Synthesis Of Kojic Acid Derivatives As Novel Tyrosinase Inhibitor And Its Mechanism Of Inhibiting Melanogenesis

Tyrosinase(TYR),also known as Polyphenol oxidase(PPO),is a metal oxidoreductase containing divalent copper ions,which is widely distributed in various plants,microorganisms,animals and our bodies.It is the key rate-limiting enzyme for melanin synthesis,browning of fruits and vegetables,wound healing and development of insects,and human aging and health are affected.Abnormal expression of TYR is associated with many diseases,especially some skin diseases,For example,high expression may induce the potential of malignant melanoma and cause skin pigmentation such as freckles,chloasma and other diseases.while low expression may lead to albinism,vitiligo and other diseases.Therefore,the expression levels and acitivity of TYR has important physiological significance.Three novel kojic acid derivatives(KADI,KAD2 and KAD3)were synthesized and identified.Further their antityrosinase activities were measured using mushroom tyrosinase as the model.The results showed that all the compounds showed significant inhibitory effects,with IC50 of monophenolase 21.58,20.51 and 19.20 ?mol/L,followed by IC50 of diphenolase 8.33,7.50 and 10.00 ?mol/L.The inhibitory mechanisms of the three compounds were reversible.The inhibitory constants(K1)were 4.95,6.30 and 7.50 ?mol/L,and the inhibitory dissociation constants(KIS)were 45.50,9.18 and 15.80 ?mol/L,respectively.The effect of the three compounds on the melanogenesis in mouse B16F10 cells were studied on the basis of mTYR.The results suggested that all the three compounds could effectively inhibit the formation of melanin and the activity of intracellular crude tyrosinase.Especially,we found that the compound KAD2 could synergistically inhibit the CREB signaling pathway?activate the Akt signaling pathwayson of TYR family proteins,and ultimately inhibit the synthesis of melanin.Further,we studied the inhibitory effect of KAD2 on pigment formation in zebrafish embryos.The results showed that KAD2 could effectively inhibit the expression of MITF and TYR.In addition,KAD2 could remarkably inhibited TYR activity and ultimately inhibit the formation of pigments.Particularly,acute toxicity tests in mice suggested that KAD2 was not toxic to mice.In addition,all the three compounds showed good free radical scavenging ability,and the effect was prominently higher than that of kojic acid.This may due to the compound has hydrogen donate groups in its structure,giving it antioxidant features.Those suggest that kojic acid derivatives can be used as a potential candidate whitening and antioxidant agent.