Anti-mycobacterial activity and acute toxicity of Erythrina abyssinica, Cryptolepis sanguinolenta and Solanum incanum
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Tuberculosis (TB) kills approximately two million people annually. Efforts to treat the disease have been made much more difficult due to development of drug resistant TB strains (MDR and XDR TB) and co-infection with HIV AIDS. There is an urgent need therefore, to search for and develop new, inexpensive and effective anti-TB drugs. Extracts from three plants, Solanum incanum, Cryptolepis sanguinolenta and Erythrina abyssinica used in traditional medicine to treat TB symptoms were screened for anti-mycobacterial properties against a Rifampicin resistant, pan sensitive and Mycobacteria avium strains. In addition, the acute toxicity profile and phytochemistry of the active extracts were studied. The chloroform extract of E. abyssinica was the most active on M. avium wild strain and the rifampicin resistant strain (MIC= 0.3 and 0.39 mg/ml respectively). Against the pansensitive strain the methanol total crude extract was most active (MIC= 0.2 mg/ml). C. sanguinolenta total crude methanol extract was also active against the three strains of mycobacteria; however S. incanum did not show activity on any of the strains. Toxicity studies showed that the two plants had an LD50 of more than 500mg/kg body weight and thus considered to be safe. E. abyssinica extracts and C. sanguinolenta total crude extract contained alkaloids, terpenoids, tannins and flavones. Saponins and phenols were not detected in all extracts. C. sanguinolenta and E. abyssinica have potential to be developed into new anti-TB drugs. The results have also validated traditional knowledge from the local people regarding the use of these species to treat TB.