Impact of feeding Brassicaceae on bioactivation of glucosinolates via bacterial myrosinase in the murine gut.
Isothiocyanates are effective chemopreventive compounds derived from glucosinolates. which are mainly contained in brassicaceous vegetables. They are formed by myrosinase that is released from myrosin cells upon plant tissue damage or by intestinal bacteria. which possess myrosinase activity. Objectives: Microbial myrosinase is induced by incubation with glucosinolates. Therefore we hypothesized. that feeding a diet rich in glucosinolates may result in an improved bioactivation of glucosinolates by bacterial myrosinase. Method/Design: Mice were fed a diet containing either broccoli sprouts (1.2% of dry mass) or in addition an extract from broccoli seeds high in glucoraphanin (4-Methylsulfinylbutyl glucosinolate) for 4 weeks. Further feeding groups received a diet containing either pak
choi sprouts (1.2% of dry mass) or in addition an extract from pak choi sprouts high in neoglucobrassicin (1-Methoxy-3-Indolylmethy glucosinolate) for 1 week. Mice that received no additives served as controls. After killing of the animals. either glucoraphanin or neoglucobrassicin was incubated with cecum contents anaerobically at 37°C. Degradation of glucosinolates and formation of metabolites were quantified using HPLC.DAD. Results: Glucosinolate concentrations remained stable during incubation without bacteria. Almost complete degradation of glucoraphanin
was observed within 24 hours of incubation with cecum contents of all feeding groups. The corresponding isothiocyanate
sulforaphane was not detected in any of the incubations. Average degradation of neoglucobrassicin within 24 hours of incubation was higher by cecal bacteria of mice fed a broccoli diet low or high in glucoraphanin (76.7 and 89.8%. respectively) compared with cecal bacteria of mice fed a pak choi diet low or high in neoglucobrassicin (46.3 and 48.0%. respectively) and of control mice (35.8%). Neoglucobrassicin. which was degraded Conclusions: Myrosinase of intestinal bacteria was constitutive. since a diet high in glucoraphanin or neoglucobrasscin did not result in an increase of bacterial activation of these glucosinolates.
Hanske, L.; Lehmann,C.; Haack, M.; Brigelius-Flohe, R.; Wiesner, M.; Mewis, I.; Schreiner, M.; Monien, B.; Glatt, H.; Blaut. M. 2011. Impact of feeding Brassicaceae on bioactivation of glucosinolates via bacterial myrosinase in the murine gut. Annals of Nutrition and Metabolism 58 (Suppl. 3), 5.