Fig. 1.

Reference xenobiotic compounds in our study have diverse chemical structures. a Categorization of the reference xenobiotic compounds used in our study according to their sources or applications. b Multi-dimensional scaling plot showing the chemical structure dissimilarity based on Tanimoto coefficients between all the reference compounds (MDS1/2 = the first and second coordinates of the multi-dimensional scaling, dashed line = a cluster of compounds with simple and similar chemical structures. All industrial chemicals are grouped into this cluster together with other compounds irrespective of their known PTC toxicity. Many compounds within the cluster are on top of each other.)