A high-level Petri net framework is introduced for the toxic risk assessment in biological and bio-synthetic systems. Unlike empirical techniques mostly used in toxicology or toxicogenomics, we propose a systemic approach consisting of a series of behavioral rules (reactions) that depend on abstract discrete "expression" levels of involved agents (species). We introduce a finite state high-level Petri net model allowing exhaustive verification (model-checking) of properties related to equilibrium alteration or appearing of hazardous behaviors. The approach is applied to the study of the impact of the aspartame assimilation into the blood glucose regulation process.