cinnamamides were further evaluated in B16F10 melanoma cells. All four cinnamamides, without cytotoxicity, exhibited higher tyrosinase inhibitory activity (67.33 - 79.67% inhibition) at 25 μM than kojic acid (38.11% inhibition), with the following increasing inhibitory order: morpholino (9) = cyclopentylamino (14) < cyclohexylamino (19) < N-methylpiperazino (4) cinnamamides. Analysis of tyrosinase activity and melanin content in B16F10 cells showed that the four cinnamamides dose-dependently inhibited both cellular tyrosinase activity and melanin content and that their inhibitory activity at 25 μM was much better than that of kojic acid. The results of melanin content analysis well matched those of the cellular tyrosinase activity analysis, indicating that tyrosinase inhibition by the four cinnamamides is a major factor in the reduction of melanin production. These results imply that these four cinnamamides with a 2,4-dihydroxyphenyl group can act as excellent anti-melanogenic agents in the treatment of pigmentation disorders.
异常的黑色素生成导致黑色素过量产生，导致色素沉着紊乱。作为黑色素生成的关键限速酶，酪氨酸酶已被认为是开发色素紊乱治疗药物的重要靶点。尽管肉桂酸具有（E）-β-苯基-α，β-不饱和羰基骨架，对抑制酪氨酸酶活性起着重要作用，但由于其低酪氨酸酶抑制活性和相对较高的亲水性，肉桂酸并未引起人们对其作为潜在酪氨酸酶抑制剂的关注。鉴于肉桂酸的结构本质上具有这种（E）骨架，并且根据我们的经验，化学结构的微小变化可以有力地影响酪氨酸酶活性，我们设计了二十种亲水性较低的肉桂酰胺衍生物作为潜在的酪氨酸酶抑制剂，并通过 Horner-Wadsworth-Emmons 反应合成。这四种肉桂酰胺（4、9、14 和 19）在 25µM 时对蘑菇酪氨酸酶的抑制作用（超过 90%的抑制率）明显强于曲酸（20.57%的抑制率）；至关重要的是，所有四种肉桂酰胺的骨架β-苯基上都有一个 2,4-二羟基。使用酪氨酸酶进行对接模拟表明，这四种肉桂酰胺的结合亲和力超过了曲酸的结合亲和力，并且与酪氨酸酶的活性位点结合更紧密。基于其酪氨酸酶抑制作用的强度，我们进一步在 B16F10 黑色素瘤细胞中评估了这四种肉桂酰胺。所有四种肉桂酰胺（4、9、14 和 19）在 25µM 时均无细胞毒性，对酪氨酸酶的抑制活性（67.33-79.67%的抑制率）高于曲酸（38.11%的抑制率），抑制顺序为：吗啉基（9）=环戊基氨基（14）<环己基氨基（19）<N-甲基哌嗪基（4）肉桂酰胺。B16F10 细胞中酪氨酸酶活性和黑色素含量的分析表明，四种肉桂酰胺均能剂量依赖性地抑制细胞内酪氨酸酶活性和黑色素含量，其在 25µM 时的抑制活性明显优于曲酸。黑色素含量分析的结果与细胞酪氨酸酶活性分析的结果非常吻合，表明这四种肉桂酰胺通过抑制酪氨酸酶是减少黑色素生成的主要因素。这些结果表明，这四种具有 2,4-二羟基苯基的肉桂酰胺可以作为治疗色素沉着紊乱的优秀抗黑色素生成剂。
