Antimycobacterial Labdane Diterpenes from <i>Leucas stelligera</i>

Abstract

Phytochemical investigation of the acetone extract of the aerial parts of <i>Leucas stelligera</i> afforded four new compounds (<b>1</b>–<b>4</b>) belonging to the labdane diterpene series as well as two known flavones, velutin (<b>5</b>) and chrysoeriol (<b>6</b>). Structure elucidation of the new compounds was carried out using 1D and 2D NMR spectroscopic data and single-crystal X-ray crystallography of compound <b>1</b>. Compounds <b>1</b>–<b>4</b> exhibited selective antimycobacterial activity against <i>Mycobacterium tuberculosis</i> with IC₅₀ values in the range 5.02–9.80 μg/mL