Fig 7.

A: Galangin accepts a π-π approach by superoxide. Initially van der Waals separated molecules, 3.50 Å, are geometrically optimized. Both reagents become closer with centroid-centroid separation stabilized 3.190 Å apart. There is a slight shortening of O-O bond distance in superoxide, 1.354 Å, from the original 1.373 Å; B: Galangin π–π superoxide from previous Fig 7A is now approached by a proton that, after minimization, becomes stabilized by formation of an O-H bond, 0.985 Å, while superoxide O-O separation is lengthened, 1.407 Å (it was 1.354 Å in Fig 7A); C: From previous Fig 7B, an additional proton is placed 2.60 Å from HO₂. Upon minimization H₂O₂ is formed, however, it is in a complex with the galangin ring, as shown by the centroid-centroid separation of 3.247 Å, shorter that the 3.50 Å π–π van der Waals separation.