AbstractThe dichloromethane extract of the aerial parts of Blumea gariepina (Asteraceae) was shown to be active against the phytopathogenic fungus Cladosporium cucumerinum and to inhibit acetylcholinesterase. In order rapidly to identify the active principles, the crude extract was analysed by on‐flow HPLC‐1H‐NMR. HPLC‐micro‐fractionation was performed and all peaks collected were submitted to assays against C. cucumerinum and acetylcholinesterase. By this means, the biological activities could be efficiently associated with selected HPLC peaks. Complementary on‐line structural data for all peaks of interest in the crude extract were obtained from HPLC‐MS and from HPLC‐UV with post‐column addition of UV shift reagents. This chemical screening strategy with integrated bioassays permitted the on‐line identification of a number of constituents and gave useful information for an efficient isolation procedure. Copyright © 2005 John Wiley & Sons, Ltd.