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Consumption of brown onions (allium cepa var. Cavalier and var. Destiny) moderately modulates blood lipids, haematological and haemostatic variables in healthy pigs


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Although garlic and onions have long been associated with putative cardiovascular health benefits, the effects of different commercially available onions and level of intake have not been studied. Therefore, the aim of the present study was to evaluate the potential health benefits of raw onions using the pig as a biomedical model. Twenty-five female (Large White x Landrace) pigs were used in a (2 x 2)+1 factorial experiment. Pigs were fed a standard grower diet supplemented with 100 g tallow/kg with the addition of Allium cepa var. cavalier or var. destiny at 0, 10 or 25 g/MJ digestible energy for 6 weeks. Overall, the consumption of onions resulted in significant reductions in plasma triacylglycerol; however, the reductions were most pronounced in pigs fed destiny onions (-26 %, P=0.042). Total plasma cholesterol and LDL:HDL ratios were not significantly different. Onion supplementation, regardless of the variety, resulted in dose-dependent reductions in erythrocyte counts and Hb levels, while the white blood cell concentrations, particularly lymphocytes, were increased in pigs that consumed onions. Furthermore, indices of blood clotting were largely unaffected by onion consumption. In conclusion, dietary supplementation with raw brown onions has moderate lipid-modulating and immunostimulatory properties. However, daily onion intake >25 g/MJ digestible energy could be detrimental to erythrocyte numbers.
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Consumption of brown onions (Allium cepa var. cavalier and
var. destiny) moderately modulates blood lipids, haematological
and haemostatic variables in healthy pigs
Ewa Ostrowska
, Nicholas K. Gabler
, Sam J. Sterling
, Brendan G. Tatham
Rodney B. Jones
, David R. Eagling
, Mark Jois
and Frank R. Dunshea
Department of Primary Industries, Victorian Institute of Animal Science, 600 Sneydes Rd, Werribee,
VIC 3030, Australia
Department of Primary Industries, Institute for Horticultural Development, VIC 3176, Australia
La Trobe University, Bundoora, VIC 3083, Australia
(Received 9 June 2003 Revised 11 September 2003 Accepted 1 October 2003)
Although garlic and onions have long been associated with putative cardiovascular health benefits, the effects of different commercially
available onions and level of intake have not been studied. Therefore, the aim of the present study was to evaluate the potential health
benefits of raw onions using the pig as a biomedical model. Twenty-five female (Large White £ Landrace) pigs were used in a
(2 £ 2)þ1 factorial experiment. Pigs were fed a standard grower diet supplemented with 100 g tallow/kg with the addition of Allium
cepa var. cavalier or var. destiny at 0, 10 or 25 g/MJ digestible energy for 6 weeks. Overall, the consumption of onions resulted in sig-
nificant reductions in plasma triacylglycerol; however, the reductions were most pronounced in pigs fed destiny onions ( 26 %, P¼0·042).
Total plasma cholesterol and LDL:HDL ratios were not significantly different. Onion supplementation, regardless of the variety, resulted in
dose-dependent reductions in erythrocyte counts and Hb levels, while the white blood cell concentrations, particularly lymphocytes, were
increased in pigs that consumed onions. Furthermore, indices of blood clotting were largely unaffected by onion consumption. In con-
clusion, dietary supplementation with raw brown onions has moderate lipid-modulating and immunostimulatory properties. However,
daily onion intake . 25 g/MJ digestible energy could be detrimental to erythrocyte numbers.
Onions: Health: Lipid metabolism: Pig
There is an increasing amount of consumer interest and
research focused on various food products that offer a posi-
tive health benefit beyond basic nutrition (‘functional
foods’). Plants from the genus Allium, particularly onions
(A. cepa) and garlic (A. sativum), have been consumed
for their putative nutritional and health benefits for centu-
ries. Although the health functionality of garlic has been
reported extensively (Bordia & Verma, 1980; Ali &
Thomson, 1995; Dorant et al. 1995; Smith & Yang,
2000; Liu & Yeh, 2001; Slowing et al. 2001), very little
is known about the specific benefits of onion (Bordia &
Verma, 1980; Ali & Thomson, 1995; Dorant et al. 1995;
Ide et al. 1997; Smith & Yang, 2000; Slowing et al.
2001). Epidemiological studies have shown a correlation
between diets rich in onion and reduced risk of stomach
cancer in human subjects (You et al. 1989), as well as an
inverse relationship with mortality from CHD in man
(Hertog et al. 1993a,b). Compounds that have been impli-
cated in providing a number of health-promoting attributes
of onion include flavonoids, particularly the flavonol
quercetin and the organosulfur compounds such as cysteine
sulfoxides (CSO) (Price & Rhodes, 1997). S compounds
from garlic, and common to onion, have been shown to
reduce plasma total cholesterol, LDL-cholesterol and tria-
cylglycerol (TG) levels in human subjects and rodents
(Bordia & Verma, 1980; Chi, 1982; Chi et al. 1982;
Qureshi et al. 1983a,b; Slowing et al. 2001); flavonols
such as quercetin have also been shown to have lipid-mod-
ulating properties (Bok et al. 2002; Glasser et al. 2002).
In the absence of clinical studies on the effects of raw
onion consumption, the present study used a pig model
to characterise the functional properties of two onion
cultivars grown in different environments and agronomic
conditions. The pig is a good animal model for human
nutrition, because of the many similarities between pigs
and man in the anatomy and physiology of the digestive
(Book & Bustad, 1974; Swenson, 1977) and cardiovascular
(Martin, 1964; Lumb, 1966) systems. Furthermore,
the advantage of the pig in biomedical research is
the similarity in the major lipoprotein subclass of LDL
* Corresponding author: Professor Frank R. Dunshea, fax þ 61 39 742 0400, email
Abbreviations: BW, body weight; CSO, cysteine sulfoxide; DE, digestible energy; TG, triacylglycerol; TXB
, thromboxane B
British Journal of Nutrition (2004), 91, 211–218 DOI: 10.1079/BJN20031036
q The Authors 2004
physico-chemical characteristics, albeit that the levels of
plasma lipids are lower in pigs than human subjects
(Chapman & Goldstein, 1976).
Materials and methods
Two varieties of onions commercially grown in the
Australian states of Tasmania (cooltemperate climate)
and Queensland (sub-tropical climate) were chosen for
the present study. Both varieties were brown onion.
A. cepa var. cavalier was grown in Gatton, Queensland
(approximately 1528 E, 288 S), while A. cepa var. destiny
was sourced from the Devonport region of Tasmania
(approximately 1458 E, 408 S). DM was determined in
triplicate by drying homogenised onion samples to a
constant weight in a force-draught oven at 1058C.
Animals and handling
All procedures were approved by the Victorian Institute of
Animal Science Animal Ethics Committee (Anonymous,
1997). Twenty-five female crossbred (Large White £
Landrace) pigs (initial body weight (BW) 41·5 (
SD 4·2)
kg) were placed in individual pens, blocked according to
initial live weight and allocated to one of five dietary treat-
ments, in a randomised block design. The blocks were
formed using the initial live weights of the pigs. Pigs
were fed approximately 90 95 % of ad libitum intake
(1·67 MJ digestible energy (DE)/kg BW
) of a dry feed
formulated to contain 16·7 MJ DE/kg and 100 g tallow/kg
to simulate the saturated fatty acid content of a western
human diet. The energy intake from fat was about 3·6 MJ
or 21·5 %. The experimental diet (Table 1) was formulated
to be in excess of protein and lysine requirements for this
class of pigs (Dunshea et al. 1993). The amino acid content
relative to lysine was kept in excess of the amino acid bal-
ance proposed as ideal by the Standing Committee on
Agriculture (1987). A vitamin and mineral premix was
omitted from the diets as it contains antioxidants and
other compounds that could mask the effects exerted by
the onion. Pigs had access to water at all times.
The five experimental treatments consisted of a control
diet with no onion added, and a low (16 g/kg BW
10 g/MJ DE) and a high (40 g/kg BW
or 25 g/MJ DE)
dose of onion for each variety of onion. The amount of
onions fed to the pigs was set at levels that can be con-
sumed by human subjects, after normalisation for the com-
parative differences in energy intake between pigs and
human subjects. The low dose would be equivalent to
about half an onion per d and the high dose equivalent to
about one and a half large onions per d in human subjects.
Onions were stored at 48C, and diets were prepared daily to
maintain stability of the active compounds found in onions.
The loose outer epidermis of the onion was removed and
the onions were then chopped in half and homogenised
in a blender for approximately 2 min. The calculated
amount of the homogenate was weighed for each pig and
mixed together with the dry feed for 2 min until the feed
reached uniform consistency. Diets were fed within 1 h
of preparation, as the thiosulfinates (the product of the
breakdown of CSO when the onions are cut-up) are
highly unstable. Pigs were weighed once per week and
the amount of dry feed and onion adjusted according to
BW. Feed refusals were collected and recorded daily.
Blood collection and analysis
Blood samples were obtained from the jugular vein by
venepuncture before feeding (fasted) on two sequential
days after 4 and 6 weeks of treatment. Blood was also col-
lected from each pig 3 h post-feeding (postprandial), since
the absorption of dietary flavanols from onions in human
blood reaches peak values between 0·7 and 2·9 h after feed-
ing (Hollman et al. 1996, 1999; Aziz et al. 1998).
On the first sequential sampling day, blood was drawn
into EDTA, clot activator and sodium citrate vacutainer
tubes, which were dedicated for blood coagulation tests
(platelet count, prothrombin time, activated partial pro-
thrombin time and fibrinogen counts) and blood biochem-
istry assays (cholesterol, TG and glucose). Two blood
smears were prepared immediately for each pig, using
blood that contained EDTA as an anticoagulant, to deter-
mine the number of white blood cells, erythrocytes, eosino-
phils, segmented neutrophils, lymphocytes, monocytes and
basophils. Blood samples were placed on ice and trans-
ported for analysis (IDEXX Laboratories Pty Ltd, Mount
Waverley, Victoria, Australia). On the second day of
sampling, three blood samples were collected in vacutainer
tubes containing EDTA, heparin and without anticoagulant
respectively. Half of the blood collected into the EDTA
tube was immediately decanted after bleeding into a tube
that contained 10 m
M-indomethacin (final concentration)
for 11-dehydro-thromboxane B
) assay. Plasma
was separated by centrifugation at 3000 rpm for 15 min
and stored at 2 208C until analysed. The rest of the
blood collected on the second day was used to determine
concentrations of plasma HDL-cholesterol (procedure no.
354L) and total cholesterol (procedure no. 401) using kit
reagents purchased from Sigma (Sigma-Aldrich Pty Ltd,
Sydney, Australia). To assess clotting capability of the
Table 1. Composition of experimental diets*
Ingredients g/kg
Wheat 679·0
Soyabean meal 91·4
Fish meal 45·7
Meat and bone meal 57·1
Blood meal 19·0
Tylan† 0·4
NaCl 1·8
L-Lys hydrochloride 0·9
DL-Met 0·1
L-Thr 0·2
Tallow 100·0
* Diet was formulated to contain 16·7 MJ digestible energy, 177 g crude
protein (N £ 6·25) and 9·4 g available lysine/kg air-dry diet; raw
onions (Allium cepa) were mixed with the dry feed at 10 or 25 g/MJ
digestible energy.
Tylosin phosphate 100 g/kg antibiotic (Elanco Animal Health, Mac-
quaire Park, NSW, Australia).
E. Ostrowska et al.212
blood, TXB
, a stable metabolite of thromboxane A
centrations (catalogue no. 519501; Cayman Chemical Pty
Ltd, Crows Nest, NSW, Australia) were measured.
Cysteine sulfoxide and quercetin analyses
The analysis of CSO in raw onion tissue was carried out
with an HPLC methodology based on that of Yoo &
Pike (1998), with the exception that the samples were
frozen at 2 708C before extraction and 10 m
amine was added to the extraction solvent (i.e. 800 ml etha-
nol/l with 10 m
M-hydroxylamine). The level of acetic acid
in the mobile phase was increased to 6 ml/l. The mean con-
centration of CSO was calculated from analysis of ten
onions of each variety. For quercetin analysis, freeze-
dried onion powder from at least three separate onions
per treatment was hydrolysed in HCl at 908C for 2 h, and
total quercetin aglycone was assayed using HPLC accord-
ing to the method described by Hertog et al. (1992).
Statistical analyses
Data was analysed by ANOVA using GENSTAT for
Windows, version 4.1 (Payne et al. 1993). The results
are presented as mean values of the fasting samples and
3 h postprandial measurements taken at weeks 4 and 6.
Each mean value, as well as growth rate and average dry
feed intake, was initially analysed using a randomised
block design that included the types of onion and two
doses (10 and 25 g onions/MJ DE) with the control (no
onion) added. These initial results indicated that the
blood measurements could usefully be divided into two
groups. These were: (1) all blood measurements other
than lipid biochemistry measurements, where there was
no evidence of onion-type effects (P. 0·05); (2) lipid bio-
chemistry measurements, where there was often evidence
of onion-type effects (P, 0·05).
For lipid biochemistry measurements (Table 2), with the
exception of cholesterol, there was no evidence of any
difference between the 10 and 25 g onions/MJ DE doses
(P. 0·01). The results are thus tabulated as the means of
each type of onion as well as the mean of no onion. For
the haematology measurements (Table 3) the main effects
of two onion doses (0, 10 and 25 g onions/MJ DE) are
tabulated together with results of hypothesis tests for the
overall dose response and the linear component of this
response. A comparison of the onion type within 10 and
25 g onions/MJ DE dose levels is also presented. In
every analysis, a residual was used that allowed for the
effect of all five treatments, as well as a blocking effect.
Results showing the interactions between bleeding time
and week-to-week variation as well as effects of dietary
onions on oxidative capacity of serum are presented else-
where (NK Gabler, E Ostrowska, SJ Sterling, BG
Tatham, RB Jones, DR Eagling, M Jois and FR Dunshea,
unpublished results).
The DM contents of the onions used in this study were 97·5
and 127·5 g/kg for cavalier and destiny varieties respect-
ively. Total CSO was 23 % higher in destiny than cavalier
onions, although this difference was not significant
(P¼0·16, Table 4). Of the three major CSO found in
onions, S-methyl-CSO and S-propyl-CSO were signifi-
cantly higher (P, 0·05) in destiny compared with cavalier
onions. Indeed, for the cavalier variety, S-propyl-CSO was
undetectable. S-propenyl-CSO was the major CSO found in
both onion varieties and there was no difference in S-pro-
penyl-CSO levels between the two varieties. The variety
destiny had a 38 % higher quercetin aglycone content
than cavalier (P, 0·05, Table 4).
All pigs offered onions remained in good health through-
out the experimental period. No signs of toxicity were
observed and onion consumption had no effect on growth
rate (830 v. 860 g/d for control and onion-supplemented
pigs respectively, P¼ 0·49) or feed intake (1816 v. 1807 g
DM/d respectively, P¼0·90). Overall, dietary onion
Table 2. The effect of two onion (Allium cepa) varieties on blood biochemistry*
(Mean values)
Onion variety Statistical significance of effect
Plasma concentration Control Cavalier Destiny
SED Overall‡ Onion§
Cholesterol (mmol/l)k 2·71 2·52 2·44 0·13 0·15 0·073
Glucose (mmol/l)k 5·70 5·88 5·98 0·22 0·46 0·26
LDL (mmol/l)k{ 1·65 1·56 1·51 0·10 0·21 0·52
HDL (mmol/l)k 1·09 0·95 0·97 0·06 0·35 0·032
LDL:HDLk 1·54 1·66 1·57 0·08 0·32 0·15
TG (mmol/l)k 0·68 0·63 0·50 0·07 0·042 0·12
TG after (mmol/l)** 0·78 0·79 0·60 0·07 0·0067 0·18
TG before (mmol/l)†† 0·57 0·48 0·41 0·09 0·25 0·16
TG, triacylglycerol.
* For details of diets and procedures, see Table 1 and p. 212.
SED for control v. cavalier or destiny;forcavalier v. destiny and control v. pooled onion, multiply the SED by 0·817 and 0·888 respectively.
P value for overall comparison of control v. cavalier v. destiny.
§ P value for comparison of control v. pooled onion.
k Mean of values taken in fasting and non-fasting states after 4 and 6 weeks of feeding (results were pooled across doses of each onion variety).
{ VLDL, intermediate-density lipoprotein and LDL concentration calculated by subtracting the HDL from total cholesterol concentration.
** Mean of values taken from non-fasting pigs after 4 and 6 weeks of onion feeding (results were pooled across doses of each onion variety).
†† Mean of values taken from fasting pigs after 4 and 6 weeks of onion feeding (results were pooled across doses of each onion variety).
Brown onions and haemostatic variables 213
supplementation tended to decrease circulating cholesterol
(2 9%, P¼0·073, Table 2). However, there was an inter-
action of onion dose £ type of onion, such that mean fast-
ing and postprandial plasma cholesterol measures were
decreased by 14 % at the low, but not at the high, intake
of cavalier onions, while plasma cholesterol was decreased
by 6 and 14 % (P¼0·009) at the low and the high intakes of
destiny onions respectively (mmol/l: control 2·71, low dose
of cavalier 2·29, high dose of cavalier 2·73, low dose of
destiny 2·55, high dose of destiny 2·33;
SED 0·15).
There was no apparent difference in plasma cholesterol
concentration between fasting and non-fasting states (2·53
v. 2·52 mmol/l respectively, P¼0·71). The mean HDL con-
centration was significantly lower (P¼0·032) in pigs that
consumed diets supplemented with onions, while LDL con-
centration was unaffected (P¼0·52). The LDL:HDL ratio
was unchanged by onion consumption (Table 2).
While overall plasma TG concentrations were not
significantly affected by dietary onion consumption
(Table 2), there was a significant (P, 0·001) interaction
in the response to different onion types and the nutritional
state of the pigs. Plasma TG concentrations were reduced
in the 3 h postprandial measurements for pigs fed destiny
but not cavalier onions (0·78 v. 0·79 and 0·60 mmol/l for
control, cavalier and destiny respectively, P¼0·0067).
Conversely, the TG concentrations were not significantly
different in fasting animals fed the different diets. There
was no difference in the plasma glucose concentrations
between pigs fed the different onion varieties or between
onion-fed and control pigs (Table 2).
The plasma erythrocyte number was reduced linearly in
response to the increased amount of onion in the diet
(P¼0·0004, Table 3). Consequently, mean Hb concen-
tration was decreased in a dose-dependent manner
(P¼0·046); however, the overall comparison of control
with low or high onion doses was not significantly different
(P¼0·13). The mean erythrocyte cell volume was higher
(P¼0·016) in pigs that consumed onions compared with
the control group.
Pigs that consumed low doses of onion, regardless of the
onion variety, had higher eosinophil, lymphocyte and total
white blood cell numbers (P¼0·034, P¼0·020 and
Table 3. The effect of onion (Allium cepa) dose on haematology and measures of immunity*
(Mean values)†
Dose (g/MJ DE) Statistical significance of effect
SED Linear§ Overallk
Erythrocytes (10
/l) 7·78 7·13 6·50 0·29 0·00040 0·0015
Hb (g/l) 134 131 124 4 0·046 0·13
MCV (fl) 53·6 55·9 59·8 2·0 0·0045 0·016
MCHC (pg) 17·3 18·1 19·2 0·8 0·028 0·083
PCV (l/l) 0·403 0·398 0·388 0·013 0·20 0·42
Basophils (10
/l) 0·38 0·34 0·38 0·06 0·82 0·80
Eosinophils (10
/l) 0·46 0·62 0·44 0·09 0·24 0·034
Lymphocyte activation{ 1·9 1·7 1·5 0·1 0·00081 0·0029
Lymphocytes (10
/l) 8·5 11·3 9·7 1·0 0·87 0·020
Monocytes (10
/l) 1·36 1·39 1·19 0·17 0·21 0·35
Neutrophil:lymphocyte ratio 0·61 0·43 0·49 0·08 0·39 0·068
Segmented neutrophils (10
/l) 5·1 4·6 4·4 0·4 0·096 0·23
WBC (10
/l) 15·7 18·3 16·1 1·1 0·46 0·016
DE, digestible energy; MCV, mean corpuscular volume; MCHC, mean corpuscular Hb concentration; PCV, packed cell volume; WBC, white blood cells.
* For details of diets and procedures, see Table 1 and p. 212.
Mean of values taken in fasting and non-fasting states at 4 and 6 weeks of feeding (for each dose, results were pooled across both onion varieties).
SED for control v. 10 or 25 g onion/MJ DE; for a comparison between 10 or 25 g onion/MJ DE, multiply the SED by 0·817.
§ P value for linear effect of dose of onion.
k P value for overall comparison of control v. 10 or 25 g onion/MJ DE.
{ Lymphocyte activation measured as slight (score 1), moderate (score 2) and high (score 3).
Table 4. Cysteine sulfoxide (CSO) and quercetin contents (mg/g fresh weight for Allium cepa var. cavalier and destiny)*
(Mean values and standard deviations for analysis of three onions picked at random)
Cavalier Destiny
Onion variety... Mean
SD Mean SD Statistical significance of effect: P
S-methyl-CSO 0·17 0·05 0·27 0·06 0·049
S-propenyl-CSO 0·71 0·17 0·72 0·16 0·92
S-propyl-CSO ND† 0·15 0·10
Total CSO 0·88 0·22 1·14 0·23 0·16
Quercetin 0·22 0·02 0·48 0·04 0·013
ND, not detected.
* For details of procedures, see p. 212.
Detection limit about 0·07 mg/g; the DM contents for cavalier and destiny onions were 97·5 and 127·5 g/kg respectively.
E. Ostrowska et al.214
P¼0·016 respectively) compared with the control pigs
(Table 3). The lymphocyte activation decreased as the
dose of onion increased, resulting in a significant linear
effect (P¼0·00081). For all haematology measures there
was no difference in the response between the two onion
varieties (Table 3).
The effect of onion supplementation on measures of
blood clotting resulted in a small, but non-significant
(P¼0·15) increase in prothrombin time in pigs fed
onions, but no effect on activated partial prothrombin
time (Table 5). The blood fibrinogen concentration and pla-
telet number were unaffected by onion consumption. The
measures of blood coagulation were not affected by
onion variety (P. 0·10) with the exception of the mean
plasma TXB
concentration, which was significantly
higher (P¼0·030) in pigs fed cavalier but not destiny
onions compared with the control pigs.
In general, consumption of raw brown onions was found to
moderately modulate blood lipids and haematological vari-
ables in healthy pigs, but the responses varied between the
two onion varieties and between doses of onions. In
addition, differences in the response to consumption of
onion were also evident between fasted and non-fasted
states. For example, the postprandial TG measurements
in pigs fed destiny onions were approximately 23 %
lower than in control pigs or the pigs fed cavalier
onions, while fasting measurements were not significantly
affected by onion consumption (Table 2). Postprandial
measurements of TG levels are useful, as they might
reveal a state of fat intolerance that cannot be detected
by the simple measurement of fasting plasma TG (Karpe,
1999). Therefore, these results suggest that the consump-
tion of destiny onions, at both doses investigated, resulted
in beneficial changes in plasma postprandial TG concen-
trations. This may lead to reduced risk of CHD and ather-
ogenesis (Zilversmit, 1979; Patsch et al. 1992).
Unlike TG, there was no significant difference between
fasting and postprandial measurement of plasma choles-
terol, which is in agreement with results from studies
with human subjects (Cohn et al. 1988). However,
onion consumption resulted in a 9 % lower plasma total
cholesterol concentration (mean fasting and postprandial
measurements) compared with the control group. There
was a more pronounced effect in pigs fed destiny onions,
where a linear decrease in plasma cholesterol in response
to dose was observed. The HDL-cholesterol fractions
were reduced in response to onion supplementation; how-
ever, the LDL:HDL ratio was unaffected. This suggests
that the removal of cholesterol from the circulation was
not enhanced, and it is likely that the cholesterol-lowering
action of destiny onions was due to a reduction in choles-
terol synthesis.
Despite similarities between pigs and human subjects,
there are some differences in lipoprotein metabolism that
must be considered. Pig blood contains lower cholesteryl
ester transfer protein activity and cholesteryl ester for-
mation than human subjects (Chapman, 1986) and treat-
ments that affect lipoprotein metabolism might have a
different impact on the levels of HDL in pigs than in
human subjects (Knipping et al. 1987). Second, LDL-
ApoB originates from VLDL catabolism in human sub-
jects, whereas it is synthesised de novo in pigs (Birchbauer
et al. 1992). Therefore, the extrapolation of these data to
adult human subjects should be treated with caution.
While the mechanisms responsible for the lowering of
lipid due to onion consumption are not clear, it has been
suggested that Allium compounds (possibly CSO and thio-
sulfinates) decrease synthesis or increase excretion of lipids
through the intestinal tract (Ali et al. 2000; Bok et al.
2002). Various garlic extracts have also been shown to
decrease the activities of NADPH-producing enzymes
and of fatty acid synthetase when fed to rats (Chi, 1982;
Chi et al. 1982), chickens (Qureshi et al. 1983b) and
pigs (Chi, 1982; Chi et al. 1982; Qureshi et al. 1983a,
1987). However, garlic extracts are generally more potent
than onion extracts. This is due to differences in the
levels and types of S compounds, which are present in
far lower concentrations in onions than in garlic. For
example, thiosulfinates are proposed to exist in garlic at
100 times the concentration found in onions (Mandon
et al. 2000).
In addition to the lipid-modulating effects of onion,
changes in blood cell counts were also evident. Raw
onion consumption reduced both erythrocyte numbers
and Hb concentrations (Table 3), although clinical anaemia
was not evident and the measures were within the normal
range for pigs (Pond & Houpt, 1978). Reductions in
Table 5. The effect of onion (Allium cepa) dose on coagulation profile of pig blood*
(Mean values)†
Onion variety Statistical significance of effect
Control Cavalier Destiny
SED Overall§
APTT (s) 22·3 22·1 23·7 1·1 0·10
Fibrinogen (g/l) 1·02 0·95 0·98 0·08 0·68
PT (s) 13·9 14·1 14·4 0·2 0·15
(pg/ml) 19·8 23·2 19·6 1·9 0·030
Platelets (10
/l) 415 391 380 30 0·66
APTT, activated partial prothrombin time; PT, prothrombin time; TBX
, thromboxane B
* For details of diets and procedures, see Table 1 and p. 212.
Mean of values taken in fasting and non-fasting states at 4 and 6 weeks of feeding.
SED for control v. cavalier or destiny onion; for a comparison between onion varieties, multiply the SED by 0·817.
§ P value for overall comparison of control v. cavalier or destiny onion.
Brown onions and haemostatic variables 215
haematocritic measurements have also been observed in
placebo-controlled studies with human subjects using
encapsulated onion (Kalus et al. 2000; Mayer et al.
2001). Onion consumption has been shown to induce
acute haemolytic anaemia in sheep (Kirk & Bulgin,
1979), horses (Pierce et al. 1972), cattle (Rae, 1999; van
der Kolk, 2000), dogs (Spice, 1976) and cats (Kobayashi,
1981), largely due to the presence of onion disulfides:
these generate H
in the presence of Hb and glutathione
S-transferase within intact erythrocytes (Munday et al.
2003). It has been suggested that the resulting haemolysis
is of the oxidative type and occurred due to removal of
damaged erythrocytes by cells of the reticulo-endothelial
system (Munday et al. 2003). Although the erythrocyte
concentrations were decreased linearly by onion consump-
tion in the present study, there was a compensatory
increase in cell volume and the amount of Hb per cell,
which implies an increased O
-carrying capacity per eryth-
rocyte. The excessive consumption of onions should be
avoided, especially by individuals with anaemia or those
whose erythrocytes are unusually vulnerable to oxidative
damage (Munday et al. 2003).
Reductions in haematocritic measures appeared to
stimulate an immune response in the pigs as evident by
the increase in white blood cell numbers, mainly due to
increased lymphocyte concentrations in pigs that consumed
onions (Table 3). Moreover, blood from pigs fed onion-
supplemented diets exhibited decreased lymphocyte acti-
vation, which is often associated with reduced cholesterol
accumulation and the reduction in formation of athero-
sclerotic plaques (Hansson, 1994).
Surprisingly, the measures of clotting mechanisms such
as prothrombin time, activated partial prothrombin time,
platelet count and fibrinogen level were largely unaffected
by onion consumption (Table 5). Other studies that inves-
tigated the effects of garlic consumption have shown
increased bleeding and clotting times (Gadkari & Joshi,
1991). Similarly, raw juice from shoots of Welsh onion
(Allium fistulosum) fed to rats for 4 weeks at a dose of
2 g/kg per d significantly increased tail bleeding time and
lowered systolic blood pressure (Chen et al. 2000). How-
ever, as these authors pointed out, the green shoots of the
onion are more potent than the bulb.
Plasma TXB
was significantly increased in pigs fed
cavalier but not destiny onions (Table 5). Previous obser-
vations have shown that raw garlic extracts significantly
decrease rabbit serum TXB
levels, while onion extracts
were found to be ineffective (Ali et al. 1999). Similarly,
in human subjects, consumption of 70 g raw onion/d,
which is equivalent to the low dose of onion administered
to the pigs in the present study, had no effect on serum
levels after 7 d of consumption (Srivastava, 1989).
The differences across studies are possibly related to the
differences in the level and type of organosulfur com-
pounds in garlic and onion, and these are known to mediate
eicosanoid metabolism (Ali et al. 2000).
Many of the biochemical effects of dietary onion con-
sumption have been largely ascribed to CSO, which are
abundant in intact onion bulbs. Garlic bulbs contain
mainly allyl-CSO and to lesser extent S-methyl-CSO,
whereas S-propenyl-CSO is the predominant S compound
in onion (Keusgen et al. 2002). Analysis of CSO in the
onions used in the present study showed that there was
little difference in total CSO between the two onion var-
ieties, but destiny had significantly higher levels of
S-methyl-CSO and S-propyl-CSO than cavalier (Table 4).
Since S-methyl-
L-CSO was found to be one of the factors
responsible for suppressing hypercholesterolaemia in the
hepatoma-bearing rat (Komatsu et al. 1998), it is possible
that the differences between responses to different onion
treatments in the present study are due to these compounds.
Another possibility for the plasma lipid and haematological
changes could result from thiosulfinates, which are the pro-
ducts of enzymatic degradation of sulfoxide compounds
upon ingestion by human subjects and animals (Earl &
Smith, 1983). Finally, it is likely that changes observed in
the present study are due to a combination of S and flavonol
compounds found in onions, of which flavonols have also
been shown to be biologically active (Taucher et al. 1996).
Flavonols have been shown to affect cholesterol synthesis
and reduce thrombotic tendencies (O’Reilly et al. 2000;
Giugliano, 2000). Quercetin is the dominant flavonol in
onions, with levels up to 490 mg/kg fresh weight (Hollman
& Arts, 1994). The quercetin contents of both varieties of
onions fed to the pigs in the present study were in the
range reported in literature, but was significantly higher in
the destiny onions. Therefore, the variation in quercetin
levels may also be responsible for some of the health bene-
fits observed in the present study. Further work needs to be
conducted to elucidate the effect of different CSO and flavo-
noid compounds in onions to identify which are responsible
for the observed biological responses in the pig.
The present study has shown that onions have functional
properties with the ability to modify lipid metabolism and
stimulate the immune system. However, the differences in
the responses observed in the present study demonstrate
the complex interaction between the onion dose and type
of onion, which may be due to the differences in the
amount of active compounds. The identification of specific
compounds in different onion cultivars and agronomic
practices would lead to a better understanding of the phys-
iological responses to onion consumption. This would aid
the development of onion production systems that provide
an increased health benefit and the development of guide-
lines for the consumption of these compounds.
The authors would like to thank Lewis Lydon (Enzazaden
Australia Ltd, Narrowmine Research Station, Narrowmine,
NSW, Australia) for sourcing the onions and Michael
Imsic (IHD, Knoxfield, Victoria, Australia) for assistance
with the HPLC analysis.
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... On the contrary, Cho and Lee (2012) noticed no improvement in the growth performance of olive flounder, Paralichthys olivaceus, with feeding onion-based diets. The growth-promoting outcomes of onions are attributed to their bioactive compounds, such as sulfur-containing compounds, cysteine sulphoxide (CSO), and S-propenyl-CSO, which have numerous health benefits (Ostrowska et al. 2004;Apines-Amar et al. 2012). A. cepa also stimulates beneficial microorganisms in the digestive system, such as bifidobacteria and lactobacilli, which have many health benefits (Gibson 1998). ...
Full-text available
The present study investigated the protective effects of dietary Allium cepa against Saprolegnia parasitica infections and the amelioration of cadmium-induced immunosuppression in Oreochromis niloticus . Saprolegnia isolates were recovered during an outbreak of saprolegniasis in farmed O. niloticus raised in a poor aquatic environment . Isolates were identified phenotypically as S. parasitica. Results were confirmed further by ITS gene sequencing. Four fish groups were kept in water with cadmium (1.5 mg/L) and fed for 30 days on a diet supplemented with crude or alcoholic extracts of A. cepa using two concentrations (0.5% or 1%). Positive (with Cd) and negative (without Cd) control fish groups were given the basal diet. The 96 h LC 50 value of Cd in tilapia was (15.1 mg/L Cd). Fish exposed to Cd showed poor growth performance parameters, abnormal biochemical measurements, impaired immunological responses, and high oxidative stress indicators. Feeding tilapia on A. cepa- supplemented diets enhanced their growth performance (WG, SGR) and improved the nonspecific immune responses (WBCs, total protein, globulins, lysozyme, myeloperoxidase, and antiproteases). The inclusion of A. cepa in the diets reduced the oxidative stress (GST, SOD) and significantly decreased fish mortality after the challenge with S. parasitica . Dietary supplementation with A. cepa reduced cadmium accumulation in fish organs and up-regulated IL-1β and IFNɣ levels. The most favorable benefits were obtained by the addition of 0.5% A. cepa extract. Our results highlight the immunostimulatory properties of A. cepa dietary supplementation for farmed tilapia and recommend its use prophylactically to control saprolegniasis and mitigate cadmium adverse effects.
... The chronic inflammatory conditions were highly related with cardiovascular risk [42]. Consumption of onions influences lipid blood chemistry and improves indices of cardiovascular health [43][44][45]. These results supported that the WOEE could suppress the inflammatory response of RAW 264.7 cells, and it could be used as a healthy food and not only as a by-product. ...
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This study was conducted to evaluate and to increase the usage of the whole onion (Allium cepa L.), which is composed of a small bulb and many leaves that are discarded as by-products before the bulbs grow. Whole onions are harvested early in immature condition, which allows the other onion bulbs to grow well. We compared its functional activities with those of quercetin, which is one of its major components. The antioxidant activities of ethanol extract from the whole onion (WOEE) were measured by DPPH and ABTS radical scavenging activities, and superoxide dismutase (SOD) and catalase (CAT) activities. The anti-inflammatory effects of WOEE were investigated in RAW 264.7 macrophages treated with LPS by analyzing cytokine levels and expressions using ELISA kits and RT-PCR assays, respectively. WOEE showed high antioxidant effects on DPPH and ABTS radical scavenging activities, and SOD and CAT activities. WOEE significantly reduced the production of nitric oxide, IL-1β, IL-6, and TNF-α, and/or their mRNA expressions in a dose-dependent manner. The results indicated that whole onions had antioxidant and anti-inflammatory effects, which were comparable with quercetin and may be used as a novel potential therapeutic candidate.
... The studies of other authors also confirm the beneficial effect of onions on the lipid profile. Onion decreased both the content of total cholesterol, its LDL-C fraction, and triacylglycerol in rats, hamsters [109,110], and pigs [53,56]. ...
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Bulbs from the Alliaceae family have been well-known and valued spices for thousands of years, not only for their unique flavor and aroma features, but also for their high nutritional and health-promoting values. Long-term or excessive consumption of these vegetables, especially raw garlic, can have side effects in the body (including in the digestive tract), causing a number of pathological changes in the intestinal wall; these changes lead, in turn, to its damage, dysfunction, and disorder development. Therefore, the aim of this study was to investigate the effect of the addition of freeze-dried vegetables from the Alliaceae family, i.e., garlic (Allium sativum L.), white onion, and red onion (Allium cepa L.) on the morphometric parameters (intestinal villi length, crypt depth, thickness of tunica mucosa, and the thickness of tunica muscle) of the jejunum of rats fed a semi-synthetic atherogenic diet (1% dietary cholesterol). In freeze-dried vegetables administered to rats, the contents of selected bioactive ingredients and their antioxidant potentials were determined. The effect of the onion vegetable supplements on growth parameters, serum lipid profile, plasma antioxidant potential, and the intestinal morphological parameters of rats loaded with cholesterol was determined. In an animal experiment, 30 male Wistar rats were divided into 5 diet groups, diet consumption and FER were studied. Supplementation of the atherogenic diet with vegetables improved the blood plasma lipid profiles and atherogenic indices, in a manner that was dependent on the type of supplementation used, with the best hypolipidemic and anti-atherosclerotic effects found in garlic use. The atherogenic diet, as well as the supplementation of this diet with the tested vegetables from the Alliaceae family, influenced the histological changes in the epithelium of the jejunum of rats. The damage to the intestinal mucosa was the greatest in animals fed an atherogenic diet supplemented with garlic. Bearing in mind that the desired beneficial therapeutic or prophylactic effects of onion vegetables (in particular garlic) in the course of various metabolic ailments (including atherosclerosis) are achieved during long-term supplementation, it is important to remember their possible cytotoxic effects (e.g., on the digestive tract) in order to achieve real benefits related to the supplementation with vegetables from the Alliaceae family.
... Joung and Jung [25] also reported the in vitro antioxidant activities of onion peel extracts in scavenging free radicals. The effect of OPP at regulating the antioxidant activities of the fish could be due to the presence of Sulphur compounds such as cysteine sulfoxide (CSO) and S-propenyl-CSO found in the dietary onion peels [32] . Sulphur been a vital component of many antioxidant enzymes and molecules, plays a crucial role in stimulating defence against reactive oxygen and nitrogen species [37] . ...
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This study evaluated the dietary effect of onion peel powder (OPP) on growth, blood chemistry, hepatic antioxidant enzymes activities and SOD mRNA responses of Clarias gariepinus. One hundred and twenty fish were randomly distributed into twelve plastic tanks and fed experimental diets for 42 days. Four diets (control, OPP-2, OPP-4 and OPP-6) were formulated with graded levels of OPP (0, 20, 40 and 60 g/kg diet) respectively. At the end of the experiment, the fish fed OPP supplemented diet exhibited significantly increased weight gain, specific growth rate (SGR) and better feed conversion ratio (FCR) compared to the control group (p<0.05). The highest values of haemoglobin (Hb) and erythrocytes (RBCs) count were observed in fish fed control diet (p<0.05). The pack cell volume (PCV, %) of the control and OPP-6 groups differs significantly (p<0.05) from other groups. Experimental fish group fed the control diet had the lowest total leukocytes (WBCs) and was significantly different (p<0.05) from other treatment groups. Dietary OPP significantly decreased (p<0.05) cortisol level when compared to the control group. The cholesterol, triglycerides and glucose values of fish fed OPP-2 were significantly higher (p<0.05) than other experimental groups including control. The antioxidant enzymes (catalase and glutathione) increased significantly (p<0.05) in fish fed graded levels of OPP diets compared to those fed the control diet. Furthermore, the control group had significantly decreased expression of superoxide dismutase (SOD) gene (p<0.05). Therefore, this study confirmed the beneficial effects of onion peel supplemented diet on growth, nutrient utilization, haematology and biochemical parameters and antioxidant enzymes activities of C. gariepinus.
... The physicochemical composition of onion has revealed that it contains many phenolic compounds, especially flavonoids [4]. Allium cepa L. represents a source of cysteine derivatives, which makes it a good antioxidant source in diet and increases its potential as a functional food [5]. These compounds, through their antioxidant properties, protect the body against oxidative stress [6]. ...
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The high water content in fresh onion bulb make it difficult to preserve. In order to remedy these situation, it can be converted into dried slices. The objective of this work was to optimize the phenolic compounds and antioxidant properties of dried onion slice. Box Behnken design was performed to determine the effect of drying temperature (25–45 °C), water activity (0.2–0.6) and drying time (12–24 h) on the moisture content, total phenolic, flavonoids content, DPPH free radical scavenging and total reducing power on dried onion slice. Desirability was fixed to obtain the best possible combination of factors to a maximum values of total phenolic and flavonoids content, DPPH free radical scavenging, total reducing power and a low level of moisture content. Data analysis showed that the factors significantly (p < 0.05) affected the responses variables. Desirability function showed that the optimal dry conditions were 20 h for drying time, drying temperature of 28 °C and water activity of 0.48. At this optimum point the moisture content, polyphenol and flavonoids content, DPPH free radical scavenging and total reducing power were respectively: 9.53%, 1060.45 mg gallic acid/100 g DM; 342.61 mg quercetin/100 g DM; 52.18 mg Trolox/100 g DM and 78.14 mg Vitamin C/100 g DM. In this overall optimum point desirability was 0.9. No significant difference (p < 0.05) was found between the experimental and predicted values of the response variables at optimum point.
... It was thought that immunostimulant effects of onion oil macerate were contained from cysteine sulfoxide (CSO) with Spropenyl-CSO as the predominant sulpur compound in onion oil. Sulphur was a component of the antioxidant enzymes (Keusgen et al., 2002;Ostrowska et al., 2004). ...
Full-text available
In this study, antioxidant enzyme activities effects of dietary supplementation of garlic(Allium sativum, Limne) oil macerate, Tunceli garlic (Allium tuncelianum, Kollman) oil macerateand onion (Allium cepa, Limne) oil macerate on antioxidant activities [catalase (CAT),glutathione reductase (GR), glutathione peroxidase (GPx) and malondialdehyde (MDA)] in seraof rainbow trout (Oncorhynchus mykiss L.) were assessed. For this aim, rainbow trout were fedwith diets containing garlic oil macerate, Tunceli garlic oil macerate, and onion oil macerate atconcentration of 10g kg-1 for 21 days. The highest CAT, GR and MDA activities were observedin onion oil macerate group, and the highest GPx activity was determined in garlic oil macerategroup. GPx levels of three experimental groups were observed higher than control group. Thisstudy reported the effects of oil macerate on sera antioxidant capacities in rainbow trout(Oncorhynchus mykiss). It was found that GPx activity of garlic oil macerate group and CAT,GR, and MDA activities of onion group in sera were significantly increased. (21) (PDF) Effects of Garlic (Allium sativum, Limne) Oil Macerate, Tunceli Garlic (Allium tuncelianum, Kollman) Oil Macerate and Oninon (Allium cepa, Limne) Oil Macerate on Antioxidant Enzyme Activities (CAT, GR GPx and MDA) of Rainbow Trout (Oncorhynchus mykiss L.). Available from: [accessed Apr 25 2020].
... Onion, cherry and mango had high TFC with small statistical differences between these foods. Onion is an important dietary source of quercetin [27,28], and cherry is a rich source of kaempferol and cyanidin [29]. All values are expressed as mg/g sample ± standard deviation of three independent measurements. ...
Full-text available
Polyphenols are naturally occurring compounds found largely in fruits and vegetables. The antioxidant properties of these polyphenols including total phenolic content (TPC), total flavonoid content (TFC), tannin content, 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), 2,2-azinobis-(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS) scavenging abilities and ferric ion reducing antioxidant power (FRAP) were measured among sixteen (16) plant foods (mango, blueberry, strawberry, black carrot, raspberry, dark grapes, garlic, ginger, onion, cherry, plum, apple, papaya, peach, pear and apricot) by modifying, standardising and translating existing antioxidant methods using a 96-well plate reader. Eighteen targeted phenolic acids and flavonoids were characterised and quantified using high-performance liquid chromatography-photometric diode array (HPLC-PDA) and verified by modifying an existing method of liquid chromatography coupled with electrospray-ionisation triple quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). While most of these compounds were accurately detected by the HPLC-PDA at a low concentration, a few polyphenols in low concentrations could be only be characterised using the LC-ESI-QTOF/MS method. Our results showed that mango possessed the highest overall antioxidant activity, phenolic acid and flavonoid content among the selected fruits. Factor analysis (FA) and Pearson's correlation tests showed high correlations among ABTS, DPPH, FRAP and phenolic acids, implying the comparable capabilities of scavenging the DPPH/ABTS free radicals and reducing ferric ions from the antioxidant compounds in the samples. Phenolic acids contributed significantly to the antioxidant activities, and flavonoids contributed more to tannin content based on the correlations. Overall, methods modified and standardized in this study can provide better understanding of high throughput technologies and increase the reliability of antioxidant data of different plant foods.
... MDA values were not affected by quercetin throughout the experiment. Quercetin-rich onions however did demonstrate to influence plasma lipid profile of pigs when fed a high-fat diet [69,70], which could relate to lower circulating levels of MDA-modified low density lipoprotein, and thus a reduced risk for coronary heart disease [71]. With regard to the small intestine, although we observed a more oxidized GSH redox pool and an increased distal jejunal GST activity on d5 post-weaning, quercetin did not further upregulate small intestinal GST as observed in the liver. ...
Full-text available
Quercetin has been shown to alleviate mucosal damage and modulate the glutathione (GSH) redox system in the colon of rodents. In the current study, we assessed whether quercetin was able to mitigate small intestinal dysfunction in weaned pigs. Here, 224 weaned piglets were fed a diet containing quercetin at either 0, 100, 300, or 900 mg/kg diet until d14 post-weaning, followed by a common basal diet until d42. Eight animals per treatment were sampled at d5 and d14 post-weaning. In these animals, the small intestinal histomorphology, barrier function, and protein abundance of occludin, caspase-3, and proliferating cell nuclear antigen were assessed. None of these parameters were affected, and neither did quercetin improve performance up to d42 post-weaning. The GSH redox system was evaluated in blood, small intestinal mucosa, and liver. Quercetin did not affect the glutathione peroxidase, glutathione reductase, and glutamate–cysteine ligase activity in these tissues. In contrast, the hepatic glutathione transferase (GST) activity was significantly increased by quercetin supplementation at d5 post-weaning of 100, 300, and 900 mg/kg. Importantly, d5 was characterized by a more oxidized GSH redox status. To conclude, dietary quercetin had little effect on the small intestine, but did upregulate hepatic GST in the occurrence of redox disturbance.
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Cardiovascular diseases (CVDs) are the leading cause of mortality worldwide and, together with associated risk factors such as diabetes, hypertension, and dyslipidaemia, greatly impact patients’ quality of life and health care systems. This burden can be alleviated by fomenting lifestyle modifications and/or resorting to pharmacological approaches. However, due to several side effects, current therapies show low patient compliance, thus compromising their efficacy and enforcing the need to develop more amenable preventive/therapeutic strategies. In this scenario, medicinal and aromatic plants are a potential source of new effective agents. Specifically, plants from the Allioideae subfamily (formerly Alliaceae family), particularly those from the genus Allium and Tulbaghia, have been extensively used in traditional medicine for the management of several CVDs and associated risk factors, mainly due to the presence of sulphur-containing compounds. Bearing in mind this potential, the present review aims to gather information on traditional uses ascribed to these genera and provide an updated compilation of in vitro and in vivo studies validating these claims as well as clinical trials carried out in the context of CVDs. Furthermore, the effect of isolated sulphur-containing compounds is presented, and whenever possible, the relation between composition and activity and the mechanisms underlying the beneficial effects are pointed out.
Background In traditional medicine, Allium cepa Linnaeus is used for the treatment of several disease conditions. Whilst reports abound on the effects of several cultivars of A. cepa L on biochemical parameters, similar information on the red cultivar is scarce. This study examines the effects of the methanol extract of the red cultivar A. cepa L on some serum biochemical parameters in experimental Wistar rats. Materials and methods Fifty-five Wistar rats were divided into three groups (A, B and C), which include 25, 25 and 5 rats, respectively. The rats in Groups A and B were sub-divided into 5 groups of 5 rats. Each rat was administered a certain dose of methanol extract of the red cultivar A. cepa L for 14 days (Group A) or 28 days (Group B). Group C rats served as the control and were administered with distilled water (10 mL/kg). Results A. cepa L administration resulted in dyslipidaemia, hyponatremia, hypokalaemia and hyperchloraemia; a significant (p < 0.05) decrease in hepatic enzymes and a significant (p < 0.05) increase in serum bicarbonate, bilirubin and its fractions. Conclusions These biochemical results indicate that the excessive and prolonged medicinal consumption of A. cepa L products beyond 7 days may induce moderate hepatic injury and mild renal dysfunction and may complicate disease conditions, such as hypertension and diabetes. Thus, in order to minimize its toxic effects, it is recommended that A. cepa L products should not be used for more than seven consecutive days or beyond a dosage of 90 mg/kg.
The effects of plant constituents on lipid metabolism were examined in swine that had been fed for 4 weeks a standard diet containing, in addition, (per kg diet) 3.15 g of the methanol serial solvent fraction garlic bulbs or 3.5 g of the petroleum ether solubles high-protein barley flour or 5 mg of the plant growth regulator, AMO 1618. All treatments suppressed 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and cholesterol 7α-hydroxylase activities. Modest increases in serum triglycerides were associated with significantly increased hepatic lipogenic activities in response to all treatments except that of the barley extract.The methanol solubles of a second lot of garlic were fractionated by HPLC and tested in an avian hepatocyte system. One component, an isoprenoid metabolite, MW 358, suppressed HMG-CoA reductase.
After ingestion of raw garlic, the components allyl methyl sulfide (1), allyl methyl disulfide (2), diallyl sulfide (3), diallyl disulfide (4), diallyl trisulfide (7), dimethyl sulfide (8), and acetone (9) in the breath of a test person were analyzed over a time period of about 30 h by means of proton-transfer-reaction mass spectrometry. While the concentrations of 2−7 reached maxima shortly after ingestion of garlic and declined to baseline values within the next 2−3 h, concentrations of 1, 8, and 9 increased much more slowly and showed enhanced values even 30 h after garlic consumption. The strong increase of the concentration of acetone might be indicative of enhanced metabolism of serum cholesterol, triglycerides, and total lipids in the blood stream. Keywords: Breath gas analysis; garlic components; proton-transfer-reaction mass spectrometry (PTR-MS)
The major flavonoids of mature onion bulb were confirmed as the 3,4′-O-diglucoside (Qdg) and 4′-O-monoglucoside (Qmg) of quercetin using a combination of chromatographic comparisons, mass spectrometry and nuclear magnetic resonance spectroscopy. These two components account for over 85% of the total flavonoids in three varieties of onion with Qdg as the main component. Quercetin is detected in these long stored onions but only at low levels of less than 2% of the total. The remaining flavonoid fraction (approx 15%) comprises upto 17 different components of which quercetin-3-O-glucoside and isorhamnetin glucoside are prominent members although each contribute less than 1% of the total flavonoid fraction. There are significant differences in the levels of Qdg and Qmg between the four different onion varieties analysed; Qdg varying from 50–1300 mg kg-1 fresh onion tissue and Qmg from 36–394 mg kg-1. Maceration of the tissue for the three varieties tested led to a loss of Qdg and the appearance of Qmg and free quercetin. In the variety Rijnsburger 50% of the Qdg was degraded in 5 h and had completely disappeared after 24 h. These changes in Qdg can be quantitatively explained by increases in Qmg and free quercetin. The possible significance of quercetin glycosides in the diet is discussed. © 1997 SCI
Total flavonol and flavone contents of foods have been determined with validated state-of-the-art methods. Quercetin dominates, and flavonol levels found in vegetables and fruits are below 10 mg kg−1. However, high concentrations are found in onions (300 mg kg−1), kale (450 mg kg−1), broccoli (100 mg kg−1), beans (50 mg kg−1), apples (50 mg kg−1), blackcurrants (40 mg kg−1), and tea (30 mg l−1). The dietary intake of flavonols varies 10-fold between countries (6–60 mg day−1). Flavones are of minor importance in the diet. Tea, wine and fruits are the most important sources of flavanols, but there are gaps in our knowledge on flavanol levels of many foods. The absorption of dietary quercetin glycosides in humans ranges from 20 to 50%. The sugar moiety is an important determinant of the bioavailability of flavonols. The presence of a glucose moiety significantly enhances absorption. The extent of absorption of flavanols in humans seems similar to that of flavonols but has been little studied. Flavonols and flavanols are extensively metabolised, as only 1–2% of them are excreted with an intact flavonoid backbone. Hepatic biotransformations include glucuronidation and sulphatation of the phenolic hydroxyls and O-methylation of catechol groups. Bacteria of the colon cleave the C-ring of the flavonoid nucleus to phenolic acids which are subsequently absorbed. Apart from conjugates, virtually no metabolites have been characterised in humans. Absorption of flavanols is rather fast, with times to reach peak values between 0.5 and 4 h. Flavanols are rapidly excreted, with elimination half-lives of 1–6 h. Quercetin glycosides show rapid to slow absorption; peak values are reached between  < 0.5 and 9 h. The type of glycoside determines the rate of absorption. Excretion of quercetin glycosides is slow: elimination half-lives are 24 h, independent of the type of glycoside. Analytical data for flavanols in foods are needed. Tea, as an important dietary source, has to be studied. Research on the bioavailability of flavonols and flavanols has to be expanded. Attention is needed for the identification and quantification of their metabolites in body fluids.© 2000 Society of Chemical Industry
Karpe F. (Karolinska Hospital, Stockholm, Sweden; and Radcliffe Infirmary, Oxford, England, UK). Postprandial lipoprotein metabolism and atherosclerosis (Review). J Intern Med 1999; 246: 341–355. Postprandial lipids and lipoproteins have been associated with the presence of cardiovascular disease in a large number of case-control studies. Because the metabolic perturbations around the postprandial situation is a key driving force for cholesterol flux between lipoproteins and tissues, together with the augmented generation of potentially atherogenic cholesterol-rich remnant lipoproteins, several hypotheses have been formulated to link excessive lipoproteinaemic response to fat intake with cardiovascular disease. Recent information on the regulation of lipoprotein remnant formation and its relation to atherosclerosis will enable us to test a pertinent clinical question: is there a direct relationship between repeated elevations of postprandial lipoproteins and development of atherosclerosis?
Pungency precursor compounds, S-methyl (Me), S-2-propenyl (allyl, Al)-, and S-propenyl (Pe)-l-cysteine sulfoxides (CSO), were determined from eight Allium species plants using high performance liquid chromatography after dansyl-Cl derivatization. Allium plants selectively contained two or three kinds of CSOs with varying amounts and proportions, corresponding to their flavors. MeCSO was a major precursor in chive and Chinese chive (0.68–1.85 mg g−1 fresh wt.) and found in all the species examined with less amounts. AlCSO was the major precursor in garlic and giant garlic (3.2–9.8 mg g−1), and was also contained in chive and Chinese chive. PeCSO was the main flavor precursor in onion, green onion, leek, and shallot (0.3–2.2 mg g−1), but also found in chive, Chinese chive, garlic and giant garlic. Garlic and giant garlic contained greatest amounts of total CSO (5.0–11.7 mg g−1), while Chinese chive, dehydrator onion, leek, shallot had moderate amounts (2.0–5.0 mg g−1). Japanese bunching onion, onion (TG 1015Y), and chive leaves contained least amounts of total CSO (<2 mg g−1). S-propyl CSO, however, was not found in any of these species. Based on the composition of the precursors, we could classify the Alliums species into three groups, such as Me-, Al-, and PeCSO dominant groups.
Welsh onion has been consumed for prevention of cardiovascular disorders. To study if it has antithrombotic effects, 9-wk-old male Sprague-Dawley rats were studied. Some rats were fed raw or boiled Welsh onion juice (2 g. kg(-1). d(-1)) for 4 wk, and the remaining acted as the control. Before and after feeding, their systolic blood pressure was measured by a tail-cuff method. Two days after the treatment period, tail bleeding time, platelet function (including platelet aggregation and adhesion), plasma levels of prostaglandins, and platelet cyclic nucleotide levels were determined. In comparison to the control, raw Welsh onion juice consumption significantly (1) lowered resting systolic blood pressure; (2) prolonged the bleeding time; (3) diminished platelet adhesion on a fibrinogen-coated surface, ADP-evoked platelet aggregation and ADP-stimulated thromboxane release; (4) elevated the concentration of cyclic AMP, but not cyclic GMP, in platelets; (5) increased the plasma level of 6-keto-prostaglandin F(1alpha), the stable prostacyclin metabolite, but not the plasma nitrite level. On the contrary, boiled Welsh onion juice consumption was totally ineffective. In conclusion, consuming raw Welsh onion juice, but not boiled juice, has blood pressure lowering and antithrombotic effects in rats. These effects may be mediated by PGI(2)-cAMP pathway.