In vitro Anti-mycobacterial Activities of Three Species of Cola plant Extracts (Sterculiaceae)

Extracts obtained from three Nigerian Sterculiaceae plants: Cola accuminata, C. nitida and C. milleni were screened for anti-mycobacterium properties using a slow growing Mycobacterium bovis ATCC 35738 (designated BCG Mexican and known to have some virulence in mouse and guinea pig)at 1000 ìg/ml using the radiometric (BACTEC)method. The extracts were also tested against six fast growing ATCC strains of M. vaccae using the broth microdilution method. The methanol extracts from both leaves, stem bark and root bark of Cola accuminata and from the leaves and stem bark of C. nitida and C. milleni were not active at the highest concentration of 1000 ìg/ml. Only the methanol extract of root bark for both C. nitida and C . milleni were found to be potent against both M. bovis and strains of M. vaccae. The minimum inhibitory concentration (MIC)of C. nitida against M. bovis is 125 ìg/ml while the MIC of C. milleni against M. bovis is 62.5 ìg/ml after at least 6 days of inhibition with growth index (GI)units lesser than or equal to the change in GI units inoculated with a 1/100 of the BACTEC inoculum for a control vial. The minimum inhibitory concentration of C. milleni against the six ATCC strain of M. vaccae ranged from 62.5 ìg/ml to 250 ìg/ml while for C. nitida ranged from 500 ìg/ml to above1000 ìg/ml. Evidently, C. milleni has the highest inhibitory activity against both M. bovis and strains of M. vaccae used. Rifampicin, the positive control used has strong activity against M. bovis at the tested concentration of 5 ìg and 10 ìg/ml and 4 to 8 ìg/ml against the six strains of M. vaccae.