PROBLEM TO BE SOLVED: To provide a method for oxidizing a natural material having a flavonoid skeleton, and a method for dyeing hair using the oxidized material.SOLUTION: The natural material having a flavonoid skeleton such as (+)- catechin is oxidized by oxygen gas in a mixed solvent of water and an alcohol under a basic condition to obtain a compound represented by general formula (2), (wherein, R10, R11, R12 and R13 indicate each independently a hydrogen atom, a hydroxy group or a methyl group R14 indicates a hydrogen atom, a hydroxy group, a galloyl group or a saccharide R15 indicates a hydrogen atom or a hydroxy group and X indicates >CH2, >C=O or >CHOH).COPYRIGHT: (C)2013,JPO&INPIT【課題】フラボノイド骨格を有する天然物質の酸化方法の提供、および該酸化物質を用いた染毛方法の提供。【解決手段】(+)-カテキンのようなフラボノイド骨格を有する天然物質を、水とアルコールとの混合溶媒中で、塩基性条件下で、酸素ガスにより酸化することにより下記一般式(2)で表される化合物が得られる。【選択図】図1
