The Science of Broccoli and its Consituents
Title
Antioxidant properties of the major polyphenolic compounds in broccoli.
Author
Plumb GW; Price KR; Rhodes MJ; Williamson G .
Address
Biochemistry Department, Institute of Food Research, Colney, Norwich, UK.
geoff.plumb@bbsrc.ac.uk
Source
Free Radic Res, 1997 Oct, 27:4, 429-35
Abstract
We have examined the antioxidant activity of the major phenolic compounds
in Broccoli: two flavonol glycosides (quercetin 3-O-sophoroside and kaempferol
3-O-sophoroside) and four hydroxycinnamic acid esters (1,2'-disinapoyl-2-feruloyl
gentiobiose, 1-sinapoyl-2-feruloyl gentiobiose, 1,2,2'-trisinapoyl gentiobiose
and 1,2-disinapoyl gentiobiose). The Trolox C equivalent antioxidant capacity
(TEAC) and inhibition of iron/ascorbate-induced lipid peroxidation of phosphatidyl
choline vesicles were measured. In the aqueous phase TEAC assay, the two flavonol
glycosides were less active than their respective aglycones. TEAC values for
the hydroxycinnamic acid esters were less than the sum of their constituent
hydroxycinnamic acids on a molar basis. Quercetin 3-O-sophoroside was a potent
inhibitor of lipid peroxidation, in contrast to kaempferol 3-O-sophoroside.
The hydroxycinnamic acid esters were highly effective at preventing lipid
damage with the exception of 1,2,2'-trisinapoyl gentiobiose. The six compounds
analysed herein demonstrate the antioxidant activity of the major phenolics
in broccoli and indicate the effect on antioxidant activity of sugar substitutions
in the phenolic B ring.
Title
Absence of the glutathione
S-transferase M1 gene increases cytochrome P4501A2 activity among frequent
consumers of cruciferous vegetables in a Caucasian population.
Author
Probst Hensch NM; Tannenbaum SR; Chan KK; Coetzee GA; Ross RK; Yu MC
Address
Institute of Social and Preventive Medicine of the University of Basel,
Switzerland.
Source
Cancer Epidemiol Biomarkers Prev, 1998 Jul, 7:7, 635-8
Abstract
The cancer protective effect of cruciferous vegetables has been attributed
to induction of phase II enzymes. But cruciferous vegetables also induce cytochrome
P4501A2 (CYP1A2), which catalyzes the metabolic activation of various procarcinogens,
including aromatic amines in tobacco. Thus, frequent intake of cruciferous
vegetables could also result in cancer-enhancing effects. GSTM1 is involved
in the detoxification of various carcinogens, but it also enhances the excretion
of isothiocyanates and possibly other enzyme inducers in cruciferous vegetables.
We, therefore, hypothesized that GSTM1 null genotype might be associated with
increased CYP1A2 activity among frequent consumers of cruciferous vegetables
because the excretion of CYP1A2 inducers contained in these vegetables may
be partially inhibited in the absence of the GSTM1 enzyme. Three hundred twenty-eight
non-Hispanic white residents of Los Angeles County (265 males and 63 females)
were genotyped for the presence or absence of GSTM1 alleles and phenotyped
for CYP1A2 activity. Information on usual dietary habits was obtained from
these subjects through in-person interviews. Among frequent (at least once
a week) consumers of broccoli, GSTM1 null individuals exhibited a 21% higher
geometric mean level of CYP1A2 activity relative to GSTM1 non-null individuals
(5.24 versus 4.32, two-sided P = 0.01). No such difference was observed in
subjects who consumed broccoli less frequently (two-sided P = 0.39). This
interactive effect of GSTM1 genotype and vegetable intake on CYP1A2 activity
also was observed when overall intake of the five cruciferous vegetables under
study (broccoli, cabbage, cauliflower, Brussels sprouts, and mustard greens)
was examined. Among weekly consumers of cruciferous vegetables, GSTM1 null
individuals showed a 16% higher geometric mean level of CYP1A2 activity relative
to GSTM1 non-null individuals (5.03 versus 4.33, two-sided P = 0.02), whereas
no difference was evident among those who consumed cruciferous vegetables
less frequently (two-sided P = 0.35). Our results suggest that cruciferous
vegetables contain CYP1A2 inducers, which are deactivated in the presence
of GSTM1.
Title
Human metabolism and excretion of cancer chemoprotective glucosinolates
and isothiocyanates of cruciferous vegetables.
Author
Shapiro TA; Fahey JW; Wade KL; Stephenson KK; Talalay P
Address
Department of Pharmacology and Molecular Sciences, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, USA.
Source
Cancer Epidemiol Biomarkers Prev, 1998 Dec, 7:12, 1091-100
Abstract
Isothiocyanates and their naturally occurring glucosinolate precursors are
widely consumed as part of a diet rich in cruciferous vegetables. When plant
cells are damaged, glucosinolates are released and converted to isothiocyanates
by the enzyme myrosinase. Many isothiocyanates inhibit the neoplastic effects
of various carcinogens at a number of organ sites. Consequently, these agents
are attracting attention as potential chemoprotectors against cancer. As a
prerequisite to understanding the mechanism of the protective effects of these
compounds, which is thought to involve the modulation of carcinogen metabolism
by the induction of phase 2 detoxication enzymes and the inhibition of phase
1 carcinogen-activating enzymes, we examined the fate of ingested isothiocyanates
and glucosinolates in humans. Recently developed novel methods for quantifying
isothiocyanates (and glucosinolates after their quantitative conversion to
isothiocyanates by purified myrosinase) and their urinary metabolites (largely
dithiocarbamates) have made possible a detailed examination of the fates of
isothiocyanates and glucosinolates of dietary crucifers. In a series of studies
in normal volunteers, we made these findings. First, in nonsmokers, urinary
dithiocarbamates were detected only after the consumption of cruciferous vegetables
and condiments rich in isothiocyanates and/or glucosinolates. In sharp contrast,
the consumption of noncrucifers (corn, tomatoes, green beans, and carrots)
did not lead to the excretion of dithiocarbamates. Moreover, the quantities
of dithiocarbamates excreted were related to the glucosinolate/isothiocyanate
profiles of the cruciferous vegetables administered (kale, broccoli, green
cabbage, and turnip roots). Second, eating prepared horseradish containing
graded doses of isothiocyanates (12.3-74 micromol; mostly allyl isothiocyanate)
led to a rapid excretion of proportionate amounts (42-44%) of urinary dithiocarbamates
with first-order kinetics. The ingestion of broccoli in which myrosinase had
been heat-inactivated also led to proportionate but low (10-20%) recoveries
of urinary dithiocarbamates. Broccoli samples subsequently treated with myrosinase
to produce the cognate isothiocyanates were much more completely (47%) converted
to dithiocarbamates. Finally, when bowel microflora were reduced by mechanical
cleansing and antibiotics, the conversion of glucosinolates became negligible.
These results establish that humans convert substantial amounts of isothiocyanates
and glucosinolates to urinary dithiocarbamates that can be easily quantified,
thus paving the way for meaningful studies of phase 2 enzyme induction in
humans.
Title
Comparison of two sample preparation techniques for sniffing experiments
with broccoli (Brassica oleracea var. italica Plenck).
Author
Ulrich D; Krumbein A; Schonhof I; Hoberg E
Address
Federal Centre for Breeding Research on Cultivated Plants, Institute for
Quality Analysis, Quedlinburg, Germany.
Source
Nahrung, 1998 Dec, 42:6, 392-4
Abstract
The suitability of the headspace solid phase microextraction (HSSPME) for
gas chromatography-olfactometry (GC-O) with aroma extract dilution analysis
in comparison to the dynamic head space sampling on a Tenax trap was tested
exemplarily by the aroma volatiles of fresh broccoli. A high number of odour
sensations in qualitative olfactometry was registered with both sample preparation
techniques. The key aroma compounds of the fresh broccoli material are represented
by high flavour dilution factors with dynamic head space sampling and headspace
SPME. The SPME method has found to be a convenient and fast technique suitable
especially for qualitative GC-O. The adsorption selectivity of the fiber and
the substance discrimination have to be taken into account for quantitative
use like aroma extract dilution analysis.
Title
Broccoli sprouts: an exceptionally rich source of inducers of enzymes that
protect against chemical carcinogens.
Author
Fahey JW; Zhang Y; Talalay P
Address
Brassica Chemoprotection Laboratory and Department of Pharmacology and Molecular
Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD 21205,
USA.
Source
Proc Natl Acad Sci U S A, 1997 Sep, 94:19, 10367-72
Abstract
Induction of phase 2 detoxication enzymes [e.g., glutathione transferases,
epoxide hydrolase, NAD(P)H: quinone reductase, and glucuronosyltransferases]
is a powerful strategy for achieving protection against carcinogenesis, mutagenesis,
and other forms of toxicity of electrophiles and reactive forms of oxygen.
Since consumption of large quantities of fruit and vegetables is associated
with a striking reduction in the risk of developing a variety of malignancies,
it is of interest that a number of edible plants contain substantial quantities
of compounds that regulate mammalian enzymes of xenobiotic metabolism. Thus,
edible plants belonging to the family Cruciferae and genus Brassica (e.g.,
broccoli and cauliflower) contain substantial quantities of isothiocyanates
(mostly in the form of their glucosinolate precursors) some of which (e.g.,
sulforaphane or 4-methylsulfinylbutyl isothiocyanate) are very potent inducers
of phase 2 enzymes. Unexpectedly, 3-day-old sprouts of cultivars of certain
crucifers including broccoli and cauliflower contain 10-100 times higher levels
of glucoraphanin (the glucosinolate of sulforaphane) than do the corresponding
mature plants. Glucosinolates and isothiocyanates can be efficiently extracted
from plants, without hydrolysis of glucosinolates by myrosinase, by homogenization
in a mixture of equal volumes of dimethyl sulfoxide, dimethylformamide, and
acetonitrile at -50 degrees C. Extracts of 3-day-old broccoli sprouts (containing
either glucoraphanin or sulforaphane as the principal enzyme inducer) were
highly effective in reducing the incidence, multiplicity, and rate of development
of mammary tumors in dimethylbenz(a)anthracene-treated rats. Notably, sprouts
of many broccoli cultivars contain negligible quantities of indole glucosinolates,
which predominate in the mature vegetable and may give rise to degradation
products (e.g., indole-3-carbinol) that can enhance tumorigenesis. Hence,
small quantities of crucifer sprouts may protect against the risk of cancer
as effectively as much larger quantities of mature vegetables of the same
variety.
Title
Selective increase of the potential anticarcinogen 4-methylsulphinylbutyl
glucosinolate in broccoli.
Author
Faulkner K; Mithen R; Williamson G
Address
John Innes Centre, Norwich Research Park, UK.
Source
Carcinogenesis, 1998 Apr, 19:4, 605-9
Abstract
The putative anticarcinogenic activity of Brassica vegetables has been associated
with the presence of certain glucosinolates. 4-Methylsulphinylbutyl isothiocyanate
(sulphoraphane), derived from the corresponding glucosinolate found in broccoli,
has previously been identified as a potent inducer of the anticarcinogenic
marker enzyme quinone reductase [NADP(H):quinone-acceptor oxidoreductase]
in murine hepatoma Hepa 1c1c7 cells. We have therefore produced a broccoli
hybrid with increased levels of this anticarcinogenic glucosinolate and tested
the ability of extracts to induce quinone reductase. A 10-fold increase in
the level of 4-methylsulphinylbutyl glucosinolate was obtained by crossing
broccoli cultivars with selected wild taxa of the Brassica oleracea (chromosome
number, n = 9) complex. Tissue from these hybrids exhibited a >100-fold
increase in the ability to induce quinone reductase in Hepa 1c1c7 cells over
broccoli cultivars, due to both an increase in 4-methylsulphinylbutyl glucosinolate
content and increased percentage conversion to sulphoraphane.
Title
Glutathione transferase null genotype, broccoli, and lower prevalence of
colorectal adenomas [see comments]
Author
Lin HJ; Probst Hensch NM; Louie AD; Kau IH; Witte JS; Ingles SA; Frankl
HD; Lee ER; Haile RW
Address
Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, California
90502, USA. henry_lin@humc.edu
Source
Cancer Epidemiol Biomarkers Prev, 1998 Aug, 7:8, 647-52
Abstract
Cruciferous vegetables, especially broccoli, may prevent cancer through
anticarcinogenic compounds. For example, broccoli contains isothiocyanates
that induce carcinogen-detoxifying enzymes. Glutathione transferase enzymes
conjugate isothiocyanates, leading to excretion. We hypothesized that broccoli
consumption in combination with the glutathione transferase M1 (GSTM1) null
genotype would be associated with a lower prevalence of colorectal adenomas
because of higher isothiocyanate levels. We used a case-control study of mainly
asymptomatic subjects aged 50-74 years who underwent a screening sigmoidoscopy
at either of two Southern California Kaiser Permanente Medical Centers during
1991-1993. Cases (n = 459) had a first-time diagnosis of histologically confirmed
adenomas detected by flexible sigmoidoscopy. Controls (n = 507) had no polyp
detected. Subjects had a 45-min in-person interview for information on various
risk factors and basic demographic data and completed a 126-item, semiquantitative
food frequency questionnaire. Blood samples were used for GSTM1 genotyping.
Subjects with the highest quartile of broccoli intake (an average of 3.7 servings
per week) had an odds ratio of 0.47 (95% confidence interval, 0.30-0.73) for
colorectal adenomas, compared with subjects who reportedly never ate broccoli.
When stratified by GSTM1 genotype, a protective effect of broccoli was observed
only among subjects with the GSTM1 null genotype (P for trend, 0.001; P for
interaction, 0.01). The observed Broccoli-GSTM1 interaction is compatible
with an isothiocyanate mechanism.
Title
Glutathione transferase null genotype, broccoli, and lower prevalence of
colorectal adenomas [see comments]
Author
Lin HJ; Probst Hensch NM; Louie AD; Kau IH; Witte JS; Ingles SA; Frankl
HD; Lee ER; Haile RW
Address
Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, California
90502, USA. henry_lin@humc.edu
Source
Cancer Epidemiol Biomarkers Prev, 1998 Aug, 7:8, 647-52
Abstract
Cruciferous vegetables, especially broccoli, may prevent cancer through
anticarcinogenic compounds. For example, broccoli contains isothiocyanates
that induce carcinogen-detoxifying enzymes. Glutathione transferase enzymes
conjugate isothiocyanates, leading to excretion. We hypothesized that broccoli
consumption in combination with the glutathione transferase M1 (GSTM1) null
genotype would be associated with a lower prevalence of colorectal adenomas
because of higher isothiocyanate levels. We used a case-control study of mainly
asymptomatic subjects aged 50-74 years who underwent a screening sigmoidoscopy
at either of two Southern California Kaiser Permanente Medical Centers during
1991-1993. Cases (n = 459) had a first-time diagnosis of histologically confirmed
adenomas detected by flexible sigmoidoscopy. Controls (n = 507) had no polyp
detected. Subjects had a 45-min in-person interview for information on various
risk factors and basic demographic data and completed a 126-item, semiquantitative
food frequency questionnaire. Blood samples were used for GSTM1 genotyping.
Subjects with the highest quartile of broccoli intake (an average of 3.7 servings
per week) had an odds ratio of 0.47 (95% confidence interval, 0.30-0.73) for
colorectal adenomas, compared with subjects who reportedly never ate broccoli.
When stratified by GSTM1 genotype, a protective effect of broccoli was observed
only among subjects with the GSTM1 null genotype (P for trend, 0.001; P for
interaction, 0.01). The observed broccoli-GSTM1 interaction is compatible
with an isothiocyanate mechanism.
Title
Preclinical and clinical evaluation of broccoli supplements as inducers
of glutathione S-transferase activity.
Author
Clapper ML; Szarka CE; Pfeiffer GR; Graham TA; Balshem AM; Litwin S; Goosenberg
EB; Frucht H; Engstrom PF
Address
Divisions of Population Science and Medical Science, Fox Chase Cancer Center,
Philadelphia, Pennsylvania 19111, USA.
Source
Clin Cancer Res, 1997 Jan, 3:1, 25-30
Abstract
Previous studies suggest that cruciferous vegetables may provide protection
against carcinogen exposure by inducing detoxification enzymes. ICR(Ha) mice
were gavaged with broccoli tablets (1 g/kg), and colon tissues were collected
after treatment. Glutathione S-transferase (GST) activity was assayed and peaked
on days 1 and 2 after treatment, respectively (P = 0.03). Elevations in GST
activity were attributed to the increased expression of mu and pi. These data
supported a clinical assessment of broccoli supplements. Twenty-nine subjects
at increased risk for colorectal cancer were randomized to group 1 (no cruciferous
vegetables) or group 2 (broccoli supplements, 3 g/day) for 14 days. Blood samples
and colon biopsies were obtained pre- and postintervention. No significant difference
was observed between the GST activities of the control and broccoli supplementation
groups posttreatment. Mean lymphocyte GST activity was 107% of baseline in the
broccoli supplementation group (range, 79-158%) and 102% of baseline in the
control group (range, 75-158 percent;). Correlation of the GST activities of
blood lymphocytes and colon mucosa taken simultaneously suggested that the GST
activity of blood lymphocytes may be used as a biomarker of the responsiveness
of colon tissue to chemopreventive regimens. Future clinical studies evaluating
cruciferous vegetables should consider using concentrated dietary supplements
in subjects with a previous history of colorectal cancer.
Author : SARACOGLU Ibrahim Adnan Prof.Dr.
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