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

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

New pimarane diterpenes and other antimycobacterial metabolites from <i>Anisochilus verticillatus</i>

<div><p>Phytochemical investigation of the acetone extract of the aerial parts of <i>Anisochilus verticillatus</i> afforded a new 8,9-secopimarane diterpene (<b>1</b>), two new isopimarane diterpenes (<b>2</b>, <b>3</b>) and the known ursolic acid (<b>4</b>), α-amyrin (<b>5</b>), β-amyrin (<b>6</b>), stigmast-5-en-3-one (<b>7</b>) and hydroxychavicol (<b>8</b>). Structures of the new compounds were elucidated with the help of 1D and 2D nuclear magnetic resonance spectroscopic data, and single crystal X-ray crystallography of compound <b>3</b>. Compounds <b>2</b> and <b>8</b> inhibited <i>Mycobacterium tuberculosis</i> H37Ra with an IC₅₀ of 11.3 (IC₉₀ of 20.0 μg/mL) and 12.5 μg/mL, respectively. Correspondingly, molecular docking studies with Extra Precision Glide revealed a correlation between score and biological activity for these compounds to describe the molecular basis for the most significant SAR results.</p></div