GARLIC
Garlic is among the oldest of the cultivated plants. Additionally, it has been
shown to have applications as antimicrobial, antithrombotic, antitumour,
hypolipidemic, antiarthritic and hypoglycaemic agents.21
Garlic has been used since the days of the Egyptians to treat wounds, infections,tumors, and intestinal parasites.
TRADITIONAL USE
In China, garlic is called da-suan. The first record of medicinal use in China comes in Tao Hong-Jing's Ming Yi Bei Lu
(Miscelhneous Records of Famous Physicians), written around 510 A.D. In China, the use of garlic has remained
essentially the same over the centuries - one of the best known treatments for dysentery caused by
microorganisms. In Thailand, the bulbs are used as a first line of treatment for skin diseases, as well as for cough, lung microorganisms, in l naiianci.tneouiDs are used as a Tirst line OT treatment Tor:abscesses, and other conditions.
In India, garlic is considered a powerful natural disinfectant. It is used as ar
antibacterial in intestinal disorders as well as a number of infectious diseases
Based on traditional use of garlic, the driving force behind modern garlic use is largely based on cultural needs. In Western cultures, garlic is used for the
prevention of disease conditions more typical of industrialized developec
societies, especially cardiovascular health and antimicrobial activity. It;
antibacterial activity was first recognized in an 1858 study by the Frenci-
microbioloeist Louis Pasteur.
LATEST SCIENCE
Garlic contains many elements and compounds including vitamins A and C, potassium, phosphorus, sulfu
(including 75 different sulfur compounds), selenium and a number of amino acids. Among the most important ofth*
compounds seems to be allicin, a sulfur-containing compound (formed when garlic is cut or crushed). It's allicin tha
gives garlic its characteristic pungent aroma and flavor. Garlic's close relatives, onions and leeks, contain simila
sulfur compounds and are also being studied for possible health benefits.
Well-documented health benefits include reducing blood lipids, such as cholesterol; reducing blood pressure
improving circulation; and helping to prevent yeast infections, colds, and flu. Other documented benefits includi
antibacterial, antifungal, antiparasitic, antioxidant, anti-inflammatory, and immunostimulant properties.
THERAPEUTIC ACTIONS OF GARLIC CONSTITUENTS
Most studies on garlic during the past 15 years have been primarily in the fields of cardiovascular and cancer
research.
A ~ USE OF GARLIC IN CARDIOVASCULAR DISEASE
i ) Atherosclerosis:
Cardiovascular studies have been mainly related to atherosclerosis, where effects were examined on serum
cholesterol, LDL, HDL, and triglycerides. Most findings suggest that garlic decreases cholesterol and triglyceride
levels in patients with increased levels of these lipids. Lowering of serum lipids bygarlic ingestion may decrease the
atherosclerosis process.
Garlic indirectly effects atherosclerosis by reduction of hyperlipidemia, hypertension, and probably diabetes
mellitus and prevents thrombus formation. In addition, in animal models, garlic causes direct antiatherogenic
(preventive) and antiatherosclerotic (causing regression) effects at the level of the artery wall."
Garlic's direct effect on atherosclerosis may be
explained by its capacity to reduce lipid content in
arterial cells and to prevent intracellular lipid
accumulation. The effect, in turn, is accompanied by
other atherosclerotic manifestations, i.e.
stimulation of cell proliferation and extracellular
matrix synthesis."
Meta analysis of the controlled trials of garlic tc
reduce hypercholesterolemia showed a significant
reduction in total cholesterol levels. The best
available evidence suggests that garlic, in an amount
approximating one half to one clove per day
decreased total serum cholesterol levels by about 9% in the groups of patients studied."
ii ) Antithrombotic properties
Garlic extracts and several garlic constituents demonstrate significant antithrombotic actions both in vitro and ii
vivo systems. The three main antipalatelet constituents in garlic are adenosine, allicin and paraffinic polysulfides
Adenosine and allicin inhibit platelet aggregation without affecting cyclooxygenase and lipoxygenase metabolites o
arachidonic acid. The trisulfides inhibit platelet aggregation as \well as thromboxane synthesis along with th<
induction of new lipoxygenase metabolites.
In addition to the antiplatelet activity, Garlic has also been found to have fibrinolytic properties. Both these activities
of Garlic make it an ideal agent in the treatment ofcardiovascular disorders."
iii ) Role in hypertension
Epidemiological studies have suggested that garlic may have protective effects against cardiovascular diseases.
Results of various clinical trials suggest that this garlic powder preparation may be of some clinical use in subjects
with mild hypertension.26 Clinical data strongly support the hypothesis that garlic intake has a protective effect on
the elastic properties of the aorta related to aging in humans thus helping in the maintenance of blood pressure."
Studies have also demonstrated the role of garlic in inhibiting the ACE enzyme for lowering the blood pressure.
iv ) Role in ischaemia and reperfusion
I Leukotriene c, LTC, and prostaglandin E, PGE,) are known to be highly potent cerebral
vasoconstrictors which are formed from arachidonic acid (AA). They enhance vascular
permeability, inducing vasogenic edema that may damage the ischemic penumbra after
ischemia and reperfusion.
Garlic extract reduces LTC, and PGE, levels following 8 and 60 min reperfusion. It may be
helpful in reducing AAmetabolite levels and preventing injury after ischemic phenomena."
Due to its antiathrogenic, antiplatelet and fibrinolytic activity, garlic has an important role in the
prevention of ischaemia.
v) Role in peripheral occlusive disease
In patients with peripheral vascular disease garlic increases the walking distance. The diastolic blood pressure,
spontaneous thrombocyte aggregation, plasma viscosity, and cholesterol concentration also decreases significantly.
Therefore, garlic may be an appropriate agent especially for the long-term treatment of an incipient intermittent
claudication.29
B ) GARLIC AS AN ANTIMICROBIAL AGENT
Garlic has antibacterial, antiviral and antifungal activity. It may work against some
intestinal parasites. Allicin, one of the active components of garlic, is found to
exhibit antibacterial activity against a wide range of Gram negative and Gram
positive bacteria, including multi-drug resistant enterotoxicogenic strains of
Escherichia coli. Garlic has been found to be bactericidal for major bacterial
pathogens of acute otitis media." It has an antifungal activity, particularly against
Candida albicans. Garlic is found to have greater anticandidal activity than
nyastatin."
Garlic has an antiparasitic activity against some major human intestinal protozoans parasites such as Entameoba
histolytica and Giardia lambia and antiviral activity. The main antimicrobial effect of allicin is due to its chemical
reaction with the thiol groups of various enzymes, e.g. alcohol reductase and RNA polymerase, which can affect
essential metabolism ofcysteine proteinase activity involved in the virulence of E.histolytica."
C ) ROLE OF GARLIC INIMMUNE FUNCTION AND CANCER
Garlic components are known to modulate certain immune functions. Garlic is reported to stimulate immunity,
including macrophage activity, natural killer and killer cells, and LAK cells, and to increase the production of IL-2,
TNF, and interferon-gamma. These cytokines are associated with the beneficial Th I antitumor response, which is
characteristic of effective cancer immunotherapies. Garlic stimulates the proliferation of macrophages and
lymphocytes and protects against the suppression of immunity by chemotherapy and ultraviolet radiation. Garlic is
clearly not a panacea for cancer, but its broad range of beneficial effects are worthy of serious consideration in
clinical trials forthe prevention and treatment of cancer."
It has been well documented that natural organosulfur compounds derived from plants such as garlic, possess
antiproliferative properties. Garlic is known to induce the differentiation and apoptosis of BCG-823 cells (the
human gastric cancer cell line)." Garlic contains several potentially important agents that possess antitumour and
anticarcinogenic properties.
In summary, the epidemiological, clinical and laboratory data have proved that garlic contains many
pharmacologically important compounds which are beneficial to human health from neoplastic diseases." Studies
document that diallyl disulphide, a constituent of garlic oil is an effective inhibitor of the growth of human neoplastic
cells. Alterations in the calcium haemostasis are likely involved in the growth inhibition / cytotoxicity caused by
diallyl disulphide.
D ) GARLIC AS AN ANTIOXIDANT
Garlic has been claimed to be effective against diseases, in the
pathophysiology of which oxygen free radicals (OFRs) have been implicated.
Effectiveness of garlic could be due to its ability to scavenge OFRs.)6 Oxygen
radical injury and lipid peroxidation have been suggested as major causes of
cancer, atherosclerosis and the aging process.)7
Sulfur containing constituents of garlic are considered responsible for
conveying the antioxidative properties of garlic preparations. Garlic extract
also reduces levels of NO and peroxides in macrophages. These data
suggest that garlic is a useful protective agent against cytotoxicity associated
with oxidized LDL and nitric oxide, and it may thus be useful for the prevention of atherosderosis and
cardiovascular diseases. Because garlic has been reported to beneficially affect serum lipid levels, platelet function,
fibrinolysis and blood pressure, this additional effect of retarding lipoprotein oxidation may contribute to the
potential antiatherosclerotic effect of garlic. Experimental results suggest that alliin metabolite allicin may be
responsible for the oxygen radical scavenging properties of garlic."
In summary, the epidemiological, clinical and laboratory data have proved that garlic contains many biologically anc
pharmacologically important compounds, which are beneficial to human health from cardiovascular, neoplastic anc
several other diseases. Presence of enzyme inhibitors such as adenosine deaminase and cyclic AMF
phosphodiesterase in garlic extracts may explain several clinical effects in the body including the antithrombotic
vasodilatory and anticancer actions. Epidemiological studies have suggested that garlic plays a significant role in the
reduction of deaths caused by malignant diseases.