Determination of relative cancer preventative effects of cruciferous vegetables.

摘要

A diet containing high amounts of cruciferous vegetables promotes health and protects against cancer. The objective of this project was to compare potency of cruciferous vegetables in vitro and in vivo by evaluating their ability to induce detoxification enzymes such as quinone reductase (QR). Our aim was to identify a means to compare potency among crucifer varieties. We fed Fisher 344 rats button or whole Brussels sprouts (BS) and found that both diets induced QR activity to the same extent. This finding has interesting implications for value-added processing of dietary supplements. An aqueous extract of BS (17 mg/mL medium) induced QR activity in cell culture to the same extent as dietary B S (17 mg/g B W) induced rat hepatic QR activity, 2.5 and 1.7-fold, respectively. However, neither in vivo nor in vitro effects of BS correlated with any analyzed compounds such as crambene or sulforaphane (SF). In contrast, effects of broccoli correlated with SF levels, both in vivo and in vitro. When rats were fed two broccoli varieties with very different glucoraphanin (GP) content, 5 and 11 μmol/g DW, both broccoli diets increased the QR activity significantly and to the same extent, showing activity did not relate to dietary GP. Analysis revealed that GP hydrolysis varied such that both broccolis produced 0.8 μmol SF/g DW. Based on SF content, broccoli extracts were as effective as pure SF in cell culture, but dietary broccoli given to rats was up to 30-fold more effective than pure SF. Urinary SF-mercapturic acid (SF-M) was similar in rats receiving dietary hydrolyzed broccoli (1.6 μmol SF/rat/day), freeze-dried broccoli (22.0 μmol GP/rat/day) and pure SF (50 μmol/rat/day) alone or added to broccoli. Also, urinary SF-M correlated with QR induction. We conclude that, whereas SF is the major broccoli component responsible for QR induction, bioavailability of purified SF is poor compared to SF within the broccoli matrix. Neither total GS levels, nor GP/SF levels within a broccoli are good measures of QR inducibility; a better measure is urinary SF-M. Over all, the whole broccoli facilitated the efficacy of SF, which implies that the whole vegetable provides better cancer preventative effects that purified SF.