Chemical-based resistance of plant was characterized by accumulating of secondary metabolites known as allelochemicals with more than 200,000 identified compounds that act in defense purposes to prevent insect’s feeding. In the absent of the herbivorous attack, a minimum level of secondary compounds were maintained as constitutive resistance to protect plant from possible harm in the ecological environment. Soon after being damaged by herbivorous, the induced-resistance was activated with increasing the production of defensive metabolites to prevent further losses. Domestication process with data exists at present reveal general trends of reduced resistance and more susceptible to herbivorous insects among cultivated crop. Our research focuses on comparing the wild-type (Rorippa dubia Persoon) and cultivated crop (Brassica oleracea) of brassica family to estimated the plant’s capability of producing allelochemicals against herbivores in both constitutive and induced-condition. Our data support the theory of modern crop varieties have reduced their herbivore resistance during the course of domestication with evident of lower foligae’s allelochemicals in both constitutive resistance (intact foliage) and induced- resistace (respond after being damage of hebivorous) in B.oleracea compare to R.dubia. These finding also help us understand the reduce of plant’s resistance via process of domestication