The antimicrobial properties of volatile oils and
their constituents from a large number of plants have been assessed and
reviewed 9-13. Recently attempts have been made to identify the component(s)
of the oils responsible for such bioactivities 9-10, 14-16.
oils including oils from Eucalyptus –
have been used to extend the shelf?life
of foods, beverages, cosmetic products and pharmaceutical. Not only this it is
pointed out that they also possess antimicrobial and antioxidant properties which
play a role in plant protection 9.
globulus oil has been widely used as a folk medicine for the treatment of upper
respiratory infections, gastritis, and diabetes 17. Traditional healers also use
eucalyptus oil to treat a wide range of diseases such as general infections, cough,
colds, flu, bronchitis, pneumonia, aching, stiffness, sore throats, and
neuralgia 18. It is also used as an antibiotic s as per the document available
19. The Eucalyptus is also reported to be used as an antifungal agent for the
treatment of some skin infections 20.
Due to warming and slightly anaesthetic effect of Eucalyptus
(as a diluted oil on the skin), it helps to relieve respiratory infections,
pain caused by rheumatic joints, neuralgia, fibrositis and muscular aches. Skin
infections such as abscesses, burns, blisters and insect bites are also claimed
to respond positively to the topical application of the essential oil or
extract. Reports also indicates it to be valuable for easing the symptoms of
shingles, chickenpox and cold sores 21.
oils of Eucalyptus also find applications in aromatherapy. A steam inhalation
with Eucalyptus is not only effective
in cold treatment but because it is also claimed to inhibit proliferation of
the cold virus 22.
Sisay reported that the value of Eucalyptus oil for medicinal
purposes is based largely on the content of a particular oil constituent:
1,8-cineole (cineole or eucalyptol) 23,24.The essential oils of Eucalyptus globules and Eucalyptus
citriodora, with about 70% of their constituent being 1,8-cineole(Eucalyptol),stimulate
respiration, and to relieve the effect
of a cough, to expel mucus, and as a vaso relaxant of the respiratory muscles.
Hot water extracts of dried leaves of Eucalyptus citriodora are
traditionally used as analgesic, anti-inflammatory and antipyretic remedies for
the symptoms of respiratory infections, such as cold, flu, and sinus congestion
and Eucalyptus urophylla also contain bioactive products that showed
antibacterial 26, antifungal 27, analgesic and
anti-inflammatory effects 25, antioxidative and
antiradical 28 activities.
Yang Suk Jun et al investigated the effects of
eucalyptus oil inhalation on patients who underwent TKR. The results showed
that eucalyptus oil inhalation was effective in reducing patient’s subjective
pain and blood pressure after surgery. These findings suggest that the
inhalation of eucalyptus oil might be a valuable nursing intervention for pain
relief after TKR 29.
Singh HP et al studied the antioxidant activity
of essential oils from fresh and dry leaves of essential oils of Eucalyptus tereticornis.
The study indicated that essential oil contains ?-pinene and 1,8-cineole and
acts as an antioxidant, with strong radical scavenging activity 30.
Santos FA et al studied antiinflammatory and
antinociceptive effects. In a mouse model of pain-causing edema in the feet,
oral administration of 1,8-cineole, which accounts for 70–90% (w/w) of the
contents of eucalyptus oil, suppressed edema formation and reduced inflammation
and pain 31. This effect of 1,8-cineole is due to its inhibition of cytokine
secretion by T-lymphocytes 32.
Gobel H et al investigated the effect of two oil
preparations on neurophysiological and experimental algesimetric headache
parameters . This study had shown that application of eucalyptus oil to a
healthy subject had a myorelaxant effect as well as promotes emotional
Silva J et al investigated the analgesic and
anti-inflammatory effects of essential oils of Eucalyptus. The study showed
that in a rat model of susceptibility to pain from a hot plate, eucalyptus oil
was not only analgesic but reduced edema formation and had an anti-inflammatory
Khaled et al investigated the Eucalyptus species and found a
large variation in their chemical composition. The major constituents of Eucalyptus
leaves essential oils are 1,8-cineol (49.07 to 83.59%) and ?-pinene (1.27 to
26.35%). He studied the antibacterial activity against Listeria ivanovii
and Bacillus cereus and found that the essential oils from E. maideni,
E. astrengens, E. cinerea, E. bicostata showed the highest
antibacterial activity against Listeria ivanovii and Bacillus cereus. Hence,
may have potential applications in food and pharmaceutical products 35.
Klocke investigated the biological activity of
Eucalyptus and cocncluded that it has significant biological activity such as mosquito
and other commercially produced oils with concentrations of cineole less than
that in E. polybractea (e.g. E. smithii and E. radiata) are either
fractionated to enhance cineole levels as required by monographs published by
ISO and various national pharmacopoeias or sold for uses where cineole content
is not so critical (e.g. aromatherapy) 37.
antimicrobial activity of eucalyptus oils and other volatile oils reflects
their composition, the structural configuration of the constituents and presence
of certain functional groups, along with potential synergistic interactions
between the constituents. The chemical nature of individual compounds within
the oil also influences the aqueous solubility, and the ability of toxic
compounds to penetrate the fungal or bacterial cell wall. However, still detailed
structure–activity relationships about the antimicrobial activity of different
classes of terpenes, are to be studied.
Griffin et al.
showed that on carbonylation of terpenoids of Eucalyptus, their bacteriostatic
activity increase but not necessarily their bactericidal activity, while
alcohols possess bactericidal rather than bacteriostatic activity against
vegetative bacterial cells 38.
researches has focused on the commercial potential, particularly in the
pharmaceutical field, of the non?volatile
constituents unlike the earlier researches which focused on the volatile
constituents of eucalypts – their essential oils. Research has indicated that
the potential for eucalyptus to be used for treatment of the most serious and
widespread illnesses and diseases may rest with some of its non?volatile
constituents, rather than with the more familiar volatile oils 39.
Alongwith the major
constituents 1,8-cineol and ?-pinene the genus also contains flavonoids,
triterpenes, long chain ketones, glycosides, acylphloroglucinol derivatives and
adducts combining more than one of these chemical entities. However, the researches
indicate that the great majority of the other bioactive metabolites in
eucalypts are acylphloroglucinols 40,41.
Four groups of
novel, highly bioactive acylphloroglucinol derivatives peculiar to the genus Eucalyptus arethe macrocarpals, euglobals,
robustadials, and sideroxylonals. These embrace a number of activities, any or
all of which could, in the longer term, be exploited commercially.
researches showed the macrocarpals, present in the leaves of E. macrocarpa, E. globulus and E. amplifolia,
have a combined isopentyl diformylphloroglucinol–sesquiterpene structure and
exhibit a range of biological activities. All are strongly antibacterial
against Gram?positive bacteria, including ones which
cause dental diseases, and some have recently been found to be active against
Gram?negative bacteria 42-45.
The study of
Nagata et al indicated that
eucalyptus leaf extracts may be useful as a potent preventative of periodontal
disease. In the study antibacterial activity was demonstrated by Macrocarpals
A, B and C against periodontopathic bacteria. P. gingivalis displayed the greatest sensitivity to macrocarpals; also, its trypsin?like proteinase
activity and binding to saliva?coated
hydroxyapatite beads were inhibited by macrocarpals 46.
Osawa et al. have showed that the
antibacterial potency may be regulated by the structure of the sesquiterpene.
The antibacterial and antiviral properties of macrocarpals appear to be due to
the diformyl phloroglucinol moiety rather than to the different sesquiterpenoid
Of the four
groups of Eucalyptus metabolites, the
euglobals are the largest, and structurally most variable. They are formyl
phloroglucinol adducts with either a mono?
or a sesquiterpenoid moiety attached. Amano et al isolated Euglobals from E. globulus 48.
Takasaki et al
showed that euglobals show strong inhibition of Epstein?Barr
virus activation, a tumour promoting substance, and this gives rise to hope
that they might, in the future, may play some role in cancer prevention 49.
Bharate et al synthesized new euglobal analogues
(named as S?euglobals) from phloroglucinol via a
biomimetic three component reaction with monoterpene. Few of the euglobal
analogues showed antibacterial activity against MRSA 50.
al isolated thecompounds 2′,6′?dihydroxy?3′?methyl?4′?methoxy?dihydro?chalcone,
eucalyptin and 8?desmethyl?
eucalyptin from E. maculata extracts.
The study also showed potent antimicrobial activities against seven micro?organisms
with minimum inhibitory concentrations (MIC) ranging from 1.0 to 31 mg/l 51.
The study of
Cheng Q et al showed that robustadials
A and B, with a combined phloroglucinol– monoterpene structure, are
antimalarial constituents of E. robusta
Satoh et al studied
the structures of sideroxylonals, dimers of a diformylphloroglu?cinol
moiety isolated from E. sideroxylon
and E. grandis. They found that the sideroxylonals are not only antibacterial
but also show strong attachment?inhibiting
activity towards the blue mussel;
sideroxylonal A is one of the most powerful antifouling agents known 53.
Aihua Song et al showed that the
essential oils from the leaves of Eucalyptus
globulus Labill from China consisted mainly
of oxygenated monoterpenes, monoterpenes and oxygenated sesquiterpenes. Of
these, 1, 8- eucalyptol (72.71 %), ?-terpineol (2.54 %), terpinen-4-ol (0.34
%), and linalool (0.24 %) were the
main oxygenated monoterpenes, while ?-pinene (9.22 %), and ?-pinene (0.4 %)
were the main monoterpenes and
?-eudesmol (0.39 %), (-)-globulol (2.77 %), and epiglobulol (0.44 %) were the
main sesquiterpene. Several significant compounds were ?-terpineol acetate (3.1
%), geranyl acetate (0.71 %), L-pinocarveol
(0.36 %), ?-sabinene (0.25 %), and terpinolene (0.19 %) 54.
Xiu-Wei Yang et al studied the chemical
constituents in fruits of Eucalyptus globules. They isolated fifteen compounds which were identified as
beta-sitosterol, betulinic acid, stigmasterol, euscaphic acid ,
2a-Hydroxybetulinic acid , macrocarpal B, macrocarpal
A, oleanolic acid, 3,4,3′-O-
trimethylellagic acid, 3-O-methylellagic acid 4′-O-(2″-O-acetyl )-
alpha-L-rhamnopyranoside, camaldulenside, 3-O-methylellagic acid
4′-O-alpha-L-rhamnopyranoside, 3-O-methylellagic acid, ellagic acid and gallic acid 55.
Gamal A investigated the phytochemistry of the Eucalyptus globulus Labill
and identified one new phloroglucinol derivative named eucalyptone G. The
antibacterial activity of the new compound has been studied. Eucalyptone G was
found to show antibacterial activity against the Gram-positive Bacillus subtilis and Staphylococcus aureus and against
Gram-negative E. coli 56.
In their study, Taur DJ et al concluded that E. globulus oil has anthelmintic
potential due to the presence of phytoconstituents: borneol, linalool, cineol, geranyl acetate, anethol, saffrol 57.
SN Sarkar showed that intra-dermal
administration of the essential oils from the leaves
of Eucalyptus hybrid and seeds of
Seseli indicum increased cutaneous
capillary permeability in Evan’s blue treated rabbits. This effect may be useful in their probable wound healing activity 58.