Antitubercular constituents from Premna odorata Blanco

Premna odorata Blanco (Lamiaceae) is a medicinal plant traditionally used in Albay Province, in southeastern Luzon, Philippines to treat tuberculosis. This study aimed to determine the antitubercular property of the crude extract and sub-extracts of the leaves, and to isolate the bioactive principles from the active fractions. Through extraction, solvent polarity-based fractionation and silica gel chromatography purification of the DCM sub-extract, compound mixtures from the bioactive fractions were isolated and screened for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using the colorimetric Microplate Alamar Blue assay (MABA). The crude methanolic extract and sub-extracts showed poor inhibitory activity against Mycobacterium tuberculosis H37Rv (MIC≥128µg/mL). However, increased inhibitory potency was observed for fractions eluted from the DCM sub-extract (MIC=54 to 120µg/mL). Further purification of the most active fraction (MIC=54µg/mL) led to the isolation of a 1-heneicosyl formate (1), 4:1 mixture of β-sitosterol (2), stigmasterol (3) and diosmetin (4), which were identified through GC–MS analysis (with dereplication) and NMR experiments. The MIC of compound 1 was 8µg/mL. The results of this study provide scientific basis for the traditional use of Premna odorata as treatment for tuberculosis. Premna odorata Blanco, an endemic Philippine medicinal plant, is a known traditional herbal medicine used to manage phlegm, stomachache, headache, cough and tuberculosis patients. Bioassay guided isolation led to the identification of compounds from the dichloromethane sub-fractions of the leaves of Premna odorata Blanco. [Display omitted] •Premna odorata is a Philippine medicinal plant used to treat tuberculosis patients.•The crude and semicrude extracts showed poor inhibitory activity against Mycobacterium tuberculosis H37Rv.•Increased activity was observed for fractions eluted from the DCM sub-extract.•Bioassay guided isolation led to active compounds from the DCM sub-fractions.•Results provide scientific basis for the traditional use of Premna odorata for TB.