The Open Agriculture Journal




ISSN: 1874-3315 ― Volume 14, 2020

Beneficial and Healthy Properties of Eucalyptus Plants: A Great Potential Use



Maria Gabriella Vecchio1, *, Claudia Loganes2, Clara Minto3
1 ZETA Research Ltd, Trieste, Italy
2 Institute for Maternal and Child Health - IRCCS Burlo Garofolo, Trieste, Italy
3 Unit of Biostatistics, Epidemiology and Public Health, Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova, Italy

Abstract

Eucalyptus (Eucapyptus spp.), an evergreen tall tree native to Australia and Tasmania, has been used since ancient times by the aboriginal population for several purposes. In particular, the species E. globulus is widely used in the pulp industry, as well as for the production of eucalyptus oil extracted on a commercial scale in many countries as raw materials in perfumery, cosmetics, food, beverages, aromatherapy and phytotherapy. The 1,8-cineole (eucalyptol), the principal and the most important constituent extracted from eucalyptus leaves, demonstrated an antimicrobial and anti-inflammatory activities. Despite the fact that the healthy effects of eucalyptus have been well established by research, further studies are necessary to investigate other prime effects of the plant and its possible implication in the treatment of a greater number of pathological conditions.

Keywords: Antibacterial, Anti-inflammatory, Antioxidant, Essential oil, Eucalyptol, Eucalyptus globulus labill.


Article Information


Identifiers and Pagination:

Year: 2016
Volume: 10
Issue: Suppl 1: M3
First Page: 52
Last Page: 57
Publisher Id: TOASJ-10-52
DOI: 10.2174/1874331501610010052

Article History:

Received Date: 04/12/2015
Revision Received Date: 09/05/2016
Acceptance Date: 11/05/2016
Electronic publication date: 31/08/2016
Collection year: 2016

© Vecchio et al. ; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.


Correspondence: Address correspondence to this author at the Zeta Research Ltd,, Via A. Caccia, 8, 34129 Trieste, Italy; Mobile: +39 3938908862; Tel/Fax: +39 040 358980; Email: mariaGVecchio@zetaresearch.com





INTRODUCTION

In recent decades, the demand for plant derived products for therapeutic uses has been increased [1Hermann R, von Richter O. Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions. Planta Med 2012; 78(13): 1458-77.
[http://dx.doi.org/10.1055/s-0032-1315117] [PMID: 22855269]
]. In many countries worldwide aromatic herbs are used in primary health care, especially in rural areas [2Kamatou GP, Viljoen AM, Gono-Bwalya AB, et al. The in vitro pharmacological activities and a chemical investigation of three South African Salvia species. J Ethnopharmacol 2005; 102(3): 382-90.
[http://dx.doi.org/10.1016/j.jep.2005.06.034] [PMID: 16099614]
], and 80% of the populations in developing countries use these traditional resources [3Begossi A. Use of ecological methods in ethnobotany: Diversity Indices. Econ Bot 1996; 50(3): 280-9.
[http://dx.doi.org/10.1007/BF02907333]
]. For this reason, the use of essential oils extracted from plants for clinical purposes have become an important topic in scientific research and industrial application thanks to the different biological activities of oils, which exercise antimicrobial [4Lo Cantore P, Shanmugaiah V, Iacobellis NS. Antibacterial activity of essential oil components and their potential use in seed disinfection. J Agric Food Chem 2009; 57(20): 9454-61.
[http://dx.doi.org/10.1021/jf902333g] [PMID: 19788240]
], antioxidant [5Dutra RC, Leite MN, Barbosa NR. Quantification of phenolic constituents and antioxidant activity of Pterodon emarginatus vogel seeds. Int J Mol Sci 2008; 9(4): 606-14.
[http://dx.doi.org/10.3390/ijms9040606] [PMID: 19325773]
] and anti-inflammatory [6Chao LK, Hua KF, Hsu HY, Cheng SS, Liu JY, Chang ST. Study on the antiinflammatory activity of essential oil from leaves of Cinnamomum osmophloeum. J Agric Food Chem 2005; 53(18): 7274-8.
[http://dx.doi.org/10.1021/jf051151u] [PMID: 16131142]
] activities. In this brief review, the authors will focus the attention on eucalyptus, which is a plant used for several purposes.

Eucalyptus (Eucapyptus spp.), is a large genus of the Myrtaceae family, which includes 900 species and subspecies. This evergreen tall tree is native from Australia and Tasmania and is the second largest genera after acacia [7Elliot WR, Jones DL. Encyclopaedia of australian plants suitable for cultivation. Melbourne: Lothian Publishing 1984.]. Since the 1850s, it has been successfully introduced into 90 countries worldwide where it is now one of the most important and widely planted genera [8Brooker MI, Kleinig DA. Field Guide to Eucalyptus. 3rd ed. Melbourne, Australia: Blooming Books 2006.]. In ancient times the eucalyptus plant was used for several purposes by aboriginal people, both as medicine and as food. Nowadays, the plant is used in forestry (timber, fuel, paper pulp), environmental planting (water and wind erosion control), as a source of essential oil (medicinal, perfumery oils), for arts and craft [7Elliot WR, Jones DL. Encyclopaedia of australian plants suitable for cultivation. Melbourne: Lothian Publishing 1984.]. Among all the species of Australian Eucalyptus, the E. globulus was widely introduced overseas [9Damjanović-Vratnica B, Đakov T, Šuković D, Damjanović J. Antimicrobial effect of essential oil isolated from Eucalyptus globulus Labill. from Montenegro. Czech J Food Sci 2011; 3: 277-84.], becoming largely cultivated in the subtropical and Mediterranean regions [10Takahashi T, Kokubo R, Sakaino M. Antimicrobial activities of eucalyptus leaf extracts and flavonoids from Eucalyptus maculata. Lett Appl Microbiol 2004; 39(1): 60-4.
[http://dx.doi.org/10.1111/j.1472-765X.2004.01538.x] [PMID: 15189289]
], as well as in Nigeria. E. globulus which has different vernacular names (eucalyptus in Bengali and in Hindi; blue-gum eucalyptus in English and Karpuramaram in Tamil [11Dixit A, Rohilla A, Singh V. Eucalyptus globulus: A new perspective in therapeutics. Int J Pharm Chem Sci 2012; 1(4): 1678-83.]), is considerably used in the pulp industry, as well as for the production of eucalyptus oil (henceforth EO), extracted on commercial scale in many countries and adopted in perfumery, cosmetics, food, beverages, aromatherapy and phytotherapy [12Buchbauer G. The detailed analysis of essential oils leads to the understanding of their properties. Perfumer and flavourist 2000.].

Eucalyptus plants draw the attention of researchers and environmentalists worldwide because it represents a fast-growing source of wood as well as a source of oil used for several purposes. The oil is extracted from leaves, fruits, buds and bark showing antibacterial, antiseptic, antioxidant, anti-inflammatory, anticancer activities [11Dixit A, Rohilla A, Singh V. Eucalyptus globulus: A new perspective in therapeutics. Int J Pharm Chem Sci 2012; 1(4): 1678-83., 13Egawa H, Tsutsui O, Tatsuyama K, Hatta T. Antifungal substances found in leaves of Eucalyptus species. Experientia 1977; 33(7): 889-90.
[http://dx.doi.org/10.1007/BF01951263] [PMID: 560980]
] and for this reason used in the treatment of respiratory diseases, common cold, influenza, and sinus congestion [14Silva J, Abebe W, Sousa SM, Duarte VG, Machado MI, Matos FJ. Analgesic and anti-inflammatory effects of essential oils of Eucalyptus. J Ethnopharmacol 2003; 89(2-3): 277-83.
[http://dx.doi.org/10.1016/j.jep.2003.09.007] [PMID: 14611892]
, 15Williams LR, Stockley JK, Yan W, Home VN. Essential oils with high antimicrobial activity for therapeutic use. Int J Aromather 1998; 8(4): 30-9.
[http://dx.doi.org/10.1016/S0962-4562(98)80079-9]
]. The aim of this paper is to provide and collect scientific information about eucalyptus plants in order to present the beneficial and healthy properties and its potential use.

Chemical Composition

E. globulus is a rich source of phytochemical compounds as flavonoids, alkaloids, tannins and propanoids, extracted in the leaf, stem and root of the plant [11Dixit A, Rohilla A, Singh V. Eucalyptus globulus: A new perspective in therapeutics. Int J Pharm Chem Sci 2012; 1(4): 1678-83.]. Several researches were conducted with the aim to isolate the phytoconstituents from the plant’s organs: several volatile constituents as 1,8-cineole (eucalyptol) aromadendrene, α-gurjunene, globulol, ß-pinene, pipertone, α-,ß-and γ-terpinen-4-ol, and allo-aromadendrene were found both in leaves and in shoots (eucalyptol is, in particular, the principal and the most important constituent found in eucalyptus, also in plant’s buds); borneol, caproic acid, citral, eudesmol, fenchone, p-menthane, myrecene, myrtenol, α-terpineol, verbinone, asparagine, cysteine, glycine, glutamic acid, ornithine and threonine were extracted from fruits [16Boulekbache-Makhlouf L, Meudec E, Chibane M, et al. Analysis by high-performance liquid chromatography diode array detection mass spectrometry of phenolic compounds in fruit of Eucalyptus globulus cultivated in Algeria. J Agric Food Chem 2010; 58(24): 12615-24.
[http://dx.doi.org/10.1021/jf1029509] [PMID: 21121679]
], while forming acid, dextrin and sucrose were extracted from flowers and the honey [17Stackpole DJ, Vaillancourt RE, Alves A, Rodrigues J, Potts BM. Genetic variation in the chemical components of eucalyptus globulus wood. G3 (Bethesda) 2011; 1(2): 151-9.
[http://dx.doi.org/10.1534/g3.111.000372] [PMID: 22384327]
]. Despite the fact that more than 18 compounds were identified in EO, eucalyptol represents the 79.85% of the total chemical composition. The EO also showed a high content of oxygenated monoterpenes, which change between each Eucalyptus species, with a potential variation in therapeutic properties [18Olayinka AJ, Olawumi OO, Olalekan AM, Abimbola AS, Idowu DI, Theophilus OA. Chemical composition, antioxidant and cytotoxic effects of Eucalyptus globulus grown in north-central Nigeria. J Nat Prod Plant Res 2012; 2(1): 1.]. The composition pattern of essential oil is affected by factors such as geographical location [19Usman LA, Zubair MF, Adebayo SA, Oladosu IA. NO M, Akolade JO. Chemical composition of leaf and fruit essential oils of hoslundia opposita vahl grown in nigeria. Am-Eurasian J Agric Environ Sci 2010; 8(1): 40-3.] and seasons [20Emara S, Shalaby AE. Seasonal variation of fixed and volatile oil percentage of four Eucalyptus spp. related to lamina anatomy. Afr J Plant Sci 2011; 5(6): 353-9.], with consequent influence on biological activities [21Salihu BK, Usman LA, Sani A. Chemical composition and antibacterial (oral isolates) activity of leaf essential oil of Ocimum gratissimum L. grown in North central Nigeria. Int J Curr Res 2011; 3(3): 022-8.]. EO is widely used in many countries like China, India, South Africa, Portugal, Brazil and Tasmania [20Emara S, Shalaby AE. Seasonal variation of fixed and volatile oil percentage of four Eucalyptus spp. related to lamina anatomy. Afr J Plant Sci 2011; 5(6): 353-9.] for perfumery, cosmetics, aromatherapy, phytotherapy products and for food and beverages preparation [22Akolade JO, Olajide OO, Afolayan MO, Akande SA, Idowu DI, Orishadipe AT. Chemical composition, antioxidant and cytotoxic effects of Eucalyptus globulus grown in north-central Nigeria. J Nat Prod Plant Res 2012; 2(1): 1-8.].

Antiseptic and Antibacterial Effects

Eucalyptus plant was used traditionally as antiseptic and for the treatment of respiratory tract infections [23Chevallier A. Encyclopedia of Medicinal Plants. St. Leonards, New South Wales, Australia: DK Publishing 2001.]: the herb is, in fact, very helpful for colds, flu, sore throats and chest infections including bronchitis and pneumonia [15Williams LR, Stockley JK, Yan W, Home VN. Essential oils with high antimicrobial activity for therapeutic use. Int J Aromather 1998; 8(4): 30-9.
[http://dx.doi.org/10.1016/S0962-4562(98)80079-9]
]. Several studies showed a moderate antimicrobial activity of EO from E. globulus both on Gram-negative (Salmonella enteritidis, Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecium, Listeria monocytogenes 4b and Listeria monocytogenes EGD-e) and a bacteriostatic activity against all strains tested (with the exception of Pseudomonas aeruginosa) [24Ait-Ouazzou A, Lorán S, Bakkali M, et al. Chemical composition and antimicrobial activity of essential oils of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco. J Sci Food Agric 2011; 91(14): 2643-51.
[http://dx.doi.org/10.1002/jsfa.4505] [PMID: 21769875]
]. This effect on bacteria may be attributed to the dominant presence of eucalyptol which, in the past, has demonstrated a strong antimicrobial activities against many important pathogens [25Bakkali F, Averbeck S, Averbeck D, Idaomar M. Biological effects of essential oils-a review. Food Chem Toxicol 2008; 46(2): 446-75.
[http://dx.doi.org/10.1016/j.fct.2007.09.106] [PMID: 17996351]
]. To strengthen these results, other researchers showed a significant activity of EO from different Eucapyptus species against various microorganisms, including human pathogen spoilage bacteria, Candida albicans [9Damjanović-Vratnica B, Đakov T, Šuković D, Damjanović J. Antimicrobial effect of essential oil isolated from Eucalyptus globulus Labill. from Montenegro. Czech J Food Sci 2011; 3: 277-84.], Propionibacterium acnes and Pityrosporum ovale [26Tsai ML, Lin CC, Lin WC, Yang CH. Antimicrobial, antioxidant, and anti-inflammatory activities of essential oils from five selected herbs. Biosci Biotechnol Biochem 2011; 75(10): 1977-83.
[http://dx.doi.org/10.1271/bbb.110377] [PMID: 21979069]
].

These studies supported the potential use of EO (specifically from E. globulus and E. bridgesiana) as natural preservative for food and pharmaceutical industries, which may be useful as an alternative antimicrobial agent in natural medicine for the treatment of numerous infectious diseases.

Antioxidant Properties

The infection process frequently induces inflammation which determines the release of free radicals from the phagocytes. Antioxidants are molecules able to scavenge reactive oxygen species or free radicals, protecting cells from damage and death. At a physiological level, these free radicals play important roles in energy production, synthesis of some biomolecules, phagocytosis, and cell growth in living systems [27Packer L, Cadenas E, Davies KJ. Free radicals and exercise: an introduction. Free Radic Biol Med 2008; 44(2): 123-5.
[http://dx.doi.org/10.1016/j.freeradbiomed.2007.05.031] [PMID: 18191747]
]. An imbalance between free radical generation and unfavorable antioxidant defenses leads to oxidative stress, resulting in DNA or tissue damage [28Jung T, Höhn A, Catalgol B, Grune T. Age-related differences in oxidative protein-damage in young and senescent fibroblasts. Arch Biochem Biophys 2009; 483(1): 127-35.
[http://dx.doi.org/10.1016/j.abb.2008.12.007] [PMID: 19135972]
, 29Wells PG, McCallum GP, Chen CS, et al. Oxidative stress in developmental origins of disease: teratogenesis, neurodevelopmental deficits, and cancer. Toxicol Sci 2009; 108(1): 4-18.
[http://dx.doi.org/10.1093/toxsci/kfn263] [PMID: 19126598]
]. It is possible to distinguish among two categories of antioxidants, the natural and the synthetic. Recently, due to the adverse effects demonstrated by synthetic antioxidants, the interest in finding naturally antioxidant molecules in foods has increased considerably [30Zheng W, Wang SY. Antioxidant activity and phenolic compounds in selected herbs. J Agric Food Chem 2001; 49(11): 5165-70.
[http://dx.doi.org/10.1021/jf010697n] [PMID: 11714298]
]. A study by Akolade and colleagues was conducted with an aim to determine the antioxidant effects of EO from E. globulus grown in Nigeria [18Olayinka AJ, Olawumi OO, Olalekan AM, Abimbola AS, Idowu DI, Theophilus OA. Chemical composition, antioxidant and cytotoxic effects of Eucalyptus globulus grown in north-central Nigeria. J Nat Prod Plant Res 2012; 2(1): 1.]. The antioxidant activity was evaluated by the ability of EO to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in methanol (DPPH assay) and the results showed that, although its activity resulted lower when compared with ascorbic acid, the EO depending on concentration, exerts radical scavenging activity. The low antioxidant capacity of the EO may be attributed to the absence of phenolics compounds (such as thymol and cavacrol) in Nigerian E. globulus leaf [18Olayinka AJ, Olawumi OO, Olalekan AM, Abimbola AS, Idowu DI, Theophilus OA. Chemical composition, antioxidant and cytotoxic effects of Eucalyptus globulus grown in north-central Nigeria. J Nat Prod Plant Res 2012; 2(1): 1.].

The major derivative compound from E. globulus are called Globulusin A and Eucaglobulin which demonstrated a suppressive effect on DPPH free radical development were examined. These molecules, in fact, scavenged DPPH free radical in a concentration dependent manner, and revealed an inhibitory activity stronger than ascorbic acid [31Hasegawa T, Takano F, Takata T, Niiyama M, Ohta T. Bioactive monoterpene glycosides conjugated with gallic acid from the leaves of Eucalyptus globulus. Phytochemistry 2008; 69(3): 747-53.
[http://dx.doi.org/10.1016/j.phytochem.2007.08.030] [PMID: 17936865]
]. According to all these assessments, and considering the various experimental methods used, eucalyptus plant is an important source of antioxidants.

Anti-inflammatory Activity

The aromatic constituents of EO are used as analgesic, anti-inflammatory, and antipyretic remedies [14Silva J, Abebe W, Sousa SM, Duarte VG, Machado MI, Matos FJ. Analgesic and anti-inflammatory effects of essential oils of Eucalyptus. J Ethnopharmacol 2003; 89(2-3): 277-83.
[http://dx.doi.org/10.1016/j.jep.2003.09.007] [PMID: 14611892]
]. Juergens et al., examined the role of eucalyptol as inhibitor of the production and synthesis of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), leukotriene B4, and thromboxane B2 in human blood monocytes, suggesting that eucalyptol is a strong inhibitor of cytokines that might be suitable for long term treatment of airway inflammation in bronchial asthma and other steroid-sensitive disorders [32Juergens UR, Stöber M, Vetter H. Inhibition of cytokine production and arachidonic acid metabolism by eucalyptol (1.8-cineole) in human blood monocytes in vitro. Eur J Med Res 1998; 3(11): 508-10.
[PMID: 9810029]
]. Moreover, in a double-blind, placebo-controlled trial, the anti-inflammatory activity of eucalyptol was evaluated in patients with severe asthma suggesting the efficacy of this molecule and a new rational for its use as mucolytic agent in upper and lower airway diseases [33Juergens UR, Dethlefsen U, Steinkamp G, Gillissen A, Repges R, Vetter H. Anti-inflammatory activity of 1.8-cineol (eucalyptol) in bronchial asthma: a double-blind placebo-controlled trial. Respir Med 2003; 97(3): 250-6.
[http://dx.doi.org/10.1053/rmed.2003.1432] [PMID: 12645832]
]. These results should help to clarify functional applications for the future of eucalyptus plant and its EO in anti-inflammatory treatments.

Cytotoxic and Toxic Features

Extracts and components isolated from some Eucalyptus species showed cytotoxic activities. In the two studies presented in this section, the cytotoxicity of the compounds derived from Eucalyptus was evaluated measuring the concentration of sample that inhibited 50% of cell growth (IC50). The first research was conducted on Cladocalol, a formylated triterpene isolated from E. cladocalyx leaves, which showed cytotoxic effect on the myeloid leukemia cell line HL-60 [34Benyahia S, Benayache S, Benayache F, et al. Cladocalol, a pentacyclic 28-nor-triterpene from Eucalyptus cladocalyx with cytotoxic activity. Phytochemistry 2005; 66(6): 627-32.
[http://dx.doi.org/10.1016/j.phytochem.2004.12.018] [PMID: 15771880]
]. The second study was carried out in Brazil and investigated the cytotoxic activity of E. benthamii EO in vitro. The authors compared the activity of EO with some other terpene compounds (α-pinene, terpinen-4-ol and γ-terpinene) on different pathogenetic cells lines, such as Jurkat (T leukemia cells), J774A.1 (murine macrophage tumor), and HeLa (cervical cancer) cells lines. The results demonstrated a cytotoxicity of EO mainly against Jurkat and HeLa cell lines comparing to the isolated terpenes, showing the potential use of E. benthamii as an alternative herbal source [35Döll-Boscardin PM, Sartoratto A, Sales Maia BH, et al. In vitro cytotoxic potential of essential oils of eucalyptus benthamii and its related terpenes on tumor cell lines. Evid Based Complement Alternat Med 2012; 2012: 342652.
[http://dx.doi.org/10.1155/2012/342652] [PMID: 22645627]
]. These studies demonstrated the cytotoxicity of EO on some cells, showing the importance to study the characteristics of this plant for its potential use in the treatment of diseases. For what concern the toxicity, the information in scientific literature related to EO showed the toxic effect of this compound when ingested. Several cases of ingestion, especially in children, were recorded (the most common effects were burning sensation in mouth and throat, abdominal pain and vomiting) [36Patel S, Wiggins J. Eucalyptus oil poisoning. Arch Dis Child 1980; 55(5): 405-6.
[http://dx.doi.org/10.1136/adc.55.5.405] [PMID: 7436478]
]. A case reported the story of a 3-years old boy who accidentally ingested EO, causing a central nervous system depression within 30 minutes [36Patel S, Wiggins J. Eucalyptus oil poisoning. Arch Dis Child 1980; 55(5): 405-6.
[http://dx.doi.org/10.1136/adc.55.5.405] [PMID: 7436478]
], while Day et al. conducted a survey to investigate the unintentional EO poisoning in children with the aim to develop a strategy for the prevention [37Day LM, Ozanne-Smith J, Parsons BJ, Dobbin M, Tibballs J. Eucalyptus oil poisoning among young children: mechanisms of access and the potential for prevention. Aust N Z J Public Health 1997; 21(3): 297-302.
[http://dx.doi.org/10.1111/j.1467-842X.1997.tb01703.x] [PMID: 9270157]
], and Webb and Pitt reported, in 7 years of study, 41 cases of EO poisoning among children under 14 years [38Webb NJ, Pitt WR. Eucalyptus oil poisoning in childhood: 41 cases in south-east Queensland. J Paediatr Child Health 1993; 29(5): 368-71.
[http://dx.doi.org/10.1111/j.1440-1754.1993.tb00537.x] [PMID: 8240865]
].

Other Positive Effects

Besides the collected data on antiseptic and anti-inflammatory properties, little is known about the influence of EO extract on the cellular components of the immune system, and in particular on the monocytic/macrophagic system, which are one of the primary cellular effectors of the immune response against pathogen attacks [39Serafino A, Sinibaldi Vallebona P, Andreola F, et al. Stimulatory effect of Eucalyptus essential oil on innate cell-mediated immune response. BMC Immunol 2008; 9: 17.
[http://dx.doi.org/10.1186/1471-2172-9-17] [PMID: 18423004]
]. The effect of EO extract on the phagocytic ability of human monocyte derived macrophages (MDMs) was investigated both in vitro and in vivo, on rat peripheral blood monocytes/granulocytes, after EO oral administration. The results demonstrated that EO is able to induce activation of MDMs stimulating the phagocytic response, decreasing the release of pro-inflammatory cytokines, acting as a complement receptor-mediated phagocytosis. Implementation of innate cell-mediated immune response was also observed in vivo after EO administration, mainly involving the peripheral blood monocytes/granulocytes [39Serafino A, Sinibaldi Vallebona P, Andreola F, et al. Stimulatory effect of Eucalyptus essential oil on innate cell-mediated immune response. BMC Immunol 2008; 9: 17.
[http://dx.doi.org/10.1186/1471-2172-9-17] [PMID: 18423004]
].

Eucalyptol showed an important activity also in the therapy of symptomatic chronic obstructive pulmonary disease, thanks to its efficacy in reducing frequency, severity and duration of inflammatory exacerbation [40Worth H, Schacher C, Dethlefsen U. Concomitant therapy with Cineole (Eucalyptole) reduces exacerbations in COPD: A placebo-controlled double-blind trial. Respir Res 2009; 10(1): 1-7. 2009/07/22]. Like menthol, EO decongests the upper respiratory tract in case of common cold activating the nasal receptors, and stimulates the bronchial epithelium, determining an expectorant and mucolytic effect [11Dixit A, Rohilla A, Singh V. Eucalyptus globulus: A new perspective in therapeutics. Int J Pharm Chem Sci 2012; 1(4): 1678-83.].

The benefits of eucalyptus extract on skin health and integrity were also reported [41Ishikawa J, Shimotoyodome Y, Chen S, et al. Eucalyptus increases ceramide levels in keratinocytes and improves stratum corneum function. Int J Cosmet Sci 2012; 34(1): 17-22.
[http://dx.doi.org/10.1111/j.1468-2494.2011.00675.x] [PMID: 21696405]
]. Several studies described a close relationship between the levels of ceramides and water-holding functions or between psoriasis or atopic dermatitis and dry skin [42Elias PM. Epidermal lipids, barrier function, and desqamation. J Invest Dermatol 1983; 80: 44-9.
[http://dx.doi.org/10.1038/jid.1983.12] [PMID: 6184422]
-44Elias PM, Schmuth M. Abnormal skin barrier in the etiopathogenesis of atopic dermatitis. Curr Opin Allergy Clin Immunol 2009; 9(5): 437-46.
[http://dx.doi.org/10.1097/ACI.0b013e32832e7d36] [PMID: 19550302]
]. It is well established that some substances (i.e. lactic acid and nicotinamide) increase ceramide levels in the stratum cornum [43Rawlings AV, Davies A, Carlomusto M, et al. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. Arch Dermatol Res 1996; 288(7): 383-90.
[http://dx.doi.org/10.1007/BF02507107] [PMID: 8818186]
, 45Tanno O, Ota Y, Kitamura N, Katsube T, Inoue S. Nicotinamide increases biosynthesis of ceramides as well as other stratum corneum lipids to improve the epidermal permeability barrier. Br J Dermatol 2000; 143(3): 524-31.
[http://dx.doi.org/10.1111/j.1365-2133.2000.03705.x] [PMID: 10971324]
], and a recent study identified and demonstrates that eucalyptus extract is able to increase the level of ceramide in human stratum corneum, improving the water holding and barrier functions [41Ishikawa J, Shimotoyodome Y, Chen S, et al. Eucalyptus increases ceramide levels in keratinocytes and improves stratum corneum function. Int J Cosmet Sci 2012; 34(1): 17-22.
[http://dx.doi.org/10.1111/j.1468-2494.2011.00675.x] [PMID: 21696405]
]. The enhancement of these functions might be the result of the increase of ceramide levels in stratum corneum, keratinocytes and epidermis, due to an increase of proteins biosynthesis involved in ceramide metabolism. The results of Ishikawa and co-workers indicate that eucalyptus extract plays an important role in ceramide metabolism and confirm the possibility to use this plant in therapeutic treatments of skin [41Ishikawa J, Shimotoyodome Y, Chen S, et al. Eucalyptus increases ceramide levels in keratinocytes and improves stratum corneum function. Int J Cosmet Sci 2012; 34(1): 17-22.
[http://dx.doi.org/10.1111/j.1468-2494.2011.00675.x] [PMID: 21696405]
].

Furthermore, sideroxylonal was extracted from the flowers of E. albens., a new molecule that showed various bio-property [46Neve J, Leone PA, Carroll AR, et al. Sideroxylonal C, a new inhibitor of human plasminogen activator inhibitor type-1, from the flowers of Eucalyptus albens. J Nat Prod 1999; 62(2): 324-6.
[http://dx.doi.org/10.1021/np980286+] [PMID: 10075775]
]. This compound exhibits inhibitory activity against human plasminogen activator inhibitor type-1 (PAI-1) which is related to the pathogenesis of arterial and thrombotic diseases. It means that the molecule extracted from E. albens . should be a novel way to enhance fibrinolysis and to prevent the development of thrombotic diseases [47Verstraete M, Collen D. Thrombolytic therapy in the eighties. Blood 1986; 67(6): 1529-41.
[PMID: 2423156]
, 48Dawson S, Henney A. The status of PAI-1 as a risk factor for arterial and thrombotic disease: a review. Atherosclerosis 1992; 95(2-3): 105-17.
[http://dx.doi.org/10.1016/0021-9150(92)90014-8] [PMID: 1418086]
].

CONCLUSION

In conclusion, studies conducted on eucalyptus plant demonstrated its biological activities, due to the multitude of compounds contained in the leafs, stem and roots [49Gilles M, Zhao J, An M, Agboola S. Chemical composition and antimicrobial properties of essential oils of three Australian Eucalyptus species. Food Chem 2010; 119: 731-7.
[http://dx.doi.org/10.1016/j.foodchem.2009.07.021]
, 50Maciel MV, Morais SM, Bevilaqua CM, et al. Chemical composition of Eucalyptus spp. essential oils and their insecticidal effects on Lutzomyia longipalpis. Vet Parasitol 2010; 167(1): 1-7.
[http://dx.doi.org/10.1016/j.vetpar.2009.09.053] [PMID: 19896276]
]. In particular, the abundance of bioactive secondary metabolites, such as terpenoids, tannins, flavonoids, and phloroglucinol derivatives confers both the antiviral and antibacterial effects [51Ghisalberti EL. Bioactive acylphloroglucinol derivatives from Eucalyptus species. Phytochemistry 1996; 41(1): 7-22.
[http://dx.doi.org/10.1016/0031-9422(95)00484-X] [PMID: 8588876]
] that explain the traditional use of the plant as an antiseptic and in the treatment of respiratory tract infections. Among the genus Eucalyptus, the species E. globulus is the most widely cultivated in the subtropical and Mediterranean regions, which reach a therapeutic importance thanks to its phytochemicals compounds. However, despite the several known healthy effects of eucalyptus plant, further studies are necessary to investigate other prime effects of the plant and the possible implication in the treatment of other pathological conditions, and in case of plant toxicity, the diffusion of injuries prevention strategies.

CONFLICT OF INTEREST

The authors confirm that this article content has no conflict of interest.

ACKNOWLEDGEMENTS

The work has been partially supported by an unrestricted grant of the Italian Ministry of Foreign Affairs and the Indian Ministry of Science & Technology.

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