Antimicrobial Phenolics and Unusual Glycerides from <i>Helichrysum italicum</i> subsp. <i>microphyllum</i>

Abstract

During a large-scale isolation campaign for the heterodimeric phloroglucinyl pyrone arzanol (<b>1a</b>) from <i>Helichrysum italicum</i> subsp. <i>microphyllum</i>, several new phenolics as well as an unusual class of lipids named santinols (<b>5a</b>–<b>c</b>, <b>6</b>–<b>8</b>) have been characterized. Santinols are angeloylated glycerides characterized by the presence of branched acyl- or keto-acyl chains and represent a hitherto unreported class of plant lipids. The antibacterial activity of arzanol and of a selection of <i>Helichrysum</i> phenolics that includes coumarates, benzofurans, pyrones, and heterodimeric phloroglucinols was evaluated, showing that only the heterodimers showed potent antibacterial action against multidrug-resistant <i>Staphylococcus aureus</i> isolates. These observations validate the topical use of <i>Helichrysum</i> extracts to prevent wound infections, a practice firmly established in the traditional medicine of the Mediterranean area