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

Chemical investigation of the methanolic extract from the twigs of Sclerocroton cornutus (Pax) led to the isolation of one new rosane diterpene-type derivative named Sapirosanic acid (1) along with nine known compounds including: xylopic acid (2), 3,3'-di-O-methylellagic acid (3), 3-3'-di-O-methyl ellagic acid-4'-O-α-L-rhamnose (4), ursolic acid (5), (20 R)-cholest-4-en-3-one (6), a mixture of stigmasterol (7) and ß-sitosterol (8) and a mixture of ß-sitosterol-3-O-ß-glucopyranoside (9) and stigmasterol-3-O-ß-glucopyranoside (10). 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 in vitro for their antibacterial activities against three multidrug-resistant Staphylococcus aureus 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.