Editor’s Note: Each month, HerbalEGram highlights a conventional food and
briefly explores its history, traditional uses, nutritional profile, and modern
medicinal research. We also feature a nutritious recipe for an easy-to-prepare
dish with each article to encourage readers to experience the extensive
benefits of these whole foods. With this series, we hope our readers will gain
a new appreciation for the foods they see at the supermarket and frequently
include in their diets.
The basic materials for this series were compiled
by dietetic interns from Texas State University in San Marcos and the
University of Texas at Austin through the American Botanical Council’s (ABC’s)
Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Perez, ABC Special
Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner,
PhD, for their contributions to this project.
By Hannah
Baumana and Maegan Davisb
a HerbalGram Associate Editor
b ABC Dietetics
Intern (Texas State, 2016)
Overview
West Indian
lemongrass (Cymbopogon citratus,
Poaceae) is an aromatic tropical perennial with long, slender, light green
leaves that grow in groups with bulbous and fibrous stems at the base of the
plant.1-3 The grass can grow from two to six feet tall, and its
leaves are approximately one inch wide with slightly toothed, saw-like margins.2
West Indian lemongrass likely originated from India, Malaysia, or Sri Lanka.1,2,4,5 It is now cultivated in tropical and subtropical countries.4 The
largest exporter of lemongrass leaves and stalks is Guatemala,5
while India is the largest producer of lemongrass essential oil, 80% of which
is exported annually.6 Lemongrass grows well in warm and humid areas
with plenty of sunshine and moisture.4 The leaves and fleshy part of
the stem are used for flavoring teas and broths in many Asian cuisines, and its
essential oil is used in cosmetics and food preservation.1-3
Phytochemicals and Constituents
West
Indian lemongrass contains an array of electrolytes and minerals, including
potassium, sodium, calcium, copper, magnesium, manganese, selenium, phosphorus,
iron, and zinc. It also contains vitamin C, as well as the B vitamins niacin,
pyridoxine, riboflavin, and folate.3 It has high carbohydrate
content, and its leaves are high in crude fiber.4
The
bioactive compounds in lemongrass include saponins, tannins, flavonoids,
phenols, and alkaloids, as well as its essential or volatile oil compounds: monoterpenes
and sesquiterpenes, including aldehydes, alcohols, and esters.7 The
essential oil has shown antimicrobial, anti-inflammatory, cytotoxic, and
antioxidant activities. The strong scent of lemongrass is attributed to citral,
a compound that accounts for 65-85% of the essential oil. The quick metabolism
and excretion rate of citral results in no significant bioaccumulation of the
compound.7 In cultured cells, citral has been shown to increase the
activity of the enzyme glutathione S-transferase, which is involved in the
elimination of xenobiotics (i.e., molecules that are foreign to the human body7),
but it is not clear to what extent, if any, this experimental research might
relate to human metabolism of preparations containing lemongrass essential oil.
Lemongrass
essential oil also contains linalool, menthol, eugenol, geraniol, myrcene, and
cinnamic aldehyde — all of which have antibacterial effects. Among these, cinnamic
aldehyde possesses the greatest antimicrobial activity, while linalool provides
the strongest antibacterial activity. Citral, geraniol, and myrcene exhibit the
strongest antifungal activity.7
Historical and Commercial Uses
Traditionally,
lemongrass has been used as a food ingredient, in cosmetics, and in folk
medicine. Lemongrass is also used as a flavoring for non-alcoholic beverages, prepared
dishes, and baked goods, and the essential oil has been used to preserve food
due to its antimicrobial activities.3 Lemongrass decoction is a
popular beverage served hot or cold in Peru, Brazil, Cuba, and India.3,4
In Thailand, lemongrass is known as takrai
and commonly is used in Thai dishes such as curries, soups such as tom kha, and in marinades for meat. In
Vietnam, lemongrass is added to salads, and in Java, it is used to prepare a
sherbet.4 Its aromatic oil is prized in soaps, perfumes, candles,
and mosquito or insect repellents.
Lemongrass has a history of medicinal use among
several cultures worldwide for a variety of conditions including digestive
disorders, fevers, menstrual disorders, joint pain, inflammation, and nervous
conditions.4 In the Philippines, lemongrass tea is used to soothe
stress, alleviate colds, fevers, and gastrointestinal distress, and manage pain
and arthritis. In the Paraná state in southern Brazil, lemongrass is a preferred
herbal medicine for pain relief and to sedate or calm the central nervous
system. In India, Cuba, Indonesia, and Brazil, lemongrass infusions/teas are
used to treat bladder disorders (including inflammatory conditions of the
urinary tract), urinary incontinence, and kidney stones.7 In
Nigeria, hot water extracts of lemongrass are used to treat hypertension,
obesity, and diabetes mellitus. It is also used there in the treatment of malaria, to
lower fevers, and to kill protozoa.
Modern Research
Lemongrass has traditional uses as an
antibacterial, antifungal, antiprotozoal, anxiolytic, and antioxidant. Though
there are few human clinical trials at the time of this writing (September
2017), modern pharmacological research has investigated lemongrass preparations
for a variety of conditions and uses: to prevent platelet aggregation, treat
malaria, alleviate digestive upset, and treat metabolic disorders including
dyslipidemia, as well as colds, flu, and pneumonia.7 As is the case
with most botanical materials, both in vitro and in vivo studies on
lemongrass suggest that its reported therapeutic properties are most likely the
result of a synergy of many compounds rather than a single compound.
Antimicrobial, Antifungal, and Antiviral Properties
The
essential oils derived from the steam-distillation of lemongrass leaves have
shown activity against 20 different bacteria (including Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Enterobacter
faecalis, Salmonella, and Shigella),
seven different yeasts (including Candida
albicans), and 15 different fungi
(including common food-storage fungi).7-9
In
vitro studies have shown that lemongrass essential oil can be more effective than
antibiotics against a certain pathogenic bacteria. Lemongrass oil appears to
increase the range of action of phenoxyethanol (a preservative for
pharmaceuticals, cosmetics, and home care products) against E. coli, Staphylococcus aureus, and Pseudomonas aeruginosa.7 As
antibiotic resistance becomes more common, the use of lemongrass essential oil shows
promise in the control of a wide range of bacterial infections.8
Citral,
linalool, myrcene, and geraniol, which are present in lemongrass essential oil,
have antifungal properties. In vitro studies with Candida albicans demonstrate linalool’s ability to reduce cell size
and cause abnormal germination, which inhibits the ability of Candida species to replicate
efficiently. Citral appears to inhibit both mycelial and yeast-form growth of C. albicans. These effects could lead to
the reduction and potential inhibition of the biofilm formation necessary for Candida species to thrive.7
A
0.1% concentration of lemongrass oil completely inhibited herpes simplex
virus-1 replication in vitro.7 In a small, randomized, controlled
trial, lemongrass tea was found to effectively treat oral thrush (a fungal
infection of the mucous membranes of the mouth that is caused by Candida species) in patients with human
immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS).10
Antioxidant Properties
Lemongrass
is a good source of protective antioxidant compounds such as vitamin C and
flavonoids.7 In the food industry, there has been increased interest
in natural methods of food preservation, and essential oils derived from plants
can be used to inhibit microorganisms that cause food spoilage and shorten the
shelf-life of food products.9 The strong inhibitory effects of
lemongrass essential oil against a wide variety of pathogens, combined with its
antioxidant potential, make it a potential food preservative.7,9
An in
vitro study demonstrated the protective effects of lemongrass against hydrogen
peroxide-induced oxidative stress and liver damage. Lemongrass intake was
associated with a decrease in hydrogen peroxide-induced elevation of liver
enzymes and a reduction of oxidative stress-induced pathological changes.7
In a rat study, citral isolated from lemongrass was shown to enhance detoxification
in the liver by inducing glutathione S-transferase, an enzyme involved in the
detoxification process.
Gastroprotective Properties
In
another rat study, lemongrass was investigated for its gastroprotective
benefits. A lemongrass extract was
found to have protective effects against stomach lesions.11 A
similar study investigated the effects of lemongrass essential oil against damage
caused by ethanol and aspirin exposure.12 The essential oil showed a
protective effect against ethanol- and aspirin-induced lesions. For people who
regularly consume alcohol or use non-steroidal anti-inflammatory drugs
(NSAIDs), these results suggest that lemongrass oil may help protect the lining
of the stomach, which can be damaged by use of NSAIDs and alcohol.
Anxiolytic Properties
In
aromatherapy, lemongrass essential oil often is used as a mood enhancer.7
While some studies support lemongrass’s sedative and anxiety-reducing effects
on the central nervous system, these effects have not been consistently
demonstrated.
Studies
on lemongrass aqueous root extract and methanolic leaf extract have
demonstrated anxiolytic effects.13,14 These effects could be related
to the flavonoids, alkaloids, and terpenoids present in lemongrass extracts,
all of which have been associated, in other plant extracts, with reduced anxiety.14
Empirical
studies show that inhalation of lemongrass essential oil has an inhibitory
effect on the central nervous system by increasing levels of the
neurotransmitter gamma-aminobutyric acid (GABA) in the brain. This suggests
that the anxiolytic effects of lemongrass essential oils may be mediated by
acting upon the GABA-benzodiazepine interaction complex.7,15
Neuropharmacological Properties
Lemongrass
water extracts (teas or broths) contain neuroprotective nutrients such as zinc,
magnesium, and folate, which are associated with improved memory,
concentration, and information processing.7 In a mouse study, lemongrass
essential oil was found to be three times more effective than sodium
thiopental, a common anesthetic, at prolonging sleep. Additionally, lemongrass
essential oil has been shown to raise the seizure threshold and reduce
convulsive episodes in rats and should be further investigated for use in
managing epilepsy in humans.
Hypoglycemic and Hyperlipidemic Properties
A rat
study examined the effects of oral intake of three different doses of lemongrass
tea on weight reduction, serum cholesterol levels, and fasting plasma glucose.16
Researchers observed a dose-dependent reduction in weight, with the higher dose
leading to a greater weight reduction, and the maintenance of low blood glucose
levels. Additionally, this study reported a significant, dose-dependent
reduction in levels of total cholesterol, low-density lipoprotein (LDL)
cholesterol, and very low-density lipoprotein (VLDL) cholesterol, while
high-density lipoprotein (HDL) cholesterol increased significantly. Levels of
triglycerides were unaffected.
In a
small open-label human clinical trial, effects of lemongrass tea on 31 patients
with hypertension were observed. Participants were given a lemongrass infusion twice
daily for 16 weeks. Lemongrass tea intake had a significant effect on reducing
blood pressure, but no significant effect on heart rate or other recorded study
parameters.4
Consumer Considerations
There is conflicting and inconclusive evidence regarding
the toxicity of lemongrass. Citral has been found to cause skin irritation such
as contact dermatitis.3,17 In the European Union (EU), citral is one
of 26 likely allergens identified by the EU Cosmetics Regulation, and all
cosmetic and home care products that contain lemongrass oil or extract must
state this on the label.18 Additionally, citral appears to induce
hepatic cytochrome P450 activity, potentially causing prescription drugs and
medications to be metabolized more quickly, which may cause adverse effects,
depending on the medication. There are also reports that citral and myrcene may
adversely affect embryos.3,17 Potential adverse effects on the
kidneys are inconclusive, but high doses or prolonged use of citral (and, by
extension, lemongrass) could be toxic to the kidneys. Liver studies also have
been conflicting and inconclusive. It is recommended that individuals with
kidney damage or liver disease, who are pregnant or lactating, and children
under the age of six should be cautious when using lemongrass.3,17
Lemongrass is a widely cultivated tropical perennial
that has been evaluated for its ability to improve soil stability and eliminate
potentially harmful substances from soils and farm field runoff.6
This wastewater often contains salts, pathogens, heavy metals, and other
pollutants that may contaminate the food web, posing serious health threats to
human and animal health. The use of fibrous-rooted plants like lemongrass and
other large, clumping members of the grass family to sequester harmful
chemicals and prevent them from entering waterways is a key practice in
bioremediation. Agricultural studies report that lemongrass and other aromatic
crops can be grown in soils contaminated by heavy metals without resulting in a
significant transfer from the soil into the essential oil fraction of the plant.
The heat required for steam distillation kills pathogens and reduces the
transfer or uptake of any heavy metals into the essential oil product.
Lemongrass grown on contaminated sites produces essential oils that are deemed
safe for therapeutic use and may be appropriate for most non-edible purposes such
as cosmetics and perfumes.
Nutrient Profile19
Macronutrient Profile: (Per 1 ounce [approx.
28 grams] fresh lemongrass)
28 calories 1 g protein 7 g carbohydrate 0 g fat
Secondary Metabolites: (Per 1 ounce
[approx. 28 grams] fresh lemongrass)
Excellent source of:
Manganese:
1.5 mg (75% DV)
Very good source of:
Iron:
2.3 mg (12.8% DV)
Good source of:
Potassium:
202 mg (5.7% DV) Folate:
22 mcg (5.5% DV)
Also provides:
Magnesium:
16.8 mg (4.2% DV) Phosphorus:
28.3 mg (2.9% DV) Riboflavin:
0.04 mg (2.4% DV) Calcium:
18.2 mg (1.8% DV) Niacin:
0.3 mg (1.5% DV) Thiamin:
0.02 mg (1.3% DV) Vitamin
C: 0.7 mg (1.2% DV) Vitamin
B6: 0.02 mg (1% DV)
DV =
Daily Value as established by the US Food and Drug Administration, based on a
2,000-calorie diet.
Recipe: Green Curry
Paste
Courtesy of Bon Appétit20
For more information on the beneficial
properties of shallot,21 ginger,22 coriander,23 and cumin,24 please see their respective Food as Medicine articles.
Ingredients:
- 2
lemongrass stalks, tough outer layers removed
- 12
serrano chiles, seeds removed and roughly chopped
- 1
large shallot, peeled and chopped
- 4
garlic cloves, peeled
- 3-inch
piece of fresh ginger, peeled and thinly sliced
- 2-inch
piece of fresh turmeric, peeled and chopped; or 1 teaspoon dried turmeric
- 1
makrut lime leaf, very finely chopped (optional)
- 1
teaspoon each ground coriander, ground cumin, kosher salt, and sugar
Directions:
- Grate
the softer inner core of the lemongrass stalks into a food processor or mortar
bowl. Add remaining ingredients and process or pound with the pestle until a
smooth paste forms.
- Curry
paste can be frozen for up to three months. Combine 1-2 tablespoons with one
can of coconut milk for the base of a curry dish.
All photo credits: ©2017 Steven Foster
References
- Van Wyk B. Food Plants of the World: An Illustrated
Guide. Portland, OR: Timber Press; 2015.
- National
Geographic. Edible: An Illustrated Guide
to the World’s Food Plants. Washington DC: National Geographic; 2008.
- Ekpenyong CE,
Akpan EE, Daniel NE. Phytochemical constituents, therapeutic applications and
toxicological profile of Cymbopogon
citratus Stapf (DC) leaf extract. Journal
of Pharmacognosy and Phytochemistry. 2014;3(1):133-141.
- Nambiar V,
Matela H. Potential functions of lemon grass (Cymbopogon citratus) in health and disease. International Journal of Pharmaceutical & Biological Archives. 2012;3(5):1035-1043.
- Department of
Agriculture, Forestry, and Fisheries. Lemongrass
Production. Pretoria, South Africa: Department of Agriculture, Forestry,
and Fisheries; 2012.
- Lal K, Yadav RK,
Kaur R, et al. Productivity, essential oil yield, and heavy metal accumulation
in lemon grass (Cymbopogon flexuosus) under
varied wastewater-groundwater irrigation regimes. Industrial Crops and Products.
2013;45:270-278.
- Ekpenyong CE,
Akpan E, Nyoh A. Ethnopharmacology, phytochemistry, and biological activities
of Cymbopogon citratus (DC.) Stapf
extracts. Chinese Journal of Natural
Medicines. 2015;13(5):321-337.
- Naik MI, Fomda
BA, Jaykumar E, Bhat JA. Antibacterial activity of lemongrass (Cymbopogon citratus) oil against some
selected pathogenic bacterias. Asian
Pacific Journal of Tropical Medicine.
2010;3(7):535-538.
- Boukhatem MN,
Kameli A, Ferhat MA, Saidi F, Tayebi K. The food preservative potential of
essential oils: Is lemongrass the answer? Journal
of Consumer Protection and Food Safety.
2014;9(1):13-21.
- Wright
SC, Maree J, Sibanyoni M. Treatment of oral thrush in HIV/AIDS patients with
lemon juice and lemon grass (Cymbopogon
citratus) and gentian violet. Phytomedicine.
2009;16(2-3):118-124.
- Sagradas J,
Costa G, Figueirinha A, et al. Gastroprotective effect of Cymbopogon citratus infusion on ethanol-induced gastric lesions in
rats. Journal of Ethnopharmacology. 2015;173:134-138.
- Fernandes CN, De
Souza HF, De Oliveria G, Costa JGM, Kerntopf MR, Campos AR. Investigation of
the mechanisms underlying the gastroprotective effect of Cymbopogon citratus essential oil. Journal of Young Pharmacists.
2012;4(1):28-32.
- Shah G, Shiri R, Dhabiliya F, Nagpal N,
Mann AS. Anti-anxiety activity of Cymbopogon
citratus (dc.) stapf leaves extracts on the elevated plus-maze model of
anxiety in mice. Pharmacognosy Journal. 2010;2(15):45-50.
- Arome
D, Enegide C, Ameh SF. Pharmacological
evaluation of anxiolytic property of aqueous root extract of Cymbopogon citratus in mice. Chronicles of Young Scientists. 2014;5(1):33-38.
- Costa C, Kohn DO, Martins de Lima V, Gargano AC, Flório JC, Costa M. The GABAergic system contributes to
the anxiolytic-like effect of essential oil from Cymbopogon citratus (lemongrass). Journal of Ethnopharmacology. 2011;137(1):828-836.
- Adeneye AA, Agbaje EO. Hypoglycemic and
hypolipidemic effects of fresh leaf aqueous extract of Cymbopogon citratus Stapf. in rats. Journal of Ethnopharmacology.
2007;112(3): 440-444.
- Gardner Z, McGuffin M, eds. American Herbal Products
Association’s Botanical Safety Handbook. 2nd ed. Boca Raton, FL: CRC Press; 2013.
- Opinion on fragrance allergens in cosmetic
products. Scientific Committee on Consumer Safety. Brussels, Belgium: European
Union Health and Consumers Scientific Committees. June 2012.
- Basic Report: 11972, Lemon grass
(citronella), raw. National Nutrient Database for Standard Reference Release
28: United States Department of Agriculture Agricultural Research Service.
Available at: https://ndb.nal.usda.gov/ndb/foods/show/3580.
Accessed September 18, 2017.
- Morocco
C. Green curry paste. Bon Appétit.
August 2016. Available at: www.bonappetit.com/recipe/green-curry-paste.
Accessed September 18, 2017.
- Bauman
H, Applegate C. Food as Medicine: Shallot (Allium
cepa var. aggregatum,
Amaryllidaceae). HerbalEGram. 2017;14(2). Available at: http://cms.herbalgram.org/heg/volume14/02February/FAMShallot.html.
Accessed September 18, 2017.
- Bauman
H, Hill K. Food as Medicine: Ginger (Zingiber
officinale, Zingiberaceae). HerbalEGram. 2015;12(3). Available at: http://cms.herbalgram.org/heg/volume12/03March/March2015_FaM_Ginger.html.
Accessed September 18, 2017.
- Bauman
H, Seibert J. Food as Medicine: Coriander/Cilantro (Coriandrum sativum, Apiaceae). HerbalEGram. 2015;12(6). Available
at: http://cms.herbalgram.org/heg/volume12/06June/June2015_FaM.html.
Accessed September 18, 2017.
- Bauman
H, Woo T. Food as Medicine: Cumin (Cuminum
cyminum, Apiaceae). HerbalEGram. 2016;13(10). Available at: http://cms.herbalgram.org/heg/volume13/10October/FAMCumin.html.
Accessed September 18, 2017.
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