Sapirosanic acid, a rosane diterpene and other chemical components from the twigs of <i>Sclerocroton cornutus</i> (Pax) (Euphorbiaceae) and their antibacterial and antioxidant activities

Abstract

Chemical investigation of the methanolic extract from the twigs of <i>Sclerocroton cornutus</i> (Pax) led to the isolation of one new rosane diterpene-type derivative named <b>Sapirosanic acid</b> (<b>1</b>) along with nine known compounds including: xylopic acid (<b>2</b>), 3,3'-di-O-methylellagic acid (<b>3</b>), 3-3'-di-O-methyl ellagic acid-4'-O-α-L-rhamnose (<b>4</b>), ursolic acid (<b>5</b>), (20 R)-cholest-4-en-3-one (<b>6</b>), a mixture of stigmasterol (<b>7</b>) and <i>ß</i>-sitosterol (<b>8</b>) and a mixture of <i>ß</i>-sitosterol-3-O-<i>ß</i>-glucopyranoside (<b>9</b>) and stigmasterol-3-O-<i>ß</i>-glucopyranoside (<b>10</b>). The structures of these compounds were elucidated by the interpretation of 1D and 2D NMR spectroscopy, electrospray ionisation mass spectrometry (ESI-MS), and comparison with literature data. Using microdilution methods, the crude extract, fractions and isolated compounds were evaluated <i>in vitro</i> for their antibacterial activities against three multidrug-resistant <i>Staphylococcus aureus</i> strains and one clinical isolate. Additionally, fractions were assayed for their antioxidant properties using 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Ferric reducing antioxidant power (FRAP) methods. The results of all these assays will also be discussed.