Demethoxycurcumin-metal complexes: Fragmentation and comparison with curcumin-metal complexes,as studied by ESI-MS/MS

Two questions are asked: the first is if the lack/presence of methoxyl moiety at aromatic ring essentially affects the stability of curcuminoid-metal complexes,and the second is if it is possible that in the metal complexes one of the possible demethoxycurcumin structures predominates. to answer the first question,the esi-ms/ms spectra were taken of ions containing demethoxycurcumin,curcumin,and metal cation (e.g.,ion [dcurc + curc-h + pb]+),and in order to answer the second question the esi-ms/ms spectra were recorded of ions containing demethoxycurcumin and metal cation (e.g.,ion [dcurc-h + zn]+). an interpretation of the mass spectra has indicated that (i) for some metals,curcumin-metal complexes are more stable than demethoxycurcumin-metal complexes and for some metals vice versa,and (ii) in demethoxycurcumin-metal complexes structure b1 [(1e,4z,6e)-5-hydroxy-7-(4- hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)hepta-1,4,6-trien-3-one] is more stable than structure b2 [(1e,4z,6e)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-7- (4-hydroxyphenyl)hepta-1,4,6-trien-3-one]. © 2013 wojciech ostrowski et al.