Antimycobacterial activity of scopoletin from ethanolic extract of Hymenodictyon floribundum (Hochst. & Steud.) B.L.Rob. Stem bark

The available tuberculosis (TB) therapies are taken for long time with complex regimens associated with adverse effects and drug-drug interactions. The emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tubercu-losis and HIV co-infections necessitates the need for continued search for new effective anti-TB alternative leads with different mechanisms of action and safety profile. The aim of this study was to isolate and characterize antimycobacterial compounds from Hymen-odictyon floribundum (Hochst. & Steud.) B.L.Rob. a plant used traditionally in the manage-ment of HIV/AIDS-related conditions. Antimycobacterial activity of the plant extracts and its constituents against Mycobacterium indicus pranii (MIP) and Mycobacterium madagas-cariense (MM) was tested using a twofold broth micro-dilution technique. Bioassay-guided isolation was used to isolate active compounds. Isolated compounds were also tested for activity against clinical isolates of Mycobacterium tuberculosis (Mtb). The crude plant ex-tract had antimycobacterial activity and its ethyl acetate fraction was the most active with minimum inhibitory concentration (MIC) values of 97 & mu;g/ml and 197 & mu;g/ml against MIP and MM respectively. Three compounds were isolated from the ethyl acetate fraction; 7- hydroxy-6-methoxycoumarin ( 1 ), 7,7'-dihydroxy-6,6'-dimethoxy-3,3'-biscoumarin ( 2 ) and 7,7'-dihydroxy-6,6'-dimethoxy-8,8'-biscoumarin ( 3 ). Compound 1 had growth inhibitory activity against MIP, MM and Mtb with MIC values of 0.2 M against MIP, 0.41 M against MM, 0.78 M against Mtb1 and 1.63 M against Mtb2. In conclusion, 7-Hydroxy-6- methoxy-coumarin exhibited moderate antimycobaterial activity. The findings from this study sup-port the use of H. floribundum by traditional health practitioners for treatment of HIV and AIDS-related conditions.& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )