What chemical is responsible for the initial breakdown of carbohydrates?

Carbohydrate molecules are broken down into smaller particles during digestion. Carbohydrate digestion starts in the mouth. The saliva in the mouth contain an enzyme called ptyalin. Ptyalin acts on the carbohydrate portion [starch] in the food and cause the initial breakdown of carbohydrate in the mouth.
Thus, PTYALIN is responsible for the initial breakdown of carbohydrates.