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This study reviewed the medicinal properties of ginger and garlic. Ginger and garlic are commonly used spices which are important in medicine due to the presence of many important phytochemical constituents and nutrients which are biologically active substances. Some chemical constituents of these medicinal plants have been reported in various literatures to contribute to the prevention and treatment of various diseases and ailments. In literatures, some of the documented properties of garlic and/or ginger include antioxidant, anti-inflammatory, rheumatologic, blood circulation and anti-cramp, anti-ulcer, anticholinergic, analgesic, antimicrobial, anti-stress, anti-cancer, immunity booster, anti-diabetic, regulation of blood pressure and treatment of cardiovascular diseases. The use of these medicinal plant materials will aid the promotion of human health system.
Keywords: Antioxidant; Diseases; Folk medicine; Garlic; Ginger; Phytochemical; Spices
Plants have been reported to have very great potential for the treatment and management of some disease conditions. Many plants have been used by tribal and folklore: in different countries for the treatment of various diseases . The medicinal value of plants lies in their bioactive phytochemical constituents. Aside from the primary use of spices as organoleptic enhancers in food preparation, they are increasingly finding other useful roles in animal health care. Currently, many spices and herbs are being investigated for their potential effects in health care. In literatures, there exist many reported findings on medicinal properties of certain spices. The rise in interest on medicinal properties of herbs and spices is consequent on the failing efficacy and toxicity associated with conventional drugs and their inaccessibility to poor rural dwellers or low-income earners. For a long time, there has been a resurgence of interest in the investigation of natural materials as a source of potential drug substance . This study reviewed two important spices: ginger (Zingiber officinale) and garlic (Allium sativum) common in the culinary of Nigeria and many countries, highlighting some of their reported medicinal properties. Several peer-reviewed articles were consulted for this purpose.
Ginger (Zingiber officinale) belongs to Zingiberaceae family. It is a flowering plant whose rhizome or root is commonly used in folk medicine and as a spice. Ginger is reported to originate from the tropical rainforests of the Indian subcontinent to Southern Asia where ginger plants show some genetic variation . Ginger is widely cultivated all over many countries such as
Nigeria, Taiwan, India, Jamaica and Bangladesh. It is reported to grow in warm climates . Ginger has been reported as one of the wildly used herbs in traditional medicine in many countries . The Chinese have used ginger for many years as a digestive aid and remedy for nausea, and to treat disorders such as rheumatism and bleeding. It was reported to have been used to treat baldness, snakebite, toothache and respiratory conditions . Ginger is considered an aphrodisiac in Arabian medicine , while some Africans believe that eating ginger regularly will aid repel mosquitos .
The oil from ginger is believed to be very medicinal. The major active ingredients in ginger oil are reported to be the sesquiterpenes, which include bisapolene, zingiberol and zingiberene . The concentrations of the active ingredients vary with growing conditions of the ginger. Ginger is used
worldwide as a cooking spice, condiment and herbal remedy.
The rhizome of ginger plant (Figure 1) has has been used as a
spice since several years across the globe.
Many studies reported several medicinal properties of ginger,
which include the following:
Anti-ulcer and anticholinergic: Ginger acts and protect
gastric mucosa against several ulcerogenic agents and is very
useful in cases of ulcerogenesis because of its antioxidant
properties [9,10]. This has both many benefits and drawbacks,
because prostaglandin has been shown to have a housekeeping
and gastro-protective function by maintaining gastric mucosal
integrity [7,11,12]. Ginger shows strong antiemetic property
by enhancing intestinal motility and inhibiting serotonin
receptors. Ginger was reported to stimulate the peripheral
anti-cholinergic and anti-histaminic receptors and antagonize
5-hydroxytreptamine receptors in the GIT [9,10].
Antioxidant, anti-inflammatory and rheumatologic
properties: Ginger was reported to show anti-inflammatory
effect through the suppression of PG synthesis and also to have
interference in cytokine signaling [6,13]. Several studies have
reported that the oil extracted from ginger had scavenging effects
due to volatile oils [6,14]. Ginger is a powerful antineoplastic
agent. In some studies, extracts of ginger suppressed cell
proliferations and also acted against resistance of cancerous
cells [15,14]. Ginger is known to exhibit a powerful antioxidant
activity due to its oil which has protective effect on DNA. This
effect has been demonstrated in some cell culture . Ginger
has preventive effect on lipid peroxidation and also inhibits or
breaks its chain [5,6,17]. Ginger modulates genetic pathway, acts
on tumor suppression of genes and modulates some biological
activities [6,12,18]. Gingerols and Paradol have been reported
to have good anti-platelet and COX-I inhibitory properties .
It was also reported that ginger exerts its anti-inflammatory
effects by the mechanisms which explain the role of inhibition
of pre-inflammatory factor like prostaglandin and leukotriene
biosynthesis which may reduce pain associated with rheumatoid
and osteoarthritis. In history, it has been proven to be used for
the treatment of rheumatic conditions [6,5,18].
Analgesic effect: Gingerols, which are the key ingredients
responsible for the activity of ginger have shown important
pharmacological effect. It is used to treat nausea after surgery
and same has been proved in several randomized clinical trials.
This effect is reported to be seen due to its action on the 5-HT3
receptor [11,20,21]. Ginger is used for the treatment of headache
and also have good effect on reducing symptoms of pain.
This effect is believed to be due to reduction in prostaglandin
synthesis. It has also been reported that ginger help to suppress
leukotriene biosynthesis by inhibiting 5-lipoxyganse .
Blood circulation and anti-cramp effects: Ginger has been
discovered to enhance blood circulation throughout the body by
stimulating the heart muscles and by diluting circulating blood.
This enhances cellular metabolism and aids to relieve certain
conditions such as cramp and tension [22,16]. The powerful
anti-inflammatory action on prostaglandin synthesis also help
in relieving menstrual cramps .
Cholesterol regulation and hypotensive properties:
Ginger extracts interferes with the biosynthesis of cholesterol,
thereby leading to decreasing cholesterol levels in animals.
Ginger extracts have antilipidemic effects, by reducing
thermogenesis and high lipids levels. They also help to increase
serum HDL-cholesterol . Ginger is very effective in lowering
blood glucose level when taken in dried form. It also decreases
triglyceride level. Long term usage has been reported to aid the
increase of high-density lipoprotein cholesterol concentrations
[5,25]. There is a study which proved the hypotensive effect of
ginger when it was given at 0.3-3 mg/kg. It aids the reduction of
atrial blood pressure by blocking calcium channel or by acting
on muscarinic receptor . Studies have suggested that ginger
may improve insulin sensitivity in body. The mineral elements
contained in ginger makes it effective for this same purpose .
Antimicrobial effects: Due to the presence of some phenolic
compounds in it, ginger has shown great antimicrobial activities
and effectiveness in controlling certain viral, bacterial and fungal
diseases. Ginger is used in many countries for the preservation of
foods . Ginger acts as anti-parasitic. Some studies reported
the in vivo potential of methanolic extract of Zingiber officinale
in the treatment of trypanosomiasis [12,14,23,26]. Gingerols
and Gingerdiol are the main anti-fungal principles, and extract
of ginger powder is effective against several antifungal diseases
. Ginger has shown antiviral effect; however, more published
literature is needed to prove this efficacy [18,28]. Ginger is
reported to be effective in management of hepatitis C virus
infection where viral clearance is affected [16,23,29]. Ginger
has also been reported to have shown good antimicrobial effect
against both Gram positive and negative bacteria; however,
severally, this effect is reduced due to heating [18,23].
Garlic (Allium sativum) is among the oldest of all cultivated
medicinal plants. It has been used as a spice, food and folklore
medicine for many years, and has been widely researched
as a medicinal plant. Garlic is a species in the onion genus,
Allium. Its close relatives include the onion, shallot and leek.
Garlic is native to Central Asia and north-eastern Iran, and
has long been a common seasoning worldwide, with a history
of many years of human consumption and use . The early
Egyptians were reported to have used garlic to treat diarrhea
and its medical power was described on the walls of ancient
temples . In Africa, particularly in Nigeria, it is used to treat
certain conditions such as abdominal discomfort, diarrhea and respiratory tract infections . In India and Europe, it was used
to treat asthma, common colds and hay fever. It was well known
to ancient people and has been used both as a food flavouring
and as a traditional medicine. The process of cooking garlic has
been reported to remove allicin, thus mellowing its spiciness
. Allicin, along with its decomposition products: diallyl
disulfide and diallyl trisulfide, are reported to be the major
contributors to the characteristic odour of garlic, with other
allicin-derived compounds, such as vinyldithiins and ajoene
. Out of the many medicinal plants, garlic (Figure 2) has
an antimicrobial property which protects the host from other
pathogens, highlighting the importance of search for natural
antimicrobial drugs .
Antioxidant, anti-inflammatory and anti-stress
properties: Whole garlic and aged garlic extract have been
reported to exhibit direct antioxidant effects and to enhance
the serum levels of two antioxidant enzymes: catalase and
glutathione peroxidase . According to Torok et al. ,
garlic (both the homogenate of 10% in physiological saline
solution and its supernatant) was able to reduce the radicals
present in cigarette smoke. It was also hypothesized that garlic
organo-sulfur compounds may be able to prevent depletion
of glutathione. Garlic ingestion may protect patients who
experience increase in reactive oxygen induced stress on liver
function . In a research, Morihara et al.  reported that
rats that were trained with endurance exercises to physical
fatigue enjoyed improved parameters of aerobic glucose
metabolism, attenuated oxidative stress, and vasodilation, when
given garlic at a dosage of 2.86g/kg for 30 min before exercise.
Given the extreme chronic stress many people now face in their
daily life, garlic may prove usefulness in countering the negative
impact of this stress on human physiology .
Anti-cancer properties: Many epidemiological, clinical
and laboratory research studies have demonstrated that garlic
has a great role in prevention of cancer, especially in relation
to digestive tract cancers. A Dutch research in the Netherlands
cohort study found a significant decrease in the development of
stomach cancer in those consuming garlic . Regular intake
of garlic reduced the risk of esophageal, stomach and colon
cancer in a human population study. This was believed to be
due to the antioxidant effect of allicin in reducing the formation
of carcinogenic compounds in the gastrointestinal tract .
Garlic was reported to reduce the risk of patients with prostate
cancer, especially those with localized disease. The reduced
risk of prostate cancer was independent of body size, intake of
other foods and total calorie intake and was more pronounced
for men with localized prostate cancer than with advanced
prostate cancer . Prostate specific antigen serum markers
were reported to significantly decreased during short term
ingestion but returned to baseline after 4 weeks. Steinmetz et
al.  reported that, for cancers anywhere in the colon, the
modest consumption of one or more servings of garlic (fresh or
powdered) per week resulted in a 35% lower risk, while a 50%
lower risk was found for cancer of the distal colon.
Treatment of cardiovascular disease: The relevant role
of garlic in coronary heart disease was carried out on rabbits
and found that even pre-existing athero-sclerotic deposits
and lesions could actually be reversed if garlic is consistently
consumed . From a study conducted in India, 432 coronary
artery disease patients were randomly grouped into two groups,
and half of them were supplied with garlic juice in milk, whereas
the other group of patients were not supplied with garlic juice.
The result of the study showed that within the three years of the
study time, nearly twice as many patients had died in the group
not supplied with garlic juice . This, therefore, shows garlic
could be effective in management of certain cardiovascular
Reduction of Atherosclerosis and hyperlipidaemia: In vitro
studies have clearly shown that garlic has an ability to suppress
low density lipoprotein (LDL) and an increased resistance
of LDL to oxidation . After 60 days of supplementation in
a study, the concentrations of low-density lipoprotein, serum
triglyceride and very low-density lipoprotein were reduced by
21, 37, and 36.7%, respectively .
Anti-diabetic property: Reports from some animal studies
support the effectiveness of garlic in reducing blood glucose
in streptozotocin-induced, as well as alloxan-induced diabetes
mellitus in mice. Ohaeri  reported that garlic can reduce
blood glucose level in diabetic mice and rabbits. From a
comparative study made between the action of garlic extract and
glibenclamide, it was reported that the antidiabetic effect of the
garlic was more effective than the glibenclamide .
Immunity booster: Garlic is reported to possess abundant
sulfur containing amino acids and other compounds that seem to
initiate increased activity in the immune system . It is one of
the impressive conductors of the body’s immune system; which
stimulates immune function by making macrophages or killer
cells more active. Supplemental nutrients like garlic is reported by Salman et al.  to be clearly needed to aid the reduction
or the relieve of some enormous pressures, which our immune
systems sustain, often caused by inadequate nutrition, cigarette
smoke, physical injury, mental tension and chemical pollution.
Its remarkable content of germanium alone offers excellent
immune stimulation. In addition to germanium, garlic has
been reported to contain thiamine, selenium, sulfur, niacin and
phosphorous . These help in boosting the immune system.
Regulation of blood pressure: Capraz et al.  documented
that garlic has probably been the most popularized spice as
a complementary therapy for blood pressure control. An in
vitro study has confirmed the vasoactive ability of garlic sulfur
compounds whereby red blood cells converts garlicorganic
polysulfides into hydrogen sulfide, which is a known endogenous
cardio-protective vascular cell signaling molecule .
Analgesic effect: A double-blind placebo-controlled research
survey using a 100% allicin yielding supplement has reported
that allicin has the ability to reduce the occurrence of common
cold and enhanced recovery from the symptoms .
Antimicrobial effects: The antimicrobial properties of
garlic are reported to be first described by Pasteur in 1958,
and since then, many research studies have demonstrated its
effectiveness and broad-spectrum antimicrobial activity against
many species of bacteria, parasites, viruses, protozoan and fungi
. Garlic is more effective with least side effects as compared
to commercial antibiotics; as a result, it is reported to be used
as an alternative remedy for treatment of various infections.
Previously conducted researches confirmed that garlic is not
only effective against Gram-positive and Gram-negative bacteria
but also possess antiviral and antifungal activities . Ajoene
is an active compound found in garlic and has been reported
to play a great role as topical antifungal agent . In another
study, garlic was reported to inhibit the growth of certain fungal
diseases as equally as the drug ketoconazole, when tested
on the fungi Malassezia furfur, Candida albicans, Aspergillus,
Cryptococcus and other Candida species .
Garlic oil may be used for the treatment of ringworm, skin
parasites and warts if it is applied externally. In a study, 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 . Allicin exhibits antiparasitic
activity against some major human intestinal parasites such
as Entamoeba histolytica, Ascaris lumbricoides and Giardia
lamblia . Entamoeba histolytica, which is the human
intestinal protozoan parasite, is reported to be very sensitive
to allicin, as only 30μg/ml of allicin totally inhibits the growth
of amoeba cultures . Some researchers have discovered
that at lower concentrations (5μg/ml), allicin inhibited 90%
of the virulence of trophozoites of E. histolytica as determined
by their inability to destroy mono-layers of tissue-cultured
mammalian cells in vitro . Garlic is also reported to be very
active against microorganisms that are resistant to antibiotics
and the combination of garlic extracts with antibiotics have
been documented to lead to partial and total synergism. Garlic
is also an alternative agent used for treating methicillin resistant
Staphylococcus aureus [63-65].
There are several evidences from literatures on the medicinal
properties of ginger and garlic. Apart from their appreciable
roles in nutrition, they have been reported to possess several
medicinal properties such as antioxidant, anti-inflammatory,
rheumatologic, blood circulation booster, anti-cramp, anti-ulcer,
anticholinergic, analgesic, antimicrobial, anti-stress, anti-cancer,
immunity booster and anti-diabetic. They also play vital roles
in regulation of blood pressure and treatment of cardiovascular
diseases. The use of these medicinal plant materials will aid the
promotion of human health system.