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Chemistry and bioactivity of Eucalyptus essential oils


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The essential olis obtained from the eucalyptus have many medicinal and commercial uses. The oils possess many bioactivities(antimicrobiol, antiviral, fungicidal, insecticidal and herbicidal activities). The commercial uses of essential oils have incresead the research on their extraction, chemical composition, bioactivity and mode of actions. Eucalyptus species differs in their chemical composition. The bioactivity of essential oils is highly associated with their unique chemical composition. The noval biological functions of eucalyptus essential oils suggest research on all eucalyptus species to fully exploit their commercial benefits. This review, disscuss the recent progresses in above reserach areas and future research prospects.
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Allelopathy Journal 25 (2): 313-330 (2010) International Allelopathy Foundation 2010
Tables: 5, Fig : -
Chemistry and bioactivity of Eucalyptus essential oils
Test Centre, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
E. Mail:
(Received in revised form: November 23, 2009)
2.1. Extraction methods
2.2. Yields of essential oils
2.3. Chemical analysis
2.4. Chemical composition
3.1. Bioactivity on organisms
3.2. Bioactivity on weeds and crops
3.3. Mechanism of bioactivity
The essential oils obtained from the eucalyptus have many medicinal and
commercial uses. The oils possess many bioactivities (antimicrobial, antiviral,
fungicidal, insecticidal and herbicidal activities). The commercial uses of essential oils
have increased the research on their extraction, chemical composition, bioactivity and
mode of actions. Eucalyptus species differs in their chemical composition. The
bioactivity of essential oils is highly associated with their unique chemical
composition. The novel biological functions of eucalyptus essential oils suggest
research on all eucalyptus species to fully exploit their commercial benefits. This
review, discusses the recent progresses in above research areas and future research
Keyword: Allelopathy, bioactivity, chemical composition, essential oils, eucalyptus.
E.H. Graham Centre for Agricultural Innovation (Industry & Investment NSW and
Charles Sturt University), Wagga Wagga Agricultural Institute, Wagga Wagga, NSW 2678, Australia,
2Industry & Investment NSW, Primary Industry, Wagga Wagga Agricultural Institute, Wagga Wagga, NSW
2650, Australia
Zhang et al
Eucalyptus (family Myrtaceae) is native to Australia, however, its few species are
indigenous to neighbouring countries (30). It grows over wide range of soils and climates,
hence, has been introduced into North and South Africa, Asia and Southern Europe (3).
The interspecific hybrids are grown in Brazil, Congo, China, Indonesia and South Africa
and small plantations in Phillippines, Vietnam, Thailand and Malaysia and South
Americas (Argentina, Chile, Paraguay and Uruguay) (35). There are approximately 700
species worldwide and only about 1% are used for industrial purposes (76). Its timber is
now used for fuel, shelterbelts, windbreaks and for hardwood fibre (86).
Its essential oils have many medicinal and commercial uses (47). They can be
used as folk medicine and are anesthetic, anodyne, antiperiodic, antiphlogistic, antiseptic,
astringent, deodorant, diaphoretic, disinfectant, expectorant, febrifuge, fumigant, hemostat,
inhalant, insect repellant, preventitive, rubefacient, sedative yet stimulant, suppurative,
tonic, and vermifuge (34). Its 9-species are used for medicinal and commercial purposes
(Table 1). Besides, E. cinerea and E. cneorifolia also possess medicinal value and E.
macarthurii in perfumery.
Table 1. Cultivated Eucalyptus species
Uses Species Country
Eucalyptus globulus Labill.
China, Portugal, Spain, India, Brazil,
Chile,Bolivia, Uruguay, Paraguay
E. smithii R. Baker South Africa, Swaziland,
E. polybractea R. Baker (syn. E.
fruticetorum F. Muell. ex Miq.)
E. exserta F. Muell. China
E. radiata Sieber ex DC. (syn. E.
australiana, E. radiata var. australiana)
South Africa, Australia
E. dives Schauer Australia
E. camaldulensis Dehnh. (syn. E. rostrata
E. citriodora Hook. China, Brazil, India Perfumery
E. staigeriana F. Muell. ex Bailey Brazil
Source : 38
Growth inhibition of plants by other plants in their vicinity has been known for a
long time. The chemical interaction between plants is referred to as allelopathy (80).
Intensive allelopathy research has been conducted in recent decades and progress has made
in analysis and identification of allelochemicals (10,37,42,51,84,116). The rapid advances
in the identification of bioactive allelochemicals in eucalyptus oils have prompted research
into potential natural herbicidal compounds for weed management in agriculture
Owing to the wide range of traditional uses and potential commercial prospects of
eucalyptus oils, extensive research on yield and chemical composition of oils has been
undertaken, as well as development of extraction and analytical techniques. This paper
Chemistry and bioactivity of Eucalyptus essential oils
reviews the progress on isolation, identification, bioactivity and mode of actions of
essential eucalyptus oils.
2.1. Extraction methods
Essential oils are secondary metabolites produced by plants in response to stress,
infection or parasitic attack. Eucalyptus oils are volatile organic compounds found in
fruits, flowers, bark, seeds, wood and roots. However, they are mainly extracted from
leaves (3,20). There are 5-extraction methods (11,19,43,45,82,90) :
(i). Hydrodistillation: It involves placing plant material and water in a container and
heating from below. The heat releases the aromatic vapour, which is condensed into liquid
containing little hydrosol (water). Total oil yield increases with increase in distillation
time, but the principle component (%) reduces accordingly (11).
(ii). Steam distillation: It involves placing the plant material in a flask and forcing steam
through the plant material to vaporize the volatile oils. It is similar to hydrodistillation, but
higher oil yield is obtained (90).
(iii). Vacuum distillation: To extract essential oils from many eucalyptus species, vacuum
distillation is done at lower temperatures, avoiding the change in essential oil chemical
composition during distillation(19).
(iv). Supercritical fluid extraction (SFE): It uses the ability of certain gases (generally
CO2 is used) to act as non-polar solvents at certain temperature and pressure. It is more
efficient and faster than hydrodistillation (82).
(v). Subcritical-water extraction (SWE): It uses hot water (100-374oC) as extractant and
high pressure. It is faster and efficient than hydrodistillation (45). The advantages are
shorter extraction time, high quality of extract, lower costs of extracting agent and
environmental friendly (43).
2.2. Essential oils Yields
The yields of eucalyptus oils from leaves depends on the species studied and
varies from 0.10 to 9.0 % on dry weight basis (Table 2). Several factors affect the
eucalyptus oils yields: tree age (5), leaf age (39,96), altitude (62), season (77), harvest time
(32) and fertilizer application (61). Young leaves contains more oil than old leaves (39),
while leaves from older trees gave slightly higher yield (5). However, oil production is
more influenced by altitude than age (62). Oil content also fluctuates with season. E.
citriodora leaves collected in Pakistan in April-May contained 0.9% oil than 1.3% in
December (77). Good eucalyptus oil yields in central Thailand were obtained between
January to July (32). Application of nitrogen, phosphorus and potassium fertilizers
increased the production of essential oils (61).
Zhang et al
Table 2. Yields of eucalyptus essential oils
Species Yield a (%) Reference
E. bakeri 1.8-3 22
E. brachycorys, E. crucis 0.75-3.75 19
E. caesia 0.97 7
E. camaldulensis 0.39 b 113
E. camaldulensis 0.25-0.46 39
E. cinerea 1.2-2.3 39
E. citriodora 0.6 16
E. citriodora 0.9-1.3 77
E. crebra 0.29-1.33 3
E. dunnii 3.67 112
E. globulus 1.3-2.7 b 96
E. grandis 0.36% b 113
E. microtheca, E. spahulata 0.38-1.88 88
E. nitens, E. denticulata 0.7-0.8 54
E. porosa 0.57 6
E. propinqua, E. pulverulenta 0.22-3.56 120
E. radiata ssp. robertsonii 6.7-8.4 97
E. radiate ssp. radiata, E. smithii 6.0-9.0 28
E. remophil, E. oleosa, E. patellaris, E. ranscontienalis, E. salubris 0.1-5.3 36
E. tereticornis 1.57-2.09 94
E. viminalis 0.5-1.2 39
aDry weight basis; bFresh weight basis.
2.3. Chemical composition
The oil composition of different eucalyptus species has been reviewed till 1998
(30). This current review collates the research advances from 1999 (Table 3). The number
of components identified and main components in essential oils from different eucalyptus
species are presented in increasing order of 1,8-cineole content. The main components are
monoterpenes (1,8-cineole, p-cymene, citronellal, citronellol, limonene, α-phellandrene, β-
phellandrene, α-pinene, β-pinene, trans-pinocarveol, terpinolene, α-terpineol, α-thujene)
and sesquiterpenes (β-caryophyllene, β-eudesmol, globulol, spathulenol and virdiflorol).
The chemical profile and main components of oils from eucalyptus leaves varied
significantly between species (88,120). For example, the main components of E.
largiflorens oil were 1,8-cineole (37.5%), p-cymene (17.4%), neo-isoverbenol (9.1%),
limonene (6.5%) and spathulenol (6.7%), while those of E. spathulata oil were 1,8-cineole
(72.5%), α-pinene (12.7%) and trans-pinocarveol (3.3%), with the absence of neo-
isoverbenol, limonene and spathulenol or at lower amounts (88). The monoterpenes, 1,8-
cineole and α-pinene, are the main components in most species, while, E. citriodora is rich
in citronellal (49.5-87%) and citronellol (8-20%). The content of 1,8-cineole in eucalyptus
oils ranges from 10-90%. Generally, the content of α-pinene is below 20%. The
composition of eucalyptus oils differs even between the trees of same species in different
periods, sites (25) and extraction method/time (11,90).
Chemistry and bioactivity of Eucalyptus essential oils
Zhang et al
Chemistry and bioactivity of Eucalyptus essential oils
Eucalyptus essential oil has range of bioactivity [antimicrobial (53,56,107),
antiviral (26), fungicidal (92,93), insecticidal (57,63), anti-inflammatory (95),
antinociceptive activity (55), antioxidant capacity (104,119) and phytotoxic (91) activity]
(Tables 4,5).
3.1. Bioactivity on organisms
3.1.1. Antimicrobial activity: Sumitra and Sharma (107) reported that E. teriticornis
essential oils had antibacterial activity against six bacteria (Staphylococcus aureus,
Bacillus cereus, Escherichia coli, Micrococcus luteus, Proteus mirabilis and Alcaligenes
faecalis). Cermelli et al. (26) showed that Haemophilus influenzae, Haemophilus
parainfluenzae and Stenotrophomonas maltophilia were the most susceptible to E.
globulus essential oils, followed by Streptococcus pneumoniae and Streptococcus
agalactiae. The highest activity was found at 1.25µ l ml-1 for H. influenzae, H.
parainfluenzae and S. maltophilia. Antiviral activity assays using virus yield experiments
indicated mild activity on the mumps virus (26).
3.1.2. Antifungal activity: E. citriodora essential oil is effective against Microsporum
nanum, Trichophyton mentagrophytes and Trichophyton rubrum (93). Pure oil controlled
M. nanum in 20 s and T. mentagrophytes and T. rubrum in only 15 s. It was more effective
than prevalent synthetic antifungal drugs (Dactrine, Nizral and Tenaderm) without any
adverse side effects on mammalian skin up to 5% concentration. E. citriodora oil has also
clinical value in dermatophytoses, when used as a broad spectrum antimycotic ointment.
E. robusta, E. rostrata, E. camaldulensis, E. tereticornis, E. globulus and E. citriodora oils
are antibacterial (66,83) and antifungal (53,56,103).
3.1.3. Insecticidal activity: E. globulus essential oil has high insecticidal activity against
Aphis gossypii (63). E. grandis and E. globulus oils are resistant to termite followed by
E. citriodora and E. urophylla oils (57).
3.1.4. Antioxidant: Eucalyptus oils also antioxidant, due to the presence of phenolic
compounds (104,119) and their radical scavenging properties (119). They can also trigger
a series of induced chemical defence responses (21,110).
3.2. Bioactivity on weeds and crops
Volatile allelochemicals derived from eucalyptus oils also have herbicidal activity
against many weed species (13,16,17,79,91). Volatile essential oils from E. citriodora was
phytotoxic to Bidens pilosa, Amaranthus viridis, Rumex nepalensis and Leucaena
leucocephala, with no germination occurring at 0.06% eucalypt oil concentration under
laboratory conditions (91). Essential oils from E. nicholii strongly inhibited the
germination of Amaranthus retroflexus, Portulaca oleracea and Acroptilon repens (79).
Zhang et al
Table 4. Bioactivity of eucalyptus essential oils on organisms
Species Bioactivity Reference
A. Antimicrobial activity
E. camaldulensis,
E. tereticornis
Antimicrobial activity 27
E. citriodora
Antibacterial activity against Escherichia coli,
Staphylococcus aureus, Proteus mirabilis, Pseudomonas
aeruginosa, Proteus vulgaris.
E. citriodora
Antimicrobial activity against Trichophyton rubrum,
Histoplasma capsulatum, Candida albicans, E.coli and
Mycobacterium smegmatis
E. globulus Antimicrobial activity against S. aureus, E. coli 4
E. maidenii Antimicrobial activity against 12 bacteria 41
E. robusta,
E. saligna
Antimicrobial activity against S. aureus, E. coli and C.
E. teriticornis
Antibacterial activity against S. aureus, Bacillus cereus, E.
coli, Micrococcus luteus, P. mirabilis and Alcaligenes
E. globulus Antiviral activity 26
B. Antifungal activity
E. camaldulensis,
E. tereticornis
Antifungal activity 27
E. citriodora Antifungal effects against mildew and wood decay fungi 106
E. dalrympleana Antifungal agent against Epidermophyton floccosum,
Microsporum gypseum and T. rubrum
E. globulus Antifungal effects against three Candida species
E. rostrata,
E. camaldulensis
Fungitoxic properties against four human pathogens:
Trichophyton mentagrophytes, Epidermophyton floccosum and
Microsporum canis
C. Insecticidal activity
E. globulus Insecticidal activity against Aphis gossypii adults 63
E. globulus Fumigant toxicities 53
E. globulus,
E. citriodora
Repellent effects against adults Apriona germarii, Psacothea
hilaris and Monochamus alternatus
E. grandis Larvicidal activity 59
E. saligna Repellent effects against Sitophilus zeamais and Tribolium
E. urophylla,
E. citriodora
Antitermite activity 57
D. Antioxidant
E. camaldulensis Antioxidative activities 104
E. staigeriana Antioxidant capacity 119
D. Others
E. camaldulensis Antinociceptive properties 55
E. citriodora,
E. tereticornis,
E. globulus
Anti-inflammatory and analgesic effects 95
E. tereticornis Relaxant effects on guinea-pig tracheal smooth muscle 29
Chemistry and bioactivity of Eucalyptus essential oils
Table 5. Biological activity of eucalyptus essential oils on plants
Eucalyptus species Bioactivity Reference
E. camaldulensis Growth inhibition against Allium cepa, Spinacia oleracea,
Lepidium sativa, Zea mays and Lycopersicon esculentum
E. citriodora Phytotoxicity against crops (Triticum aestivum and Oryza sativa) 17
E. exserta,
E. urophylla
Growth inhibition against Raphanus sativus and Lactuca sativa 118
E. camaldulensis Growth inhibition against Echinochloa crus-galli, Avena fatua
and Rumex acetosella.
E. citriodora Inhibition on germination and growth against Cassia occidentalis
and E. crus-galli
E. citriodora Phytotoxicity against weeds (Amaranthus viridis and E. crus-
E. citriodora Herbicidal activity against Anagallis arvensis, Chenopodium
album and Spergula arvensis
E. citriodora Herbicidal activity against Bidens pilosa, A. viridis, Rumex
nepalensis and Leucaena leucocephala
E. citriodora Germination inhibition in Parthenium hysterophorus 100
E. globulus Germination inhibition in Amaranthus retroflexus and Portulaca
E. globulus Germination inhibition in P. hysterophorus 49
E. nicholii Herbicidal activity against A. retroflexus, P. oleracea and
Acroptilon repens
The eucalyptus oils are also herbicidal against Parthenium hysterophorus, Cassia
occidentalis, Echinochloa crus-galli and A. viridis (16,17,100). Thus compounds in
eucalyptus oils have potential for further use as natural herbicides.
However, the phytotoxic activity of eucalyptus oils can also cause damage to
some crops (64,118). Batish et al. (13,17) found that eucalyptus oils from E. citriodora not
only inhibited weed (A. viridis and E. crus-galli) growth, but also caused injuries to wheat
(Triticum aestivum), maize (Zea mays), radish (Raphanus sativus) and rice (Oryza sativa).
It is therefore critical to maximise the herbicidal activity of eucalyptus oils against weeds
but at the same time to minimise the negative impact of crop growth.
3.3. Mechanism of oil bioactivity
Antibacterial and antifungal compounds may target various cell structures or
chemical pathways, such as cell wall degradation, membrane damage, dissipation of the
proton motive force, decrease in extracellular protease activity, o-lipopolysaccharide
rhamnose content, ergosterol content or unsaturated fatty acids (23,44,72,73). However,
research data are very limited on the mechanism of antimicrobial and antifungal activity of
eucalyptus oils. The mode of actions of essential oils and chemical compounds from other
plant species may assist the understanding of the possible mechanism involved in
eucalyptus oil bioactivity.
Cox et al. (31) reported that tea tree (Melaleuca alternifolia) essential oils
inhibited the growth of E. coli through reduction in glucose-dependent respiration and
Zhang et al
enhanced leakage of intracellular K+. Cytoplasmic membrane damage was reported in S.
aureus after treatment with tea tree oil or its main monoterpene components, leading to
lysis, the loss of 260-nm-absorbing material and the loss of tolerance to NaCl (24). It was
shown that the oils of E. citriodora exerted its antimicrobial activity through the
synergistic action of citronellal and citronellol (58).
The antifungal mechanism of Thymus spp. essential oils against yeasts and
filamentous fungi was identified due to the inhibition of germ tube formation (74), with
additional impairment of ergosterol biosynthesis in some strains (75). Rapid propidium
iodide (PI) penetration into cells detected by flow cytometry assays indicates that the
fungicidal effect is through primary cell membrane damage rather than secondary
membrane damage caused by metabolic impairment. The biochemical nature of the
monoterpenes suggests they probably act as a solvent of the cell membrane. The major
components of Thymus spp. essential oils such as carvacrol, thymol and p-cymene
exhibited similar fungicidal activity against Candida species with synergistic effects noted
for thymol/p-cymene and thymol/1,8-cineole mixtures (74). The synergism helps explain
the differences in bioactivity between essential oils and their pure major compounds.
The bioactivity mechanism of eucalyptus oils on plants reduces cell survival,
chlorophyll content, RNA contents, acid soluble carbohydrate and water soluble
carbohydrate (50). Moradshahi et al. (64) found that the presence of different
concentrations of crude volatile oils from E. camaldulensis decreased the mitotic index in
the root apical meristem of Allium cepa, affected the Hill reaction in isolated spinach
(Spinacia oleracea) chloroplast and reduced peroxidase activity in Lepidium sativa, E.
crus-galli, Avena fatua, Rumex acetosella, Z. mays and Lycopersicon esculentum. Under
laboratory conditions, volatile oils from lemon-scented eucalypt (E. citriodora) decreased
weed emergence and earlier seedling growth by severely inhibiting photosynthetesis and
respiration at 0.06% (93) and 0.07% (15) concentration levels. Rapid electrolyte leakage in
the leaf tissue suggested that the mode of actions of the eucalyptus oils is a result of the
disruption of membrane integrity (15). α-Pinene, one of the common monoterpenoids from
eucalyptus oils, has been regarded as a key compound contributing to the disruption effect
(102). From these studies, it can be concluded that eucalyptus species suppress the growth
of other plant species by affecting several biochemical and physiological processes.
Progress has been made toward better understanding of relationship between the
observed biological activity and the key bioactive chemical components of eucalyptus oils.
Major compounds, such as 1,8-cineole, α-pinene, β-pinene, p-cymene, limonene,
citronellal and citronellol are principle bioactive compounds in essential oils.
Sartorelli et al. (83) reported that E. robusta oil is more active than E. saligna oil
against both E. coli and S. aureus due to the higher concentrations of the monoterpenes α-
pinene, β-pinene and limonene. Pure solutions of 1,8-cineole and α-pinene are bioactive
against Pseudomonas tolaasii, exhibiting bacteriostatic activity at 7.0 µl ml-1 and
bactericidal activity at 10.0 µ l ml-1 (105). Antibacterial activity of citronellal and
citronellol suggest that most monoterpenes in eucalyptus oils are antibacterial (85,87). The
Chemistry and bioactivity of Eucalyptus essential oils
relationship between the chemical composition and antifungal activity has also been
documented. Su et al. (106) reported that the chemical components and antifungal
activities varied significantly among E. urophylla, E. grandis, E. camaldulensis, and E.
citriodora, with E. citriodora the most effective for controlling mildrew. E. urophylla, on
the other hand, was least effective, suggesting that antifungal activity is associated with
citronellal and citronellol, two major compounds in the essential oils of E. citriodora. This
conclusion was supported by antifungal tests using the pure citronellal and citronellol
compounds (46).
Antitermite properties of eucalyptus oils are conferred by monoterpene α-pinene,
followed by monoterpenes p-cymene and 1,8-cineole, while the other components in the
oils were less effective (57). α-Pinene has stronger larvicidal activity than pure 1,8-cineole,
suggesting that α-pinene is a principal larvicidal component of E. grandis essential oils
The phytotoxic and herbicidal activities of eucalyptus oils are highly related to
chemical composition of essential oils, with E. citriodora essential oils being strongly
phytotoxic (13,65,100). The monoterpenes (citronellal, citronellol, 1,8-cineole and α-
pinene) inhibited the germination and initial seedling growth of C. occidentalis, A.
conyzoides, E. crus-galli, Cassia obtusifolia and Z. mays (1,81,98,99,102). Singh et al.
(101) assessed the phytotoxicity of citronellal against Ageratum conyzoides, Chenopodium
album, P. hysterophorus, Malvastrum coromandelianum, C. occidentalis and Phalaris
minor. Emergence of A. conyzoides and P. hysterophorus was inhibited by citronellal at a
concentration of 50 µ g g-1 (sand) and the weed emergence and early seedling growth of
other species were completely inhibited at 100 µ g g-1.
The bioassay results suggest that the bioactivity of eucalyptus oils may be due to
their monoterpene components. However, essential oils are a complex chemical mixture
and they possess higher activities than their individual components (52). Therefore, total
bioactivity of essential oils may be due to the combined effects of several minor
components or the synergistic effect of essential oil components (12,52).
Eucalyptus essential oils are widely used in many industries and mainly in
therapeutic natural medicine (108).
Eucalyptus is a traditional medicinal plant to treat cold, flue, fever, diabetics and
bronchial infections (70,92,95) or to prevent and control other pathogenic diseases (4,109).
Eucalyptus oil based products are used as topically applied medication to relieve muscular
pain and as solvent/sealer in dentistry (3) and as disinfectant (38). The bioactive
components identified from eucalyptus essential oils may develop new classes of analgesic
and anti-inflammatory drugs (95).
Similarly, the insecticidal activity of eucalyptus oils could provide opportunities
for new biodegradable products for pest control. The oil is used as an insect repellent since
1948 (48) and now many commercial repellents are available in US and China (14). A
commercial mosquito repellent has also been developed from p-manthane-3,8-diol isolated
from E. citriodora (14). Kegley et al. (48) has reported that eucalyptus oil based products
ranked 4th amongst the insecticides used for repelling insects from beehives.
Zhang et al
The widespread use of synthetic herbicides has resulted in the rapid evolution of
herbicides-resistant weeds and increasing public concern over the impact of synthetic
herbicides on human health and the environment (114). Alternative weed management
options based on natural products are being sought (33), with essential oils from plants
receiving much attention due to their ready availability and low cost (8,33). A commercial
herbicide with the active ingredient cinmethylin, has been developed based on the natural
chemistry of 1,8-cineole, the major monoterpene in eucalyptus essential oils (40). A
myriad of compounds are present in eucalyptus essential oils and determination of their
chemical structure and bioactivity may provide novel leads for development of herbicides
with new modes of action.
Eucalyptus oils are widely used in fragrance industry (soaps, detergents, creams,
lotion, deodorizer, perfumes) and as flavouring agents in food industry (38,69,78).
Eucalyptus oils are also used as a flotation agent in the mining industry (3) and as a source
of citronellal for the chemical industry (38).
Eucalyptus essential oils are gaining increasing interest due to their varied
commercial applications particularly as insect repellents, fragrants and traditional
medicines. Despite the commercial prospects, till now only limited eucalyptus species
have been studied. Considering that the chemical composition of eucalyptus oils and its
associated biological activities varies significantly between species, other species deserves
further attention. It should be emphasized that the research into eucalyptus oil chemistry
may lead to the development of natural pesticides with new mode of actions.
The relationship between the bioactivity and chemical composition has been
reported, yet information on the mode of actions of eucalyptus oils is limited. Modern
molecular and biochemical approaches have provided excellent research tools to facilitate
the study of mechanisms of action and the biosynthesis of essential oils.
Progress has been made in identification of genes responsible for essential oil
biosynthesis in peppermint (Mentha piperita), with subsequent metabolic engineering
significantly altering essential oil composition and yield. This success in genetic
manipulation of essential oil biosynthesis in peppermint suggests similar improvements in
eucalyptus essential oil production may be possible. An extensive review on the advances
in genetic transformation of eucalypts indicates that significant progress has already been
made into understanding eucalyptus genetics. Quantitative trait loci associated with
essential oil biosynthesis in E. grandis × E. urophylla hybrids have already been identified.
Future modification of eucalyptus essential oil biosynthesis will require close collaboration
between plant biologists, biochemists and molecular biologists as well as plant breeders to
develop products for new applications.
Authors acknowledge the funding support from Meat and Livestock of Australia.
Chemistry and bioactivity of Eucalyptus essential oils
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Chemistry and bioactivity of Eucalyptus essential oils
... The leaves of E. tereticornis contained ursolic acid and ursolic acid lactone, [3,4] flavonoids sideroxylin, 8demethylsideroxylin and 7-methoxy-aromadendrin, [5] phenolic compounds, saponins, steroids and flavonoids, [6,7] lignins, [8] acyl phloroglucinols euglobal T1 and euglobal II c, [9] triterpene ester tereticornate A and B and betulonic acid. [10] Leaf essential oil was composed of α-pinene, 1,8-cineole, β-citronellal, (-)isopulegol, β-citronellol, [11][12][13][14][15][16][17] sesquiterpenes (caryophyllene, eudesmol, globulol, spathulenol and virdiflorol) and monoterpenes (1, 8-cineole, citronellal, citronellol, limonene, pinenes, trans-pinocarveol, terpinolene and thujene). [15] The leaf oil from Guangxi province contained eucalyptol, alpha-pinene, isopinocarveol; the fruit oil possessed alpha-pinene, eucalyptol, and D-limonene. ...
... [10] Leaf essential oil was composed of α-pinene, 1,8-cineole, β-citronellal, (-)isopulegol, β-citronellol, [11][12][13][14][15][16][17] sesquiterpenes (caryophyllene, eudesmol, globulol, spathulenol and virdiflorol) and monoterpenes (1, 8-cineole, citronellal, citronellol, limonene, pinenes, trans-pinocarveol, terpinolene and thujene). [15] The leaf oil from Guangxi province contained eucalyptol, alpha-pinene, isopinocarveol; the fruit oil possessed alpha-pinene, eucalyptol, and D-limonene. [18] The bark yielded betulinic acid, saponins, tannins, steroids and flavonoids, [18] hexadecanoic acid, methyl ester, quercetin and rhamnazin. ...
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Eucalyptus tereticornis Sm. (family Myrtaceae), is a native to eastern Australia and southern New Guinea, planted all over India after teak. A leaf decoction is drunk to cure asthma, burns, body pain, fever, influenza, diarrhoea, pulmonary problems and rheumatism. Vitis vinifera L. (family Vitaceae), is a long-stemmed, woody vine found in Mediterranean region, central Europe, and southwestern Asia. Its leaves are used to treat boils, diarrhoea and toothache. Our study was planned to isolate chemical constituents from methanolic extracts of the leaves of E. tereticornis and V. vinifera and to characterize their structures on the basis spectral data analysis. The methanolic extract of leaves of E. tereticornis afforded a known fatty acid ester identified as n-tricosanyl n-octadec-9-en-1-oate (n-tricosanyl oleate, 1), a new unsaturated aliphatic keto alcohol characterized as n- tricos-3β-ol-16-one-17(Z)-ene (2) and two new acyl coumarins and their structures have been established as 6-hexacosanoxycoumarin (6-cerotinoxycoumarin, 3) and n-(21′α-hydroxyoctacosanoxy) coumarin or (6-(21′α-hydroxymontanoxy) coumarin (4). The methanolic extract of the leaves of V. vinifera on subjection to silica gel column furnished steroidal esters characterized as stigmast-5-en-3 β-yl n-octadec-9, 12-dienoate (β- sitosterol linoleate, 5) and stigmast-5-en-3β-ol-3β-olyl n-docos-11-enoate (β-sitosterol 3β- cetoleate, 6).
... The main EOL constituents were 1,8-cineole (83.3%), α-terpineol (4.6%), and ortho-cymene (3.3%), while significant compounds found in EOT were 1,8-cineole (65.6%), α-terpinyl acetate (7.6%), ortho-cymene (7.5%), and α-terpineol (3.6%). EOs of Eucalyptus species are well known to be rich in 1,8-cineole [7,24,25]. Indeed, for our EOs, the oxygenated monoterpenes were the first significant class (95.5, 93.7, and 82.2% in fruits, leaves, and twigs, respectively) represented essentially by 1,8-cineole. 1,8-Cineole was found to be highly abundant (up to 86% in fruits) compared to all the previous studies on E. gunnii EOs. ...
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The chemical composition, insecticidal, repellence, and antibacterial capabilities of essential oils (Eos) produced via hydrodistillation of several Eucalyptus gunnii Hook. f. components were evaluated. Using GC and GC/MS, we identified 23 compounds throughout the plant's various components. These compounds were split evenly across the branches, leaves, and fruits, with 23, 23, and 21 compounds. 1,8-Cineole (65.6-86.1%), α-terpinyl acetate (2.7-76.1%), ortho-cymene (3.3-7.5%), and -terpineol (3.3-3.5%) were the most often detected oxygenated monoterpenes. Antibacterial activity was evaluated in all three EOs with moderate effect except for Dickeya solani (CFBP 8199), for which twigs EO (EOT) exhibited greater efficacy, and leaves EO (EOL) were shown to have more potent antibacterial activity against all tested strains. The most sensitive species was Dickeya solani (CFBP 8199) (MIC 2 mg/mL), whereas the most resistant was Dickeya dadantii (CFBP 3855) and Pectobacterium carotovorum subsp. carotovorum (CFBP 5387). Plant extracts varied in their fumigation, contact toxicity, and repellent bioassay potentials, with EOT and EOL showing promise as effective repellents and EOT as a moderately toxicant. research is needed to fully understand the medicinal properties of E. gunnii. Further studies are necessary to establish the safety and efficacy of E. Gunnii extracts for medicinal use.
... Different parts of the plant have been used to produce essential oils (EOs), but in the leaves these oils were most plentiful [2]. The EOs from Eucalyptus species rich in eucalyptol have traditionally been utilized as disinfectants, insect repellents, febrifuges and to treat respiratory illnesses [3]. Nowadays, they are used in many pharmaceutical and cosmetics industries [2]. ...
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This study was carried out to characterize the chemical composition of the essential oils from seven Eucalyptus species (E. griffithsii, E. hemiphloia, E. lesouefii, E. longicornis, E. pyriformis, E. viminalis, and E. wandoo), as well as their phytotoxic and antibacterial activities. The essential oils were analyzed by GC/MS and the potential in vitro phytotoxicity was evaluated against germination and radical elongation of Raphanus sativus, Lolium multiflorum, and Sinapis arvensis seeds. The antibiofilm activity was studied against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. Eucalyptol was the most abundant component in all essential oils studied (ranging from 40.8% for E. lesouefii EO to 73.6% for E. wandoo) except for that of E. pyriformis where it was present but at 15.1%. E. pyriformis was the most active against both germination and radical elongation of S. arvensis. The action of all essential oils proved to be highly effective in inhibiting the bacterial adhesion process of the five strains considered. In light of these results, these essential oils could have potential applications both in the agricultural and health fields.
... Eucalyptus oil has antibacterial and antifungal activity, this is however dependent on the 1,8-cineole content (at least 70%) of the oil (3,18). It also showed antioxidant activities, spasmolytic and cytotoxic effects (2,20). On the other hand, there are few studies on the essential oil composition of Eucalyptus torquata (21)(22)(23)(24)(25)(26)(27). ...
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The genus Eucalyptus belonging to the Myrtaceae family, consists of tall, evergreen trees with leathery leaves. They are indigenous to Australia and contain about 900 species and subspecies. One important use is production of essential oils, which are valuable in both medicinal and pharmaceutical industries. There are about 62 species of Eucalyptus naturalized to Cyprus including E. camaldulensis and E. torquata. The essential oil constituents of leaves of these two species of Eucalyptus collected from Northern Cyprus were isolated by hydro-distillation and analyzed by GC and GC/MS, simultaneously. E. camaldulensis oil yield was higher (2.4%), and major compounds identified were α-phellandrene (10.3%) and β-phellandrene (30.6%), respectively. These compounds were followed by p-cymene (8.2%), bicyclogermacrene (6.1%) and spathulenol (9.3%). On the other hand, E. torquata oil yield was relatively lower (1.6%), with major compounds being α-pinene (18.6%), 1,8-cineole (18.8%), β-eudesmol (10.3%) and torquatone (29.2%).
... The family provides relevant ecosystems services, e.g. as a food source for pollinators and fruit-eating animals (Culmsee et al. 2011), and some of its members are also economically important (Mudiana 2016;Chandra and Mishra 2007;Purwaningsih and Kartawinata 2018;Kesharwani et al. 2018). It includes timber species rich in essential oils (Zhang et al. 2010; Barbosa et al. 2013), and that are used in furnishings (Binghong et al. 2019). Additionally, several genera of Myrtaceae exhibit pharmacological activities, and some of them produce consumable fruits (Musthafa et al. 2017;El-Saber Batiha et al. 2020). ...
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Given the difficulties for rapid biodiversity assessments in understudied regions, DNA barcoding appears as a suitable alternative. Still, this approach relies heavily on accurate reference sequence databases for correct taxonomic assignments. In this study, we evaluated the effectiveness of matK, rbcL, and ITS regions for the identification of Myrtaceae species with emphasis on the megadiverse genus Syzygium from Sumatra, Indonesia; and analyzed the applicability of species-tree inference for species assignment using barcode markers. ITS was the most variable barcode region (42.6% of variable sites), followed by matK (25.7%), and rbcL (14.9%). In terms of assignments of sequences using the BLAST algorithm, all markers were effective for genus-level attribution. For assignments at species rank, rbcL was able to attribute 30.15% of the samples at the species level, followed by matK (26.47%), and ITS (17.21%). These results are largely related to the availability of reference sequences for Myrtaceae in the databases since for the 27 species analyzed in this study, only 8 species had reference sequences for all three barcode regions available in GenBank. The species-tree inference based on the combination of matK, rbcL, and ITS markers recovered 41% of the species as monophyletic clades with strong node support. Due to its high level of differentiation, we recommend the ITS region as the most efficient barcode marker for the identification of Syzygium, and the traditional core-barcodes (matK + rbcL) as add-on barcodes.
... Examples of these welldocumented studies have shown a wide range of biological activities-anticancer [28,29], repellent [30][31][32][33][34][35], antimicrobial [18,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54], antitussive [55], antioxidant [56][57][58] and immune response activities [18,59]. Several reviews have compiled a large number of other activities, such as antihyperglycemic, anthelmintic, antihistaminic, anti-inflammatory, antimalarial, anti-HIV, anti-dental plaque formation, insecticide, herbicidal, acaricidal and nematicidal activities, and use for treatment of skin disorders [10,[60][61][62][63][64][65][66][67][68]. ...
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Eucalyptus plants have attracted the attention of researchers and environmentalists worldwide because they are a rapidly growing source of wood and a source of oil used for multiple purposes. The main and the most important oil component is 1,8-cineole (eucalyptol: 60%–85%). This review summarizes the literature reported to date involving the use of 1,8-cineole for the treatment of disorders. Additionally, we describe our efforts in the use of eucalyptol as a solvent for the synthesis of O,S,N-heterocycles. Solvents used in chemistry are a fundamental element of the environmental performance of processes in corporate and academic laboratories. Their influence on costs, safety and health cannot be neglected. Green solvents such as bio-based systems hold considerable additional promise to reduce the environmental impact of organic chemistry. The first section outlines the process leading to our discovery of an unprecedented solvent and its validation in the first coupling reactions. This section continues with the description of its properties and characteristics and its reuse as reported in the various studies conducted. The second section highlights the use of eucalyptol in a series of coupling reactions (i.e., Suzuki–Miyaura, Sonogashira–Hagihara, Buchwald–Hartwig, Migita–Kosugi–Stille, Hiyama and cyanation) that form O,S,N-heterocycles. We describe the optimization process applied to reach the ideal conditions. We also show that eucalyptol can be a good alternative to build heterocycles that contain oxygen, sulfur and nitrogen. These studies allowed us to demonstrate the viability and potential that bio solvents can have in synthesis laboratories.
... Another common terpenoid present in EOs from many Eucalyptus species, α-pinene, played a key-role in root cell membranes' disruption [24,25]. Even eugenol possessed a weed-suppressing ability, negatively affecting the photosynthetic efficiency and the energy metabolism of different weed species [19]. ...
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The phytotoxicity and eco-compatibility of essential oils (EOs) from Eucalyptus gunnii (EG) and E. pulverulenta ‘Baby Blue’ (EP), cultivated in Italy for their cut foliage, were investigated. Leaf micromorphology, EOs phytochemical characterization, and phytotoxicity were analysed. EP revealed a significantly higher oil gland density and a higher EO yield with respect to EG. In both EOs, 1,8-cineole was the major compound (~75%), followed by α-pinene in EG (13.1%) and eugenol in EP (7.5%). EO phytotoxicity was tested on both weeds (Lolium multiflorum, Portulaca oleracea) and crops (Raphanus sativus, Lactuca sativa, Lepidium sativum, Solanum lycopersicum, Pisum sativum, Cucumis sativus). EG EO inhibited germination of P. oleracea, R. sativus, and S. lycopersicum seeds (ranging from 61.5 to 94.6% for the higher dose used), while affecting only radical elongation in S. lycopersicum (ranging from 66.7 to 82.6%). EP EO inhibited germination of P. oleracea and R. sativus (ranging from 41.3 to 74.7%) and affected radical elongation of L. sativum and L. multiflorum (ranging from 57.4 to 76.0%). None of the EOs affected the germination and radical growing of L. sativa, P. sativum, and C. sativus. Moreover, EP EO was more active than EG EO in inhibiting α-amylase, a key enzyme for seed growth regulation. Brine shrimp lethality assay showed that both EOs are safe for aquatic organisms, suggesting their high eco-compatibility. The data collected provide useful information for future applications of these EOs in agriculture as safe and selective bioherbicides.
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The complex taxonomy of Eucalyptus genus, the renewed interest in natural compounds able to combat microbial strains, the overuse of synthetic pesticides, the consequent request for alternative control methods were the reasons for this research. The essential oils (Eos) of Eucalyptus bosistoana, Eucalyptus melliodora, Eucalyptus odorata, Eucalyptus paniculata, Eucalyptus salmonopholia, and Eucalyptus transcontinentalis were analyzed by GC/MS and their potential phytotoxic activity was evaluated against the germination and radicle elongation of Sinapis arvensis, Raphanus sativus and Lolium multiflorum. The antibiofilm activity was assayed against both Gram-positive (Staphylo-coccus aureus and Listeria monocytogenes) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii) bacteria. Monoterpenoids were the most representative constituents in all EOs and eucalyptol was the dominant component except in E. melliodora EO, in which p-cymene was the most abundant. In phytotoxic assays, the EOs from E. odorata and E. paniculata were the most active against germination and radical elongation of the tested seeds. Finally, the Eucalyptus EOs proved their capacity to effectively inhibit the adhesion process of all five pathogen strains, with percentages often reaching and exceeding 90%. These Eucalytpus EOs could have possible em-ployments in the food, health and agricultural fields.
Two new galloyl glucosides, galloyl-lawsoniaside A (4) and uromyrtoside (6), were isolated from the polar fraction of Uromyrtus metrosideros leaf extract along with another four previously identified phytochemicals (1, 2, 3, and 5). The structures of these six compounds were characterised using low and high-resolution mass spectrometry (L/HRMS) and 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy. These compounds were not toxic to human peripheral blood mononuclear cells (PBMCs) at 10 μg/mL over 24 h, yet showed significant in vitro suppression of proinflammatory cytokines involved in the pathogenesis of inflammatory bowel disease (IBD). Specifically, the release of interferon γ (IFN-γ), interleukin (IL)-17A, and IL-8 from phorbol myristate acetate/ionomycin (P/I) and anti-CD3/anti-CD28-activated cells were significantly suppressed by compounds 4 and 5. Interestingly, no effect on tumour necrosis factor (TNF) release was observed. These results show that the newly characterised compound 4 has promising cytokine suppressive properties, which could be further investigated as a candidate for IBD treatment.
A Roll-on is a type of liquid preparation packed in a container with an applicator consisting of a revolving ball at the top of the dispenser. Herbal roll-on contains the volatile oils used to treat different pains such as headaches, joint pains, neck aches, etc. It is also used in the treatment of cold and nasal congestion. It contains a mixture of volatile oils such as eucalyptus oil, camphor oil, thyme oil, lavender oil, rosemary oil, chamomile oil, menthol etc. These oils are generally used to treat stress, relieve pain, migraine, anti-inflammatory, treat anxiety, relieve sinus tensions, etc. This topical pain reliever containing all-natural ingredients causes a pleasing sensation helpful to counteract the pain.
Antimicrobial activities of volatile oils of Ocimum gratissimum, Citrus sinensis, C. maxima and Eucalyptus globulus obtained through steam distillation using Clavenger-type apparatus were examined on clinical isolates of some human pathogenic fungi and bacteria using ditch – plate method. The fungal organisms used include Tinea rubrum, T. megninii while the bacteria are Staphylococcus aureus, Escherchia coli, Pseudomonas aeruginosa . All the organisms were mostly susceptible to the volatile oil of O. gratissimum while their susceptibilities to other oils varied. Journal of Pharmacy & Bioresources Vol. 2(2) 2005: 120-123
Botanical drug for fungal infections is a supplement to synthetic drug. Thus is formulated from the essential oil of Eucalyptus dalrympleana. The oil of E. dalrympleana was most potent antifungal agent, which completely inhibited the mycelial growth of test pathogens, Epidermophyton floccosum, Microsporum gypseum and Trichophyton rubrum. The minimum inhibitory concentration (MIC) of the oil was found to be 0.3 mul ml(-1) for aforesaid pathogens. The oil (0.3 mul ml(-1)) also exhibited potency against heavy doses of inocolum (30 mycelial discs each of 5 mm diameter). Moreover, this oil preparation did not adversely affect mammalian skin upto 5% level. Further, oil was used in the form of ointment for topical testing on patients, attending out patient department (OPD) of M.L.N. Medical College, Allahabad, At the end of medication, 50.0% of patients recovered completely and 40.0% showed significant improvement. No KOH negative cases of relapse were observed when patients were reexamined after two months following treatment. It indicates the absence of relapse. The ointment was found to be cost effective (INR 1.0/g), has long shelf life (48-months) and devoid of any adverse effects. Thus, the oil preparation could be used as a potential antifungal agent after the successful completion of multicentre clinical trial.
The Eucalyptus citriodora Hook. essential oil is the richer and more economical source of citronellal - a substance used in perfumery, therapeutic industries. The exploration of this substance show excellent trade perspectives. Environmental factors can effect yield composition and the quantity of the essential oil and the main components yield from the fresh leaves of E. citriodora in different seasons in the municipalities of Minas Gerais State. Crops were grown in February and august of 2005 in the municipalities of Bom Sucesso, Sao Bento Abade and Sao Joao del Rei. The essential oil was obtained through hydrodistillation and ulterior hydrolate centrifugation. The raw material moisture was determined. The essential oil yield was showed in volume per weight with moisture free Basis (BLU). The essential oil components were identified by using gas chromatography coupled to masses spectrometry (GC-ME). Results showed that the essential oil content was influenced by both period and place of te growth. The harvest conducted in Sao Joao del Rei in February showed the biggest yield. Cromatographic data showed changes in the chemical composition. Citronellal was the major component with contents between 67 to 87% followed by citronellol with levels between 8 to 20%.
The present work had as objective to study the influence of the nutritional deficiencies on the leaf biomass and the production and quality of the Eucalyptus citriodora essential oil. The plants were cultivated in vases at the green house. In the first three months after the plantation, the seedlings grew in complete nutritive solution. From the four to the eleven months of age, they were cultivated in solutions with omission of N, P, K, Ca, Mg, S and B. At the end of this period its heights and diameters at the plant base level were measured. Soon after, the plants were collected seeking the quantification of the leaf biomass, evaluation of the nutritional status and determination of the content and quality of the essential oil. From the obtained results we can conclude that the omission of N and B affected, more than other nutrients, the plant growth, deficiency symptoms and leaf and essential oil production. It was not verified significant differences among the treatments for percentile yield of oil as well as citronellal content. Increases of the K concentration and relationships K/Mg and K/Ca in the leaves increased the citronellal concentration.
The application of leaf extracts of Eucalyptus globulus decreased the seed germination of sorghum with increase in the leaf extracts concentration. The extracts also inhibited the shoot and root length of sorghum seedlings with increase in Eucalyptus extracts concentration but the number of lateral roots was increased. The extracts also influence the biochemical parameters (protein content, sugar content, total phenol content and nitrate reductase activity).