Four labdanes with a 8 alpha,15-epoxy ring (8 alpha,15-epoxylabdan-16 beta-oic acid; 8 alpha,15-epoxy-16-norlabdan-13-one; 8 alpha,15-epoxy-16-norlabdane; and 16-acetoxy-8 alpha, 15-epoxylabdane) and the known compound ambreinolide were isolated from the hexane extract of the aerial parts of the grass Eragrostis viscosa. The structures of all compounds were established based on spectroscopic data and the X-ray analysis of 8 alpha,15-epoxy-16-norlabdan-13-one. The hexane extract presented moderate activity against the snail Biomphalaria glabrata. 8 alpha,15-Epoxylabdan-16 beta-oic acid showed no mutagenic activity for doses up to 1000 mu g/plate and no significant clastogenic activity for doses up to 100 mu g/ml. (C) 2010 Elsevier Ltd. All rights reserved.