Two new dibenzyl-<i>γ</i>-butyrolactone lignans with cytotoxic activity from <i>Himalaiella heteromalla</i>, an Indian Himalayan plant

Two new (−)-parairesinol (<b>3</b>), lappaol G (<b>5</b>), and three known (<b>1</b>, <b>2</b>, and <b>4</b>) dibenzyl-<i>γ</i>-butyrolactone lignans were isolated from the Indian Himalayan herb <i>Himalaiella heteromalla</i>. Their structures were characterised by NMR and mass data analysis. <i>In vitro</i> cytotoxic study revealed that arctiin (<b>4</b>) showed promising growth inhibition across seven human cancer cells, with potent activity against Mia-PaCa-2 cells. Notably, compounds <b>3</b> and <b>5</b> did not demonstrate significant cytotoxicity up to 80 μM concentrations.