Design, synthesis of Cinnamyl-paeonol derivatives with 1, 3-Dioxypropyl as link arm and screening of tyrosinase inhibition activity in vitro

This study aimed to obtain tyrosinase inhibitors for treating hyperpigmentation. A series of cinnamyl ester analogues were designed and synthesized with cinnamic acid (CA) and peaonol compounds. The safety, melanin content and inhibitory effects of all target compounds were evaluated. In the enzymatic activity test, the inhibitory rate of compounds 8, 13 and 14 had stronger inhibitory activity with the IC50 values of 20.7 μM, 13.98 μM and 15.16 μM, respectively than the positive drug kojic acid (IC50 with 30.83 μM). The cytotoxicity evaluation showed that compounds 13 and 14 have higher safety than the other compounds to the proliferation of B16F10 cells. The result of the melanocyte test supported that compound13 has stronger cellular tyrosinase inhibitory activity than kojic acid and arbutin at 100 μM and 200 μM. The enzyme kinetics mechanism revealed that compound 13 was a non-competitive inhibitor while compounds 8 and 14 were mixed inhibitors. For the experiments of melanin content and tyrosinase activity in the B16F10 melanona cells, the inhibition rates of compounds 8, 14 and 13 were with 19.62%, 20.59% and 23.83%, respectively. In addition, compound 13 revealed the highest inhibitory activity to tyrosinase in the melanocyte with inhibition rates of 23.83%, which was better than kojic acid and arbutin (19.21% and 20.45%) at the same concentration. In the anti-melanogenesis experiment, compounds 8 and 13 had better anti-melanin effects than kojic acid from 25 μM to 100 μM. In summary, the results indicated that compounds 8, 13 and 14 had better tyrosinase inhibitory activity and anti-melanogenesis activity. Especially, the compound 13 has potentiality to develop novel tyrosinase inhibitors and whitening agents. The docking studies results revealed that the functional group of compound 13 mostly depends on the phenolic hydroxyl moiety, and its hydroxyl group did not insert into the active site of tyrosinase, which was in agreement with the results of the kinetics study.