Effect of 2-hydroxy-1, 4-naphthoquinone, a Natural Dye of Henna, on Aldehyde Oxidase Activity in Guinea Pig Liver

摘要

2-hydroxy-1,4-naphthoquinone (HNQ; Lawsone, CAS 83-72-7) is the main dye ingredient found in the natural plant of Henna ( Lawsonia inermis ). The percentages of superoxide anion (O₂^.) and hydrogen peroxide (H₂O₂,) formation during the oxidation of 100 μM phenanthridine by guinea pig aldehyde oxidase have been measured and found to be 6-10% and 85-90%, respectively. The effect of HNQ on the initial rates of phenanthridine oxidation, hydrogen peroxide formation and superoxide anion with aldehyde oxidase was investigated and compared with those of xanthine oxidase . It was found that HNQ is a specific inhibitor of aldehyde oxidase in vitro . In this study, HNQ inhibits the production of superoxide anion and substrate oxidation more potently than hydrogen peroxide . Thus, the site of interaction is thought to be flavin semiquinone, FADH^.. The IC₅₀ value of HNQ with phenanthridine oxidation by aldehyde oxidase is 9.3±1.1 μM, which in excess of 15 fold of maximal plasma concentrations (C_max) of HNQ, indicating a high degree of safety margin. The interaction of HNQ with aldehyde oxidase has been also investigated using different electron acceptors including, oxygen, potassium ferricyanide and cytochrome c and found to be equipotent.