title: In vitro and in silico studies of the inhibitory effects of some novel kojic acid derivatives on tyrosinase enzyme.
abstract: OBJECTIVE
  Tyrosinase is a key enzyme in pigment synthesis. Overproduction of melanin in parts of the skin results in hyperpigmentation diseases. This enzyme is also responsible for the enzymatic browning in fruits and vegetables. Thus, its inhibitors are of great importance in the medical, cosmetic and agricultural fields.
  
  
  METHODS
  A series of twelve kojic acid derivatives were designed to be evaluated as tyrosinase activity inhibitors. The potential inhibitory activity of these compounds was investigated in silico using molecular docking simulation method. Four compounds with a range of predicted tyrosinase inhibitory activities were prepared and their inhibitory effect on tyrosinase activity was evaluated. The antioxidant properties of these compounds were also investigated by in vitro DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydrogen peroxide scavenging assays.
  
  
  RESULTS
  Compound IIId exhibited the highest tyrosinase inhibitory activity with an IC50 value of 0.216 ± 0.009 mM which was in accordance with the in silico ΔGbind results (-13.24 Kcal/mol).
  
  
  CONCLUSIONS
  Based on the docking studies, from the twelve compounds studied, one (IIId) appeared to have the highest inhibition on tyrosinase activity. This was confirmed by enzyme activity measurements. Compound IIId has an NO2 group which binds to both of Cu(2+) ions located inside the active site of the enzyme. This compound appeared to be even stronger than kojic acid in inhibiting tyrosinase activity. The DPPH free radical scavenging ability of all the studied compounds was more than that of BHT. However, they were not as strong as BHT or gallic acid in scavenging hydrogen peroxide.
authors.affiliation: Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Azizeh
authors.initials: A
authors.lastname: Asadzadeh
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Hajar
authors.initials: H
authors.lastname: Sirous
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Morteza
authors.initials: M
authors.lastname: Pourfarzam
authors.affiliation: Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Parichehreh
authors.initials: P
authors.lastname: Yaghmaei
authors.affiliation: Department of Biochemistry, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Fassihi
authors.initials: F
authors.lastname: Afshin
keywords: Antioxidant activity; In silico studies; Kojic acid; Tyrosinase