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8 Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil: Overview and Biological Activities

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Economic and pharmacological significance of the essential oils of members of the genus Cymbopogon is rapidly increasing. Lemongrass (Cymbopogon flexuosus), wild lemongrass (C. citratus), palmarosa (C. martinii) and citronella (C. winterianus) are the elite essential oil producing aromatic grasses of the genus Cymbopogon. Lemongrass essential oil is mainly comprises of cyclic and acyclic monoterpenes. Citral (a racemic mixture of two isoforms geranial and neral) is the major constituent which gives a characteristic lemon like aroma to lemongrass oil. Lemongrass oil and citral are mainly used in flavors, fragrances, cosmetics and pharmaceuticals. Beside citral is also used for the synthesis of vitamin B and ionones. In this chapter we have thoroughly discussed the various aspects of lemongrass essential oil like biosynthesis, accumulation, chemical compositions and biological properties. C li c k h e r e t o b u y AB B Y Y P D F Trans fo r m e r 2 .0 w w w .A B B Y Y .c o m C li c k h e r e t o b u y AB B Y Y P D F Trans fo r m e r 2 .0 w w w .A B B Y Y .c o m
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1 Amity Institute of Biotechnology, Amity University, Uttar Pradesh, Sector-125,
Noida-201 303 (UP), India
* Corresponding author: E-mail: deepakganjawala73@yahoo.com
8
Lemongrass (Cymbopogon flexuosus Steud.)
Wats Essential Oil: Overview and Biological
Activities
DEEPAK GANJEWALA1*AND ASHISH KUMAR GUPTA1
ABSTRACT
Economic and pharmacological significance of the essential oils of
members of the genus Cymbopogon is rapidly increasing. Lemongrass
(Cymbopogon flexuosus), wild lemongrass (C. citratus), palmarosa (C.
martinii) and citronella (C. winterianus) are the elite essential oil
producing aromatic grasses of the genus Cymbopogon. Lemongrass
essential oil is mainly comprises of cyclic and acyclic monoterpenes. Citral
(a racemic mixture of two isoforms geranial and neral) is the major
constituent which gives a characteristic lemon like aroma to lemongrass
oil. Lemongrass oil and citral are mainly used in flavors, fragrances,
cosmetics and pharmaceuticals. Beside citral is also used for the synthesis
of vitamin B and ionones. In this chapter we have thoroughly discussed
the various aspects of lemongrass essential oil like biosynthesis,
accumulation, chemical compositions and biological properties.
Key words:Cymbopogon, Citral, Geraniol, Essential oil, Lemongrass,
Palmarosa, MEP pathway, Acetate-MVA pathway
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234 RPMP Vol. 37: Essential Oils–II
INTRODUCTION
Lemongrass, palmarosa and citronella are the most important essential
oil (EO) yielding members in the genus Cymbopogon. Their EOs has
immense commercial values in flavours, fragrances, cosmetics,
perfumery, soaps, detergents, toiletry, tobacco products and
pharmaceuticals (Ganjewala et al., 2008). It is also used for the synthesis
of vitamin A and ionones (b-ionones, methyl ionone, etc.); synthetic
citral, derived from conifer turpentine is normally used for these
purposes (Dawson, 1994). Lemongrass EO is mainly composed of cyclic
and acyclic monoterpenes such as, citral (3,7-dimethyl-2,6-octadienal;
a mixture of two isomer geranial and neral), geraniol, citronellol,
citronellal, linalool, elemol, 1,8-cineole, limonene, â-carophyllene,
methylheptenone, geranyl acetate and geranyl formate.
In recent years medicinal and pharmacological significance of
lemongrass EO and its major constituent citral has been rapidly
increased. A number of studies have revealed many useful bioactivities
such as such as, antimicrobial, allelopathic, anthelmintic, anti-
inflammatory, anticancer, antioxidant, insect and mosquito repellent
of lemongrass extract, oil, citral and citral derived compounds
In India, lemongrass (C. flexusosus and C. citratus) are cultivated in
Kerala, Assam, Maharashtra and Uttar Pradesh. Apart from India,
they are also cultivated in large scale in Brazil, Maxico, Dominica, Haiti,
Medagascar, Indonesia and China. India produces around 1000 tones
of lemongrass oil per year and is exported to America, England,
Germany, Australia and Japan.
OVERVIEW OF THE GENUS CYMBOPOGON
The name Cymbopogon is derived from Greek words “Kymbe” (boat)
and “pogon” (beard) referring to the flower spike arrangement. The
genus Cymbopogon comprises of about 140 species, which are indigenous
in tropical and sub-tropical areas of Asia and cultivated in South and
Central America, Africa and other Tropical countries (Soenarko, 1997;
Rao, 1997; Khanuja et al., 2005; Padalia et al., 2011; Shah et al., 2012).
Of the 140, about 45 species occur in India. These are tufted perennial
C4 grasses with numerous stiff stems arising from short rhizomatous
rootstocks. A number of species of Cymbopogon such as lemongrass (C.
flexuosus), wild lemongrass (C. citratus), palmarosa (C. martinii),
citronella java (C. winterianus) and jamarosa (hybrid of C. nardus x C.
jwarancusa) are the natural sources of essential oils among others
(Husain, 1994; Khanuja et al., 2005; Ganjewala et al., 2008). These
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235
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
species of Cymbopogon differs from each other in oil content and quality,
however morphological differences at the intra and inter-species level
are often blurred (Sangwan et al., 2001). Genetic diversity at the DNA
level in Cymbopogon species has been discerned by random amplified
DNA polymorphic technique using random primer (Sangwan et al.,
2001).
EOs of a number of species of the genus Cymbopogons including
lemongrass, wild lemongrass, palmarosa and citronella have been
extensively investigated for their chemical compositions and
bioactivities (Sidibe et al., 2001; Khanuja et al., 2005; Ganjewala et al.,
2008). EOs of the Cymbopogon spp. are mainly composed of cyclic and
acyclic monoterpenes like citral (3,7-dimethyl-2,6-octadienal; a mixture
of two isomer geranial and neral), geraniol, citronellol, citronellal,
linalool, elemol, 1,8-cineole, limonene, b-carophyllene, methylheptenone,
geranyl acetate and geranyl formate. It is believed monoterpenes have
been derived mainly from geranyl diphosphate (GPP) through different
secondary transformations such as, isomerization, acetylation,
deacetyaltion, cyclization, hydroxylation and dehydrogenation etc.
(Banthorpe & Charlwood, 1980; Croteau, 1987). Very recently, an
enzyme geraniol synthase (GES) has been characterized from basil,
Cinnammum and perilia which utilize GPP for the formation of geraniol
(Iijima et al., 2004; Yang et al., 2005; Ito & Honda, 2007). GPP the
universal precursor of monoterpenes is however synthesized by the
fusion (head to tail) of the two C5 units called isopentenyl diphosphate
(IPP) and its isomer dimethylallyl diphosphate (DMAPP). The IPP in
turn is synthesized either from cytosolic acetate-mevalonate (MVA) or
plastidic D-methyl-erythritol-4-phosphate (MEP) or Rohmer pathways.
The MEP pathway is however believed to the source of monoterpenes
formation in plants while the sterols and diterpenoids are derived from
acetate-MVA pathway (Rohmer et al., 1993; Mccaskill & Croteau, 1998;
Luthra et al., 1999).
Lemongrass and other members of the genus Cymbopogon
biosynthesize and accumulate EOs predominantly in the young and
rapidly expanding leaves and floral tops/inflorescence (Singh et al., 1990;
Dubey et al., 2003a; Ganjewala & Luthra, 2007a). Our previous study
has shown that lemongrass cultivar OD-19 accumulated citral in specific
cells of the parenchymal tissue which are referred as oil cells (Luthra
et al., 2007). The EO biosynthesis and accumulation is a carefully
regulated process and markedly influenced by the ontogeny,
developmental stages of the concerned plant parts/organs and
environmental conditions (Luthra et al., 1991; Singh et al., 1991; Dubey
et al., 2000; Ganjewala et al., 2008). However, in lemongrass only little
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236 RPMP Vol. 37: Essential Oils–II
work has been carried out in relation to EO biosynthesis and regulation
compared to the other well studied plant families like lamiaceae and
pinaceae. Also, lacking is the fundamental information of molecular
biology of EO and monoterpene biosynthesis.
Lemongrass EO oil is mostly used in pharmaceuticals, flavours and
perfumery industries (Guenther, 1950). It is also used for the synthesis
of vitamin A and ionones (â-ionones, methyl ionone, etc.); synthetic
citral, derived from conifer turpentine is normally used for these
purposes (Dawson, 1994). However, the original use of lemongrass was
probably as a food flavouring in Asia; the leaves are cooked with foods
especially curries and peeled stems are available in local markets. Fresh
leaves crushed in water are used as hair wash and toilet water in India.
The major EO constituent citral is used in perfumery, cosmetic and
pharmaceutical industries for controlling pathogens (Guynot et al.,
2003). Another major constituent geraniol present in lemongrass
cultivar GRL-1 and palmarosa oil is most widely used in perfumery,
soaps, detergents and cosmetics for rose like smell. Geranyl acetate
(acetate esters of monoterpenoids) has been reported to influence the
quality of essential oils. Lemongrass oil is also used as a powerful
mosquito repellent. The citral is used as antifungal (Rodov et al., 1995),
bactericidal (Asthana et al., 1992; Kim et al., 1995) and insecticidal
agents (Rice & Coats, 1994). Lemongrass oil might be used as
preservative (Arora & Pandey, 1977) and in inhibition of sensitization
reactions whereas the left over of lemongrass could be as a raw material
for cellulose pulp and paper production. The EO of C. citraus is widely
used by the perfumes, cosmetics industries and in traditional medicine
for various purposes (Sadiq & Khayat, 2010).
MAJOR ESSENTIAL OIL YIELDING CYMBOPOGON SPECIES
Cymbopogon spp. display wide variation in morphological characters
and essential oil composition at inter and intra species level and over
the year’s different chemo cultivars varying in their aroma have been
selected or breed by crossing with other cultivars or closely related
species. The most common economically sound species of the genus
Cymbopogon viz., C. flexuosus, C. citratus, C. martinii var. motia and
sofia, C. nardus var.nardus, C. pendulus, C. winterianus, C. jwarancusa
and C. khasianus yields essential oils of vivid composition referred as
lemongrass oil, palmarosa oil, citronella oil, ginger grass or rusa oil
(Rao, 1997; Gupta & Jain, 1978; Kumar et al., 2000). The unique
characteristics of these aromatic grasses are that they have wide
adaptability to grow in different types of soils in different agri-climatic
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237
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
conditions and cropping sequences. In India, total area under cultivation
of these aromatic grasses is more than 40 thousands hectares,
distributed mainly in Assam, Kerala, Madhya Pradesh, South Gujarat,
Karnataka, Maharashtra, Andhra Pradesh and Uttar Pradesh (Husain,
1994). In the following section we have elaborately discussed major
elite species of the genus Cymbopogon.
Lemongrass (C. flexuosus)
Cymbopogon flexuosus (Nees ex Steud) Wats is commonly known as
lemongrass and locally it is called Cochin or Malabar grass (Fig. 1). It
is tufted perennial grass, with numerous stiff stems arising from a short,
rhizomatous rootstock (Weiss, 1997). The leaf-blade is linear, tapered
at both ends and can grow to a length of 50 cm and width of 1.5 cm
(Sugumaran et al., 2005). The leaf-sheath is tubular in shape and acts
as a pseudostem. This plant produces flowers at matured stages of
growth (Jaganath et al., 2000). Conversely, flowering has never been
observed under cultivation due to rapid harvesting time. The rhizome
produces new suckers that extend vertically as tillers to form dense
clumps. Lemongrass can tolerate a wide range of soils and climatic
conditions. However, vigorous growth is obtained on well-drained sandy
loam soil with high fertility and exposed to sunlight (Sugumaran et al.,
2005). In lemongrass, tiller growth usually begins at the apical meristem
where cell division occurs, followed by pro-duction of axillary buds and
the emergence of new tillers. Lemongrass is commonly cultivated as a
Fig. 1: A full view of lemongrass plantation
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238 RPMP Vol. 37: Essential Oils–II
ratoon crop and first harvested at 4 to 6 months after planting followed
by subsequent harvests at 2 to 3 month interval (Joy et al., 2006).
Harvesting is done by cutting at 20 cm above the ground level
(Sugumaran et al., 2005).
Lemongrass is indigenous to India and grown in Kerala, Assam,
Maharashtra and Uttar Pradesh. Apart from India, lemongrass is also
cultivated in large scale in Brazil, Mexico, Dominica, Haiti, Madagascar,
Indonesia and China. The oil from lemongrass is referred as East Indian
lemongrass oil. The first variety of lemongrass selected was OD-19 from
Kerala in India followed by OD-408 and OD-440 (Kurikose et al., 1987).
Thereafter, a number of important cultivars have been developed during
the course of study of genetic diversity and chemogenetical improvement
in a citral producing lemongrass (cultivar OD-19). Some of the important
lemongrass cultivars are GRL-1 (geraniol rich lemongrass), Krishna,
Cauveri, Pragati, Chirharit, CKP-25 and SD-68. Among these Krishna
is most popular through out India and was developed at Central Institute
of Medicinal and aromatic Plants (CIMAP), Bangalore centre. Krishna
yield high bio mass (25-28 Mt/hectare) with high oil yield (230-250 kg./
hact.) due to high % of oil in bio mass.CKP-25 is another successful
variety which gives good result even in less rainfall area. CKP-25 was
developed by Regional Research laboratory (RRL), Jammu. Chirharit
is very popular in Tarai region of Uttarakhand as same remains green
through out year producing high quantity of bio mass although % of oil
recovery is less due to cold climate in such region. Nima variety is known
for its unique citrus clean odor as same contains less grassy component
like methyl heptenone. Also this variety can be grown in west land
containing very high salt. All of the above cultivars of lemongrass yield
essential oil highly rich in citral except GRL-1 which yields geraniol
rich essential oil (Patra et al., 1997). Thus could be easily distinguished
from other cultivars by the presence of high amount of geraniol (89.39%).
Lemongrass has been used in medicine in India for more than 2000
years. However, its use for distillation is about 100 years old and the
first distillation in India was started in about 1890 during the British
period from wild grass in Kerala. The total annual world production of
East Indian lemongrass oil used to be 1500 tonnes
Wild Lemongrass (C. citratus)
It is also an important of species in the genus Cymbopogon which is a
tropical perennial aromatic grass having dense fasicles of leaves from
a short/oblique annulate, sparingly branched rhizome. The oil of C.
citratus is referred as West Indian lemongrass oil which is characterized
by the presence of very high amount of citral. West Indian name however
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239
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
is misnomer as the grass is not indigenous to West Indies but was
cultivated to a limited extent. There is hardly any production of
lemongrass oil in West Indies now. The tea made from its leaves is
popularly used as antispasmodic (Devi et al., 2011), analgesic, anti-
inflammatory, antipyretic, diuretic and sedative (Liete et al., 1986; Sadiq
& Khayat, 2010). It is also used as antiseptic, antifever, antidyspeptic,
carminative, tranquilizer, stomachic and antihypertensive agent
(Borreli & Izzo, 2000). A number of previous studies have also reported
its anti-inflammatory, antiseptic, diuretic, neurobehavioral,
antimicrobial, and fungistatic activities (Carlini et al., 1986; Carbajal
et al., 1989; Francisco et al., 2011). In Mexico, C. citratus is used as a
sedative (Tortoriello & Romero, 1992) while in Brazil, an infusion or
the cold juice of the leaves has been employed as a sedative and analgesic
(Simon et al., 1980; Hiruma-Lima et al., 2002). An antinociceptive effect
of C. citratus has been detected in the rodent hot plate test, an
experimental procedure related to central activity (Viana et al., 2000).
It has been also recommended against generalized anxiety disorder and
epilepsy in experimental procedures in mice (Costa et al., 2006; Blanco
et al., 2009). The leaves decoction has been shown to have antioxidant
property (Cheel et al., 2005). The stalk or stem of C. citratus is reported
to have a small relaxation effect on perfused mesenteric arteries (Runnie
et al., 2004).
Both lemongrass and wild lemongrass are closely related on the basis
of other features like morphology, chemical constituents, geographical
distribution and RAPD analysis (Sharma et al. 2000; Sangwan et al.,
2001; Khanuja et al., 2005). The strong lemon-like odour of the oil is
because of the presence of citral, the main constituent of the essential
oil and hence the name lemongrass. Essential oils of both the
lemongrasses contain 75-80% of citral but West Indian oil is considered
inferior as it is less soluble in 70% alcohol as compared to East Indian
lemongrass oil. The lower solubility in 70% alcohol is due to presence of
myrcene, an olefinic terpene, which polymerises on exposure to air and
light. The major producer of West Indian lemongrass oil is Guatemala
producing approximately 250 tones of oil. The total world production of
lemongrass oil is approximately 1000-1500 tones. India and Guatemala
are the major producers. Smaller amounts are produced in China, Brazil,
Indonesis and Haiti (Virmani et al., 1988).
Other Cymbopogon Species
Cymbopogon martinii also known as Rosha grass is a tall perennial
sweet scented grass 5-8 feet high used for the extraction of geranium
oil which is extensively used as perfumery raw material in soaps, floral-
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240 RPMP Vol. 37: Essential Oils–II
rose like perfumes, cosmetics preparation and in the manufacture of
mosquito repellent products (Rajeswara Rao, 2001). It is used
traditionally in treatment of diabetes. The plant has also been
documented in Ayurveda for treatment of urinary tract infection, as
anti-inflammatory and as diuretic (Mishra, 2002). Cymbopogon
pendulus has been recently distilled in India to a limited extent.
Essential oil of this grass is also contains 70-80% citral. However, it is
much hardier than the two previous species and can be cultivated in
adverse soil and climatic conditions. Cymbopogon nardus is a perennial
grass cultivated in Southeast Asia. Its oil is known as citronella oil,
and has been traditionally used as mosquito repellent, household
fumigant, or fragrance agent in food commodities, soaps and cosmetics
(Chomchalow, 1993; Jantan et al., 1999; Nakahara et al., 2003).
Cymbopogon olivieri (Boiss.) is a plant growing in South East of Iran.
The main constituents of this species are alkaloids, saponins and
essential oil (Carpenter,2001). The essential oil of C. olivieri which
grows in India contains 3-pinene, myrcene, pulgone and piperitone as
the major constituents (Rajendrudu, 1983) and displayed interesting
anti-fungi activity. Cymbopogon ambiguus A.Camus.is a native
Australian lemongrass species found on rocky hillsides throughout the
Northern Territory of Australia (Latz, 1995). The leaves have been used
traditionally to treat chest infections, sores, muscle cramps as well as
headache and associated complaints (infusions and decoctions) (Grice
et al., 2011; Latz, 1995; Lassak & McCarthy, 1983; Barr et al., 1988).
Little is known about the chemical constituents present in C. ambiguus
apart from a GC-MS study by Barr et al. (1988), which identified
camphene, borneol, limonene, a-pinene, a-terpineol, camphor,
isoborneol, 4-terpineol, myrcene, b-ocimene as being present in the
essential oil.
EXTRACTION OF ESSENTIAL OIL
Lemongrass oil is extracted by various ways such as, the solvent,
accelerated solvent, Soxhlet (Sargenti & Lancas., 1997), dense carbon
dioxide (Carlson et al., 2001), solid-phase matrix (Pham-Tuan et al.,
2001), and supercritical fluid (Schaneberg and Khan, 2002) extraction
methods. However, the common procedure of extracting essential oil is
by the hydro-distillation method (Kulkarni et al., 2003). Essential oils
are extracted from fresh plant material (whole plant or leaves) and air
dried aerial parts using hydro-distillation technique in Clevenger-type
apparatus for 3 hours. The essential oil collected after distillation is
dried over anhydrous Na2SO4 to remove moisture and stored in sealed
vials under refrigeration. In some cases hydro-distillation is carried at
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241
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
100°C for 6 h in an all glass Dean and Stark apparatus modified to
allow lowest phase return (Sukari et al., 2008). In such cases, usually
10 ml of the n-hexane are added, to trap the condensed oil, through the
top of the condenser. Later and hexane is collected every hour. Then,
new portion of hexane is added through the condenser. Essential oil is
also extracted with diethylether which is later evaporated. The mixtures
are combined and dried over anhydrous Na2SO4 for 24 h and then
filtered. Finally, the hexane solution is evaporated or removed by using
a rotary evaporator (Eyela N-1001, Tokyo Rikakikai, Japan) at 40°C to
give a yellowish essential oil which is then stored at 4°C for further
analysis. The oil yields are calculated on the basis of fresh weight and
dry weight of the material (v/w) (Padalia et al., 2011; Sukari et al.,
2008).
Determination of Essential Oil Content
For determination of essential oil content oil samples are removed after
freeze drying and then weighed with a balance. The percentage yield of
essential oil is determined using the formula described by Rao et al.
(2005) where the amount of essential oil recovered (g) was determined
by weighing the oil after moisture was removed. The essential oil
percentage was calculated as follows:
ESSENTIAL OIL YIELD AND COMPOSITION
An EO is defined as the product obtained by hydro-distillation, steam
distillation or dry distillation or by a suitable mechanical process
without heating (for Citrus fruits) of a plant or some parts of it (Rubiolo
et al., 2010). They are aromatic oily liquids, volatile, characterized by a
strong odour, rarely coloured, and generally with a lower density than
that of water. Essential oils only represent a small fraction of plant’s
composition; nevertheless they confer the characteristics by which
aromatic plants are used in the food, cosmetic and pharmaceutical
industries (Pourmortazavi et al., 2004). EOs have a complex composition,
containing from a dozen to several hundred components. The great
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242 RPMP Vol. 37: Essential Oils–II
majority of components identified in essential oils includes terpenes
(oxygenated or non-oxygenated), with monoterpenes and sesquiterpenes
prevailing. Nevertheless, allyl- and propenylphenols (phenylpropanoids)
are also important components of some essential oils (Cavaleiro, 2001).
Gas liquid chromatography (GLC) and gas chromatography-mass
spectrometry (GC-MS) has been the most applied analytical techniques
for essential oil analysis (Masada, 1976) followed by the supercritical
fluid extraction-gas chromatography (Liu et al., 1993). Due to the
complexity of essential oil compositions, sophisticated instruments
such as, high performance liquid chromatography in combination with
gas chromatography (HPLC-GC) (Mondello et al., 1996) is the preferred
analysis. HPLC is effective for a broad class separation of a sample,
which can be introduced into a GC for further high resolution
separation.
The EO of lemongrass and other members of Cymbopogon have been
exhaustively investigated for chemical compositions (Nath et al., 1994;
Mathew et al., 1996; Sahi et al., 1997; Sharma et al., 1999; Sidbi et al.,
2001; Nath et al., 2002; Khanuja et al., 2005; Ganjewala et al., 2008;
Ganjewala, 2009). Lemongrass yields 1 to 2% EO on a dry weight basis
which contains mainly citral (Schaneberg & Khan, 2002; Carlson et al.,
2001; Pengelly, 2004). Other unusual active components are limonene,
citronellal, b-myrcene and geraniol (Schaneberg & Khan, 2002;
Ganjewala et al., 2008). EOs of most of the Cymbopogon spp. are mainly
characterized by citral, geraniol, citronellol, citronellal, linalool, elemol,
1,8-cineole, limonene, b-carophyllene, methyl heptenone, geranyl acetate
and geranyl formate (Lewinsohn et al.,2008; Sidibe et al., 2001; Khanuja
et al., 2005; Ganjewala et al., 2008). The citral imparts characteristic
lemon like aroma to EOs of the Cymbopogon spp. (Husain, 1994). The
EO of palmarosa (C. martinii), however has high content of geraniol
(90%) which gives it a characteristic rose like odor. Besides, geranyl
acetate present in the palmarosa EO is reported to influence the quality
of EOs (Ganjewala & Luthra, 2009). EOs of the lemongrass cultivars
OD-19 and GRL-1 are comprises of several monoterpenes viz., citral,
geraniol, borneol, isopulegol and 6-methyl hept-5-en-2-one, geranyl
acetate, g-terpinene, a-thujene, a-pinene, sabinene, n-decanol, a-
terpenyl acetate, b-caryophyllene, a-humulene, germacrene D, b-
bisabolene and g-cadinene (Nath et al., 1994; Mathew et al., 1996; Sahi
et al., 1997; Sharma et al., 1999; Sidbi et al., 2001; Nath et al., 2002;
Khanuja et al., 2005; Ganjewala et al., 2008; Ganjewala, 2009). The EO
of C. parkeri is consisted of bicyclic monoterpenes, piperitone and
sesquiterpenes, isointermedeol (Baqheri et al., 2007; Kumar et al., 2008).
Isointermedeol is a major component in the EO of lemongrass and
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243
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
possess anticancer properties (Kumar et al., 2007). Structures of some
of these monoterpenes are presented in Fig. 2.
Fig. 2: Structures of some chemical constituents of lemongrass essential oil.
1, citral a; 2, citral, b; 3, citronellol; 4, citronellal; 5, geraniol; 6, geranyl
acetate; 7, limonene; 8, linalool; 9, nerol; 10, cis-ocimene; 11,
piperitone; 12, a-terpineol, 13, thujane; 14, a-bisabolol, 15,
isointermedeol; 16, borneol; 17, a-pinene; 18, b-pinene
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244 RPMP Vol. 37: Essential Oils–II
Previously, the author has studied EO compositions of eight
lemongrass cultivars. The study revealed that seven of the eight EOs
had citral (75-85%) as major constituent, while only one cultivar GRL-
1 had geraniol (90%) as major component (Ganjewala et al., 2008).
Khanuja et al., (2005) have also reported similar variation in the EO
content and composition in 19 Cymbopogon taxa and discerned
phylogenetic relationship among these taxa. The EO of C. confortiflorus
and C. nardus var. confortiflorus were very rich in geraniol (68% and
46%) whereas C. nardus var. nardus and C. winterianus had very little
amount of geraniol. The EO of C. pendulus, C. flexuosus and C. citratus
were mainly consisted of citral with 80-84% of the total monoterpene
content (Khanuja et al., 2005).
C. citratus root oil consisted of ten components with longifolene
(577%) and selina-6-en-4-ol (20.03%) as major constituents (Li et al.,
2005). Shoot EO however has shown an entirely different chemical
composition consisting of 12 components with citral (88%) as the major
constituent (Li et al., 2005). The EO of C. giganteus showed a
distinguished composition due to the presence of cis- and trans-p-1(7),8-
menthadien-2-ol (19.9% and 22.3%), cis- and trans-p-2,8-menthadien-
1-ol (10.1% and 14.3%) (Alitonoua et al., 2006). Similarly, C.
schoenanthus L. Spreng from Tunisia also has a distinguished EO
composition due to the presence of limonene (10.5–27.3%), b-
phellandrene (8.2–16.3%), d-terpinene (4.3–21.2%) and a-terpineol (6.8–
11.0%) (Khadria et al., 2008). The GC-FTIR study of the EO of palmarosa
has revealed the presence of geraniol (65%) and geranyl acetate (20%)
as major constituents (Prashar et al., 2003). Palmarosa leaf and flower
essential oil are also dominated by geraniol 53.41% and 69.63%
respectively in leaf and flower oil (Nirmal et al., 2007). In addition,
piperitone (6.0%) in flower and nerol (24.76%) and á-pinene (4.32%) in
leaf essential oils are also identified (Nirmal et al., 2007). The EO Java
citronella is mainly comprises of geraniol (40.06%), citronellal (27.44%)
and citronellol (10.45%) (Quintans-Junior et al., 2008). Another study
has revealed the presence of 23 compounds in the EO of citronella with
citronellal (27%), trans-geraniol (23%), citronellol (10%), limonene and
linalool as major constituents (Simic et al., 2008; Lorenzo et al., 2000).
The EO composition of C. nardus has been found identical to citronella
oil with dominance of the geraniol, citronellal, and citronellol. However,
EO of C. nardus harvested from India also has other constituents such
as, a-terpineol, cis-sabinene and carvone (Delespaul et al., 2000). The
EO of C. parkeri from Iran has unique composition with presence of
piperitone (81%) as major component and other minor constituents such
as, germacrene-D (5%), santolinyl acetate (2.1%) and a-eudesmol (2.1%)
(Baqheri et al., 2007).
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245
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
It has been evident from the above studies that the EO content and
compositions of various Cymbopogon species are markedly fluctuated.
Furthermore, their content and compositions are greatly influenced by
climatic, seasonal and diurnal factors. In most of the cases, EO content
and compositions are reported to be governed by the developmental
stages of the plant parts/ organ and tissues. The author has carried out
studied on developmental and ontogenic variation in the EO content
and compositions in lemongrass and its elite cultivars (Ganjewala et
al., 2008; Ganjewala, 2009).
ESSENTIAL OIL BIOSYNTHESIS IN LEMONGRASS
Lemongrass biosynthesize and accumulate EO predominantly in the
young and rapidly expanding leaves and floral tops (Singh et al., 1990;
Dubey et al., 2003a; Ganjewala & Luthra, 2007a). Our studies in
lemongrass cultivar OD-19 revealed that it accumulate EO in the
parenchymal cells which are referred as oil cells (Luthra et al., 2007).
As discussed previously, EO oils are composed of complex mixtures of
cyclic and acyclic monoterpenes. Monoterpenes are the C10 compounds
which are mainly derived from geranyl diphosphate (GPP) through
various secondary transformations such as, isomerization, acetylation,
deacetyaltion, cyclization and dehydrogenation etc. (Banthorpe &
Charlwood, 1980; Croteau, 1987). GPP which is believed to be a universal
precursor of monoterpenes is synthesized by the fusion in head to tail
fashion of the two C5 units called isopentenyl diphosphate (IPP) and its
isomer dimethylallyl diphosphate (DMAPP). In plants, IPP is
biosynthesized by two major pathways the cytosolic acetate-MVA and
newly discovered plastidic Methyl-D-Erythritol-4-Phosphate (MEP) or
Deoxy-xylulose-5-phosphate (DOXP) or Rohmer pathway (Fig. 3). The
acetate-MVA pathway is responsible for the biosynthesis of sterols,
sesqui- and tri-terpenes while the MEP pathway for the plastidic
isoprenoids such as, carotenoids, phytol side chain of chlorophyll,
plastoquinone-9, hemi-, mono- and di-terpenes (Rhomer et al., 1993;
Lichtenthaler et al., 1997; Eisenrich et al., 1997; Lichtenthaler, 1999;
Luthra et al., 1999; Rohmer, 2003).
Acetate-MVA pathway
In brief, cytosolic acetate-MVA pathway (Fig. 3) starts with sequential
condensation of the three acetyl-CoA that leads to the formation of 3-
hydroxy-3-methylglutaryl-coenzyme-A (HMG-CoA). The HMG-CoA is
then converted into mevalonate in an irreversible reaction catalyzed
by 3-hydro-3-methylglutaryl-coenzyme-A reductase (HMG-CoA
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246 RPMP Vol. 37: Essential Oils–II
reductase or HMGR) (Singh et al., 1989; Bach, 1995). The conversion of
HMG-CoA into mevalonate is the committed step of the acetate-MVA
pathway. The HMGR is a key enzyme in cytosolic acetate-MVA pathway
but its activity could not be correlated with the rate of biosynthesis of
plastid bound prenyl lipids like chlorophyll and carotenoids. The
mevalonate is then sequentially phosphorylated and decarboxylated
by the enzymes mevalonate kinase, mevalonate-5-phosphate kinase and
mevalonate-5-diphosphate decarboxylase to generate IPP. Studies
conducted in lemongrass and palmarosa using radiolabel substrates
[2-14C]-acetate, 14CO2, [
14C]-sucrose have indicated the acetate-MVA
origin of the EO (Singh et al., 1990; Luthra et al., 1993; Ganjewala &
Luthra, 2007a). Also, these studies have revealed that EOs are
predominantly biosynthesize and accumulates only in the young and
rapidly expanding leaves in lemongrass and inflorescence in palmarosa
(Singh et al., 1990; Dubey et al., 2003; Ganjewala & Luthra, 2007a).
MEP pathway
The MEP pathway is restricted to the plastid compartment in the cell
(Kleinig, 1989; Rohdich et al., 2000). The first step of the MEP pathway
is the formation of 1-Deoxy-D-xylulose-5-Phosphate (DOXP) by transfer
of a C2-unit derived through pyruvate (hydroxyethyl-thiamine) to GA-
3-P, in a thiamin-dependent transketolase- type reaction (Schwender
et al., 1997). Next few steps involve formation of 2-C-methyl-D-
erythritol-4-phosphate (MEP) which is consecutively converted into 4-
diphosphocytidyl-methylerythritol (CDP-ME), 4-diphosphocytidyl-
methylerythritol (CDP-MEP) and methyl-erythritol 2, 4-
cyclodiphosphate (ME-cPP). These steps are catalyzed by enzymes, CDP-
ME synthase, CDP-ME kinase and ME-cPP synthase. Methyl-erythritol
2, 4- cyclodiphosphate (ME-cPP) is converted to hydroxymethylbutenyl
4-diphosphate (HMBPP) by an enzyme hydroxymethylbutenyl 4-
diphosphate synthase. HMBPP is finally converted into a mixture of
IPP and DMAPP by the enzyme HMBPP reductase (Eisenreich et al.,
1991; Eisenreicha et al., 1994) (Fig. 3).
The MEP pathway of IPP formation is yet not fully elucidated in
lemongrass. However, the efforts to elucidate MEP using [13C]-glucose
in combination of NMR spectroscopy in lemongrass has been initiated.
The potential of using 13C-glucose-NMR spectroscopy to elucidate
metabolic pathways in plants has long been recognized. To investigate
the biosynthetic origin of isoprenoids building blocks of secondary
metabolites, the pathway-independent precursor 13C-glucose, which
produces distinctly different labeling patterns of the individual isoprene
units for the MEP and acetate-MVA pathways is generally employed
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247
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
Fig. 3: Acetate-MVA and MEP pathways of IPP formation in plants. CDP-
ME: 4-(cytidine-5'-diphospho)-2-C-methyl-D-Erythritol, CDP-MEP: 4-
Diphosphocytidyl-2C-methyl-D-erythritol 4-phosphate, DMAPP:
dimethylallyl diphosphate, DXP: 1-deoxy-D-xylulose 5-phosphate, GA-
3-P: glyceraldehyde 3-phosphate, GPP: geranyl diphosphate, HBMPP:
4-hydroxy-3-methylbut-2-enyl diphosphate, IPP: isopentenyl
diphosphate, ME-cPP: 2C-methyl-D-erythritol 2,4-cyclodiphosphate,
MEP: 2C-methylerythritol 4-phosphate, Enzymes CMK: 4-(cytidine-
5'-diphospho)-2-C-methyl-D-Erythritol kinase, CMS: 4-
Diphosphocytidyl-2C-methyl-D-erythritol 4-phosphate synthase, DXR:
1-deoxy-D-xylulose 5-phosphate reductoisomerase, DXS: 1-deoxy-D-
xylulose 5-phosphate synthase, HDS: 4-Hydroxy-3-methylbut2-en-yl-
diphosphate synthase, MCS: 2C-methyl-D-erythritol 2,4-
cyclodiphosphate synthase, HMGS: 3-hydroxy-methylglutaryl-CoA
synthase, AACT: Acetoacetyl-CoA transferase, HMGR: 3-hydroxy-
methylglutaryl-CoA reductase, MVK: mevalonate kinase, PMK: 5-
phopspho-mevalonate kinase, PMD: mevalonate-5-diphosphate
decarboxylase, IDI: isopentenyl-diphosphate isomerase.
(Rohmer, 1999). Given that glucose is a general intermediary metabolite,
the isotope from the preferred carbohydrate can be diverted to virtually
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248 RPMP Vol. 37: Essential Oils–II
all metabolic compartments and intermediates in plant cells (Eisenreich
et al., 2004).
BIOSYNTHESIS OF GERANIOL AND CITRAL
In lemongrass and palmarosa, geraniol and citral biosynthesis proceeds
via three steps (Fig. 4). In the first step, phosphatases catalyze the
removal of pyrophosphate (PPi) from GPP to form geraniol. In the second
step, thus formed geraniol gets acetylated to form geranyl acetate by
Fig. 4: Pathways for the formation of geraniol and citral in lemongrass. GPP,
geranyl diphosphate. GES: geraniol synthase, GPPase:
geranyldiphosphatase, GDH: geraniol dehydrogenase, GAE: geranyl
acetate esterase, GAT: geranyl acetate transferase
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249
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
the action geraniol-acetyl transferase and in the third step newly formed
geranyl acetate slowly hydrolyzes to form gain geraniol by the action of
geranyl acetate esterase (GAE) as a function of leaf/inflorescence
development. Hence, the levels of geraniol in lemongrass and palmarosa
is controlled and regulated by these three enzymatic steps. In contrast,
recently published few reports have claimed that in basil, cinnamomum
and perilia geraniol is produced from GPP by the action of a specific
enzyme geraniol synthase (GES) and not by the above three step
mechanism. Enzyme geraniol synthase (GES) has been cloned and
characterized from basil, cinnamomum and perilia (Iijima et al., 2004;
Yang et al., 2005; Ito and Honda, 2007). Though the mechanism of action
of GES is yet not fully understood structural similarity of geraniol with
its precursor GPP, has hypothetically allowed for an alternative
mechanism of simply breaking the phosphoester bond by a phosphatase
to generate geraniol. The enzyme GES has not been reported from
lemongrass or any other members of the Cymbopogon. In lemongrass,
geraniol is a precursor of citral. An NADP+-dependent geraniol
dehydrogenase enzyme catalyzes the conversion of geraniol into citral
(Sangwan et al., 1993).
ESSENTIAL OIL ACCUMULATING SITE
In members of the genus Cymbopogon essential oils are stored in
glandular micro-hairs. In lemongrass EO accumulating sites were
detected using Schiff’s reagent which gives purple colour after
specifically interacting. Based on this method it was found that
lemongrass accumulated EO in the leaf mesophyll cells commonly
adjacent to non-photosynthetic tissue and in between vascular bundles
which are referred as oil cells (Fig. 5) (Lewinsohn et al., 1998; Luthra et
Fig. 5: Essential oil accumulating cells in the leaf parenchymal tissues of
lemongrass
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250 RPMP Vol. 37: Essential Oils–II
al., 2007). The compartmentalization of EO accumulating sites in
lemongrass has important regulatory roles as it prevents other
metabolically active cells from these often toxic components. In citronella
EO accumulates in five types of glandular micro hairs found on adaxial
surface of the epidermis (Iruthayathas & Herath, 1982).
ESSENTIAL OIL BIOSYNTHESIS AND PRIMARY METABOLIC
PATHWAYS
Essential oil biosynthesis is tightly linked with primary metabolic
pathways. The substrates/or precursors, co-factors, energy (ATP) and
reducing power (NADPH) required for the EO biosynthesis is mainly
derived from the primary metabolic pathways (Singh et al., 1990;
Ganjewala & Luthra, 2007). The EO biosynthesis is most likely co-
coordinated to primary metabolism at the rate with which the substrate
can ‘branch off’ from primary pathways and ‘funnel’ into secondary
biosynthetic routes (Singh et al., 1991).
In lemongrass studies using radio labeled sucrose have found that
the rate of metabolism of sucrose and mobilization of starch is most
rapid in immature and young (10-15 day old) leaves to insure efficient
supply of substrates/or precursors, co-factors, energy and reducing power
for various biosynthetic activities and EO biosynthesis (Singh et al.,
1990; Ganjewala & Luthra, 2007). The rapid rate of sucrose metabolism
and starch mobilization are in accordance with exceptionally higher
activities of acid invertase and â-amylase during early stages of leaf
and inflorescence development in lemongrass and palmarosa,
respectively (Dubey et al., 2003). Products and transient starch
breakdown could be in situ respired and/or exposed to carbon
heterotrophic cells in the form of sucrose. It is believed that in vivo
synthesis of EO is directly influenced by the presence of sucrose or
equivalent products of the photosynthesis, which in turn, might be
controlled by the balance between production of photosynthate and their
utilization. In lemongrass and palmarosa EOs are presumably
synthesized via acetate-MVA pathway and the major route of precursor
and co-factors generation appears to be sugar-phosphate metabolism
via glycolysis and pentose phosphate pathway (Mccaskill & Croteau,
1995). The catabolism of carbohydrates leads to in vivo generation of
ATP, reduced nucleotides and the substrate for monoterpene
biosynthesis. Generation of acetyl-CoA, ATP and reducing power are
produced by oxidative pathways (Singh et al., 1990; Ganjewala & Luthra,
2007). Any fluctuation in the primary metabolites and variation in
enzyme activity of energy and reducing power yielding reactions affects
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251
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
the rate of EO biosynthesis. Moreover, in lemongrass incorporation of
metabolic inhibitors (i.e. sodium fluoride, sodium arsenate, sodium
borate, 2,4-dinitrophenol and aminooxyacetic acid) of oxidative
pathways along with [2-14C]-acetate have resulted in significant
reduction of the rate of EO biogenesis, thus suggesting the tight
relationship of oxidative pathways and EO biosynthesis (Singh et al.,
1990; Ganjewala & Luthra, 2007).
FACTORS INFLUENCING EO CONTENT AND COMPOSITION
Several factors such as, temperature, light intensity, soil moisture,
fertilizers, and developmental stages of the plant/parts greatly influence
EO content and composition of lemongrass (Ganjewala et al., 2008). In
lemongrass and palmarosa net EO production is dependent on the early
growth stages of leaf and inflorescence, respectively (Singh et al., 1989).
In general, EO production is directly proportional to the yield of biomass
of the plant/plant parts. In lemongrass, younger leaves produces EO of
higher quality with very high citral content (75%) whereas from older
leaves has low level of citral when harvested at a given point.
Developmental Regulation of EO Biosynthesis
The most important characteristic character of the EO accumulation is
its dependence on the developmental stages of the concerned plant parts/
organs. The EO accumulation is greatly influenced by the ontogeny of
the leaves (in lemongrass) and/or inflorescence (in palmarosa), their
origin, their expansion to full development and finally their loss through
senescence. The EO yield and proportion of the citral in lemongrass is
closely related to leaf growth stages (Singh et al., 1989). In lemongrass
80% of the EO is accumulated in the earlier (10-25 day old) leaf
developmental phases (Singh et al., 1989; Ganjewala et al., 2008). Any
alteration in the EO content is reflected by the changes in the citral
content. Similarly changes in EO content and composition with increase
in leaf age have been observed in citronella (Luthra et al., 1991). In
citronella relative percentage of geraniol and citronellol in the oil
increased with corresponding decrease in geranyl acetate and citronellyl
acetate as leaves grow older (Luthra et al., 1991). Also, leaf ontogeny
has mimicked similar changes with steady increase in amount of
citronellol, geraniol and citronellal and corresponding decline in amount
of geranyl acetate and citronellyl acetate as leaf expands. Towards
senescence/maturity, amount of EO, citronellal and geraniol decreased
significantly (Luthra et al., 1991). Developmental and ontogenic
variation in EO content and composition were also studied in lemongrass
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cultivars (Ganjewala et al., 2008). In palmarosa, the geraniol content
in the oil increased from 64.8% at vegetative stage to 81.4% at flowering
stage with corresponding decrease in geranyl acetate content (Dubey
et al., 2001). Best quality palmarosa EO is obtained from harvest at
early seed formation stage.
Seasonal Variation
Climate/seasons and diurnal factors also affect EO content and
composition of lemongrass (Singh et al., 1989). It is reported that
maximum amount of citral in the EO is accumulated during days when
temperature is highest (Singh et al., 1979). In lemongrass only EO yield
is affected by seasonal fluctuation but the citral content remained
unaffected. The EO content in ten diverse but highly selected clones of
lemongrass varied during the year with maximal EO yield in the May
whilst lowest in the September (Singh et al., 1989). Similarly, in C.
citratus EO and citral content recorded maximum during the dry hot
season which declined during rainy season (Oliveros-Belardo & Aureus,
1977). The EO obtained from lemongrass grown in Tarai climate of
Uttar Pradesh had maximum citral content in October and June whilst
lowest during the rainy season (Duhan et al., 1976). In citronella java
EO, citronellal and geraniol contents were recorded maximal during
months of October and November, while September harvest gives more
citronellal (Malwatkar et al., 1984).
In case of palmarosa, summer harvest yields EO with lesser geraniol
and higher geranyl acetate contents. The growth stage and harvesting
time in particular adapto-climatic conditions have a profound influence
on quality of palmarosa oil (Gulati et al., 1970; Gupta et al., 1978). The
EO composition of C. nardus indigenous to Sri Lanka is influenced by
temperature, when the temperature was low amount of citronellal in
the oil was highest and when the temperature was high amounts of
minor constituents such as, borneol and monoterpene hydrocarbons were
high.
BIOLOGICAL ACTIVITIES OF LEMONGRASS OIL AND ITS
CONSTITUENTS
The bioactive potential of lemongrass oil and constituents are rapidly
increasing which is reflected from growing number of reports being
published. Since lemongrass oil is easily available, has a pleasant aroma,
non-toxic and safe it is becoming increasingly popular in
pharmaceuticals and medicines. Semio-chemical properties of the
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253
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
lemongrass oil has been promising in integrated pest management
programme as this property may lead to development of alternatives to
synthetic chemical pesticides (Kumar et al., 2007). In the past and in
recent times a number of researchers have investigated bioactive
potential of lemongrass oil and its constituents with the mechanism of
their action using animal models and cell systems. EOs obtained from
various Cymbopogon species have displayed many useful and novel
bioactivities such as, antimicrobial, allelopathic, anthelmintic, anti-
inflammatory, anticancer, antioxidant, insect and mosquito repellent.
Essential oil of C. citratus has been found most promising due to its
wide variety of bioactivities. Plamarosa & citronella EO oils also possess
useful bioactivities particularly insect repellent and anthelmintic
activities whereas EO of C. schoenanthus has antioxidant properties.
Most of the bioactivities of lemongrass oil has been attributed to its
one or more major chemical constituents namely citral and geraniol
(Santoro et al., 2007; Alitonoua et al., 2006; Kumar et al., 2008; Sharma
et al., 2009; Li et al., 2005). Some of the important bioactivities of citral
are antimicrobial (Kakrala et al., 2009; Silva et al., 2008; Singh et al.,
2011; Aiemsaard et al., 2011; Saddiq & Khayyat, 2010), antiviral (Astani
et al., 2010), anti inflammatory (Katsukawa et al., 2010; Ortiz et al.,
2010a,b; Lee et al., 2008), anti-leishmanial (Machado et al., 2012; Santin
et al., 2009), inhibitory activity against cytokines (Bachiega & Sforcin,
2011), chemopreventive (Chaouki et al., 2009), allelopathic (Chaimovitsh
et al., 2012), aldose reductase inhibitor (Pingle et al., 2011), spasmolytic
(Devi et al., 2011), antiadipogenic (Modak & Mukhopadhaya, 2011),
repellent (Donald et al., 2011), anti parasitic (Cardoso et al., 2010),
larvicidal (Freitas et al., 2010), cognitive (Yang et al., 2009) activities.
Other oil constituents such as limonene and borneol has immuno-
stimulatory, analgesic and anaesthetic properties (Toro-Arreola et al.,
2005; Granger et al., 2005) whereas geraniol, geranyl acetate, á-bisabolol
and isointermedeol possess different types of bioactivities.
Isointermedeol present in lemongrass oil has anticancer properties
(Kumar et al., 2008). Some of the important bioactivities of the EO of
lemongrass and other Cymbopogon species have been discussed in the
following section.
Antimicrobial Activities
Due to rapidly developing resistance of pathogenic microorganisms
against currently available drugs/ treatment there is urgent need for
searching new alternative antibiotics/drugs. Since lemongrass oil and
its constituents has shown strong antimicrobial potential they offer
alternative therapeutics/drugs to currently available antibiotic
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254 RPMP Vol. 37: Essential Oils–II
medicine. Antimicrobial properties of the EO and constituents in general
are determined in terms of minimum inhibitory concentration (MIC).
MIC is the concentration of the EO required for the 50% inhibition of
the growth of microorganisms.
Lemongrass EO and citral displayed potent antifungal activity against
C. albicans, C. glabrata, C. krusei, C. parapsilosisandC. tropicalis (Silva
et al., 2008). Other oil components citral, geraniol and myrcene exhibited
significant antibacterial activities against four strains of clinically isolated
bovine mastitis pathogens, includingS. aureus, Streptococcus
agalactiae,Bacillus cereusandEscherichia coli(Aiemsaard et al., 2011).
Essential oil distilled from C. nervatus inflorescence displayed
antibacterial action against Shigella dysenteriae and Klebsiella
pneumoniae (El-Kamali et al., 2005) while the C. densiflorus oil possessed
wide spectrum antibacterial action against Gram positive and Gram
negative bacteria (Takaisi-Kikuni et al., 2000). The EO of C. nardus has
significant inhibitory effect on the growth of Aspergillus niger. A dose of
800 mg/ml of EO caused cytological modifications on growth of the
mycelium, damaged the plasma membrane and mitochondrial structural
organization in A. niger (De Billerbeck et al., 2001). Essential oil of C.
citratus ahowed similar inhibitory effects on the growth, lipid content
and morphogenesis in A. niger ML2-strain (Helal et al., 2006). Scanning
electron and transmission microscopic observation of A. niger hyphae
treated with EO detected ultra structural alterations in the hyphae, which
perhaps developed due to treatment with EO. Fumigation of A. niger
with EO caused significant loss in Ca2+, K+ and Mg2+ ions from mycelium
and blocked aflatoxin B production (Helal et al., 2006; 2007). The oil of C.
citratus has been very useful in the treatment of oral and vaginal
candidiasis. The citral in the oil is responsible for powerful inhibitory
effects on growth of a number of yeast such as, Candida oleophila,
Hansenula anomala,Saccharomyces cerevisiae,S. uvarum,
Schizosaccharomyces pombe and Metschnikowia fructicola (Abe et al.,
2003) and filamentous fungi, Alternaria alternata,Aspergillus niger,
Fusarium oxysporum and Penicillium roquefortii (Irkin et al., 2009). The
EO and powder of C. citratus is used to control storage deterioration and
aflatoxin contamination of melon seeds caused by Aspergillus flavus,A.
niger,A. tamarii and Penicillium citrinum (Bankole et al., 2005). The
advantages of this treatment are that the essential oil does not affect the
biochemical composition of the seeds and has strong effects comparable
to that of a commercial fungicide iprodione making essential oil a better
and safe natural control.
Palmarosa EO showed striking antiyeast activity against
Saccharomyces cerevisiae which is attributed to major oil constituent
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255
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
geraniol (Prashar et al., 2003). Plausible mechanism underlying
antiyeast activity involves (i) excessive K+ ion leakage from yeast cells
due to geraniol and (ii) alterations in the yeast cell membrane
composition (changes in the level of saturated and unsaturated fatty
acids) induced by EO treatment resulting in growth inhibition.
Palmarosa EO also showed similar antiyeast effects against
dermatophytes and filamentous fungi (Prasad et al., 2009). Unlike EO
of other Cymbopogon species, EO of C. parkeri has shown substantial
activity against phytopathogenic fungi, namely Rhizoctonia solani,
Pyricularia orizea and Fusarium oxysporum (Hajieghrari et al., 2006)
In the recent years citral has been rapidly emerged as most promising
monoterpene among others due to its tremendous bioactive potential.
Literature survey has revealed tremendous bioactive potential of citral
particularly antibacterial and antifungal potentials. Citral and its
oxidative products known as epoxides have been found to be very useful
in the treatment of fungal diseases (Saddiq & Khayyat, 2010). Infect,
the epoxides have more powerful antifungal properties than the citral
by displaying very strong inhibitory action on the growth of fungi such
as, P. italicum, Rhizopus stolonifer and methicillin resistant bacteria
Staphylococcus aureus. They were found more competent than the
standard antibiotics nalidixic acid, ampicillin and nitrofurantoin.
Several conjugated acid derivatives of citral were also showed similar
strong antimicrobial properties and comparatively much more powerful
than standard antibiotics chloramphenicol and nystatin (Singh et al.,
2011).
The antibacterial potential of lemongrass EO and constituents can
be increased by mild heat treatment of the microorganisms.
Furthermore, efficacy of the EO constituents can be enhanced if
combination of the two or more EO constituents in appropriate
concentration is used to treat bacteria. Several studies on antimicrobial
properties of lemongrass oil and citral have substantiated these facts.
The antimicrobial activities of the three terpenes namely, citral, linalool
and b-pinene was tremendously enhanced when bacteria were given
mild heat treatment at 55 °C for 15 minute. Also, more potent
antimicrobial activity was observed when the bacteria were treated
with a combination of three terpenes mixed with each other in
appropriate concentration (Belletti et al., 2010). Citral caused
inactivation of E. coli wild type strain BJ4 by inducing sub-lethal injury
to both cytoplasmic and outer membrane (Somolinos et al., 2010).
However, the inactivation of E. coli was more prominent when they
were given mild temperature treatment but not any change in efficacy
of citral seen when given pulsed electric field (Somolinos et al., 2010).
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256 RPMP Vol. 37: Essential Oils–II
However, citral did not show any effects against the rpoS null mutant
strain of E. coli BJ4L1 indicating that this mutant strain might have
evolved resistance mechanism against citral. Uses of mutant strains
have been useful in elucidation and understanding of the mechanism
of microbial inactivation bycitral. Thermal inactivation of E. coli
0157:H7 by citral in the citrate phosphate buffer and apple juice is also
reported (Espina et al., 2010). The study further confirmed that efficacy
of citral is significantly increased when bacteria are treated citral in
combination of heat treatment. It also reduces their potential negative
effects. Lemongrass EO and citral is also used to prevent microbial
spoilage and to check growth and survival of pathogenic microorganisms
during storage (Belleti et al., 2008).
Citral can also act as synergistic agent with conventional drugs like
fluconazole which makes it even more effective antimicrobial agent.
The antifungal and anti candidal potential of citral has been assessed
by determining minimum fungicidal concentration (MFCs) and
fractional inhibitory concentration (FIC) index, respectively. Citral has
shown excellent synergistic activity with fluconazole against a
fluconazole resistant strain of C. albicans (Zore et al., 2011). It inhibited
the growth of C. albicans cells by hindering of different phases of the
cell cycle, most likely initiating apoptosis by intervening S phase of the
cell cycle. Citral with other monoterpenes like eugenol, nerilidol and
alpha-terpineol produce irreversible ultra structural changes in
Trichophyton mentagrophytes (Park et al., 2009). Amides such as, 5,9-
dimethyl-deca-2,4,8-trienoic acid amides and 9-formyl-5-methyl-deca-
2,4,8-trienoic acid synthesized from citral and citronellol also act as a
potent bacterial NorA efflux pump inhibitors (Thota et al., 2008).
Anti-inflammatory and Antioxidant Activities
Essential oil of C. citratus rich in citral content displayed significant
anti-proliferative effect against Trypanosoma cruzi and trypanocidal
activity against the parasite (Santoro et al., 20070). Essential oils of
lemongrass and other members of the genus Cymbopogon have also
been known for their strong antioxidant properties. Antioxidants are
substances with ability to scavenge free radicals. The antioxidant
activities of EOs are determined using the DPPH assay. A member of
the genus C. schoenanthus owns antioxidant properties; its EO has the
ability of scavenging of free radicals and anti-acetylcholine esterase
activity (Khadria et al., 2008). Similarly, leaf extracts of C. citratus
prepared with methanol and methanol-water has exhibited powerful
antioxidant properties (Khadria et al., 2008; Cheel et al., 2005).
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257
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
Traditionally lemongrass is also known for analgesic and anti-
inflammatory properties, however only little work has been carried out
to substantiate these effects of lemongrass oil. Only recently, a few
research groups have undertaken studies to investigate anti-
inflammatory properties of lemongrass EO and its constituent citral.
Sforcin et al. (2009) among others have tested the anti-inflammatory
properties of lemongrass water extract in mice model. They evaluated
anti-inflammatory effects in the mice model after treating them with
lemongrass water extract. In the treated mice the production of IL-1b
and IL-6 from macrophages has been halted which was most likely due
to the anti-inflammatory action of lemongrass water extract.
Lemongrass EO and citral have also significance in the management of
anti-inflammatory and anti-lifestyle-related diseases (Katsukawa et al.,
2010). Citral is reported as a suppressor of cycloxygenase-2 (COX-2)
expression and activator of peroxisome proliferator-activated receptors
(PPARs)-a and g in human macrophage-like cells U937 (Katsukawa et
al., 2010). Cyclooxygenase (COX) is a key enzyme in prostaglandin
biosynthesis which exists in two isoforms COX-1 and COX-2 in most
cells (Simmons et al., 2004) whereas the PPARs are members of a nuclear
receptor family of ligand-dependent transcription factors. The PPAR
subfamily has three isotypes, PPARa,b/d, and g, which play different
roles in lipid and carbohydrate metabolism, cell proliferation and
differentiation, and inflammation hence considered to be the best
molecular targets against lifestyle-related diseases (Michalik et al.,
2006; Sonoda et al., 2008). Citral has the capability of suppressing both
LPS-induced COX-2 mRNA and protein expression in human
macrophage-like U937 cells, in dose-dependent manner. Furthermore
it also induced the mRNA expression of the PPARa-responsive carnitine
palmitoyltransferase 1 gene and the PPARg-responsive fatty acid
binding protein 4 gene. These remarkable properties of the citral makes
it suitable therapeutic agent in life-style related diseases (Katsukawa
et al., 2010). An earlier study by Lee et al. (2008) has also reported the
anti inflammatory effects of citral in lipopolysachharide (LPS)-
stimulated RAW 264.7 cells. The anti-inflammatory activity activity of
the citral is thought to be due to its inhibitory effects on NO production
via suppression of iNOS expression and NF-kappa B activation in
RAW264.7 cells (Lee et al., 2008). Essential oil of C. insularimontanum
which has rich proportion of citral also exhibited potent anti-
inflammatory activity in croton oil-induced mice ear edema rats. These
effects of citral were also most likely due to its similar inhibitory effects
on NO production (Lin et al., 2008). Similar inhibitory effects of citral
on NO pathway and blockade of calcium channels via VOC and/or
receptor operated calcium channel have been suggested for its
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258 RPMP Vol. 37: Essential Oils–II
spasmolytic activity in isolated rabbit elium (Devi et al., 2011).
Cymbopogon citratus is reported to possess potential
immunomodulatory effect on cytokines production (IL-6, IL-1b and IL-
10) by peritoneal macrophages from BALB/c in vitro (Bachiega & Sforcin,
2011) reported. The inhibitory effect of citral on cytokines production
has been attributed responsible for its anti-inflammatory activity. A
possible mechanism for the anti-inflammatory activity of citral could
be the inhibition of the transcription factor NF-kB (Bachiega & Sforcin,
2011). Certainly the above studies have paved the way for future
implication of lemongrass EO and citral in the management of anti-
inflammatory and anti-life style related disorders.
Anticancer and Chemo-preventive Activity
Recently published several reports have revealed the anticancer and
chemo-preventive properties of lemongrass EO and constituents
however with relatively less information on its mechanism of action.
Puatanachokchaia et al. (2002) have for the first time reported the
anticancer properties of lemongrass on hepatocarcinogenesis induced
using diethylnitrosamine in male Fischer 344 rats. Later more few
more studies have recognized anticancer properties of citral like a
new inducer of caspase-3 activity in the tumour cell lines. Citral caused
DNA fragmentation and enhanced the caspase-3 catalytic activity
which eventually induced apoptosis in several hematopoietic cell lines
(Dudai et al., 2005). Kumar et al. (2008) and Sharma et al. (2009)
have carried out detailed studies of anticancer properties of the
lemongrass EO which provided deeper insight in to the mechanisms
of action of anticancer properties. Kumar et al. (2008) have reported
the anticancer activity of lemongrass EO and its constituent,
isointermedeol in human leukaemia HL-60 cells. The study revealed
that lemongrass EO and isointermedeol (ISO) induced apoptosis in
human leukaemia HL-60 cells most likely by down regulation of
NF-kB expression and caspase activation through apical receptors and
mitochondrial signaling pathways. They suggested that significantly
increased levels of cytochrome c in mitochondria following EO
treatment of cell line might have played a role in triggering apoptosis.
Sharma et al. (2009) have also reported similar anticancer activity of
lemongrass EO in human cancer cell lines HL-60, murine Ehrlich and
Sarcoma-180 tumors. Treatment of cancer cell lines with EO caused
some morphological changes favouring induction of apoptosis in the
tested cell lines. Major morphological changes observed were
chromatin condensation, fragmentation of the nuclei and apoptosis in
the tested cell lines (Sharma et al., 2009).
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259
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
Citral like a number of other plant natural products has been found
to be beneficial for health and chemoprevention of carcinogenesis. Citral
has shown chemo-preventive effects in human breast cancer cell line
MCF-7 and on cyclo-oxygenase activity. It has significantly inhibited
cell proliferation and induced apoptosis which resuled in arrest of cell
cycle in human breast cancer cell line MCF-7. Citral and retinoids also
has the ability to modulate cell viability, metabolic stability, cell cycle
progression and distribution in the lung carcinoma cell line A549 (Farah
et al., 2010a). Citral act as specific inhibitors of retinoid metabolism
thus could be employed to ascertain the specificity of retinoid impacts
on the lung carcinoma cell model. Citral due to its ability to modulate
metabolic integrity, cell cycle distribution and cell survival may be
promising in the lung carcinoma model (Farah et al., 2010b).
Allelopathic, insect repellent and anthelmintic activities
Lemongrass EO and their major constituents are reported to function
as allelochemicals. Allelo-chemicals are substances which affect insect
biology and behaviour hence used in biocontrol. The EO of C.
schoenanthus is reported to function as allelochemical and used to
control Callosobruchus maculates development in cowpea stock (Ketoh
et al., 2005; 2006). Citronella EO also reported to own allelo-chemical
properties that affected the growth of Spodoptera frugiperda larvae
(Labinas et al., 2002). In addition, citronella extract has insect repellent
activity that is why it is used to prevent cartoons containing muesli
and wheat germ from beetles (Wong et al., 2005). Palmarosa variety
sofia EO also showed repellent action against malaria causing
mosquitoes Anopheles sundaicus (Das et al., 2003). It is also having
strong pesticidal activity against insect infestation and used to protect
stored wheat and grain from the beetles Callosobruchus chenesis and
Tribolium castaneum (Kumar et al., 2007). Palmarosa EO demonstrated
significant anthelmintic activity against the nematode Caenorhabditis
elegans and Indian earthworm Pheretima posthuma (Kumaran et al.,
2003; Nirmal et al., 2007). On the other hand, the EO of C. citratus
exhibits alleopathic activity on seed germination and seedling growth
of corn and barnyard grass (Li et al., 2005).
Anti-protozoan Activity
Several research groups have reported anti-protozoan potential of citral
rich EO against diverse parasitic protozoa (Santoro et al., 2007a, b, c;
Santin et al., 2009). The first report published was on anti-protozoan
activity of citral against a bloodstream trypomastigotes Trypanosoma
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260 RPMP Vol. 37: Essential Oils–II
cruzi (Santoro et al. 2007a). Cardoso and Soares (2010) have also
reported trypanocidal activity of the citral against T. cruzi causing cell
death of the two developmental forms epimastigote and trypomastigote
of T cruzi. Trypomastigotes (bloodstream forms) is one of the important
developmental stages of the T. cruzi that has been adapted for living in
specific environments inside the vertebrate hosts. During the life cycle
T. cruzi undergo intracellular differentiation from trypomastigotes to
amastigotes (and then back to trypomastigotes) which is essential for
evading the host’s immune response and maintaining the infection in
the mammalian host. Therefore these differentiation stages are potential
targets for development of new trypanocidal drugs.
Other useful Bioactivities
Essential oil of lemongrass and other species of the genus Cymbopogon
also displayed many more other useful less studied bioactivities such
as, antinociceptive, anxiolytic-type, and neurobehavioral activity
(Bankole et al., 2005; Viana et al., 2000; Costa et al., 2006; Blanco et al.,
2009; Adeneye et al., 2007). Wild lemongrass (C. citratus)leaf aqueous
extracts has hypoglycaemic and hypolipidaemic effects in Wistar rats
augmenting its possible therapeutic roles in Type 2 diabetes mellitus
(Adeneye et al., 2007). Citronella EO oil in Brazilian folk medicine is
used as analgesic and anxiolytic agents (Sharma et al., 2009) and has
anticonvulsant and depressant activity on central nervous system of
rodents (Quintans-Junior et al., 2008). In addition, citronella oil
exhibited significant inhibitory effects on the growth of several weeds
like Ageratum conyzoides,Chenopodium album,Parthenium
hyterophorus,Malvastrum coromendelianum,Cassia accidentalis and
Phalaris minor (Singh et al., 2006). Citronella oil mainly comprises
citronellal which perhaps exerts multiple effects on the biochemistry
and physiology of the weeds and inhibits their emergence. It mainly
impairs the photosynthetic and respiratory metabolism, disrupts
cuticular wax, clogs stomata, shrinks epidermal cells and causes rapid
electrolyte leakage (Singh et al., 2006).
Citral demonstrated anti-clastogenic activity on micronucleus system
in mouce treated with nickel chloride (Rabbani et al., 2006). This
property of citral is believed to be due its negative effects on micronuclei
formation and positive on superoxide scavenging activity. Lemon juice
and C. citratus infusion has been found highly effective yet safe in the
treatment of the treatment of oral candidiasis in an HIV patients in
South Africa compared to a group those using gentian violet aqueous
solution (Wright et al., 2009). Yang et al. (2009) for the first time reported
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261
Lemongrass (Cymbopogon flexuosus Steud.) Wats Essential Oil
biphasic effects of citral on spatial learning and memory in rats. Citral
mainly regulated the synthesis of retinoic acid (RA), which exerts a
vital function in the development and maintenance of spatial memory
(Di Renzo et al., 2007). Citralis a potent volatile anti-microtubule
compound which effectively disrupts microtubules of Arabidopsis
seedlings within minutes after exposure tomicromolar concentrations
of citralin the gaseous phase (Chaimovitsh et al., 2009). It also less
efficiently disrupts animal microtubules but does not disrupt actin
filaments. Citral also has allelopathic property (Chaimovitsh et al.,
2012). Citral and myrcene possess leishmanicidal activity against
Leishmania infantum,L. tropica and L. major (Machado et al., 2012).
Citral and other essential oil constituents like myrcene and geraniol
are capable of inhibiting activity aldolase reductase an enzyme of polyol
pathway which is linked to diabetes and its complications (Pingle et al.,
2011).
Citral has negative effects on female reproductive system but its
effects on male reproductive system were not known until recently. Now,
it has became clear from the report of Ilayperuma (2008) that it has
similar negative effects on male reproductive system in rat model in
which it caused reduction in weights of the testes, epididymis, seminal
vesicles, prostate and plasma testosterone levels. Citral showed anti
adipogenic effects in male Sprague-Dawley rats (Modak &
Mukhopadhaya, 2011). Citral can ameliorate diet-induced obesity by
increasing energy dissipation (and also reduced lipid accumulation) and
improves insulin sensitivity and glucose tolerance. Undoubtedly, in the
present scenario of increasing prevalence of obesity and
diabetes,citralmay prove as novel agent in its management.
CONCLUSIONS
Essential oils of lemongrass, wild lemongrass, palmarosa and citronella
owing to their specific aromatic and medicinal properties are broadly
used in flavor, fragrance, perfumery, cosmetics and pharmaceuticals.
In the past several years pharmacological and medicinal significance
of the lemongrass EO and its constituents has been tremendously.
Lemongrass EO of diverse origin and compositions are mainly consisted
of monoterpene fractions, with large proportion of citral and geraniol.
Despite the immense commercial significance of the lemongrass EO
only little work has been done so far towards understanding of EO
biosynthesis and regulation. Most major breakthroughs in areas of
monoterpene biosynthesis and regulations have come from the
exhaustive research work done in members of Lamiaceae, Pinaceae,
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262 RPMP Vol. 37: Essential Oils–II
Rutaceae, Myrtaceae and Asteraceae families. The most important
breakthrough was the elucidation of the MEP pathway and
characterization and cloning of enzymes/genes of this pathway. The
cDNAs of MEP pathways genes has made possible metabolic engineering
of the monoterpene biosynthetic pathway in order to improve yield and
composition of the EO in many plants. Unfortunately, the genus
Cymbopogon remained isolated from the benefits of the recent
advancement to improve EO yield and quality. In view of the high
commercial value of lemongrass EO full understanding of the EO
biosynthesis and molecular regulatory processes is highly desirable for
manipulation of the oil yield and quality.
Nevertheless, tremendous progress has been made towards
investigating biological activities of the lemongrass EO and its major
constituent citral and geraniol. Particularly, past decades has been most
productive in recognition of a number of useful bioactivities of EO and
citral such as, antimicrobial, anti protozoan, anti inflammatory and
chemo-preventive properties. Citral derivatives such as alkenyl amides
and epoxides are specially becoming very useful as they can be exploited
as novel drugs against bacteria and fungi. Also, EO and citral may find
applications in the management of the anti-inflammatory and anti-
lifestyle-related diseases. Also, there are opportunities to develop a new
anti-protozoan drug based on citral. Chemo-preventive properties of citral
could also be useful in chemoprevention of various carcinomas. However,
more therapeutic investigations would require prior to clinical trails in
carcinoma models. In conclusion we believe that the preliminary
knowledge of the developmental and seasonal regulation of the EO
biosynthesis in lemongrass and vast knowledge of their bioactive potential
would be of great help in developing lemongrass leaf as a model system
to understand more deeply EO biosynthesis and regulation in future.
ACKNOWLEDGEMENTS
Corresponding author of this article is grateful to Dr. Ashok Kumar
Chauhan, Founder President and Atul Chauhan, Chancellor, Amity
University, Uttar Pradesh, Noida, India for providing necessary facilities
and support. Also, I duly acknowledge research grant from Council of
Scientific and Industrial Research (CSIR), New Delhi.
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... Lemongrass is endogenous to India, Sri Lanka, Brazil and Myanmar. India is a major exporter of lemongrass among these with an exportation capacity of about 1000 tons worldwide every year, predominantly to America, England and Australia (Ganjewala and Gupta 2013). ...
... Essential oil in lemongrass is primarily a mixture of cyclic and acyclic monoterpenes which are chiefly derived from geranyl diphosphate (GPP) which acts as the precursor for monoterpenes biosynthesis (Ganjewala and Gupta 2013). The GPP is formed by the condensation of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) units. ...
... Lemongrass plants store EO in its leaf parenchymal cell, also known as 'oil cells' (Ganjewala and Gupta 2013). As lemongrass leaves expands, they synthesise EO more rapidly during early days of their development. ...
Chapter
Full-text available
Lemongrass (Cymbopogon flexuosus) is an aromatic perennial grass grown extensively for its essential oil. Lemongrass oil is chiefly a mixture of various cyclic and acyclic bioactive monoterpenes. We reviewed lemongrass oil and its biosynthesis in the present chapter along with its biochemical composition. Furthermore, we attempted to explore both the possible routes for essential oil biosynthesis in lemongrass, i.e. mevalonate and non-mevalonate pathways, and how these pathways intertwined with each other. Lemongrass oil has high commercial potential in medicinal, cosmetic, food and energy industries. Regarding the pharmacological properties, a wide array of biological activities has been observed in lemongrass oil such as antimicrobial, insecticidal, analgesic and anticancer properties as well as its efficacy as insect-repellent. The later sections were dedicated for the analysis of insecticidal property of the lemongrass oil and the mechanism working behind this phenomenon where it was observed that in addition to synergistic effects, various components of lemongrass oil can also induce specific neurotoxic and cytotoxic responses in insects.
... However, these EOs have high commercial value for their wide range of applications including antibacterial, antioxidant, and anti-inflammatory properties. It is believed that biosynthesis of lemongrass EO directly depends on the availability of photosynthates (Ganjewala and Gupta, 2013). Regarding this, we found that various factors have strong direct or indirect correlation with EO content in lemongrass (Fig. 9). ...
Article
Lemongrass (Cymbopogon flexuosus (Steud.) Wats) is an aromatic grass with great industrial potential. It is cultivated for its essential oil (EO) which has great economical value due to its numerous medicinal, cosmetic and culinary applications. The present study was conducted on silicon nanoparticles (SiNPs) application to lemongrass with the objective of overall agronomic enhancements. Graded concentrations (50-200 mg L⁻¹) of SiNPs were exogenously applied to lemongrass leaves. The physiological and biochemical analyses revealed that 150 mg L⁻¹ SiNPs is the optimum concentration for lemongrass plants. This concentration triggered photosynthetic variables, gas exchange modules and activities of enzymes involved in EO (geraniol dehydrogenase) and nitrogen (nitrate reductase) metabolism as well as in the antioxidant system (catalase, peroxidase and superoxide dismutase). These SiNPs-induced metabolic changes altogether significantly (p≤0.05) enhanced overall plant growth and yield. Moreover, SiNPs treatments assisted in palliating lipid peroxidation and H2O2 content in lemongrass leaves which added further advantage to plant metabolism. Overall, data indicates SiNPs elicit beneficial effects on lemongrass growth and yield through inducing various physiological and biochemical responses. This renders high possibility that similar objectives could be achieved with SiNPs biotechnological application on further related agronomic crops as well as in diverse industries.
... In lemongrass, younger leaves produce EO of higher quality with very high citral content (75%), where as older leaves have a low level of citral when harvested at a given point. Lemongrass EO consists mainly of citral, a mixture of geranial and neral isomers (40% and 32% respectively) (Ganjewala & Gupta, 2013). In this study, the proportions were 41.8% geranial and 33% general, corroborating with the literature. ...
Article
Full-text available
The objective of the study was to determine the antimicrobial activity antibiofilm and to identify the main components of the essential oil (EO) obtained from the leaves of Cymbopogon flexuosus. The antibacterial and antibiofilm activity was determined against Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Salmonella Typhimurium ATCC 14028 and Listeria monocytogenes ATCC 19117. The effect of EO on biofilm was evaluated by quantifying viable cell number (CFU) and biomass by crystal violet (CV) analysis. The composition of the essential oils was determined by GC / FID and GC / MS. The results showed action against L. monocytogenes, S. aureus and S. Typhimurium with MIC and MBC values of 3.9 μL mL-1, thus showing satisfactory antimicrobial activity, given this was the lowest concentration tested. For the antibiofilm activity, a significant reduction (P < 0.05) was observed for S. typhimurium and S. aureus. Biofilm biomass significantly reduced only for S. aureus and P. aeruginosa. EO presented the geranial and neral isomers as major components.
... Recently, different studies have revealed many useful antimicrobial, anti-inflammatory, anticancer, antioxidant and insecticidal activities of the EO of Lemongrass (LG) from Cymbopogon flexuosus DC. (Poaceae; Ganjewala and Gupta 2013). ...
Article
Multi-drug resistant uropathogens are responsible for urinary tract infections. The antibacterial activity of seven essential oils, oregano, thyme, clove, arborvitae, cassia, lemongrass, tea tree) was investigated by agar diffusion method, followed by determination of minimum inhibitory (MIC) and bactericidal (MBC) concentrations against five multidrug resistant isolates namely Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloaceae, Morganella morganii, Proteus mirabilis. Oregano, thyme, cassia had antibacterial activity with inhibition zones ranging 25–39 mm; clove, arborvitae, tea tree and lemongrass 12–15 mm. The essential oils showed antibacterial activities with MICs ranged from 0.005% (w/v) to 0.5% (w/v). Thyme had the same MIC and MBC on all strains. The effects of the vapors of the essential oils were also tested by placing the oils on the underside of the Petri dish lid. Thyme, oregano and cassia essential oils strongly inhibited the growth of the clinical strains of bacteria tested in vapor phase. This study demonstrates the potential of investigated essential oils as natural alternatives for further application in hospital therapies in order to retard or inhibit the bacterial growth. For the first time antibacterial effects of essential oils (clove, arborvitae, tea tree, lemongrass, and cassia) were evaluated against Enterobacter cloaceae and Morganella morganii clinical isolates.
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Monoterpenes, a class of isoprenoid compounds, are extensively used in flavor, fragrance, perfumery, and cosmetics. They display many astonishing bioactive properties of biological and pharmacological significance. All monoterpenes are derived from universal precursor geranyl diphosphate. The demand for new monoterpenoids has been increasing in flavor, fragrances, perfumery, and pharmaceuticals. Chemical methods, which are harmful for human and the environment, synthesize most of these products. Over the years, researchers have developed alternative methods for the production of newer monoterpenoids. Microbial biotransformation is one of them, which relied on microbes and their enzymes. It has produced many new desirable commercially important monoterpenoids. A growing number of reports reflect an ever-expanding scope of microbial biotransformation in food and aroma industries. Simultaneously, our knowledge of the enzymology of monoterpene biosynthetic pathways has been increasing, which facilitated the biotransformation of monoterpenes. In this article, we have covered the progress made on microbial biotransformation of commercial monoterpenes with a brief introduction to their biosynthesis. We have collected several reports from authentic web sources, including Google Scholar, Pubmed, Web of Science, and Scopus published in the past few years to extract information on the topic.
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Endophytic fungi Cladosporium cladosporioides (F1-MH810309) and Cladosporium tenuissimum (F2-MN715834) from the leaf of wild Cymbopogon martinii (MT90507) were isolated and selected based on the persistent occurrence during different seasons of the year. They were identified based on the morphological features and molecular characterization (ITS sequence), and later deposited at NCBI. Phytochemical studies on F1, F2 and host extracts showed the presence of alkaloids, flavonoids, phenols, terpenoids and tannins. The GC-MS of F1 extract (control) under the axenic condition revealed compounds like hexadecane, heptadecane,2,4-Ditert-butylphenol, E-14 hexadecenal, geraniol, geranyl acetate and cubenol similar to the host. The GC-MS of F2 extract (control) revealed metabolites that were unique. Further, both F1 and F2 were cultured in the supplementation of different concentrations (5%, 10%, 15% and 20%) of the host plant extract (an-axenic condition). The GC-MS of F1 extracts (test) exhibited good growth and showed the gradual increased production of terpenoid compounds whereas the F2 (test) did not show any growth. These compounds such as hyrdoxymenthol, nor-borneol, cedralacetate, α-cyclogeraniol, campesterol, β-cyclogeraniol, linalool oxide,2,3-boranediol, citronellyltiglate and 2,3-pinanediol were produced in a minor quantity and were known as biotransformed forms of the precursor compounds present in the host extract. In comparison, only F1 was able to produce terpenoids similar to the host species both in axenic and an-axenic conditions. Hence from the current study, the endophytic fungus F1 isolated from wild C. martinii for the first time can serve as a better resource for the bioprospection of an important terpenoid and its metabolites.
Article
Cymbopogon species from the Poaceae family are widely distributed in the Himalayan region of India and commonly used as flavors, fragrances, cosmetics, and pharmaceuticals. It is known to contain compound citral, which give the lemon scent to many of the plants of the cymbopogon genera. The essential oil of Cymbopogon flexuosus has high polyphenolic content which is responsible for antioxidant properties. Beside citral is also used for the synthesis of vitamin B and Ionones. The bioactive potential of Lemongrass and constituent are rapidly increasing which is reflected from growing number of reports being published. The present study was to know the chemical composition and in vitro antioxidant activity of essential oil of C. flexuosus from Uttarakhand. The essential oils of Cymbopogon collected in the region of Uttarakhand were obtained by hydrodistillation of the leaves and analyzed for chemical composition by GC/MS. The antioxidant activity of essential oils at different concentrations was determined against DPPH radical activity and vitamin C as the standard antioxidant compound. The IC50 value and percentage of DPPH inhibition were recorded. Twenty-five compounds were identified in essential oil extracted from leaves representing 93.15% of the oil composition. The yield of essential oil of Cymbopogon was 0.6 + 0.1 %and the major compound in the essential oil was citral (a racemic mixture of two isoforms geranial and nearl) followed by heptenone(1.98%) , linalool(1.65%), geraniol (1.47%), ?-caryophyllene (1.14% ) , limonene (0.92%), nearl acetate (0.82%), citronellal(0.44 %) and citronellol (0.22%). Radical scavenging capacity (Inhibition, %) of the C. flexuosus essential oil was high (78.19+1.11) at the concentration level of 150 ?g/ml and IC50 value of the essential oil was 43.67?g/ml. The data of this study encourages to consider the essential oil of C. flexuosus as a source of bioactive compounds which may add great industrial value to this crop.
Article
Cymbopogon martinii belongs to the family Poaceae and provides an aromatic essential oil of large applications in fragrance, perfumery, cosmetics and pharmaceuticals. The essential oil from this genus has two dominating monoterpenes, geranyl acetate and geraniol. Owing to the tremendous applications of the essential oil from this genus, knowledge of the biochemical and molecular regulatory processes and expressions of genes involved in terpenoid biosynthesis pathway, is highly desirable to improve the quality and yield of essential oil. We performed high-throughput transcriptome sequencing of C. martinii for identification of the genes related to terpenoids biosynthesis using Illumina HiSeq-2000 platform. In the present study, approximately 286,309,78 reads of high quality were generated. De novo assembly yielded 96,470 unigenes (≥200 bp) and 84,168 (≥500 bp). Functional annotation of total 96,470 (56%) unigenes was done. More than 4500 enriched unigenes were assigned to 367 KEGG pathways among various categories, i.e. protein processing, cellular processes, metabolism, steroid biosynthesis, and others. 913 unigenes in the metabolism category were assigned to 287 metabolic pathways linked with secondary metabolism. To explore the putative functions of six genes encoding alcohol dehydrogenase, geranyldiphosphate synthase, fernasyldiphosphate synthase, aldehyde dehydrogenase, aldo-keto reductase and alcohol acyltransferase expression patterns were studies using qRT-PCR. We have also identified 60 transcription factors in C. martini transcriptome using Plant Transcription factor database. To the best of our knowledge, this is the first-ever report on the C. martinii inflorescence transcriptome which will facilitate the understanding of the molecular mechanisms of essential oil biosynthesis in the genus Cymbopogon and related plant families.
Article
Full-text available
The study reports efficacy of Melissa officinalis L. essential oil (MOEO) as a safe plant-based insecticide against Tribolium castaneum Herbst (TC) by induction of oxidative stress. MOEO nanoencapsulation in chitosan matrix was performed to enhance its bioefficacy. GC–MS analysis of MOEO depicted geranial (31.54%), neral (31.08%), and β-caryophyllene (12.42%) as the major components. MOEO showed excellent insecticidal potential in contact (100% mortality at 0.157 μL/cm²) and fumigant bioassays (LC50 = 0.071 μL/mL air) and 100% repellency at concentration ≤ 0.028 μL/cm². Increased reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and decreased ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) at the LC50 dose suggested significant oxidative stress on TC in MOEO treatment sets. The encapsulated MOEO exhibited enhanced activity as fumigant (LC50 = 0.048 μL/mL air) and showed significant antifeedant activity in situ (EC50 = 0.043 μL/mL). High LD50 value (13,956.87 μL/kg body weight of mice) confirmed favorable toxicological profile for non-target mammals. The findings depict potential of nanoencapsulated MOEO as an eco-friendly green pesticide against infestation of stored food by TC.
Chapter
Humans for centuries have used plants to relieve discomfort and treat various health ailments. Medicinal herbs are used throughout developed and developing countries as home remedies, over-the-counter drug products and raw materials for the pharmaceutical industry, and represent a considerable proportion of the universal drug market. The medicinal value of plant depends on the nature of plant constituents, known as active principal or active constituent, present in it. Active constituents are those chemical substances, which are exclusively responsible for remedial activity of plant and serve as lead compounds in drug discovery and design. Traditional systems of medicine, modern medicines, folk medicines, food supplements, nutraceuticals, pharmaceutical intermediates and synthetic drugs are invariably dependent on the proportionate presence of active constituents found in plants. Nutrition plays an important role in the growth and development of all crop plants. The contribution of macro- and micronutrients in building indispensable organic compounds and in almost all plant life processes shows the noteworthy and diversified role of these minerals in the modification of plant metabolism. Severity or insufficiency of these minerals causes varied effects in plant metabolism. The role and contributions of various mineral elements can be revealed through their regulatory role played in metabolism of medicinal and aromatic plants. Secondary plant metabolism is a function of concentrations of minerals in the soil. Important mineral elements present in soil are transferred to plant areas where their need arises, thereafter governing various physiological activities. Therefore, biosynthesis and accumulation of these bioactive molecules in a plant system are broadly dependent on the availability and accessibility of mineral elements in the soil. This review chapter is an attempt to understand how essential mineral nutrients affect active constituents of selected medicinal and aromatic plants viz. fennel (Foeniculum vulgare), mentha (Mentha arvensis, Mentha piperita, Mentha citrata), lemongrass (Cymbopogon flexosus), Artemisia (Artemisia annua), turmeric (Curcuma longa), ginger (Zingiber officinale), periwinkle (Catharanthus roseus), Aloe vera (Aloe barbadensis).