This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Substances containing a phenolic moiety are often metabolized to quinones whose high reactivity not only makes them difficult to study but may also be responsible for their toxicity. Some of these precursors have clear health benefits, and some quinones themselves are used in cancer therapy, whereas others are deleterious. For example, dietary intake of phytoestrogen, genistein (Gen), seems to play a preventive role in breast cancer (BC) whereas prolonged exposure to chemically similar mammalian estrogens is clearly associated with elevated incidence of BC. Although both can be metabolized to reactive quinones, the catechol estrogen quinones (CEQs) modify DNA by redox cycling and/or depurination via a Michael addition.