Antitubercular constituents from Premna odorata Blanco

Ethnopharmacological relevance

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.

Materials and methods

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).

Results

The crude methanolic extract and sub-extracts showed poor inhibitory activity against Mycobacterium tuberculosis H₃₇Rv (MIC≥128 µg/mL). However, increased inhibitory potency was observed for fractions eluted from the DCM sub-extract (MIC=54 to 120 µg/mL). Further purification of the most active fraction (MIC=54 µg/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 8 µg/mL.

Conclusions

The results of this study provide scientific basis for the traditional use of Premna odorata as treatment for tuberculosis.