3,4-Benzocoumarin is a kind of the expanded structure of coumarin derivatives.Coumarin is a chemical compound in the benzopyrone chemical class that can be found in many natural species. Coumarins possess variety of biological activities and unique photophysical properties. 3,4-Benzocoumarin, a AOH‐like compound , has the sensibility of the antibody with an IC50 of 919.2 ng/mL.