Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves

BACKGROUND: In this paper, we have studied the essential oils chemical composition of the leaves of seven Eucalyptus species developed in Tunisia. Eucalyptus leaves were picked from trees growing in different arboretums in Tunisia. Choucha and Mrifeg arboretums located in Sedjnene, region of Bizerte (Choucha: E. maideni, E. astrengens et E. cinerea; Mrifeg : E. leucoxylon), Korbous arboretums located in the region of Nabeul, North East Tunisia with sub-humid bioclimate, (E. lehmani), Souiniet-Ain Drahem arboretum located in region of Jendouba (E. sideroxylon, E. bicostata). Essential oils were individually tested against a large panel of microorganisms includingStaphylococcus aureus (ATCC 6539), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC29212), Listeria ivanovii (RBL 30), Bacillus cereus (ATCC11778). RESULTS: The yield of essential oils ranged from 1.2% to 3% (w/w) for the different Eucalyptus species. All essential oils contain α-pinene, 1,8-cineol and pinocarveol-trans for all Eucalyptus species studied. The 1,8-cineol was the major compound in all species (49.07 to 83.59%). Diameter of inhibition zone of essential oils of Eucalyptus species varied from 10 to 29 mm. The largest zone of inhibition was obtained for Bacillus cereus (E. astrengens) and the lowest for Staphylococcus aureus (E. cinerea). The essential oils from E. maideni, E. astrengens, E. cinerea (arboretum of Bizerte), E. bicostata(arboretum of Aindraham) showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus. CONCLUSION: The major constituents of Eucalyptus leaves essential oils are 1,8-cineol (49.07 to 83.59%) and α-pinene (1.27 to 26.35%). The essential oils from E. maideni, E. astrengens, E. cinerea, E. bicostatashowed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus, they may have potential applications in food and pharmaceutical products.

Essential oils from two Eucalyptus from Tunisia and their insecticidal action on Orgyia trigotephras (Lepidotera, Lymantriidae)

BACKGROUND: Essential oils extracted from aromatic and medicinal plants have many biological properties and are therefore an alternative to the use of synthetic products. The chemical composition of essential oils from two medicinal plants (Eucalyptus globulus and E. lehmannii) was determined and, their insecticidal effects on the third and fourth larval stages of Orgyia trigotephras were assessed. RESULTS: Larvae were collected from Jebel Abderrahmane (North-East of Tunisia), conserved in groups of 50/box (21 × 10 × 10 cm) at a temperature of 25°C. Larvae were tested for larvicidal activities of essential oils. Each oil was diluted in ethanol (96%) to prepare 3 test solutions (S1 = 0.05%, S2 = 0.10% and S3 = 0.50%). Essential oils were used for contact, ingestion and Olfactory actions and compared to reference products (Bacillus thuringiensis and Decis). Olfactory action of essential oils shows that larvae mortality is higher than contact action, lower than ingestion action. MTM and FTM of S3 of E. lehmannii were respectively 1 h 32 min and 1 h 39 min are higher than those of E. globulus (MTM = 51 min and FTM = 1 h 22 min 34 sec). Contact action of E. lehmannii oil shows low insecticidal activity compared to E. globulus. MTM are respectively (1 min 52 sec and 1 min 7 sec), FTM are (2 min 38 sec, 1 min 39 sec), are the shortest recorded for S3, on the third stage of larvae. The fourth stage of larvae, MTM are (2 min 20 sec and 2 min 9 sec), FTM are (3 min 25 sec, 3 min 19 sec). Ingestion action of essential oils is longer than the contact action, since the time of death exceeds 60 minutes for all species. CONCLUSION: Results shows that essential oils have a toxic action on nerves leading to a disruption of vital system of insects. High toxic properties make these plant-derived compounds suitable for incorporation in integrated pest management programs.

Patogenesia do óleo essencial e homeopatias de Eucalyptus citriodora em plantas de feijão (Phaseolus vulgaris) / Pathogenesis of essential oil and homeopathies of Eucalyptus citriodora in bean plants (Phaseolus vulgaris)

A homeopatia baseia-se no princípio da cura pelos semelhantes, e na experimentação no indivíduo sadio, doses mínimas e medicamento único. O uso de tratamentos a base de soluções dinamizadas aplicadas em vegetais aumentou nas ultimas décadas, sendo assim necessária a experimentação patogenésica para aplicação de todos os princípios homeopáticos e consolidação da Matéria Vegetal Homeopática. O ensaio patogenésico com plantas de feijão tratadas diariamente via pulverização e irrigação utilizando óleo essencial de Eucalyptus citriodora em diluições (0,5 e 1%) e dinamizados (12 e 30CH) revelaram sintomas externos semelhantes aos provocados por Pseudocercospora griseola, agente causal da mancha angular em feijoeiro. O estudo patogenésico com E. citriodora levanta a possibilidade deste ser utilizado no controle da mancha angular de acordo com o princípio homeopático da cura pela similitude.

Homeopathy is based on the principle of cure by similarity and on the prescription of minimal doses and single medicine to healthy individuals. In plants, performing treatments on the basis of drug dynamisation has increased in the recent decades. In these treatments, it is necessary to conduct a pathogenetic experimentation in order to apply homeopathic principles and to consolidate homeopathic plant material. Through a pathogenetic test with bean plants treated daily by pulverization and irrigation, using diluted and dynamized essential oil of Eucalyptus citriodora - (dilutions: 0.5 and 1%) (oil dynamisation: 12 and 30CH) -, there appeared external symptoms similar to those symptoms caused by Pseudocercospora griseola, i.e., the causal agent of angular leaf spot of bean. The pathogenetics study with E. citriodora raises the possibility of its application to control angular leaf spot in bean plants in accordance with the homeopathic principle of cure by similarity.