Article

Effect of Onion Consumption on Cardiovascular Disease in Human Intervention Studies: A Literature Review

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Abstract

Onion (Allium cepa L.) production in Korea has increased gradually over the past 15 years, placing second in food consumption survey with 20.6 g daily intake in 2006. Onions, used as an ingredient in many dishes and accepted by almost all traditions and cultures, have been reported to have a range of health benefits which include anticarcinogenic, antiasthmatic, antibiotic, and antioxidative effects. These effects may be attributable to a powerful flavonoid pigment-containing compounds, such as quercetin and alk(en)yl cysteine sulphoxides (ACSOs). Although antiplatelet and antithrombotic activities of onion have been confirmed by many of in vitro or animal studies, only a few human intervention studies have been examined. The majority of human studies identified that onion improves some cardiovascular markers such as lipid profile and platelet coagulant. With regard to antioxidative effects, somewhat positive effects are confirmed through strengthening the resistance of oxidative DNA damage in lymphocyte and urine, while most studies failed to find inhibitory effects on LDL oxidation. The discrepancies among studies might be ascribed to producing area, processing methods of onion, dosage, subject characteristics, study duration, and measurement methods. In this review, we focused on the preventive effect of cardiovascular disease through onion consumption in human intervention studies.

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... 8 Most of these mechanisms, which have been proved under in vitro and in vivo conditions, have resulted in positive human health effects attributed in part to the presence of polyphenols. 9,10 In this sense, it is widely known that onion is one of the richest sources of dietary flavonols and contributes to a large extent to the overall intake of flavonols. 2 It is important to highlight that a well-balanced dietary intake has been associated with a reduced risk of various pathological conditions such as cardiovascular diseases, cancer, neurodegenerative diseases, and diabetes 11−13 and has also been recognized as a contributor to allergy control in epidemiological studies. ...
Article
The flavonol content and anti-inflammatory and antioxidant activities of onion treated by high-pressure processing (HPP) and HPP combined with freeze-drying and pulverization (HPP-FD-P) were evaluated. Allium cepa L. var. cepa, 'Recas' was treated at T1 (200 MPa/25 °C/5 min), T2 (400 MPa/25 °C/5 min), and T3 (600 MPa/25 °C/5 min). After treatment, HP-treated and untreated samples were frozen (diced onion, HP-treated). Subsequently, part of the diced samples was freeze-dried and pulverized (pulverized onion, HP-treated and freeze-dried). Flavonol content and anti-inflammatory and antioxidant activities (hyaluronidase inhibiting activity, NO(•), ABTS(•+), and DPPH(•) scavenging capacity, ferric reducing antioxidant power, and antioxidative capacity by photochemiluminescence) were measured in nonhydrolyzed and hydrolyzed extracts. Hydrolysis was carried out in order to evaluate the effect of HPP and HPP-FD-P on both anti-inflammatory and antioxidant activities of extracts mainly containing aglycone forms. HPP-FD-P increased quercetin 3,4'-diglucoside, quercetin 4'-glucoside, quercetin 3-glucoside, and isorhamnetin 3,4'-diglucoside extractability. The present study suggests that HPP (especially treatment at 400 MPa) and HPP-FD-P may be of benefit for obtaining functional ingredients from onion, as suggested by increased NO(•) scavenging capacity and maintenance of the antioxidant activity mainly in hydrolyzed extracts.
... In this sense, the potential efficacy of onion consumption in the prevention of vascular damage have been highly supported by its hypolipidemic, antiinflamatory, antihypertensive, antidiabetic, antithrombotic, and antihyperhomocysteinemia effects [15,16]. Specific phytochemicals (flavonols, sulphur compounds) and nutritional compounds (dietary fibre) present on its matrix have been pointed out as main promoters of those cardioprotective effects [17][18][19]. However, the advantage of consuming the natural product instead of those separated compounds must be taken in consideration since interactions and synergistic effects shall be present and responsible for some specific health benefits. ...
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The effect of garlic and onion on alimentary hyperlipemia, induced by feeding 100 g butter, has been studied in 10 healthy subjects. The freshly extracted juice of 50 g of garlic or onion, as well as an equivalent amount of their ether-extracted essential oils, was administered randomly on four different days during a one-week period. Garlic and onion have a significant protective action against fat-induced increases in serum cholesterol and plasma fibrinogen and decreases in coagulation time and fibrinolytic activity. The essential oil fraction, which contains all the taste and odour, exactly duplicated the beneficial effects of whole garlic and onion. It is, therefore, concluded that the active principle of garlic and onion is the essential oil, which chemically is a combination of sulphur-containing compounds, mainly allyl propyl disulphide and diallyl disulphide.
Article
Organosulfur compounds (OSCs) present in garlic and onion oil have been shown to inhibit chemical carcinogenesis. In this study, we compared the chemopreventive efficacy of five lipid- and four water-soluble OSCs using the murine nuclear aberration assay. Administration of diallyl sulfide and S-allyl cysteine p.o. at a dose of 200 mg/kg 3 h prior to i.p. 1,2-dimethylhydrazine (DMH) injection (20 mg/kg) significantly inhibited colonic nuclear damage in female C57Bl/6J mice by 47% and 36%, respectively. The inhibitory effect of S-allyl cysteine was found to be dose dependent. The other OSCs did not affect the level of DMH-induced nuclear toxicity. Furthermore, the incidence and frequency of colonic tumors induced by DMH (20 mg/kg, 10 weekly i.p. injections) in female CF-1 mice were significantly inhibited by S-allyl cysteine pretreatment, given 3 h prior to each carcinogen injection. These data indicate that the allyl group coupled to a single sulfur atom might play an important structural role in inhibition of DMH-induced colonic nuclear toxicity and carcinogenesis. OSCs containing allyl groups stimulated glutathione S-transferase activity in both the liver and colon. However, their saturated analogues stimulated little or no hepatic and colonic glutathione S-transferase activity. Induction of hepatic and colonic glutathione S-transferase might assist in detoxification of carcinogens and could be necessary for some aspects of chemoprevention.
Article
The effects of onion and ginger consumption on platelet thromboxane production were examined. Volunteers, all Danish women, consumed either 70 g raw onion or 5 g raw ginger daily for a period of 7 days. Each participant in each (onion or ginger) group served as her own control. TxB2 determination was made in serum obtained after blood clotting. The following are the results. TxB2 (pmol/ml serum): (i) onion group--before consumption 910 +/- 327, after consumption 1005 +/- 713 (Mean +/- SD, N = 5); (ii) ginger consumption 782 +/- 482, after consumption 498 +/- 164 (Mean +/- SD, N = 7).
Article
In vitro effects of an oily extract of onion were examined on the metabolism of arachidonic acid (AA) in human platelets. Onion was found to reduce the formation of thromboxane and lipoxygenase products from exogenous arachidonic acid in platelets; it did not inhibit the incorporation of AA into platelet phospholipids. While not affecting the platelet phospholipase activity it did reduce the formation of thromboxane B2 and lipoxygenase products in platelets that were prelabelled with arachidonic acid and then activated by A23187. This suggests that onion inhibits the formation of AA metabolites by exerting its effect at steps later than the liberation of AA. With concentrations of onion extract producing abolition of AA-induced aggregation, only partial inhibition of aggregation was observed with ADP- and epinephrine-induced aggregation. Onion did not inhibit A23187 induced aggregation. The results suggest that inhibition of platelet aggregation by onion is mediated largely by its effect on platelet thromboxane production.
Article
In the present study, eight organosulfur compounds from garlic and onions were studied for their inhibitory effects on benzo[a]pyrene (BP)-induced neoplasia of forestomach and lung of female A/J mice when administered 96 and 48 h prior to carcinogen challenge. These compounds had one, two or three linearly connected sulfur atoms. They included the four allyl group-containing derivatives: allyl methyl trisulfide (AMT), allyl methyl disulfide (AMD), diallyl trisulfide (DAT), and diallyl sulfide (DAS), and also four corresponding saturated compounds in which propyl groups were substituted for the allyl groups. All four allylic compounds inhibited BP-induced neoplasia of the forestomach. The saturated analogs were almost without inhibitory activity, indicating the importance of the allyl groups. DAT, which contains two allyl groups, was more potent than AMT, which contains only one allyl group, thus providing further evidence for the role of allyl groups in the inhibitory effects observed. DAS and AMD, but not DAT or AMT, inhibited pulmonary adenoma formation. The fact that in the lung the monosulfide and disulfide inhibited, but the trisulfide did not inhibit, indicates that the number of sulfur atoms in the molecule can control the organ sites at which protection against carcinogenesis will occur. All four allylic compounds induced increased glutathione S-transferase (GST) activity in the forestomach, but varied in their capacity to induce GST in lung, liver and small bowel. Their saturated analogs produced little or no induction. In evaluating relationships between diet and cancer, it would be useful to consider the possible role of garlic and onion organosulfur compounds as protective agents. In addition, further studies of this class of chemicals might lead to the identification and development of useful new chemopreventive compounds.
Article
Aqueous extracts of onion, garlic and ginger were found to inhibit aggregation induced by ADP, epinephrine, collagen and arachidonate in a dose-dependent manner in vitro. In the case of onion and garlic extracts relatively much higher volumes were need to bring about even a modest inhibition (by ca. 13-18%) of thromboxane synthesis in washed platelets from labelled AA. On the other hand a good correlation was found between the amounts of ginger extract needed to inhibit platelet aggregation and those to inhibit platelet thromboxane synthesis. Ginger extract reduced also platelet prostaglandin-endoperoxides. A dose-related inhibition of platelet thromboxane- and prostaglandin (PGF2 alpha, PGE2 and PGD2) synthesis was affected by ginger extract. Extracts of onion, garlic and ginger inhibited biosynthesis of prostacyclin in rat aorta from labelled AA. Ginger extract mildly inhibited the synthesis of prostacyclin from endogenous pool of AA in rat aorta; the other two extracts were without effect.
Article
The selective alpha, blocker prazosin was used to abolish Prinzmetal's variant angina in six patients. All had had an acute transmural myocardial infarction, after which the anginal attacks with transient ST segment elevation developed, and three of them had already suffered from variant angina prior to the infarction. Therapeutic trials with high doses of nifedipine, verapamil, nitrates, beta blockers, and (in one case) phenoxybenzamine were ineffective in all six patients. Prazosin, 8 to 30 mg/day combined with low-dose nitrates or nifedipine completely abolished the attacks in four patients, markedly reduced their frequency and intensity in one patient, and had to be stopped in the sixth one because of hypotension and dizziness. Except for this last patient, the drug was well tolerated by all the others, and no changes in blood pressure were observed. In four patients discontinuation or reduction of prazosin resulted in exacerbation of symptoms, but its renewal was followed by disappearance of the attacks. Since the mean follow-up period in this study was 4 to 6 months, further evaluation appears necessary concerning the long-term effects of this drug in Prinzmetal's variant angina.
Article
This review article describes the different receptors, second-messengers and mechanisms involved in platelet activation. Several platelet agonists have well-defined receptors at the platelet membrane of which a number are single polypeptides with 7 hydrophobic transmembrane domains. These receptors are connected, via GTP regulatory proteins, with cytoplasmic second-messenger-generating enzymes. Phospholipase C and adenylate cyclase are the two best-known enzymes, generating inositol triphosphate (IP3) and diacyl glycerol from phosphatidylinositol biphosphate and cyclic AMP from ATP respectively. The intraplatelet free calcium level, which is critical for the activation status of the platelet, is increased by IP3 and is lowered in the presence of rising cyclic AMP concentrations. Shape-change occurs with small increases in intraplatelet calcium, while aggregation and secretion of granules take place at higher calcium, levels. The role of myosin and actin filaments and of transmembrane glycoproteins is further discussed.
Article
The recent explosion of interest in the bioactivity of the flavonoids of higher plants is due, at least in part, to the potential health benefits of these polyphenolic components of major dietary constituents. This review article discusses the biological properties of the flavonoids and focuses on the relationship between their antioxidant activity, as hydrogen donating free radical scavengers, and their chemical structures. This culminates in a proposed hierarchy of antioxidant activity in the aqueous phase. The cumulative findings concerning structure-antioxidant activity relationships in the lipophilic phase derive from studies on fatty acids, liposomes, and low-density lipoproteins; the factors underlying the influence of the different classes of polyphenols in enhancing their resistance to oxidation are discussed and support the contention that the partition coefficients of the flavonoids as well as their rates of reaction with the relevant radicals define the antioxidant activities in the lipophilic phase.
Article
The effects of aqueous extracts of raw and boiled garlic and onions were studied in vitro on the collagen-induced platelet aggregation using rabbit and human platelet-rich plasma. A dose dependant inhibition of rabbit platelet aggregation was observed with garlic. Onion also showed dose-dependent inhibitory effects on the collagen-induced platelet aggregation but this inhibition was of a lesser magnitude compared to garlic when related to dose. The concentration required for 50% inhibition of the platelet aggregation for garlic was calculated to be approximately 6.6 mg ml(-1) plasma, whereas the concentration for onion was 90 mg ml(-1) plasma. Boiled garlic and onion extracts showed a reduced inhibitory effect on platelet aggregation. Garlic but not onion significantly inhibits human platelet aggregation in a dose-dependent fashion. The potency of garlic in inhibiting the collagen-induced platelet aggregation is approximately similar to that of rabbit platelets (8.8 mg ml(-1) produced 50% inhibition of platelet aggregation). The results of this study show that garlic is about 13 times more potent than onion in inhibiting platelet aggregation and suggest that garlic and onion could be more potent inhibitors of blood platelet aggregation if consumed in raw than in cooked or boiled form.
Article
Quercetin is a typical flavonoid present mostly as glycosides in plant foods; it has attracted much attention for its potential beneficial effects in disease prevention. In this study, we examined human volunteers after the short-term ingestion of onion, a vegetable rich in quercetin glucosides. The subjects were served diets containing onion slices (quercetin equivalent: 67.6-93.6 mg/day) with meals for 1 wk. Quercetin was only found in glucuronidase-sulfatase-treated plasma, and its concentration after 10 h of fasting increased from 0.04 +/- 0.04 microM before the trial to 0.63 +/- 0.72 microM after the 1-wk trial. The quercetin content in low-density lipoprotein (LDL) after glucuronidase-sulfatase treatment corresponded to <1% of the alpha-tocopherol content. Human LDL isolated from the plasma after the trial showed little improvement of its resistance to copper ion-induced oxidation. It is therefore concluded that conjugated metabolites of quercetin accumulate exclusively in human blood plasma in the concentration range of 10(-7) approximately 10(-6) M after the short-term ingestion of vegetables rich in quercetin glucosides, although these metabolites are hardly incorporated into plasma LDL.
Article
Einfluß der Zwiebel als ein wesentlicher Bestandteil der Mittelmeerkost auf den arteriellen Blutdruck und die Fließfähigkeit des Blutes Mittelmeerkost wirkt lebensverlängernd. Eine entscheidende Komponente der Kost ist die Zwiebel. Eine pharmakologische Spontanwirkung 5 h nach der Einnahme von Zwiebelolivenölmazeratkapseln auf den arteriellen Blutdruck konnte in einer offenen und einer randomisierten, Plazebo-kontrollierten, doppelblinden Cross-over-Phase-I-Untersuchung an anscheinend gesunden Probanden gesichert werden. Zeitgleich mit der Blutdruckabnahme wurden Plasmaviskosität und Hämatokritwerte signifikant gesenkt. Dies spricht für eine vasodilatatorische Wirkung des Zwiebelolivenölmazerates. Die Klebrigkeit der Thrombozyten wurde gesenkt. Die Effekte waren bei Probanden mit eingeschränkter Fließfähigkeit des Blutes stärker ausgeprägt als bei solchen mit normaler Fließfähigkeit.
Article
Einfluß eines Zwiebel- Olivenöl -Mazerates mit den wesentlichen Bestandteilen der Mittelmeerkost auf den Blutdruck und die Blutfluidität 24 Patienten mit arterieller Hypertonie (WHO-Stadium I) wurden eine Woche lang täglich mit 4 Kapseln eines Zwiebel Olivenöl Mazerates, das die wesentlichen Bestandteile der Mittelmeerkost enthält, oder Plazebo behandelt. Zur Messung des Akuteffektes auf den Blutdruck wurdevor und 5 h nach der ersten Einnahme der 4 Kapseln Verum bzw. Plazebo der Blutdruck gemessen. Zur Bestimmung des Langzeiteffektes wurde der Blutdruck auch nach einer Woche der Einnahme von täglich 4 Kapseln bestimmt. Nach einer 2 wöchigen Wash out Phase mit anschließendem Cross- over erfolgte die 2. Studienphase, die in identischer Weise durchgeführt wurde. Zusätzlich wurde während des gesamten Zeitraums der Blutdruck viermal täglich von den Patienten selbst gemessen. Zu den oben genannten Meßzeitpunkten wurden auch rheologische Parameter (Thrombozytenaggregation, Erythrozy tenaggregation, Plasmaviskosität, Hämatokrit) bestimmt. Zwiebel Olivenöl Mazerat Kapseln führten zu einer signifikanten Senkung des systolischen und einer tendenziellen Senkung des diastolischen Blutdrucks. Ferner wurde die Blutfluidität verbessert, da der Hämatokrit abnahm. Alle genannten Effekte konnten akut und nachder einwöchigen Applikationbeobachtet werden.
Article
Welsh onion has been consumed for prevention of cardiovascular disorders. However, its underlying mechanisms are still unclear. This study investigated whether Welsh onion extracts can alter human platelet function (ie, platelet adhesion, aggregation, and thromboxane release). To clarify the underlying mechanisms, we also measured the intracellular calcium ([Ca2+]i) and cyclic nucleotide levels in platelets. Our results showed that 1) boiled extracts directly induced platelet aggregation in a dose-dependent manner; 2) raw extracts inhibited platelet adhesion and ADP-evoked platelet aggregation, while boiled extracts enhanced them; 3) raw green extract suppressed ADP-stimulated platelet [Ca2+]i elevation and thromboxane production, whereas boiled green extract enhanced them; 4) raw green extract elevated platelet cAMP level, whereas boiled green extract had no effect on cAMP level. Furthermore, the boiled green extract, but not the raw extract, induced pronounced platelet morphological changes. In conclusion, raw extracts of Welsh onion inhibit platelet function in vitro while boiled extracts activate platelets.
Article
A number of studies suggest that dietary intake of onions is of benefit to cardiovascular health. Onion juice inhibits in vitro human platelet aggregation. To study the in vivo effect of onion on platelet aggregation, 11 dogs were prepared with mechanically damaged and stenosed coronary arteries. Periodic platelet-mediated thrombus formation followed by embolization produced cyclic flow reductions (CFR). In five dogs, 0.09 +/- 0.01 mL/kg onion juice administered intravenously abolished CFR within 20 min. This was followed by a 60 +/- 14% (P = 0.002) reduction in collagen-induced ex vivo whole-blood platelet aggregation. Six dogs were given 2.0 g/kg raw onion homogenate intragastrically. CFR were eliminated within 2.5-3 h in five of the dogs. This was accompanied by a 44 +/- 24% (P = 0.04) reduction in ex vivo aggregation. These findings suggest that the consumption of raw onion may help prevent platelet-mediated cardiovascular disorders. However, in vitro incubations of onion juice demonstrated that the platelet inhibitory response was significantly greater in dog blood than in human blood.
Article
The flavonol quercetin is known to be rapidly metabolized after ingestion by enterocytes and bacteria in the intestinal tract which may influence the biological, e.g. antioxidative potency of this compound. Therefore, quercetin and several of its possible metabolites were compared with regard to their antioxidant activity and their capacity to inhibit hepatocellular cholesterol biosynthesis. Using the 2,2,-diphenylpicrylhydrazyl radical scavenger assay, all compounds with an ortho diphenolic structure acted as strong antioxidants. In contrast, in a cellular assay focusing on lipid peroxidation in cultured rat hepatocytes challenged with tert.-butylhydroperoxide only the lipophilic compounds quercetin and 3,4-dihydroxytoluene were active. Concerning the inhibition of cholesterol biosynthesis, 3,4-dihydroxytoluene surprisingly mimicked the effect of quercetin in primary rat hepatocytes, but much less so in HepG2 cells. All other metabolites were almost ineffective in both cell types. These results suggest that some of the biological functions of flavonoids detectable by in vitro assays may persist in vivo as long as comparably potent metabolites are systemically present.
Article
A number of sulfur-containing amino acids and peptides are found in allium plants such as onion and garlic that have physiologic functions. In HepG2 cells, S-propyl cysteine decreased the secretion of apolipoprotein B100. The compound reduced the secretion of newly synthesized triacylglycerol and cholesterols from radiolabeled acetate. We associated the decrease of apolipoprotein B100 secretion to the length of the acyl-chain of the sulfur-containing amino acids. The present study suggests that foods containing S-propyl cysteine including onions have beneficial effects.
Article
In the present study, we investigated whether onion has antithrombotic effect in streptozotocin (STZ)-induced diabetic rats. In diabetic rats, serum thromboxane B(2) (TXB(2)) level was elevated compared to that in normal, and this elevation in diabetes was significantly inhibited by treatment with onion (0.5 g/ml/kg/day, i.p.) for 4 weeks. In normal rats, the serum TXB(2) level remained unaltered after the treatment with onion. To investigate in vitro effect of onion, we examined its effect on TXB(2) formation, platelet aggregation and arachidonic acid (AA)-release in platelets from diabetic and normal rats. Onion showed a significant inhibitory effect on collagen- or AA-induced TXB(2) formation with greater potency in diabetic platelets than in normal. Similarly, more potent inhibitory effects of onion in diabetes were observed in collagen- or AA-induced platelet aggregation and collagen-induced AA release response. In conclusion, these results suggest that onion can produce more beneficial antithrombotic effect in diabetes.
Article
Onion (Allium cepa L.) is botanically included in the Liliaceae and species are found across a wide range of latitudes and altitudes in Europe, Asia, N. America and Africa. World onion production has increased by at least 25% over the past 10 years with current production being around 44 million tonnes making it the second most important horticultural crop after tomatoes. Because of their storage characteristics and durability for shipping, onions have always been traded more widely than most vegetables. Onions are versatile and are often used as an ingredient in many dishes and are accepted by almost all traditions and cultures. Onion consumption is increasing significantly, particularly in the USA and this is partly because of heavy promotion that links flavour and health. Onions are rich in two chemical groups that have perceived benefits to human health. These are the flavonoids and the alk(en)yl cysteine sulphoxides (ACSOs). Two flavonoid subgroups are found in onion, the anthocyanins, which impart a red/purple colour to some varieties and flavanols such as quercetin and its derivatives responsible for the yellow and brown skins of many other varieties. The ACSOs are the flavour precursors, which, when cleaved by the enzyme alliinase, generate the characteristic odour and taste of onion. The downstream products are a complex mixture of compounds which include thiosulphinates, thiosulphonates, mono-, di- and tri-sulphides. Compounds from onion have been reported to have a range of health benefits which include anticarcinogenic properties, antiplatelet activity, antithrombotic activity, antiasthmatic and antibiotic effects. Here we review the agronomy of the onion crop, the biochemistry of the health compounds and report on recent clinical data obtained using extracts from this species. Where appropriate we have compared the data with that obtained from garlic (Allium sativum L.) for which more information is widely available.
Article
Organosulfur compounds in onion extracts are formed following the lysis of the S-alk(en)yl-L-cysteine sulfoxides by alliinase. These compounds inhibit the aggregation of human blood platelets and offer the potential for positive cardiovascular health benefits. An experiment was designed to examine temporal and temperature effects on onion-induced antiplatelet activity. Platelet aggregation is induced by various agonists, including ADP, collagen, and thrombin. Unexpectedly, all freshly-juiced onion extracts (ca. 5 minutes post-juicing) appeared to exhibit both an agonist-free aggregation peak (AFP) and a platelet inhibitory peak (PIP) characteristic of inhibition of platelet aggregation. The AFP was minimal by 30 minutes and dissipated in all treatments by 120 minutes, while the PIP increased as onion extracts aged and did not change after 30 minutes at 25 degrees C. This finding confirms the observation that the in vitro platelet inhibitory activity of onion organosulfur compounds is time dependent. Freshly-prepared onion extracts were incubated with the ADP scavenger enzyme apyrase (E.C. 3.6.1.5). AFPs were abolished in apyrase-treated extracts, suggesting that this response may have been due to free ADP in onion extracts, although an amount of ADP required to generate such a response would be unexpected in onion extracts. In addition, platelet aggregates were not observed in the AFP, suggesting this response may be associated with changes in light transmission through platelet rich plasma that are not associated with platelet aggregation. Artifacts of analysis are, therefore, possible when assessing onion-induced antiplatelet activity with freshly-juiced extracts. Temporal formation of platelet-inhibiting organosulfur compounds should be taken into account during both in vitro and in vivo assessment of onion-induced antiplatelet activity.