Antiasthma activity of Eucalyptus grandis essential oil and its main constituent: Vasorelaxant effect on aortic smooth muscle isolated from nomotensive rats
Asthma is a chronic inflammatory disorder of the airways. It is characterized by an inflammation of the airways causing dysfunction. Asthma is associated with widespread airflow obstruction and increase in airway responsiveness to a variety of stimuli. An asthma attack is accompanied by wheezing, shortness of breath, chest tightness and coughing. The anti-asthmatic and anti-cough activities of the essential oils and 1,8-cineole on rats were assessed. These activities were induced and challenged with histamine and acetylcholine using an ultrasonic nebulizer for asthma and exposure to ammonia for coughs. Anti-inflammatory activities of the essential oils and 1,8-cineole were determined using the cotton pellet granuloma test. Muscle contraction studies where carried out using the vascular reactivity on aortic smooth muscle. The oils exhibited concentration dependent anti-asthma and anti-cough activities. Significantly, 1,8-cineole isolated and purified from the essential oil showed a concentration dependent anti-inflammatory, anti-cough and anti-asthma activity and The essential oils showed vasorelaxant activity. The ability of the essential oils and 1,8-cineole to directly dilate smooth muscle and relieve the stress of bronchial contraction and obstruction of the airways passage validates the use of Eucalyptus grandis as an anti-asthmatic and anti-cough agent. It is concluded that the essential oils have the potential to be used as an anti-asthma and anti-cough therapy. This study also justifies its use by traditional healers in the treatment of asthma and coughs in Zulu folklore medicine.