Caffeic acid causes metal-dependent damage to cellular and isolated DNA through H2O2 formation.

Pulsed field gel electrophoresis showed that caffeic acid induced DNA strand breaks in cultured human cells in the presence of Mn(II). With alkali treatment, DNA single-strand breaks were observed. The strand breakage was increased by the treatment of buthionine sulphoximine (a GSH synthesis inhibitor) and 3-aminotriazol (a catalase inhibitor) and decreased by catalase, indicating the involvement of HO. The DNA damage was decreased by -phenanthroline, indicating the involvement of transition metal ion. Damage to isolated DNA from c-Ha--1 protooncogene was investigated by a DNA sequencing technique. Caffeic acid caused DNA damage hi the presence of Cu(II) but not in the presence of either Mn(II) or Fe(III). Caffeic acid plus Cu(II) induced piperidine-labile sites frequently at thymine residues, especially of the 5′-GTC-3′ and 5′-CTG-3′ sequences. Typical OH scavengers showed no inhibitory effects. The inhibitory effects of bathocuproine and catalase on Cu(II)-mediated DNA damage suggest that Cu(I) and HO have important roles in the production of active species causing DNA damage. The Cu(II)-mediated DNA damage was enhanced by pre-incubation of caffeic acid with Mn(II). Mn(II) or Cu(II)-catalyzed autoxidation of caffeic acid produced HO with efficiency of Mn(II) > Cu(II). These results suggest that in the presence of Mn(II) or Cu(II), caffeic acid produces HO, which is activated by transition metals to cause damage to DNA and probably in cultured cells. [ABSTRACT FROM PUBLISHER]