BB - DIfE

42
�4 DNA adducts (1–5), detected by the 32Ppostlabeling
technique, in human buccal
mucosa before (A) and after (B) chewing
raw broccoli, as well as (C) in endogenous
DNA after a 2-h incubation of broccoli
homogenate. 0, point of sample application.
adducts in the buccal mucosa (Fig. �4 ).
Rats fed raw broccoli showed one of
these characteristic adducts (adduct
spot 3 in Fig. �4 ) in all tissues investigated
(including gut, liver, lung, and kidney)
and sometimes also the minor
adduct spot 5; the adducts were absent
in control rats. We are attempting
to identify the chemical structure of
this adduct and its causing agent. We
are studying the influence of the
preparation (e.g. cooking) and the variety
of broccoli (and other Brassica vegetables)
on the formation of DNA
adducts in rat tissues. Likewise, the
mutagenic potential of the adduct
remains to be determined under in vivo
conditions, as well as the possible relationship
with protective effects of
Brassica plants. It is known that chemoprevention
by Brassica is due, at least in
part, to the induction of defense systems
against reactive molecules. Such
an induction makes most sense, if the
inducer has the potential to damage the
organism. In case of such a two-sided
activity of a broccoli constituent, the
dose could be important for the balance
of favorable and adverse effects.
Alternatively, these effects may be due
to different agents, offering the possibility
to enhance beneficial effects by
choosing appropriate plant varieties
and cooking procedures.
In co-operation with the Department
Biochemistry of Micronutrients we
intend to specify effective exposure levels,
active components, and mechanisms
involved in protective effects of
Brassica vegetables and to explore relationships
to possible adverse effects.
In co-operation with the Department
of Gastrointestinal Microbiology we
could demonstrate that various secondary
metabolites from vegetables and
fruit (e.g., glucobrassicin from broccoli
und arbutin from pears) can be bioactivated
to DNA-reactive metabolites by
enzymes from specific species of intestinal
bacteria.
A
0
�4 DNA-Addukte in humaner Mundschleimhaut
vor (A) und nach (B) dem Kauen von
rohem Broccoli, und zum Vergleich in Broccoli-
DNA (C) nach zweistündiger Inkubation von
Broccoli-Homogenat. Nach Verdau der DNA
wurden die modifizierten Nukleotide mit
32 P-Phosphat markiert, zweidimensional auf
Dünnschichtplatten chromatografiert und
autoradiografisch visulaisiert. 0, Auftragstelle;
1–5, Addukte.
(z.B. Glucobrassicin aus Broccoli und
Arbutin aus der Birne) durch Enzyme spezifischer
Darmbakterienarten zu DNAreaktiven
Substanzen umgesetzt werden
können.
B
0
C
0
1
1
2
2
5
5
3
3
Technische Mitarbeiterinnen
Sabine Braune
Christine Gumz
Andrea Katschak
Brigitte Knuth
Elisabeth Meyer
Martina Scholtyssek
Jutta Schwenk
4
4