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Journal of Medicinal Plants Studies 2016; 4(6): 72-79
ISSN 2320-3862
JMPS 2016; 4(6): 72-79
© 2016 JMPS
Received: 11-09-2016
Accepted: 12-10-2016
Dr. Md Khorshed Alam
Hakim Said Eastern Medical
College and Hospital, Dhaka,
Bangladesh
Dr. Md Obydul Hoq
Hakim Said Eastern Medical
College and Hospital, Dhaka,
Bangladesh
Dr. Md Shahab Uddin
Hakim Said Eastern Medical
College and Hospital, Dhaka,
Bangladesh
Correspondence
Dr. Md Khorshed Alam
Hakim Said Eastern Medical
College and Hospital, Dhaka,
Bangladesh
Medicinal plant Allium sativum = A Review
Dr. Md Khorshed Alam, Dr. Md Obydul Hoq and Dr. Md Shahab Uddin
Abstract
Garlic Allium sativum the Liliaceae family, is among the oldest of all cultivated plants. It has been used
as a medicinal agent for thousands of years. Garlic is one of the most important bulb vegetables, which is
used as spice and flavoring agent for foods Garlic adds to taste of foods as well as it helps to make them
digestible. Garlic contains different useful minerals, vitamins and many other substances used for health
of human beings. It is rich in sugar, protein, fat, calcium, potassium, phosphorous, sulfur, iodine fiber and
silicon in addition to vitamins. It possesses high nutritive value. Furthermore, garlic has pharmaceutical
effects and used to cure a vast conditions including blood pressure and cholesterol, cancer,
hepatoprotective, anthelmintics, anti-inflammatory, antioxidant, antifungal and wound healing, asthma,
arthritis, sciatica, lumbago, backache, bronchitis, chronic fever, tuberculosis, rhinitis, malaria, obstinate
skin disease including leprosy, leucoderma, discoloration of the skin and itches, indigestion, colic pain,
enlargement of spleen, piles, fistula, fracture of bone, gout, urinary diseases, diabetes, kidney stone,
anemia, jaundice, epilepsy, cataract and night blindness. Garlic products are used as sources of medicine
in many ways in human beings in their day today life. As a result, researchers from various disciplines
are now directing their efforts towards discovering the medicinal values of garlic on human health. The
main interest of researchers in the medicinal values of garlic is its broad-spectrum therapeutic effect with
minimal toxicity.
Keywords: Garlic, medicinal plant, allicin, antihypertensive, antidiabetic. antiatherosclerosis
1. Introduction
Garlic (Allium sativum) is among the oldest of all cultivated plants. It has been used as a spice,
food and folklore medicine for over 4000 years, and is the most widely researched medicinal
plant (Milner 1996) [35]. Codex Ebers, an Egyptian medical papyrus dating to about 1550 B.C.,
includes 22 therapeutic formulations that mention garlic as an effective remedy for a variety of
ailments including heart problems, headache, bites, worms and tumors (Block 1985) [8].
According to the Bible, the Jewish slaves in Egypt were fed garlic and other allium vegetables,
apparently to give them strength and to increase their productivity (Rivlin 2001) [48]. In ancient
Greece, garlic was consumed to treat intestinal and lung disorders (Farbman et al. 1993) [21]. In
India, garlic has been used for centuries as an antiseptic lotion for washing wounds and ulcers.
During World War II, garlic was used to treat the wounds of soldiers (Essman 1984) [18]. Many
workers have researched on garlic’s insecticidal, antimicrobial, antiprotozoal and antitumor
activities (Bolton et al; 1982) [9]. In traditional Chinese medicine, Islamic medicine, folklore
medicine and the Ayurvedic system of medicine, several spices and herbs including garlic are
described to possess medicinal properties e.g. anti-thrombotic, hypolipidemic and anti-
hypertensive (Makheja 1990 and Moyers 1996) [36, 37]. In the homeopathic system, garlic is
also an effective remedy for many ailments. In China, garlic tea has long been recommended
for fever, headache, cholera and dysentery. In rural Japan, miso-soup containing garlic is used
as a remedy for the common cold with headache, fever and sore throat (Sato et al. 2000) [53].
More recently, garlic has been reported to be effective in various ailments such as
cardiovascular diseases because of its ability to lower serum cholesterol (Bordia et al. 1977)
[10]. A component of garlic, S-methylcysteine sulfoxide (SMCS), has been shown to reduce
both blood cholesterol and the severity of atherosclerosis (Sainani et al. 1979) [54]. Garlic has
protective effects against stroke, coronary thrombosis, atherosclerosis, platelet aggregation, as
well as infections and vascular disorders. However, we must note that there is considerable
controversy concerning the cholesterol lowering effects of garlic and a number of studies have
reported that some garlic preparations do not lower serum cholesterol. The fibrinolytic activity
of garlic in both man and experimental animals has been reported.
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Journal of Medicinal Plants Studies
Many claims of an antibiotic action, a hypoglycemic effect,
antitumor, antioxidant and antithrombotic properties have also
been attributed to the garlic extracts (Alnaqeeb et al. 1992) [2].
2. Botanical Description
Other members of the onion genus, Allium, include A. cepa
(onion), A. schoenoprasum (chives), A. ascalonicum (shallots),
and A. porrum (leeks). Allium sativum is further divided into
two subspecies, A. sativum var. sativum, also known as
softneck garlic, and Allium sativum var. ophioscorodon, also
known as hardneck garlic. Both varieties are composed of an
underground bulb made up of cloves, which are prophylls
enclosed by dry membranous skins and held together by a
basal plate. The variations differ in that hard neck garlic’s bulb
is composed of six to eleven cloves, circled around a
centralized woody stalk. This variety of garlic has a scape that
curls at the top, but it is generally removed after it curls one to
three times. This is because if it continues to grow, less energy
can be utilized towards the bulb. Eventually, the scape would
give rise to bulbils, containing miniature cloves. The bulbils
are occasionally accompanied by white or light purple flowers,
although these are sterile. Softneck garlic does not have a
flowering top and contains up to twenty-four cloves per bulb.
The stem is central and soft, hence the name, and the cloves
are layered with larger ones on the outside. Allium sativum is
the more common variation, many studies involving garlic do
not specify which subspecies is used, but chemical and
biological action are assumed to be similar. Allium sativum is
sterile and hence is grown asexually from cloves, not requiring
a pollinator. It grows best in mild climates, through hardneck
varieties are better adapted to colder environments. Allium
sativum is a perennial species, as are most members of the
genus. Garlic is composed of very strong organosulfur
compounds that serve as secondary metabolites as described in
the section entitled chemistry and pharmacology. These
compounds are responsible for the very pungent smell and
taste of raw garlic and act as defenses against predators (Block
2010) [11].
2.1 Bulb
Rounded, composed of up to about 15 smaller bulblets known
as cloves. Cloves and bulbs are covered by a whitish or
pinkish tunic (papery coat).
2.2 Leaves
Four to twelve long, sword-shaped leaves attached to an
underground stem.
2.3 Flowers
Borne in a dense, spherical cluster on a spike (flower stalk) up
to 25 cm long. The young flower head is enclosed in a long-
beaked pair of enclosing bracts, which become papery and
split to reveal the flowers. Individual flower stalks arise from a
common point. Flowers are greenish-white or pinkish with six
perianth segments (sepals and petals) about 3 mm long.
Bulbils (asexual propagules), which resemble tiny cloves, are
often interspersed among the flowers.
2.4 Fruits
Flowers usually abort before developing to a stage at which
fertilisation could take place.
2.5 Seeds
Not usually produced in the wild but have been produced
under laboratory conditions. With a black coat, similar to
onion seeds, but approximately half the size.
3. Vernacular Names
Synonyms : Allium sativum L.
Sanskrit : Lasuna, Rosona, Yovanesta
English : Garlic, poorman’s treacle
Bangali : Rosun
Hindi : Lashan, lahsun
Arabic : Saun Taum
German : Knoblauch, Lauch
Greek : Allidion, Skorodon
Italian : Aglio
Chinese : Syun tauh
Urdu : Lehsun
Malayalam : Veluthulli.
4. Unani description:
Unani name : Lehsun, Fum, Thoum, Thum
Botanical name : Allium sativum L.
Synonyms : Allium sativum, Garlic, Saun Taum,
Lehsun, Lashan, lahsun.
Properties : Mizaj 3rd Order Warm and Dry
Maza : Bitter and acrid
Boo : Radio-active and acrid
Muzir : Mehrooreen (for persons with hot
temperament)
Mukhrij : Expels Balgham (Phlegm)
Nafa-e-Khas : Phlegmatic and stomach related
diseases.
5. Important formulations
Important Unani formulations containing Allium sativum are as
follows:
Garlic parls
Qurch Ziabetis
Sarbat Lahsun (B.N.U.F 2010)
6. Classification of Allium sativum
Kingdom : Plantae
Subkingdom : Tracheobionta
Superdivision : Spermatophyta
Division : Magnoliophyta
Class : Equisetopsida
Subclass : Magnoliidae
Superorder : Lilianae
Order : Asparagales
Family : Amaryllidaceae
Genus : Allium
7. Chemistry and Pharmacology
Sulfur compounds are the main chemical constituents
responsible for Allium sativum’s taste, smell, and likely for its
biological effects. When a garlic clove is intact, glutamyl
cysteins are the primary sulfur components (Powolyny and
Singh 2008) [47]. These are hydrolyzed to form alliin. When
garlic is crushed by chewing, chopping, etc., the alliin
promptly reacts with the enzyme alliinase to form allicin; after
30 seconds the reaction is 97% complete. Allicin is a diallyl
thiosulfinate that accounts for 70-80% of the thiosulfinates
present in Allium sativum (Harunobu et al. 2001) [23]. Allicin is
also highly unstable and quickly decomposes to yield sulfur
compounds when oxidized such as diallyl sulfide (DAS),
diallyl disulfide (DADS), diallyl trisulfide (DATS), ajoene,
and hydrogen sulfide (Banerjee and Maulik 2002) [12]. The
pathways of this reaction can be seen in Figure 1. DAS,
DADS, DATS and ajoene are all oil soluble (Miroddi et al.
2011) [38].
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Journal of Medicinal Plants Studies
Fig 1: Chemical structures of organ sulfur compounds involved in reactions with allicin. (Image source: Powolny and Singh 2008) [47].
8. Chemical Manipulation
When garlic is manipulated to produce alternate forms, the
unstable sulfur compounds react and hence alter active
chemical constituents. It is important to note that these
changes in chemistry can alter the bioavailability of the
compounds. Unfortunately, many studies do not specify the
actions taken, which could possibly account for
inconsistencies in reported data. Traditionally used in its raw
form, garlic is now often heated, dehydrated, and aged. Only
freshly crushed garlic has hydrogen sulfide, which is suspected
to have significant cardioprotective effects as a vasodilator
(Mukherjee et al. 2009) [39]. Garlic powder can be made
through dehydrating the plant with heat, but when high
temperatures are applied to garlic, alliinase is deactivated and
hence cannot react with alliin to form allicin (Tsai et al. 2011)
[59]. This explains why cooked garlic has a mellower flavor
than raw garlic. Powder can retain some allicin content if the
cloves are frozen before being pulverized; acetone removes the
water and alliin and alliinase remain separate yet intact until
water is added, at which point allicin is formed. While
dehydration during the powdering process does not destroy
alliinase like heat does, more than half of the alliin is lost.
While levels are lower than with raw garlic, dried garlic does
contain alliin and alliinase, as explained above. Alliinase is
deactivated by the acidic environment of the stomach
(Touloupakis and Ghanotakis 2011) [60]. Freeman and Kodera
(1995) [22] also came to this conclusion by exposing
dehydrated garlic powder to simulations of the gastrointestinal
fluids; allicin production decreased by 99%, presumably due to
the lack of allinase. This suggests that it could be beneficial to
further research the affects of dehydrated garlic powder when
taken in a capsule with an enteric coating to protect it from
stomach acid. These studies also show that manipulating
garlic’s form leads to changes in the active constituents and
could lead to data inconsistencies in studies.
Garlic can also be aged by soaking it in aqueous ethanol and
then extracting and concentrating essential compounds. When
allicin is dissolved in oils, the major compound in the final
product is S-Allylcystein (SAC) while ajoene, the most stable
component of garlic, is also present (Rahman 2002) [49].
Kodera et al. (2002) [29] suggest that SAC could pass through
the gastrointestinal tract without decomposing and
successfully be absorbed. Kodera et al. (2002) [29] also suggest
that SAC might be stable in blood, whereas allicin is unstable
in blood and cannot reach target organs via circulation
(Harunobu et al. 2001) [23].
9. Pharmacological activities
Due to its biological active component allicin and its
derivative, garlic has been used as a medicine to cure a wide
range of diseases and conditions related the heart and blood
system including high blood pressure, high cholesterol,
coronary heart disease, heart attack, and “hardening of the
arteries” (atherosclerosis) as pronounced (Mikaili et al. 2013)
[40].
Amagase (2006) [3] noticed out garlic is used to prevent
various types of cancer comprising colon cancer, rectal cancer,
stomach cancer, breast cancer, prostate cancer, prostate cancer
and bladder cancer, and lung cancer. It is also used to treat
Cardiovascular disease including: Antilipemic,
antihypertensive, anti-atherosclerotic, an enlarged prostate
(benign prostatic hyperplasia; BPH), diabetes, osteoarthritis,
hayfever (allergic rhinitis), traveler's diarrhea, high blood
pressure late in pregnancy (pre-eclampsia), cold and flu. It is
also used for building the immune system, preventing tick
bites, and preventing and treating bacterial and fungal
infections.
Furthermore, Pendbhaje et al. (2000) [46] listed out the
pharmaceutical activities of garlic. The plant is effective to
treat fever, coughs, headache, stomach ache, sinus congestion,
gout, rheumatism, hemorrhoids, asthma, bronchitis, shortness
of breath, low blood pressure, low blood sugar, high blood
sugar, and snakebites. It is also used for fighting stress and
fatigue, and maintaining healthy liver function. In addition to
this, Jung et al. (2000) [26] reported that garlic is also used to
promising effect against to asthma, arthritis, sciatica, lumbago,
backache, bronchitis, chronic fever, tuberculosis, rhinitis,
malaria, obstinate skin disease including leprosy, leucoderma,
discolouration of the skin and itches, indigestion, colic pain,
enlargement of spleen, piles, fistula, fracture of bone, gout,
urinary diseases, diabetes, kidney stone, anemia, jaundice,
epilepsy, cataract and night blindness. Garlic paly crucial role
in area of pharmaceutical and used for the treatment of
cardiovascular and other demise causing ailments including:
9.1 Antibacterial activity
Garlic is a broad spectrum antibiotic, killing a wide variety of
bacteria. Dr. Tariq Abdullah, a prominent garlic researcher
stated in the August 1987 issue of Prevention: “Garlic has the
broadest spectrum of any antimicrobial substance that we
know of — it is antibacterial, antifungal, antiparasitic,
antiprotozoan and antiviral.” This property belongs to the
garlic constituent allicin, which is released when you cut a
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Journal of Medicinal Plants Studies
garlic clove. This is the chemical that gives fresh garlic its
strong biting flavor, and you need to use fresh garlic to get a
reliable antibiotic effect. Garlic appears to have antibiotic
activity whether taken internally or applied topically.
Researchers found that the urine and blood serum of human
subjects taking garlic had activity against fungi (Caporaso et
al. 1983) [16].
9.2 Antiviral activity
Garlic and its sulfur constituents verified antiviral activity
against coxsackievirus species, herpes simplex virus types 1
and 2, influenza B, para-influenza virus type 3, vaccinia virus,
vesicular stomatitis virus, human immunodeficiency virus type
1 and human rhinovirus type 2. The order of compounds found
in garlic for virucidal activity was, ajoene > allicin > allyl
methyl thiosulfinate > methyl allyl thiosulfinate; no activity
was found for the polar fractions, alliin, deoxyalliin, diallyl
disulfide, or diallyl trisulfide. Several laboratory tests have
shown that garlic is an effectual treatment for both the
influenza B virus and herpes simplex virus. Two independent
researchers in Japan and Romania have found that garlic is
able to protect living organisms from the influenza virus (Tsai
et al., 1985) [61]. Most recently, a double blind placebo con-
trolled study has shown significant protection from the
common cold virus. As conducted by The Garlic Centre,
published in Advances in Therapy, this is the first serious
work to show prevention, treatment and reduction of re-
infection benefits from taking Allimax Powder capsules once
daily (Josling, 2001) [27].
9.3 Antifungal activity
Ajoene is an active compound found in garlic which plays a
great role as topical antifungal agent (Ledezma and Apitz-
Castro, 2006) [32]. Garlic has been shown to inhibit growth of
fungal diseases as equally as the drug ketoconazole, when
tested on the fungi Malassezia furfur, Candida albicans,
Aspergillus, Cryptococcus and other Candida species (Shams-
Ghahfarokhi et al., 2006) [56]. A report from a Chinese medical
journal delineates the use of intravenous garlic to treat a
potentially fatal and rare fungal infection of the brain called
Cryptococcus meningitis. In the report, the Chinese compared
the effec-tiveness of the garlic with standard medical treatment
which involved a very toxic antibiotic called Amphotericin-B.
The study revealed that, intravenous garlic was more effective
than the drug and was not toxic regardless of its dosage
(Lemar et al., 2007) [33].
A study found that Candida colonies were substantially
reduced in mice that had been treated using liquid garlic
extract. The study also revealed that garlic stimulated
phagocytic activity. This implies that infections such as
Candida may be controlled because garlic stimulates the
body’s own defenses. Garlic oil can be used to treat ring-
worm, skin parasites and warts if it is applied externally.
Lesions that were caused by skin fungi in rabbits and guinea
pigs were treated with external applications of garlic extract
and began to heal after seven days (Sabitha et al., 2005) [57].
9.4 Antiprotozoal activity
Garlic is effective in treating intestinal parasites has been
known for a long time. An extract of garlic was effective
against a host of protozoa such as Opalina ranarum, Opalina
dimidicita, Balantidium entozoon, Entamoeba histolytica,
Trypanosoma, Leishmania, Leptomonas and Crithidia (Reuter
et al, 1996) [50]. In addition, it was efficacious at killing wild-
type amoebae isolated from the diseased fish, slowing the
clinical signs of amoebic gill disease (AGD). However, it is
necessary to study the toxicity and pathological effect of garlic
on Atlantic salmon before using garlic to treat AGD in farmed
Atlantic salmon.
9.5 Antiparasitic activity
Many herbalists worldwide recommend garlic as a treat-ment
for intestinal parasites. In some cultures, children infested with
helminthes are treated with enemas containing crushed garlic.
One of the traditional Chinese medical treatments for intestinal
diseases is an alcoholic extract of crushed garlic cloves.
Allicin exhibits anti-parasitic activity against major human
intestinal parasites such as Entamoeba histolytica, Ascaris
lumbricoides and Giardia lamblia (Kalyesa et al., 1975) [75].
Entamoeba histolytica, the human intestinal protozoan
parasite, is very sensitive to allicin, as only 30 μg/ml of allicin
totally inhibits the growth of amoeba cultures (Mirelman et al.,
1987) [41]. Moreover, researchers have found that at lower
concentrations (5 μg/ml), allicin inhibited 90% the virulence of
trophozoites of E. histolytica as determined by their inability
to destroy mono-layers of tissue-cultured mammalian cells in
vitro (Ankri et al., 1997) [4].
9.6 Wound Healing activity
Successful wound healing depends upon angiogenesis, and
impaired angiogenesis is a hallmark of the chronic wounds
encountered with diabetes and venous or arterial insufficiency.
To intervene and improve wound closure, it is essential to
investigate the effects of different natural remedies in wound
healing. Study was done on the chicken dorsum skin excision
wound assay to investigate the influence of different
concentrations of aged garlic solution (AGS) on wound
healing. Gross, histopathology, scanning electron microscopy
(SEM) and computer-based three-dimensional (3D) image-
probing techniques were utilized to determine the effects of
AGS on wound closure, re-epithelialization, dermal matrix
regeneration and angiogenesis (Jalali et al. 2009) [24].
9.7 Anti- Diabetic activity
A number of animal studies support the effectiveness of garlic
in reducing blood glucose in streptozotocin-induced as well as
alloxan-induced diabetes mellitus in rats and mice. Most of the
studies showed that garlic can reduce blood glucose level in
diabetic mice rats and rabbits. One Iranian study evaluated oral
administration of garlic extract for 14 days on the level of
serum glucose, total cholesterol, triglycerides, urea, uric acid,
creatinine, in normal and streptozotocin-induced diabetic rats.
Administrations of the garlic extract significantly decreased
serum glucose, total cholesterol, triglycerides, urea, uric acid,
creatinine, aspartate amino transferase and alanine amino
transferase levels, while increased serum insulin in diabetic
rats but not in normal rats (p<0.05). Interestingly, a
comparison was made between the action of garlic extract and
glibenclamide, a well-known antidiabetic drug. The
antidiabetic effect of the garlic was more effective than that
observed with glibenclamide (Eidi et al. 2006) [19].
Unfortunately, the effect of garlic on humans with diabetes is
not well studied as is fraught with conflicting results (Zhang et
al. 2001) [65].
9.8 Antihypertensive activity
Garlic powder is used to cure hypertensive. According to
Silagy and Neil (1994) [55] garlic extracts has a significant
reduction in systolic blood pressure (SBP) and in diastolic
blood pressure (DBP) and act as anti-hypertensive.
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Journal of Medicinal Plants Studies
9.9 Anti-tumor Effects
Garlic extracts used as inhibition of cancer development in the
presence of known tumor promoters and Sulphurous
components present in garlic are believed to be liable to evade
the developing of cancerous cells in stomach, liver, and other
organs of human as described by Pendbhaje et al. (2000) [46].
9.10 Liver Protective/Detoxification Effects
It has been reported that aged Garlic Extract have liver
protective effects. It has demonstrated in vivo from the liver
toxins: carbon tetrachloride, paracetamol (acetaminophen) and
bromobenzene (Amagase 2000). It has been shown to inhibit
both the formation and bioactivation of liver carcinogenic
nitrosamines and has prevented the mutagenic effects of
aflatoxin B1as pronounced (Borek1998) [14].
9.11 Antioxidative and Radioprotective Effects
Borek (2001) [13] reported that aged garlic extract and its
various constituents have proven an array of antioxidant and
radio-protective effects in studies. They have been shown to
protect white blood cells from radiation damage, liver cells
from lipid peroxidation and vascular endothelial cells from
oxidant injury and enhance antioxidative enzyme systems in
cells. They have been shown to scavenge hydrogen peroxide,
to inhibit the formation of TBA-RS, to protect the heart from
cardiotoxic, anticancer drug doxorubicin, to protect the
kidneys from the antibiotic gentamicin as described by Oshiba
et al (1990) [43].
9.12 Diuretic and Digestive activity
IT has reported that garlic acts as a diuretic which helps to get
rid of body liquids. It may act as a
very useful resource in case of rheumatism, gout, arthritis,
hidropesia, edemas. It eases digestion by stimulating the liver,
the gall bladder and the pancreas although its use should be
avoided when existing hyperchloridia (stomach acidity) and
also when having frail stomachs (Eat it raw or crushed and
mixed with butter) (Ali 1995) [5].
9.13 Anti-cancer Activity
In looking at multiple studies, Powolny and Singh (2008) [47].
conclude that organosulfur compounds such as DAS, DADS,
and DATS act by arresting the cell cycle of cancerous cells.
Data from Miroddi et al. (2011) [28] and Omar and Al-Wabel
(2009) [44] support this, showing that these allyl derivatives act
as antioxidants and arrest the cell cycle. DATS was found to
have the most significant role by Powolny and Singh (2008)
[47], and is even a potential skin cancer fighting compound
(Wang et al. 2010) [62]. More specifically, garlic acts as anti-
inflammatory agent by altering cytokines and inhibiting NF-
kB activity in surrounding tissues (Keiss et al. 2003) [30]. In a
study using human promyeloleukemic cells, Dirsch et al.
(1998) [17] found that ajoene prompted apoptosis in cancerous
cells but not healthy ones; this might be due to peroxide
production. In an in-vitro study involving rats, Jastrzebsk et al.
(2007) [25] found that raw garlic had the strongest antioxidant
activity. Tsai et al. (2011) [59]. reviewed animal and cell studies
and found an inverse correlation between consumption of
garlic and presence of cancerous cells, suggesting it has
anticancer effects.
9.14 Cardio protective activity
Garlic is a popular supplement well-perceived as a healthy
choice among people looking to increase cardiovascular
wellness. Approximately 4% of all cardiovascular disease
patients and 30% of cardiovascular patients who use herbal
supplements take garlic (Yeh et al. 2006) [64]. Known risk
factors for cardiovascular disease include inflammation, high
cholesterol, high homocysteine, high blood pressure, diabetes
and dementia, including its most common form, Alzheimer's
disease. Indeed, as early as the 1920’s and 1930’s (Schlesinger
1926) [52], numerous studies do bear the beneficial
cardiovascular effects. Garlic is well reported to scavenge
oxidants, increase superoxide dismutase, catalase, glutathione
peroxidase, and glutathione levels, as well as inhibit lipid
peroxidation and inflammatory prostaglandins. Garlic also
reduces cholesterol synthesis by inhibiting 3-hydroxy-3-
methylglutaryl-CoA. Garlic has been shown to inhibit LDL
oxidation, platelet aggregation, arterial plaque formation,
decrease homocysteine, lower blood pressure, and increase
microcirculation, which is important in diabetes, where
microvascular changes increase heart disease and dementia
risks. Garlic may also help prevent cognitive decline by
protecting neurons from neurotoxicity and apoptosis, thereby
preventing ischemia- or reperfusion-related neuronal death and
by improving learning and memory retention (Borek 2006) [7].
Garlic may also possess anti-inflammatory abilities to suppress
the nuclear factor-kappa B activation pathway (Aggarwal et al.
2004) [1].
9.15 Alzheimer’ Disease Protective activity
Known for its neuroprotective abilities in vitro (Peng et al.
2002) [45], aged garlic has been looked to for multiple benefits
that some researchers believe may address a number of
underlying mechanisms which contribute to the classic
Alzheimer beta-amyloid plaque. According to one author,
garlic: “is expected to produce cumulative benefits and exhibit
enhanced neuroprotection by virtue of being “natural statin”,
“natural NSAID”, “natural anti-oxidant”, “natural anti-
apoptotic agent” and “memory enhancer”, a combination of
many single-ingredient synthetic pharmaceutical drugs
currently used for Alzheimer's therapy, only with least adverse
effects (Chauhan 2006) [15].” Unfortunately, there is a dearth of
clinical studies showing of aged garlic extract in relation to
Alzheimer's pathology, except for reports showing improved
behavior in senescence accelerated mice after garlic treatment
(Nishiyama et al. 2001) [42]. Given the multiple-mechanistic
possibilities and minimal risk associated with its use, garlic
seems a prudent recommendation for prevention and
treatment. Since aged garlic is best studied in relation to
Alzheimer’s it may be the best form to employ.
10. Dosage
A commercial garlic product should provide a daily dose equal
to at least 4000mg (one to two cloves) of fresh garlic. The
cloves may be diced and mixed with wildflower honey for
palatability. This dosage translates to at least 10mg alliin or a
total allicin potential of 4000ug (Murray et al. 2006) [34]. In
dried form this would be 300-mg of garlic powder tablet
(standardized to 1.3 percent alliin or 0.6 percent allicin yield)
two to three times per day, or 7.2 g of aged garlic extract per
day (Tattelman 2005) [58]. In tincture form from fresh bulb as a
1:2 in 95 % alcohol, the dosage can be 40 drops up to six times
per day.
11. Adverse effects of garlic
The main adverse effect commonly associated with garlic
intake is breath odor, especially when raw forms of the herb
are used. Nausea and vomiting are other major adverse effects
and care should be taken in consuming high quantities.
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Journal of Medicinal Plants Studies
Although an entire bulb produces little juice, it is potent and
can act as a strong emetic, even in small quantities. Although
garlic generally poses little in terms of safety issues, there are
isolated cases of topical garlic burns (Friedman et al., 2006) [20]
and anaphylaxis (Yin and Li, 2007) [63]. Rare garlic allergy has
been attributed to the protein allinase, which has induced
immunoglobulin E (IgE) mediated hypersensitivity responses
from skin prick testing (Kao et al., 2004) [28]. As a result, the
literature has generally cautioned against using garlic while
using anticoagulant therapy. There is a reported case of
spontaneous spinal or epidural hematoma in an 87 years old
man, with associated platelet dysfunction related to excessive
garlic ingestion (Saw et al., 2006) [51].
12. Conclusion
Garlic, from crushed to capsules, is consumed throughout the
world. This abstract demonstrates by documented studies the
benefits of garlic for its anti-microbial, antioxidant and anti-
inflammatory potential. It has been used to treat cardiovascular
diseases, including atherosclerosis, strokes, hypertension,
thrombosis and hyperlipidemias, as well as uses in
Alzheimer’s, diabetes, and cancer. Most impressive and
unique are its use and safety in children. Although some
studies show medicinal benefits of garlic, there are others
which do not. Clearly more studies are needed. Fresh and
powdered garlic are popular for food seasoning and should
continue to be used. Today, with the ever-growing resistant
organisms, garlic, taken alone or with other herbal antibiotics
such as grape seed extract or ginger, remains a powerful
antimicrobial agent. Clearly more studies are needed to refine
the use and improve the efficacy of this important plant
medicine.
13. Acknowledgements
The authors acknowledge the inspired provided by Dr. Alhaj
Hakim Md. Yousuf Harun Bhuyan, honorable chief
mutaowalli & managing director, Hamdard Laboratories
(Waqf) Bangladesh, Kazi Mansur-Ul-Huq, Honorable
Chairman, Managing Committee, Hakim Said Eastern Medical
College & Hospital and Director Information and Public
Relation - Hamdard Bangladesh and Lt. Colonel Mahbubul
Alam Chowdhury (Ret:), Honorable Director, Hamdard
Foundation Bangladesh, for the preparation of this manuscript.
14. Conflicts of Interest
The authors declare no conflict of interests.
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