Quercetinase enzymatic activity consists in the addition of dioxygen onto flavonoids, some natural polyphenol compounds, leading to the production of both molecular carbon monoxide and to the structurally related depside compound. Experimental studies have reported degradation rates of various flavonoids by such enzymes that can not be directly correlated neither to the number nor to the place of the hydroxyl groups. In order to decipher the role of these functions, we have theoretically characterised the stationary points of various flavonoids oxygenolysis mechanisms by density functional quantum methods. Thus in the present study are reported the main energetic, structural and electronic features that drive this degradation. Together with previous analysis from MD simulations taking into account the dynamic behaviour of the substrate embedded in the enzyme cavity, the present results show that the role of the enzyme, in terms of structural and electronic effects, can not be neglected. Thus, we propose here that deformations of the substrate induced by the enzyme could originate the differences in the degradation rates experimentally observed.