TYR inhibitors(Hangzhou Normal University)

Tyrosinase is the key rate-limiting enzyme for melanin synthesis. The accumulation and excessive production of melanin lead to skin pigmentation. Therefore, tyrosinase is the target of tyrosinase inhibitors to control melanin synthesis. Only a few TYR inhibitors have been proven to be effective and safe to treat skin pigmentation. This highlights the importance of developing new tyrosinase inhibitors. Based on the reported tyrosinase inhibitors with phenylalanine structure, a series of novel phenylalanine derivatives were synthesized and investigated as mTYR inhibitors. The results demonstrated that most of these derivatives had more potent mTYR inhibitory activities than positive controls. Compound 3e was found to be the strongest inhibitor with an IC₅₀ value of 4.86 ± 0.026 μM. The Lineweaver-Burk plots of mTYR inhibition kinetics revealed that the selected compounds 2d and 3e were reversible and competitive inhibitors. In addition, molecular docking results of compounds 2d and 3e show they could compete with the substrate for the active center, including mTYR and hTYR. And the ADME prediction of selected derivatives assess the potential druglikeness. These results indicated that this class of compounds could be used as leads for developing new TYR inhibitors.

Natural phenolic compounds, such as anthocyanins and arbutin, have demonstrated significant potential as tyrosinase (TYR) inhibitors. However, the application of anthocyanins in biological systems is hindered by their instability under alkaline conditions, elevated temperatures, and light exposure. In contrast, arbutin exhibits superior stability while also functioning as a TYR inhibitor. To overcome these limitations, this study developed an Anthocyanin-α-Arbutin Co-amorphous (AAC) system aimed at enhancing both the stability of anthocyanins and their TYR inhibitory properties. Kinetic studies revealed that anthocyanins, arbutin, and AAC act as reversible mixed-type TYR inhibitors, with competitive inhibition as the predominant mechanism. Each compound exhibited distinct inhibition sites. Fluorescence analysis demonstrated that anthocyanins induce a fluorescence burst in TYR, likely attributed to Tyr residues, whereas α-arbutin and AAC enhance the fluorescence intensity of TYR. Moreover, α-arbutin and AAC were found to decrease the microenvironmental hydrophobicity surrounding tyrosine (Tyr) residues while increasing it around tryptophan (Trp) residues, suggesting potential conformational changes in tyrosinase. Molecular docking analysis indicated that hydrogen bonding and π-π stacking interactions occurred between anthocyanins and arbutin in the AAC system. Specifically, anthocyanins primarily interacted with TYR through π-π and π-alkyl interactions, while α-arbutin predominantly bound to TYR via hydrogen bonding. Consistent with the interaction study, α-arbutin was found to associate with tyrosinase mainly through hydrogen bonding and van der Waals forces. These findings provide novel insights into the interactions between anthocyanins and α-arbutin in the context of food science and lay a foundation for the development of innovative TYR inhibitors.