8707
Percutaneous transdermal absorption of esculetin ( 6 , 7 - dihydroxycoumarin ) , an oxidative damage inhibitor , was evaluated by means of in vitro permeation studies in which vertical Franz - type diffusion cells and pig ear skin were employed .
 Chemical: esculetin; Chemical: 6 , 7 - dihydroxycoumarin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: esculetin; Chemical: 6 , 7 - dihydroxycoumarin