Anti-mycobacterial activity of root and leaf extracts of Anthocleista djalonensis (Loganiaceae) and Diospyros mespiliformis (Ebenaceae)

Abstract

We screened the aqueous and methanol leaf and root extracts of Anthocleista djalonensis, Diospyros mespiliformis, and their combinations for possible anti-mycobacterial activities using Mycobacterium smegmatis as a surrogate screen. These plants are reputed among folk practices as potent remedy in the management of tuberculosis and leprosy cases. In the sensitivity screening study, only the methanol extracts of A. djalonensis and D. mespiliformis showed anti-mycobacterial activity, while the aqueous extracts exhibited no inhibitory activity on M. smegmatis. The minimum inhibitory concentration (MIC) of the methanol leaf and root extract of A. djalonensis against M. smegmatis were 125 μg/ml. The MIC of the methanol leaf and root extracts of D. mespiliformis is 167 and 250 μg/ml, respectively. In the interaction studies, four out of nine decimal combinations of the two medicinal plant extracts exhibited synergism with fractional inhibitory concentration indices <1 and a negative activity index values. The 8:2 ratio of D. mespiliformis and A. djalonensis exhibited the greatest degree of antimycobacterial synergy against M. smegmatis. The result of this study supports the claims of efficacy reported in the folk use of these plants in mycobacterial infection and the plants could therefore be investigated further and harnessed as potent antimycobacterial agents