expected to lead to an ion at m z 439 and cleavage of the interflavonoid bond with retention of charge on the bottom unit would be expected to lead to an ion at m z 441 close examination of fig5 b shows that both m z 439 and m z 441 ions are present indicating that both the upper unit and the lower unit in the dimer are catechin epicatechin gallates loss of part of the gallic acid group c 7 h 4 o 4 leads to an ion at m z 729 in this case the oxygen atom bonded to the monomer unit stays attached leading to a catechin like structure the ion at m z 577 corresponds to a second loss of c 7 h 4 o 4 fragmentation 2 or it could correspond to a retro diels alder rda fragmentation from the ion having already lost one c 7 h 4 o 4 unit conclusions from mass spectrometric data the positive and negative data taken together indicate that the substance isolated in the peak f2 has a molar mass of 882 contains two gallate groups and consists of both an upper unit and a lower unit which are catechin epicatechin gallates it is not possible from.