The first mention of garlic appears in a Sumerian recipe written in about 3000 BC. The Assyrians also used garlic as a food, brewed as a tea or mixed with wine for a variety of medicinal purposes and to strengthen the system and ward off diseases. In ancient India, there are records in the Sanskrit language documenting the use of garlic remedies about 5000 years ago and the Ebers papyrus written in 1550 BC appears to contain the first mention of garlic in Egyptian medicine. This codex gives 22 uses for garlic, including treatments for heart problems, tumours, headaches, worms and bites. The Holy Bible also mentions garlic as a common food in Egypt.
Athletes in the early Olympic games used to eat garlic before competitions to gain strength and Greek soldiers ate it before battle. It was used as a battlefield medicine to prevent infection in wounds. Hippocrates himself recommended garlic for infections, cancer, leprosy and digestive problems. Galen, the greatest physician of Roman history, referred to garlic as thrice rusticorum, 'peasant's heal all a name which eventually reached England in the Middle Ages as 'poor man's theriacle', and it was known in Arabia as theriaka-al-fuqara (theriac of the poor). It has been suggested that the wild ancestor of garlic was a flowering form producing seeds on aerial 'bulbils'. Under different soil and climate conditions, and different methods of cultivation in the ancient centres of civilisation, other varieties arose.
A hardy perennial, native to Central Asia and cultivated worldwide, garlic requires a fertile soil and a warm, sunny climate. The culture is annual or biannual.' It is grown by dividing the bulb and is harvested late the following summer.
A perennial, erect, bulbous herb, 30-60 cm tall (Plate 6), strong smelling especially when 1 crushed. The underground portion consists ? of a compound bulb giving rise above ground to a number of narrow, keeled, grass-like leaves. The leaf blade is linear, flat, solid, 1.0-2.5 cm wide, 30-60 cm long, and has an acute apex. The leaf sheath, form a pseudostem. The inflorescence is umbellate; the 31 scape coiled at first and subtended by a membranous, long-beaked spathe, splitting on one side and remaining attached to the umbel. Small bulbils are produced in the inflorescences. The flowers are variable in number and sometimes absent, seldom open and may wither in the bud. They occur on slender pedicles, consisting of a perianth of six segments, about 4-6 mm long and pinkish. There are six stamens with the anthers exserted and a superior, three-locular ovary. Seeds are rarely produced.
Ayurveda uses garlic as a tonic, to build the health in general rather than treat a particular disease, although it recognises garlic's effects on the digestive, respiratory, nervous, reproductive and circulatory systems. In Unani medicine garlic is used to treat dysentery, intestinal infection, colic in children, arthritis and food poisoning. In south-west America it is used as a cough remedy, and the Appalachians used garlic for treating pneumonia and chest colds. It is also recommended for earaches and deafness. In Thailand it is eaten to avoid diarrhoea from parasites and a decoction of fresh bulb is taken orally as an anti-inflammatory. The crushed bulb is also used as a poultice on inflamedjoints. In France it is used to treat allergies, arteriosclerosis, arthritis, asthma, urinary incontinence, bronchial diseases, acne, emphysema, hypertension and liver diseases. A hot water extract of fresh bulb has been taken in Yugoslavia for treating diabetes. In the West Indies extracts of the bulb are taken for hypertension and rubbed on the abdomen to facilitate parturition and in Africa it is used as an antibacterial for sore throats, infected wounds and boils. The essential oil is occasionally used as an antispasmodic, antimicrobial, diuretic, antiasthma tic and emmenagogue.
The bulb is used in fungal infections and swelling of the tongue, oral blisters and wounds, rheumatism, contagious abortion, tetanus, milky diarrhoea, abdominal pain, asthma, polyuria, sores, compound fracture, epilepsy and swelling of the kidney.
Allicin, mercaptan, ally methyl thiosulphinate, ally methyl trisulphide, ally propel disulphide, dually disulphide, dually heptasulphide, dually hexasulphide, dually pentasulphide, dually sulphide, diallyl tetrasulphide, diallyl trisulphide, dimethyl disulphide, methyl allyl thiosulphinate, S-allyl cysteine sulphoxide, and others.
Sativoside- B 1, proto-desgalactotigonin
Alanine, arginine, aspartic acid, asparagine, histidine, leucine, methionine, phenyl alanine, proline, serine, threonine, tryptophan, valine:
Citral, geraniol, linalool, (X- and j3-phellandrene, and others.
Calcium, phosphorus, iron, iodine, cobalt, copper, sodium, potassium, selenium and zinc.
P-Carotene, biotin, niacin, riboflavin, ascorbic acid, thiamin, folic acid and others
Kaempferol, quercetin, rutin.
?- L-glutam?l- S - meth?l- L-c?steine sulphoxide, ?-L-glutam?l-S-meth?l-L?c?steine, ?-L-glutam?l-S-all?l-L-c?steine, ?- L-glutam?l- L-phen?lalanine, ?-L-glutam?l-S-prop?lc?steine, ?-L-glutamyl- S -(2-carboxy- propyl) -cysteinyl-gly cine!
Immunomodulatory activity: Aged garlic extracts (AGE) have shown immunomodulatory activity in various experimental models. In the immunoglobulin (Ig)E-mediated allergic mouse model, AGE significantly decreased the antigen-specific ear swelling induced by picryl chloride ointment to the ear and intravenous administration of anti-trinitrophenyl antibody. In the transplanted carcinoma cell model, AGE significantly inhibited the growth of sarcoma-bearing mice. In a psychological stress model, AGE significantly prevented the decrease in spleen weight and restored the reduction of anti-SRBC haemolytic plaque forming cells caused by electrical stress. These studies suggest that AGE may be an immune modifier, maintaining the homeostasis of immune functions. Dially sulphide (OAS) showed chemopreventive effects at several organ sites in rodents after administration of chemical carcinogens, possibly by inhibiting carcinogen activation via cytochrome P450-mediated oxidative metabolism. It also exerted a protective effect on N -nitrosodimethylamine (NO MA)-induced immunosuppression of humoral and cellular responses in BALB/c mice. This effect may,at least in part, be due to its ability to block bioactivation of NOMA by the inhibition of cytochrome P450 2E1."
Antiageing activity: The Hayflick system of cellular ageing in culture method was adopted to evaluate garlic for its effects on long-term growth characteristics, morphology and macromolecular synthesis of human skin fibroblasts. The rejuvenating effects were demonstrated after the addition of garlic extract into a normal cell culture medium, which supported serial subculturing for over 55 population doublings in 475 days. This suggests anti ageing and other beneficial effects on human fibroblasts, in terms of the maximum fproliferative capacity and morphological f characteristics.
Hypolipidaemic activity: Rats fed with a sucrose-rich high-fat diet had a higher level of triglycerides and cholesterol in the serum, liver and kidneys. When the animals were given ethanol (instead of water) to drink, triglycerides and cholesterol levels in the liver and kidneys significantly increased although serum levels did not change significantly. However, when the sucrose-rich high-fat diet fed rats were given garlic extracts, these lipid levels were significantly reduced to almost the same extent in both cases. An ethanol and high-fat, high-cholesterol diet fed to rats markedly increased the total lipids in the liver and cholesterol and triglyceride levels in the serum, liver and kidneys. When ethanol was mixed with garlic oil (0.5%) and fed to these animals, lipid levels were significantly reduced to near those seen in untreated control rats. Garlic oil may enhance the catabolism of dietary cholesterol and fatty acids." In an experiment using female kid goats, the concentration of serum lipids and cholesterol in animals fed with cholesterol was increased but was lower in those fed with garlic. The involvement of fatty streaks and spots in the aorta was maximal in kids fed cholesterol alone but minimal in those fed with both cholesterol and garlic, indicating that garlic produced both hypocholesterolaemic and antiatherosclerotic effects in the goat.
Hepatoprotective activity: S-Allylmercaptocysteine (SAMC), a water-soluble organosulphur compound, was shown to protect mice against acetaminophen (APAP)-induced liver injury at a dose of 100 mg/kg (PO). When given 2 and 24 hours before APAP administration (500 mg/kg, PO) it suppressed the plasma alanine aminotransferase activity significantly. The mode of action was suggested to be the inhibition of cytochrome P450 2El activity. Pretreatment with SAMC also suppressed the increase in hepatic lipid peroxidation and the decrease in hepatic reduced coenzyme Q9 (CoQ9H2) levels, indicating another mechanism of action of SAMC may be its antioxidant activity.
Spennatogenic activity: A water extract of garlic was administered to male mice in drinking water (100 mg/kg/day) for 3 months. A significant increase in the weight of the seminal vesicles and epididymides, as compared to controls, was observed and the sperm count was significantly elevated.
Antibacterial activity: Garlic has long been recognised as a natural antibiotic and recent publications indicate that the extract has broad-spectrum antimicrobial activity against bacteria and fungi. Many of these are medically significant and garlic shows promise as a broad-spectrum therapeutic agent." Louis Pasteur was the first to describe its antibacterial effects. Garlic exhibits activity against both Gram-positive and Gram-negative bacteria and is effective against those strains that have become resistant to antibiotics. Resistance to garlic itself has not been seen. The raw juice was found to be effective against many common pathogenic bacteria-intestinal bacteria, which are responsible for diarrhoea in humans and animals. The combination of garlic with antibiotics leads to partial or total synergism. Helicobacter pylori, a bacterium implicated in the aetiology of stomach cancer and ulcers, is inhibited by garlic in vitro and the incidence of stomach cancer is lower in populations with a high intake of Allium vegetables. A study carried out to evaluate the antibacterial properties of garlic before and after heat treatment used test microorganisms including Escherichia coli, Salmonella typhimurium, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus, Mycobacterium phlei, Streptococcus faecalis, Bacillus cereus and Micrococcus luteus. Raw garlic bulb inhibited all of the test strains except the antibacterial activity within 20 minutes of heat treatment at 100?C. Allicin, one of the active principles of freshly crushed garlic, has a variety of antimicrobial activities. In the pure form it was found to exhibit antibacterial activity against a wide range of Gram-negative and Gram-positive bacteria, including multidrug resistant enterotoxicogenic strains of E. coli. It had antiviral and antifungal activity, particularly against Candida albicans, and antiparasitic activity against Entamoeba histolytica and Giardia Lamblia. These effects are thought to be mediated through reaction with the thiol groups of various enzymes, including alcohol dehydrogenase, thioredoxin reductase and RNA polymerase. These can affect essential metabolism of cysteine proteinase activity involved in the virulence of E. histolytica.
Antidermatophytic activity: The aqueous extract of garlic demonstrated activity against 88 clinical isolates of dermatophytes using an agar dilution technique. The isolates included Microsporum canis (50), M. audouinii (5), Trichophyton rubrum (6), T. mentagrophytes (5), T. violaceum (12), T. simii (5), T. verrucosum (1), T. erinacei (1) and Epidermophyton floccosum (2).
Antiviral activity: The in vitro antiviral activity of garlic extract (GE) on human cytomegalovirus (HCMV) was shown using tissue culture, plaque reduction and early antigen assay. A dose-dependent inhibitory effect was evident when applied simultaneously with HCMV and the effect was stronger when the mono layers werepretreated with GE. In addition, the antiviral effect persisted in infected cells long after the garlic was removed from the culture medium and was strongest when applied continuously. It was therefore suggested that clinical use of GE against HCMV infection should be long term and the prophylactic use of GE is recommended for immunocompromised patients.
Anticancer activity: Epidemiological and laboratory studies provide insight into the anticarcinogenic potential of garlic and its constituent compounds. Both water- and lipid-soluble allyl sulphur compounds are effective in blocking many chemically induced tumours, thought to be partly related to inhibition of nitrosamine formation and metabolism. However, blocking the initiation and promotion phas5 of various carcinogens, including polycyclic hydrocarbons, provides evidence that garlic and its constituents can affect several phase! and II enzymes. The ability to prevent experimentally induced tumours in a variety of sites, including the skin, mammary gland\ and colon, suggests a general mechanism of action. Changes in DNA repair and in immunocompetence may also account for some of this protection. Some allyl sulphur compounds can effectively retard tumour proliferation and induce apoptosis and changes in cellular thiol and phosphorylation stains may account for some of these properties. There is further evidence that organosulphur compounds, including diall1 sulphides, can inhibit the induction and growth of cancer and epidemiological studies? have suggested that consumption of garlic can decrease cancer incidence.25 The effect or pretreatment with DAS on experimental1y induced nuclear aberrations (NA) and ornithine decarboxylase (ODC) activity in rat glandular stomach mucosa was studied and a significant and dose-dependent inhibition was found for both, supporting the epidemiological evidence for the chemopreventive effect of garlic on gastric ulcer. A 50% aqueous extract of garlic significantly inhibited precancerous lesions of the oesophagus induced by N-methyl-N?amyl-nitrosamine, and increased the percentage of peripheral T-lymphocytes in rats. The results suggested a preventive action against carcinoma of the oesophagus, which could be attributed to increasing the immunity. Administration of garlic (250 mg/kg PO, three times a week) effectively suppressed 4-nitroquinoline I-oxide (4NQO)-induced tongue carcinogenesis in the rat, as revealed by an absence of carcinomas in the initiation phase and their reduced incidence in the postinitiation phase. These results suggest that garlic may exert its chemopreventive effects by modulating lipid peroxidation and enhancing the levels of reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione S-transferase (GST). Diallyl sulphide (DAS), at doses above 50 mg/kg administered 1 hour before 1,2-dimethylhydrazine (DMH) in male rats partially reduced the numbers of y-glutamyl trans peptidase and glutathione-S?transferase-P positive foci. In comparison, all doses of DAS (25-100 mg/kg) completely prevented liver necrosis by DMH (200 mg/kg), suggesting that low doses of DAS, which reduce DMH binding, appear more likely to inhibit hepatocarcinogenicity by reducing the promoting influences of postnecrotic regeneration rather than preventing initiation.29 The anti tumour activity of pure garlic oil against tumours of the cervix has also been demonstrated, in that treatment before and after insertion of a 3-methylcholanthranene thread in the uterus of rats led to a reduction of 22 % in cervical weight compared to the control Phorbol myristate acetate-induced tumour promotion was also inhibited by garlic oil in a dose?dependent manner.
Antimutagenic Activity: The acetone extract of garlic was tested in the Ames test against a variety of known mutagens and significant activity found, providing further evidence for the chemoprevention of cancer.32 An aqueous extract prepared from garlic bulbs also markedly suppressed both E. coliWP2 trp?and E. coliWP2 trp- uvrA-induced mutagenesis by 4-nitroquinoline I-oxide (4NQO), but not that induced by uv. It may be inactivating the electrophilic group(s) of 4NQO or inhibiting metabolic activation.
Antioxidant effects: Garlic is claimed to be effective against those diseases in which the pathophysiology of oxygen free radicals (OFRs) has been implicated, due to its ability to scavenge OFRs. Allicin produced concentration-dependent decreases in 2,3 and 2,5-dihydroxybenzoic acid (DHBA) generated by photolysis of hydrogen peroxide, by scavenging hydroxyl radicals, but not the formed hydroxyl adduct products. It also prevented lipid peroxidation in liver homogenates in a concentration?dependent manner. The results suggest that allicin has antioxidant activity. The effect of AGE on oxidant injury in bovine pulmonary artery endothelial cells was shown after overnight preincubation. AGE (1-4 mg/ml) pretreatment significantly prevented the loss of cell viability induced by hydrogen peroxide. Both AGE and s-allyl cysteine (SAC) exhibited dose-dependent inhibition of lactate dehydrogenase (LDH) release and lipid peroxidation (TBA-RS) production induced by hydrogen peroxide leading to the protection of vascular endothelial cells. Similar results were obtained on lipid peroxidation in mice liver homogenate, shown by a decrease in hyaluronic acid depolymerisation induced by oxygen and an inhibition of adenosine deaminase activity.'
Antiatherosclerotic activity: Garlic extract protected endothelial cells from oxidised LDL-induced injury in endothelial cells (EC), by preventing intracellular glutathione depletion and by minimising release of peroxides from endothelial cells and macrophages. This indicates a role in the prevention of atherosclerosis.
Diuretic activity: Intravenous administration of purified fractions of garlic to anaesthetised rabbits elicited a dose-dependent diuretic and natriuretic response. A gradual decrease in heart rate but not arterial blood pressure was observed. The electrocardiogram was not affected.
Antiplatelet activity: In a randomised, double-blind study of normal healthy individuals, the effect of AGE was evaluated in doses between 2.4 and 7.2 g/day vs. equal amounts of placebo. Adherence of platelets was inhibited by AGE in a dose-dependent manner when collagen was the adhesive surface. Adhesion to von Willebrand factor was reduced at 7.2 g/day AGE but adherence to fibrinogen was inhibited at all levels of supplementation. Thus, AGE appears to exert selective inhibition of platelet aggregation and adhesion, which are considered to be important in the development of cardiovascular events such as myocardial infarction and ischaemic stroke. Adenosine and guanosine, isolated from Allium sativum, showed a significant inhibitory activity against both primary and secondary aggregation of human platelets induced by 2 M AD P.The effects of aqueous extracts of raw and boiled garlic were studied in vitro on collagen-induced rabbit and human platelet aggregation. Boiled garlic was less effective than raw garlic.
Antihypertensive activity: Garlic juice inhibited contractions of isolated rabbit and guinea pi! aortic rings induced by norepinephrine and contractions of tracheal smooth muscles induced by acetylcholine and histamine. Furthermore, garlic juice inhibited the spontaneous movements of rabbit jejunum and guinea pig ileum and reduced the force of contraction of isolated rabbit heart in a concentration-dependent manner. These data suggest that the hypotensive action of garlic juice may be due, at least in part, to a direct relaxant effect on smooth muscles." An aqueous ethanol extract of garlic administered to conscious unrestrained rats showed antihypertensive activity.42
Larvicidal activity: The crude extract was effective against Aedes fluviatilis at 1 ppm concentrations.
Anthelmintic activity: Minced garlic at a concentration of 200 mg/l showed 100% anthelmintic activity in carp infested with Capillaria spp. The hexane extract in equivalent amounts showed a 75% effectiveness while the aqueous extract showed no anthelmintic effect. Ammonium potassium tartrate (1.5 mg/ml) used as a comparison gave 86% anthelmintic effectiveness.
The level of safety is reflected by its worldwide use as a food. Ingestion of fresh garlic bulbs, extracts or the oil may occasionally cause heartburn, nausea, vomiting and diarrhoea. LD50 measurements in animals were too high to be relevant.