Knowledge of herbs has been recorded since at least 2000 BC in ancient civilizations such as the Middle East, Egypt, China and India. In 100 AD Dioscorides, a Greek physician wrote “De Materia Medica”, a herbal reference book listing 600 herbs. It was translated into different languages and used until the 17th Century. Herbs have active constituents, which are responsible for their medicinal actions and are often used together for synergistic (or greater) effect.