Swiemagalins A-C: three new phragmalins from the stem barks of Indonesian <i>Swietenia mahagoni</i> and cytotoxic activities

This study aimed to isolate three new phragmalin-type limonoids, swiemagalins A-C (<b>1</b>-<b>3</b>), as well as two known limonoids (<b>4</b> and <b>5</b>) from the stem barks of Indonesian <i>Swietenia mahagoni</i>. Compounds <b>1</b>-<b>3</b> were classified as highly oxygenated phragmalin-type limonoids, with <b>1</b> featuring an opened D-ring and bulky substituents, while <b>2</b> and <b>3</b> possessed a seco-<i>δ</i>-lactone moiety and a biosynthetically unique C-C connectivity in D-ring. The planar structures and absolute configurations were determined through a combination of extensive spectroscopic methods. These included High-Resolution Electrospray Ionisation Mass Spectrometry (HR-ESI-MS), Infra-red (IR) spectroscopy, comprehensive Nuclear Magnetic Resonance (NMR) analyses, Electronic Circular Dichroism (ECD), and quantum chemical calculations using Time-Dependent Density Functional Theory (TD-DFT). Cytotoxic activity of <b>1</b>-<b>5</b> was evaluated against human breast cancer (MCF-7) and normal kidney (CV-1) cell lines.