An investigation of biologically active compounds from the alga Dictyopteris undulata by bioassay-guided fractionation has led to the isolation and identification of zonarol, chromazonarol, zonaroic acid and the hitherto unreported isozonaroic acid. Their structures were determined by chemical transformation, GC and GC- MS comparison of transformed intermediates and by spectroscopic means. X-ray crystallography of zonarol confirmed the gross structure of this compound and also gave the relative stereochemistry at C- 9 and C- 10 as trans. All of these compounds were found to exhibit antimicrobial activity. Some also showed activity against L1210 cells and antiviral activity.

Keywords: Bioactivity-guided isolation; Antimicrobial; Antiviral; L1210 cells