Callistemon Citrinus (Curtis) Skeels as A Source of Antitubercular Compounds

Abstract Tuberculosis (TB) is still a principal cause of death in the world. There is considerable emphasis for search of novel drugs against TB due to increased Mycobacterium tuberculosis drug resistance and co infection with Human Immunodeficiency virus (HIV) that are challenging to treat. Callistemon citrinus (Curtis) skeels is one of the medicinal plants that are used in treatment of tuberculosis by local communities in Uganda. Though crude extracts from the plant have shown antimycobacterial activity in-vitro, the specific phytochemicals responsible for this activity are not known. The study aimed at isolating and characterizing compounds from C. citrinus and testing the compounds on different strains of M. tuberculosis. Methods: Chromatographic and spectroscopic methods were used for isolation and characterization of pure compounds, while Microplate Alamar Blue Assay (MABA) was used to determine its efficacy on sensitive and resistant strains of M. tuberculosis. Results: Betulinic acid, ursolic acid and epicatechin were isolated from C. citrinus. Epicatechin had minimum inhibitory concentration values of 3.4 μg/ml, 5.9 μg/ml and 3.9 μg/ml on the pan sensitive, rifampicin resistant and isoniazid resistant strains respectively. Betulinic acid and ursolic acid had MIC values of 29.3 μg/ml and 30.1 μg/ml respectively on the pan sensitive strain. Conclusion: Our results substantiate the use of C. citrinus in traditional medicine for treatment of tuberculosis and this activity is related to presence of ursolic acid, betulinic acid and epicatechin.