Antimicrobial and efflux pumps inhibitory activities of Eucalyptus grandis essential oil against respiratory tract infectious bacteria

Abstract

Essential oils obtained by hydrodistillation from the fresh and dry leaves of Eucalyptus grandis were analyzed by gas chromatography (GC) and gas chromatography mass spectrometry (GC-MS). The main components of the fresh leaf oil were α-pinene (29.6%), p-cymene (19.8%), 1,8-cineole (12.8%) and αterpineol (6.4%). While, the dry leaf oil had 1,8-cineole (47.4%), limonene (13.3%), α-pinene (7.5%) and spathulenol (7.1%). The antimicrobial activities of the essential oils were tested against respiratory tract infectious microorganisms (Klebsiella pneumoniae, Staphylococcus aureus and Moraxella catarrhalis) using the microdilution-broth methods. The minimum inhibitory concentration and minimum bactericidal concentration values of the oils ranged between (0.31 to 1.25) mg/ml and (0.63->5) mg/ml respectively. The minimum bactericidal concentration values caused the release of cytosolic lactate dehydrogenase (membrane damage) which ranges from 8 to 24% in comparison with Triton-X-100. The accumulation of rhodamine 6G in bacterial cells showed that the essential oils were effective as efflux pump inhibitors. The results of this study support the use of the plant in folk medicine.

In vitro antibacterial and cytotoxic activity of leaf extracts of Centella asiatica (L.) Urb, Warburgia salutaris (Bertol. F.) Chiov and Curtisia dentata (Burm. F.) C.A.Sm - medicinal plants used in South Africa

“…The extracts were tested for their Efflux pump inhibitory activity using the method of Maesaki et al (1999) [ 26 ] with some modifications as described by Soyingbe et al (2015) [ 50 ]. The percentage accumulation of R6G inside cells after exposure to glucose, essential oil and standards was calculated from the formula: …”

Antiasthma activity of Eucalyptus grandis essential oil and its main constituent: Vasorelaxant effect on aortic smooth muscle isolated from nomotensive rats

“…The details of the collection and the identification of the plant and the hydrodistillation of the essential oil from the leaves have already been reported (Soyingbe et al, 2015). The oil was dried over anhydrous sodium sulfate, dissolved in methanol and then stored at -4°C until required.…”

“…Eucalyptus grandis is a medicinal plant indicated by Zulu traditional healers for the treatment of respiratory tract infections, bronchial infections, asthma and coughs; it is administered via steam inhalation and also as a concoction which is taken for the treatment of asthma. The essential oil, obtained by hydro-distillation of the leaves of the plant exhibited antimicrobial activity against clinical isolates and respiratory tract infectious bacteria (Soyingbe et al, 2013;2015). The main constituent of the oil was identified as 1,8cineole (Soyingbe et al, 2013;2015).…”

“…The essential oil, obtained by hydro-distillation of the leaves of the plant exhibited antimicrobial activity against clinical isolates and respiratory tract infectious bacteria (Soyingbe et al, 2013;2015). The main constituent of the oil was identified as 1,8cineole (Soyingbe et al, 2013;2015). Essential oil isolated from eucalyptus species are also widely used in pharmacological industries (Gomes Carneiro et al, 1998).…”

Effect of Nebulized Eucalyptus for Preventing Ventilator-Associated Pneumonia in Patients under Mechanical Ventilation: A Randomized Double Blind Clinical Trial

“…The use of a nebulizer is one of the recommended methods for the delivery of antibiotics and other antimicrobial extracts to the inferior airways of ventilated patients [19].…”