Chemical constituents and antimycobacterial studies of the leaf extracts of Pavetta crassipes K. Schum

Abstract

Six known compounds; β-sitosterol, ursolic acid, methyl chlorogenate, ethyl chlorogenate, rutin and mannitol were isolated from the leaf extracts of Pavetta crassipes (Rubiaceae), a Nigerian medicinal plant used in the indigenous treatment of tuberculosis. Separation and isolation of the compounds were achieved by chromatographic techniques and the structures of isolated compounds were established by spectroscopic and chemical methods. The isolated compounds were screened for antimycobacterial activities against Mycobacterium tuberculosis H37Rv employing the green fluorescence protein reporter microplate assay and the broth microdilution method. Ursolic acid, methyl chlorogenate and ethyl chlorogenate were found moderately active in the broth microdilution assay with MICs of 200, 100 and 50 µg/ml, respectively while methyl chlorogenate and ethyl chlorogenate were active in the protein reporter microplate assay with MICs of 200 and 100 µg ml-1, respectively. The presence of antimycobacterial terpenoids and quinate esters in leaves of Pavetta crassipes provides scientific evidence for the ethnomedicinal use of the plant as a traditional anti-tuberculosis remedy.

Keywords

• Pavetta crassipes
• Spectroscopy
• Antimycobacterial activity
• Broth microdilution assay
• Green fluorescent protein reporter microplate assay