Effect of the essential oils of garlic and onion on alimentary hyperlipemia

Evaluation of the modifying influence of arecanut on the garlic-modulated hepatic detoxication system enzymes, sulfhydryl content, and lipid peroxidation in mice

This paper evaluates the potential effects of arecanut (Areca catechu, L.), an important ingredient of betel quid, on the garlic (Allium sativum, L.)-modulated activities of hepatic detoxication system enzymes, acid soluble sulfhydryl content, and lipid peroxidation in mice. Mice were fed on either a normal diet or a diet containing 0.25%, 0.5%, or 1% (w/w) arecanut for 45 days. During the last 10 days of treatment oral administration of garlic at the dose level of 20 or 100 mg/kg body weight/day was supplemented. Significant modulation in the activities of phase I and phase II enzymes, -SH content, and malondialdehyde (MDA) level by garlic was observed. Garlic-modulated alterations in glutathione S-transferase (GST) activity and -SH content were decreased, while cytochrome b5, cytochrome P-450, and MDA levels were further augmented by the arecanut plus garlic treatments.

Preventive action of garlic on aflatoxin B1-induced carcinogenesis in the toad Bufo regularis

The action of fresh minced garlic and garlic oil on aflatoxin B1- (AFB1) induced carcinogenesis in the toad Bufo regularis was studied. Feeding toads with AFB1 induced tumors in 19% of the animals. Animals given AFB1 together with fresh garlic or garlic oil showed a significant reduction in tumor incidence. The tumor incidences were 3% and 9% in animals given AFB1 plus garlic and AFB1 plus garlic oil, respectively. In all three groups, the tumors were located in the liver (hepatocellular carcinomas), in addition to the kidney in animals treated with AFB1 alone and together with garlic. The kidney tumors were diagnosed as metastatic deposits from the primary liver tumors. It is speculated that one or more constituents of garlic may be responsible for inhibition of AFB1-induced carcinogenesis in B. regularis.

Role of cytochrome P4502E1 in alcoholic liver disease pathogenesis

The intragastric tube feeding model is ideal for the study of the role of dietary factors and the effect of drugs on experimental alcoholic liver disease (ALD), since the model allows us to study the effect of a single variable in the diet on the pathology of liver where the blood alcohol level (BAL) is maintained over 150 mg%. By varying the dietary fatty acid composition we showed that the pathology was worsened by increasing linoleic acid or polyunsaturated fatty acids (PUFAs) in the diet where cytochrome P4502E1 (CYP2E1) was increased posttranslationally by high BAL. Concomitant with the increase in CYP2E1 there was evidence for an increase in lipid peroxidation (LP) by microsomes. Protein adducts of the products of LP were increased in the blood. Isoniazid (INH) enhanced this process and the pathology of ALD when INH was fed at therapeutic levels with ethanol. Preliminary studies show that diallyl sulfide, which inhibits and destroys liver CYP2E1 selectively, also modified the pathologic effects of ethanol. Thus we postulate that CYP2E1 induction plays a central role in the pathogenesis of ALD.

Chemopreventive action of garlic on methylcholanthrene-induced carcinogenesis in the uterine cervix of mice

The present paper reports the chemopreventive action of garlic on 3-methylcholanthrene (MCA)-induced carcinogenesis in the uterine cervix of virgin young adult Swiss albino mice. Insertion of sterile cotton thread impregnated with beeswax containing approximately 600 micrograms of MCA inside the canal of uterine cervix results in the appearance of precancerous and cancerous lesions in the cervical epithelium. In this experimental cervical carcinogenesis model system, if garlic was administered orally at the dose level of 400 mg/kg body wt./day for 2 weeks before and 4 weeks following carcinogen thread insertion. The cervical carcinoma incidence, as compared with that of the positive control (73%), was 23%. This decline in the incidence of carcinoma was highly significant (P less than 0.01). Hyperplastic and dysplastic changes did not show any definite correlation with the garlic treatment.

Garlic, onions and cardiovascular risk factors. A review of the evidence from human experiments with emphasis on commercially available preparations

1. Claims for beneficial effects on cholesterol levels, fibrinolytic activity, and platelet aggregation are attributed both to fresh garlic and onions (or their extracts) and to commercially available preparations. 2. Regarding fresh garlic, the claims have been confirmed, but so far only at very high dosages. 3. For onions and commercially available supplements contradictory results have been reported. 4. All published trials showed severe methodological shortcomings. Some trials were not randomized and/or not blinded whilst this was possible, and in only one of every three studies more than 25 patients participated in each treatment group. In no trial was prognostic comparability of the treatment and the control groups ascertained. At the moment there is inadequate scientific justification for garlic supplementation.

Effect of dried garlic on blood coagulation, fibrinolysis, platelet aggregation and serum cholesterol levels in patients with hyperlipoproteinemia

The effects of intake of dried garlic on blood coagulation, fibrinolysis, platelet aggregation, serum cholesterol levels, and blood pressure were studied in 20 patients with hyperlipoproteinemia over a period of four weeks. Fibrinogen and fibrinopeptide A significantly decreased by 10%. Streptokinase activated plasminogen and fibrinopeptide B beta 15-42 significantly increased by about 10%. Serum cholesterol levels significantly decreased by 10%. Systolic and diastolic blood pressure decreased. ADP and collagen induced platelet aggregation were not influenced.

Garlic (Allium sativum) and onion (Allium cepa): a review of their relationship to cardiovascular disease

Garlic and onion have been used for millenia in the traditional medical practice of many cultures to treat cardiovascular and other disorders. Both Allium species, their extracts, and the chemical constituents of these plants have been investigated for possible effects on cardiovascular disease risk factors--both definite (hyperlipidemia, hypertension and hyperglycemia) and suspected (platelet aggregation and blood fibrinolytic activity). Action of these Allium species on blood coagulability is more clearly defined than their effect on the other risk factors. While many of the studies have serious methodological shortcomings, there is some evidence to suggest that use of certain formulations of garlic and/or onion is accompanied by favorable effects on risk factors in normal subjects and in patients with atherosclerotic disease. The possibility of toxicity resulting from acute and chronic ingestion of large amounts of these plants or their extracts is unresolved. Accordingly, further clinical and epidemiological studies are required before the role of these plants in the prevention and control of cardiovascular disorders is understood and can be realized. Additional research in this area is recommended.

Ajoene, the antiplatelet principle of garlic, synergistically potentiates the antiaggregatory action of prostacyclin, forskolin, indomethacin and dypiridamole on human platelets

Ajoene, the major antiplatelet compound derived from garlic, synergistically potentiates the antiaggregatory action of prostacyclin, forskolin, indomethacin and dypiridamole. For collagen-induced platelet aggregation in human PRP, the ID50 for ajoene is 95 +/- 5 microM. However, in the presence of the antiaggregatory drugs mentioned above, the ID50 for ajoene decreases more than what would be predicted on the basis of simple additive effects. Similarly, the ID50 for prostacyclin decreases from 1 nM to 0.15 nM in the presence of 80 microM ajoene. Isobolic curves for the various combinations of ajoene with prostacyclin or indomethacin exhibit departure from linearity, as predicted for a potentiated synergism between ajoene and these drugs. Dypiridamole, which in PRP has very little effect on the dose-response curve for ajoene, when assayed in whole blood decreases the ID50 for ajoene by a factor of four. These results demonstrate that the antithrombotic potential of ajoene is substantially increased in the presence of physiologically and pharmacologically active antiplatelet agents.

The genus Allium. Part 2

Allium is a genus of some 500 species belonging to the family Liliaceae. However only a few of these are important as food plants, notably onion, garlic, chive, leek, and rakkyo. Such plants have been used for many centuries for the pungency and flavoring value, for their medicinal properties, and, in some parts of the world, their use also has religious connotations. The flavors of members of the genus Alliums, in addition to having certain characteristics, are also complex, being derived enzymically from a number of involatile precursors. In addition to there being variation of flavor between different alliums, there are also considerable changes that occur as a result of cooking and processing. Of course, these are of importance to the consumer and food technologist-processor. The review will introduce the subject by an historical perspective and will set this against data on the present cultivation and usage of commercially cultivated alliums. The chemical composition of these plants will be discussed, emphasis being given to nonvolatile constituents which are, perhaps, less often considered. Discussion of the volatile constituents, which will include mention of the methods currently used for their analysis and for the determination of "flavor strength", will be mainly concerned with literature taken from the last 5 years. In considering the extent and nature of allium cultivation and processing, factors affecting the nutritional value and quality will be highlighted. The medicinal properties of garlic and onion oils have been much studied over the last decade and the review will include critical assessment of this area and also will touch on the more general properties (antimicrobial, antifungal, antibacterial, and insecticidal) of these oils. Finally mention will be made of the antinutritional, toxic, or otherwise undesirable effects of alliums, for example, as inadvertent components of animal diets, tainting of milk and other food products. It is our intention to review the literature up to mid-1984.

The genus Allium--Part 1

Alliums have been grown for many centuries for their characteristic, pungent flavor and medicinal properties. The present review, which includes references published up to the middle of 1984, is primarily concerned with the chemical composition, flavor, and physiological properties of these crops, their extracts, and processed products. Special emphasis is placed upon the relationship between the organoleptically and biologically active components of onion and garlic. Following a brief historical introduction, current production of commercially important alliums is described and their botanical origins and interrelationships are explained. Following consideration of the major economic diseases and pests of alliums, the agronomic, husbandry, and practices associated with their cultivation are described, particular emphasis being placed upon the storage and processing of onion and garlic. The detailed, overall chemical composition and nutritional value of members of the genus Allium are presented in Section 7; after an outline of the origin and nature of flavor components and precursors, the flavor volatiles of individual members are presented. The effects of agronomic, environmental, and processing practices on chemical and flavor content and quality are considered in Section 9. The following section deals critically with the human and animal studies which have been conducted into the medical and therapeutic properties of alliums, emphasis being placed upon the studies into the antiatherosclerotic effect of onion and garlic and their essential oils. After a study of antimicrobial properties of alliums and their effects on insects and animals, an overview is presented which highlights unexplored or inadequately studied areas and suggests rewarding areas for future research.

The genus Allium--Part 3

Allium is a genus of some 500 species belonging to the family Liliaceae. However, only a few of these are important as food plants, notably onion, garlic, chive, leek, and rakkyo. Such plants have been used for many centuries for their pungency and flavoring value, for their medicinal properties, and in some parts of the world, their use also has religious connotations. The flavors of members of alliums, in addition to being characteristic, are also complex, being derived enzymically from a number of involatile precursors. As well as there being variation of flavor between different alliums there are also considerable changes that occur as a result of cooking and processing. These are, of course, of importance to the consumer and food technologist/processor. The review will introduce the subject by an historical perspective and will set against this data on the present cultivation and usage of commercially cultivated alliums. The chemical composition of these plants will be discussed, emphasis being given to nonvolatile constituents which are, perhaps, less often considered. Discussion of the volatile constituents, which will include mention of the methods currently used for their analysis and for the determination of "flavor strength," will be mainly concerned with literature taken from the last 5 years. In considering the extent and nature of allium cultivation and processing, factors affecting the nutritional value and quality will be highlighted. The medicinal properties of garlic and onion oils have been extensively studied over the last decade and the review will include critical assessment of this area; it will also touch on the more general properties (antimicrobial, antifungal, antibacterial, and insecticidal) of these oils. Finally, mention will be made of the antinutritional, toxic, or otherwise undesirable effects of alliums, for example, as inadvertant components of animal diets, tainting of milk, and other food products. It is our intention to review the literature up to mid-1984.

The effect of garlic extracts on contractions of rat gastric fundus and human platelet aggregation

Garlic has been extracted and separated chromatographically into various fractions which show different degrees of activity as inhibitors of platelet aggregation and smooth muscle. The most potent smooth muscle inhibitor fraction had little activity on platelet aggregation, but microgram ml-1 concentrations greatly reduced the contractions of rat gastric fundus to prostaglandin E2 and acetylcholine. Material in this fraction may contribute to some of the claimed therapeutic effects of garlic involving smooth muscle. Its identity is not known, but is different from allyl sulphide, dimethyl sulphide and diallyl disulphide. These compounds eluted earlier on liquid chromatography than the most active fraction, and they showed only modest inhibitory activity against prostaglandin E2 and acetylcholine on rat fundus.

Allium sativum (garlic)--a natural antibiotic

Allium sativum (garlic) has been recognized not only as a spice but also as a substance which exerts a control on microorganisms. Recent publications indicate that garlic extract has broad-spectrum antimicrobial activity against many genera of bacteria and fungi. The active component (allicin) has been isolated and characterized. Because many of the microorganisms susceptible to garlic extract are medically significant, garlic holds a promising position as a broad-spectrum therapeutic agent. Furthermore, garlic plants may also play an important role in the ecological control of pathogenic microorganisms in nature.

Effects of garlic extract and of three pure components isolated from it on human platelet aggregation, arachidonate metabolism, release reaction and platelet ultrastructure

We studied the effect of the methanol extract of garlic bulbs (EOG) and of three pure components isolated from it (F1, F2, F3), on human platelet aggregation induced by ADP, epinephrine, collagen, thrombin, arachidonate, PAF, and the ionophore A-23187. Incubation of PRP with EOG, either in methanol or in homologous PPP, inhibits platelet aggregation induced by all of the above mentioned agonists. F1, F2, and F3 also inhibit platelet aggregation, however, F3 was about four times more potent. Addition of EOG or F3 to platelets that have already been irreversibly aggregated by 10 microM ADP, induces rapid deaggregation. Inhibition of aggregation was still present after three hours. The inhibitory effect persisted even after the treated platelets were Gel-Filtered (GFP) or separated from plasma through a metrizamide gradient and resuspended in new homologous PPP. Thrombin-induced release of ATP from GFP was inhibited by 75-80% after EOG or F3 treatment. Incorporation of [3-H]-arachidonate by intact platelets was decreased by 50-60% in treated platelets. However, platelets incubated with the inhibitors after incorporation of radiolabeled arachidonate, although did not aggregate, produced, after thrombin activation similar amounts of radiolabeled TXB2 and lipoxygenase products as the controls. Electron microscopy of inhibited platelets, in the presence of thrombin, showed no degranulation but an increase of spherical forms. Our results suggest that the effects described might be mediate by a perturbation of the physicochemical properties of the plasma membrane rather than by affecting arachidonate or calcium metabolism in the cells. Chemical structures of F1, F2 and F3 have been provisionally assigned: F1 is diallytrisulfide, F2 is 2-vinyl-1,3-dithiene, and F3 is most probably allyl 1,5-hexadienyltrisulfide.

The long-term use of garlic in ischemic heart disease--an appraisal

The hypocholesterolemic and fibrinolysis-enhancing properties of garlic were assessed in patients with ischemic heart disease (IHD) and in healthy control subjects. The peak of blood fibrinolytic activity (BFA) achieved at the 4th week of garlic therapy was not sustained despite its continuous use and returned to about the pre-garlic values at the 12th week. Garlic withdrawal did not cause any further change in BFA. Under the same conditions serum total cholesterol (STC) values did not show any significant change. Both of the foregoing features were observed in the IHD as well as in the control group. Garlic therapy for 12 weeks did not cause any appreciable changes in serum triglyceride, beta-lipoprotein, plasma fibrinogen levels or coagulation time in either IHD or control subjects. The evidence cited above does not appear to substantiate the prevalent popular belief in the efficacy of garlic in the management of IHD either as a hypocholesterolemic or as a fibrinolytic agent.

Comparative effect of clofibrate, garlic and onion on alimentary hyperlipemia

The effect of clofibrate on the same subjects in similar test conditions were used as a control to verify the alleged beneficial effects from garlic and onion on alimentary hyperlipemia in normals and in cases with ischemic heart disease. The results showed that clofibrate checked the fat-induced (a) rises of serum triglyceride and plasma fibrinogen, and (b) falls of coagulation time (CT) and blood fibrinolytic activity (BFA). Only garlic had a clofibrate-like effect on CT but both garlic and onion checked the postprandial fall of BFA. Clofibrate, however, increased BFA even above the fasting level. Serum cholesterol and beta-lipoprotein were not appreciably affected by fat with or without any drug. Thus, surprisingly, the so-called beneficial effects of garlic and onion were not seen in subjects who had shown significant changes after clofibrate.

The effect of fried versus raw garlic on fibrinolytic activity in man

The effect of fried and raw garlic on blood fibrinolytic activity has been compared in 20 patients with ischaemic heart disease. Three blood samples were collected on the first day of the study and similarly on the 2nd and 7th days after garlic administration, either in raw or fried form. Fibrinolytic activity increased by 72% and 63% within 6 h of administration of raw or fried garlic, respectively. The elevated levels were maintained up to 12 h. In the second part of the study, raw or fried garlic was administered for 4 weeks to patients with ischaemic heart disease and fibrinolytic activity was measured at weekly intervals. It showed a sustained increase, rising to 84.8% at the end of 28th day when raw garlic was administered. Similarly, with fried garlic the rise was 72%. The study shows that: (i) both raw and fried garlic significantly enhance fibrinolytic activity (FA); (ii) garlic enhances FA within hours of administration; (iii) FA continues to rise with continued administration of garlic; (iv) frying removes the strong acrid smell of garlic, but preserves its useful effect on FA.

Fatty acids, fibrinogen and blood flow: a general mechanism for hyperfibrinogenemia and its pathologic consequences

Plasma fibrinogen is elevated in various stressful states and conditions in which active mobilization of free fatty acids (FFA) occurs. Reduction of plasma FFA by an assortment of hypolipidemic drugs is consistently followed by a decrease in the accompanying hyperfibrinogenemia. A direct link between FFA and fibrinogen has been demonstrated in animals, and in experiments employing incubated liver slices. Based on these clinical and experimental observations, we postulate that hepatic fibrinogen synthesis is stimulated by FFA. Since fibrinogen is a major determinant of whole blood viscosity, erythrocyte aggregation, and sludging of red cells in terminal and pre-terminal blood vessels, we propose that microcirculatory blood flow may be impaired in the presence of chronically elevated plasma FFA levls. Consequently, hypolipidemic drugs may be effective in prevention of circulatory complications associated with FFA-induced hyperfibrinogenemia.

Changes in shape of erythrocytes in rabbits on atherogenic diet and onion extracts

The effects of administration of cholesterol alone and of cholesterol and fresh whole onion extract, on the shape of erythrocytes, were studied in albino rabbits. In animals on a cholesterol-enriched diet, the erythrocytes changed shape and showed an increased tendency to aggregate, whereas they retained their normal appearance in animals on cholesterol and onion extract, and did not differ from those of normal control rabbits.

Effect of garlic on human platelet aggregation in vitro

In 6 healthy adults the effect of essential oil of garlic on platelet aggregation was studied in vitro with an aggreganometer. The blood was collected in a siliconized centrifuge tube containing sodium citrate. The aggregating agents used were ADP, epinephrine and collagen. In each subject aggregation was studied 3 times: (i) initial fasting control; (ii) immediately after (i) but with essential oil of garlic drawn into the syringe together with the sodium citrate; (iii) 5 days after feeding 0.5 mg of essential oil of garlic daily. Addition of essential oil of garlic inhibited in-vitro platelet aggregation induced by ADP, epinephrine or collagen; the effect was dose-related. Oral administration of garlic also decreased platelet aggregation. Thus, garlic seems to inhibit some aspects of thrombus formation.

Controlled trial of the effect of cycloalliin on the fibrinolytic activity of venous blood

Cycloalliin is a natural constituent of onion, sulphur-containing but odourless. It was synthesised for this randomised double-blind study; its effect on fibribolytic activity and platelet aggregability was tested in venous blood from 18 male volunteers. It increased the former to a highly significant degree but had no effect on the latter. It was well tolerated and harmless in the single oral dosage used.

Effect of essential oil of onion and garlic on experimental atherosclerosis in rabbits

The effects of the essential oils of onion (extracted from 2 g of raw onion per kg body weight) and garlic (extracted from 1 g of raw garlic per kg body weight) have been observed on experimental atherosclerosis produced by cholesterol feeding (0.5 g/kg) in rabbits. The rise in serum cholesterol and serum triglycerides was significantly reduced by both onion and garlic during the 4-month period of study. Cholesterol feeding significantly increased beta-(P less than 0.01) and pre-beta (P less than 0.001) lipoproteins while decreasing the alpha-fraction (P less than 0.001). Onion and garlic both prevented these changes. The beta/alpha ratio, which was initially 1.6 : 1, rose to 4.5 : 1 and 5.7 : 1 at the end of 2 months and 4 months of cholesterol feeding. However, this ratio did not increase significantly, both at the 2-month and 4-month period, when onion and garlic were added. Fibrinolytic activity significantly increased with onion (P less than 0.001) and garlic (P less than 0.001) while feeding only cholesterol actually decreased it (P less than 0.001). Onion and garlic reducec aortic atheroma by about half. It is suggested that the essential oils of onion and garlic protect against experimental atherosclerosis by preventing the fall in the alpha lipoprotein fraction and by enhancing fibrinolytic activity, as well as by lowering the serum cholesterol and triglyceride levels.

The protective action of essential oils of onion and garlic in cholesterol-fed rabbits

The effects of the essential oils of onion and garlic have been investigated in cholesterol-fed rabbits and have been compared with the effects of clofibrate. The marked rise in serum cholesterol and blood coagulability that followed 3 months of cholesterol feeding (0.2 g/kg/day) was significantly reduced by the essential oils of both onion and garlic. Fibrinolytic activity was actually increased even above the normal control levels. The essential oils of onion and garlic (equivalent to 1 g/kg/day of raw bulbs) proved more effective than clofibrate in the usual clinical dose of 33 mg/kg/day. Garlic was even more effective than onion. Cholesterol feeding increased the average lipid content of aorta from 5.95 to 13.75 mg/100 mg dry weight. With addition of clofibrate, onion or garlic the values were 7.79, 6.23 and 5.28 mg/100 ml, respectively. Thus it can be seen that the essential oils effectively prevent lipid acculation in the rabbit oarta.