ent-Labdane glycosides from the aquatic plant Potamogeton lucens and analytical evaluation of the lipophilic extract constituents of various Potamogeton species

Two new ent-labdane glycosides, one known furano- ent-labdane and a new hydroxylated fatty acid were isolated from the dichloromethane extract of the freshwater aquatic plant Potamogeton lucens. The new compounds were assigned the structures of β- d-glucopyranosyl-8(17),13 -ent-labdadien-16,15-olid-18-oate, 18-β- d-glucopyranosyloxy-8(17),13 -ent-labdadien-16,15-olide and 13( R)-hydroxy-octadeca-(9 Z,11 E,15 Z)-trien-oic acid by spectroscopic means. The algicidal activity of these compounds was tested against Raphidocelis subcapitata. Based on our previous study of Potamogeton pectinatus, other constituents were identified in P. lucens by LC–UV–MS, LC–NMR and GC–MS. The lipophilic extract profiles of both species are presented. Two other species, Potamogeton perfoliatus and P. crispus, were also investigated by analytical comparison of their non-polar extracts. The distribution of ent-labdanes characterized in Potamogeton is summarized. Two new glycosylated ent-labdanes diterpenes, one known furano- ent-labdane, and a new hydroxylated fatty acid were isolated from Potamogeton lucens. Other ent-labdanes were identified in the non-polar extract of P. lucens by LC–UV–MS analysis.