Several iridoid glucosides found in several Oleaceae species such as the olive tree, privet tree and so on. Iridoid glucosides have iridoid group and glucose group. The Olive tree (Olea europaea) is a species of small tree in Oleaceae species, and olive fruit is of major agricultural importance in the word as the source of olive oil. Olive leaves and fruits contain many kinds of iridoid glucosides. However, this compound itself is stable, does not have any of the activities, and is kept in the vacuoles or cytosol of the leaf cell. Several researches reported that iridoid glucoside would be chemical defense compound in Oleaceae species. When the leaves are mechanically damaged by herbivore like olive weevil and cell compartments are broken, enzymatic activity localized in organelles separate from iridoid glucosides starts to activate iridoid glucosides into a very strong protein denaturant. Nevertheless the importance of iridoid glucosides, it has not yet elucidation "HOW" "WHERE", "WHEN" iridoid glucosides biosynthesized in Oleaceae species like olive tree. To investigate the role of iridoid glucosides in chemical defense, we first started to analyze endogenous levels of iridoid glucosides with/without an olive weevil, and isolated a β-D-glucosidase from olive tree. We demonstrate that biochemical function of β-D-glucosidase the chemical analysis of iridoid compounds in chemical defense.