Evaluation of the Anti-asthmatic and Antitussive Effects of Aqueous Leaf Extract of Ocimum gratissimum in Rodents

Abstract

Background: Ocimum gratissimum Linn (Lamiaceae) is an aromatic plant popular for it culinary uses. The aqueous leaf extract is used in ethnomedicine for the treatment of various diseases including asthma and cough. The purpose of this study was to evaluate the anti-asthmatic, antitussive and muco-suppressant effects of the aqueous leaf extract (OGE) in rodent species. Methods: Ovalbumin-sensitized guinea pigs were exposed to 0.2% histamine aerosol in a glass chamber. Latency to preconvulsive dyspnea (PCD), tracheal fluid volume and viscosity were measured. For the antitussive screening, guinea pigs were exposed to 7.5% citric acid aerosol in a glass chamber and the bouts of cough pre and post-acute exposure were recorded. Mucus expectoration was estimated in mice after seven-day treatment with OGE. Results: Latency to preconvulsive dyspnea was not significantly increased by doses of 100, 200 and 400 mg/ kg of OGE when compared with distilled water-treated sensitized guinea pigs. Tracheal fluid volume but not viscosity was significantly (p<0.0001) reduced by all the doses of OGE when compared with distilled water-treated sensitized guinea pigs. Also, the doses of OGE significantly reduced (p<0.0001) the number of cough bouts when compared with distilled water control. All the doses of extract significantly (p<0.003) reduced phenol red dye expectoration from mice tracheae. Conclusion: The aqueous leaf extract of O. gratissimum does not protect against acute bronchospasms but possesses antitussive and muco-suppressant effects that may be helpful in asthmatics. Central mechanism may be contributory to the antitussive effect. These results lend credence to its ethnomedicinal use in the treatment of these diseases.