Efficacy of Cryptolepis sanguinolenta root extract on slow-growing rifampicin resistant Mycobacterium tuberculosis

We report here, the results from total crude methanol extract as well as serial ether, chloroform, and methanol extracts of the root of Cryptolepis sanguinolenta (Lindl) Schltr that were screened against three strains of Mycobacterium tuberculosis. The strains used included the pan sensitive H37Rv, the rifampicin-resistant TMC-331 and a wild strain of Mycobacetrium avium (MA) isolated from a Ugandan patient. The disc diffusion method was used for susceptibility tests on solid Middle brook 7H10 while the minimum inhibitory concentration(MIC) and minimum bactericidal concentration (MBC) were determined by the microtitre plate method using  Middle brook 7H9 broth. We report that the total crude methanol extract showed the highest activity against H37Rv and TM-331 with complete clearance of quadrants at 50 mg/ml and zones of inhibition of 10.0 to 11 mm at 25 mg/ml concentration although it was not effective against M. avium. The corresponding MIC values were 1.17 mg/ml for H37Rv and 1.56 mg/ml for TMC-331. The values for isoniazid were 0.25 and 9.38 µg/ml for H37Rv and TMC-331, respectively, while for rifampicin the MIC value was 0.25 µg/ml for H37Rv but it was not active on TMC-331. Acute toxicity test gave an LD50 of 758.5 mg/kg body weight while the phytochemical analysis showed the presence of alkaloids, tannins and flavonoids.   Key words: Anti-mycobacterial, in vitro activity, medicinal plant, Cryptolepis sanguinolenta, Mycobacterium tuberculosis, Mycobacterium avium, rifampicin, isoniazid.