INTRODUCTION:

E. tereticornis is the most common eucalyptus belonging to Myrtaceae family. It is widely planted in India. The plant height is about 20 to 50 m, and trunk girth is about 2 m. The trunk is straight, and is typically unbranched. The bark is basically shed and it looks like irregular sheets having smooth surface. It is colored in blue, gray andwhite. It has thin, green leaves about 10 to 20 cm long and1 to 3 cm wide. Flowers occur in inflorescences and flowers colour may be cream, yellow,white, red, or pink. Fruit is a small woody capsule and they are roughly cone shaped (1).

There are about 170 species found in India, but only few species which are grown on plantation scale for the forestation purpose are E. grandis, E. citriodora, E. globulus, and E. camaldulensis. The most important species are E. tereticornis and it is also known as E. hybrid and Mysore gum. E. tereticornis and other species of eucalyptus are found throughout India (2).

The common name of E. tereticornis are forest red gum, bastard box, blue gum, flooded gum, grey gum, mountain gum, Queensland blue gum, red gum, red ironbark, red irongum and slaty gum (3).

E. tereticornis has great medicinal importance. It has various medical properties like stimulant, anaesthetic and antiseptic etc. Oil and leaves of the E. tereticornis are most useful part. Eucalyptus oil is used extensively as medicine. Oil is used internally as well as externally. Internally it is used as stimulant and it also possesses antiseptic and anaesthetic properties. Oil is also used for the treatment of diarrhoea and dysentery. Leaves, if chewed, possess wound healing properties. Decoction of leaves is also used to reduce fever and improve pulmonary associated difficulties (4). The resin part of the E. tereticornis is used as astringent (5).

Phytochemical constituents:

The preliminary phytochemical screening found triterpenoids, steroid, lignins, fatty acids, flavonoids, saponins, tannins, inositol derivatives and phenolic compounds (6,7). The leaves of E. tereticornis is good source of essential oil and it contains Camphene, Carvone, Citral, Citronellal, Geranyl acetate, Limonene, Linalool oxide and Triterpene esters (Tereticornate A and B) are the key source of the E. tereticornis (8). The essential oil is also composed of α-pinene, α-phellandrene, β-phellandrene, γ-terpinene, 4-terpineol, α-terpineol, p-cymene, and spathulenol (9). The chief compounds of E. tereticornis are sesquiterpenes (caryophyllene, eudesmol, globulol, spathulenol and virdiflorol) and monoterpenes (1, 8-cineole, citronellal, citronellol, limonene, pinene, pinene, trans-pinocarveol, terpinolene, thujene) (10).

Pharmacological action:

Fungicidal and antioxidant activity:

E. tereticornis contains citronelal 44.8 % and geraniol 9.78 %. The essential oilof E. tereticornis showed fungicidal activity(11). Kaur et al, extracted and characterized the essential oils from the leaves of E. tereticornis and determined its antioxidant and antifungal activity against phytopathogenic fungi. Essential oil 0.5 – 10.0 ppm exhibited antifungal activity against Fusarium oxysporum, Rhizoctonia solani and Heminthosporium oryzae and essential oil at 25-200 µg/ml showed antioxidant activity(12).

Anti-Filarial activity:

Ursolic acid (UA) isolated from the leaves of the E. tereticornis. UA showed anti-filarial activity against human lymphatic filarial parasite Brugia malayi using in vitro and in vivo assays. The UA was found lethal to microfilariae i.e. LC100: 50; IC50: 8.84 µM and female adult worms was LC100: 100; IC50: 35.36 µM. UA evaluatedin vivo in B. malayi-M. coucha model showed about 54% macrofilaricidal activity. About 56% sterility and no adverse effect was found on the host(13).

Hepatoprotective activity:

Saraswat et al, isolated Ursolic acid from leaves of E. tereticornis. In ethanol induced hepatotoxicity model, it showedabout 48%–54% decrease in the viability and about 42%–54% reduction in the biochemical parameters like aspartate transaminase (AST)and alkaline phosphatase (ALP). However, ursolic acid at concentration of 1–100 µg/mL showed hepatoprotective effect about 12%–76% on alcohol induced hepatocyte toxicity by restoring the altered parameters. (14).

Analgesic and anti-inflammatory effect:

Silva et al, evaluated the analgesic and anti-inflammatory effects of essential oil extracts from three species like Eucalyptus citriodora (EC), Eucalyptus tereticornis (ET), and Eucalyptus globulus (EG).Acetic acid induced writhing method and hot plate method was used to evaluate analgesic activity. For anti-inflammatory test paw edema was induced by carrageenan (subplantar) at 200 μg/paw into the right hind paw of the rats. On intraperitonial (i.p.) administration of essential oils of EC, ET, and EG 0.1, 10, and 100 mg/kg each showed decreased number of acetic acid-induced writhes in mice. Whereas in case of hot plate test by similar administration at 10 and 100 mg/kg each significantly prolonged reaction time after 30 min treatment as compared to the control groups.Further by administration at 100 mg/kg of essential oils of EC, ET, and EG significantly reduced edema of the rat hind paws (15).

Immunomodulatory effect:

Maurya et al, isolated and characterized triterpenoids and ursolic acid from E. tereticornis and mice were orally administred at dose of 1, 3 and 10 mg/kg body weight for a period of 28 days and showed immunomodulatory activity due to high binding affinity to human receptor(16).

Myorelaxant effect:

Lima et al. studied the effects of the essential oil of E. tereticornis (EOET) on rat trachea in vitro. In tracheal rings EOET potentiated the contractions induced by acetylcholine (ACh). Contractions induced by K⁺ (60 mM) were also potentiated by α- or β-pinene the chief constituents of EOET, but were reduced by EOET. Findings suggested that EOET has myorelaxant effects on rat airways, but potentiates ACh-induced contractions.(17). Coelho-de-Souza et al evaluated the effect of essential oil on gunea-pig tracheal smooth muscle. After administration of essential oil at 10 - 1000 microg/mL, itrelaxes the tracheal basal tonus. So essential oil produced significant myorelaxant effects on guinea- pig isolated trachea(18).

Antihyperglycemic effect:

The Ethyl acetate extract of E. tereticornis at 300mg/kg showed beneficial effects on blood glucose level against streptozotocin (25 mg/kg) induced diabetic rats(19). E. tereticornis bark dried powder extract at 200 μg/ml was screened and possess anti-hyperglycemic potential (20). At dosages of 5 mg/20 g mouse of Eucalyptus tereticornis extract showed decreases in blood glucose levels (BGLs)(21).

Antibacterial effect:

Four different concentration of leaves of E. tereticornis extract i.e., Limonene (3, 4, 5, 6 μL), 1, 8-Cineole (8, 9.5, 11, 12.5 μL), Terpinen-4-ol (14, 15, 16, 17 μL), and pH (5, 6, 7, 8) showed antibacterial activity against Escherichia coli with different zones of inhibition and maximum zone of inhibition was recorded to be 28.6 mm(22). The methanolic bark and leaf extracts of E. tereticornis were evaluated against gram-positive bacteria like Streptococcus mutans, Staphylococcus aureus and gram-negative bacteria like Escherichia coli and fungus like Candida albicans showed antimicrobial activity with zone of inhibition ranging between 17mm and 27mm(23). The fresh leave of E. tereticornis was extracted and screened at different concentration such as 60µl 70µl, 80µl, 90µl and 100 µl against gram-positive bacteria like Staphylococcus aureus and Enterococcus faecalis and gram-negative bacteria like Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa and showed significant antimicrobial activity(24).

E. tereticornis essential oils showed antibacterial activity against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Micrococcus luteus, Proteus mirabilis and Alcaligenes faecalis (25). Chemical composition of leaf oil of the E. tereticornis was determined by high resolution of gas chromatography (GC) and mass spectrometry (MS) and determined following components such as p-cimene, β-phellandrene, spathulenol, γ-terpinene, and α-phellandrene and these components exhibited antimicrobial activities (26). Badrunnisa et al. evaluated antimicrobial activity of ethanolic and methanolic extract of E. tereticornis against P. aeruginosa, B. cereus, and B. thuragenisis and they found that ethanol leaf extract was more potent than the methanol extract. They also found minimum inhibitory concentration (MIC) of the ethanol extract of E. tereticornis were 0.2, 0.5 and 2.0 mg/ml respectively while methanol leaf extract showed MIC of 50, 25, and 10 mg/ml respectively for B. Cereus, B.thuringiensis and Pseudomonas (27).

Larvicidal effect:

The essential oil extract of E. Tereticornis was tested against mature and immature mosquito vector Anopheles stephensi Liston (Diptera). It showed strong larvicidal, pupicidal and adulticidal activity (28).

CONCLUSION:

E. tereticornis has great medicinal importance. Eucalyptus oil is used extensively as medicine. The plant is enriched with number of phytochemical constituents like triterpenoids, steroid, lignins, fatty acids, flavonoids, saponins, tannins, inositol derivatives and phenolic compounds. These constituents possess various pharmacological action such as Fungicidal, antioxidant, Anti-Filarial, Hepatoprotective, Immunomodulatory, Myorelaxant, Antihyperglycemic, Antibacterial, Larvicidal, Analgesic and anti-inflammatory etc.

CONFLICT OF INTEREST STATEMENT:

We declare that we have no conflict of interest.

ACKNOWLEDGEMENT:

The authors are grateful to Indian Council of Medical Research (ICMR), New Delhi, India (45/5/2013/ BMS/TRM) for providing financial aid in the form of fellowship.

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Received on 15.01.2018 Modified on 12.02.2018

Research J. Pharm. and Tech 2018; 11(6): 2677-2680.

DOI: 10.5958/0974-360X.2018.00496.1