A mixture of purified polyphenol oxidases (PPO), or acetone powders prepared from fruits and vegetables, and polyphenolic compounds (PPs) totally eliminated a methylmercaptan odor. 2-Methyl-thiochlorogenic acid was isolated from the reaction mixture of methylmercaptan and chlorogenic acid with burdock acetone powder. Further, the formation of 5-methylthiochlorogenic acid and 2,5-bis(methylthio)-chlorogenic acid was suggested. These facts demonstrate that the o-quinone compounds formed from o-diphenols by PPO rapidly reacted with methylmercaptan. The oxidation reaction of PPs by using acetone powder containing PPO or peroxidase is considered to be more effective for removing bad smells from our mouths and from the environment.