Antialgal ent-labdane diterpenes from Ruppia maritima

Seven ent-labdane diterpenes have been isolated from Ruppia maritima. The s tructures 15,16-epoxy-ent-labda-8(17),13(16),14-trien-19-al; 15,16-epoxy-en t-labda-8(17),13(16),14-trien-19-ol acetate; methyl 15,16-epoxy-12-oxo-ent- labda-8(17),13(16),14-trien-19-oate; 15,16-epoxy-ent-labd-8(17),13E-dien-15 -ol and 13-oxo-15,16-bis-nor-ent-labd-8(17)-ene have been assigned to the f ive new compounds by spectroscopic means and chemical correlations. The phy totoxicity of the diterpenes has been assessed using the alga Selenastrum c apricornutum as organism test. (C) 2000 Elsevier Science Ltd. All rights re served.