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Influence of
temperature and ontogeny on the levels of glucosinolates in broccoli (Brassica
oleracea Var. italica) sprouts and their effect on the induction of mammalian
phase 2 enzymes.
J Agric Food Chem 2002 Oct 9;50(21):6239-44
Pereira FM, Rosa E, Fahey JW, Stephenson KK, Carvalho R, Aires A.
Department of Plant Science and Agricultural Engineering, Universidade de
Tras-os-Montes e Alto Douro, Apartado 1013, 5001-911 Vila Real, Portugal.
Broccoli inflorescences have been recognized as components of healthy diets on
the basis of their high content of fiber, vitamin C, carotenoids, and
glucosinolates/isothiocyanates. Broccoli sprouts have been recently shown to
have high levels of glucoraphanin (4-methylsulfinylbutyl glucosinolate), the
precursor of the chemoprotective isothiocyanate, sulforaphane. This study
evaluated the effects of temperature and developmental stage on the
glucosinolate content of broccoli sprouts. Seedlings cultivated using a 30/15
degrees C (day/night) temperature regime had significantly higher glucosinolate
levels (measured at six consecutive days postemergence) than did sprouts
cultivated at lower temperatures (22/15 and 18/12 degrees C; p < 0.001). Both
higher (33.1 degrees C) and lower (11.3 degrees C) constant temperatures induced
higher glucosinolate levels in sprouts grown to a uniform size. Glucosinolate
levels were highest in cotyledons and lowest in roots of sprouts dissected both
early and late in the 11 day developmental span investigated. Nongerminated
seeds have the highest glucosinolate levels and concordantly greater induction
of mammalian phase 2 detoxication enzymes. Levels decline as sprouts germinate
and develop, with consistently higher glucosinolate content in younger
developmental stages, independent of the temperature regime. Temperature stress
or its associated developmental anomalies induce higher glucosinolate levels,
specific elevations in glucoraphanin content, and parallel induction of phase 2
chemoprotective enzymes.
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