Phytochemistry is in the strict sense of the word the study of photochemical. These are chemicals derived from plants. In a narrower sense the terms are often used to describe the large number of secondary metabolic compounds found in plants. Many of these are known to provide protection against insect attacks and plant diseases. They are exhibit a number of protective functions for human consumers. Phytochemistry is widely used in the field of Chines medicine especially in the field of herbal medicine.