Glehnia littoralis is a species of plant in the "carrot family", Apiaceae, known by several common names including beach silvertop and American silvertop in English, and bei sha shen and shan hu cai in Chinese. The genus was named after Russian botanist Peter von Glehn. The plant is perhaps best known as a Chinese herbal remedy for cough. It contents naphthisoxazole A. From the underground parts of Glehnia littoralis FR. Schmidt ex Miquel (Umbelliferae), 26 compounds, including two new lignan glycosides [giehlinosides A (1) and B (2)], a new neolignan glycoside [glehlinoside C (3)], and a new phenylpropanoid glycoside 14-[beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranosyloxyl-3-methoxypropiophenone (4)1, were obtained and their structures were determined by analysis of their spectral data. The 1,1-diphenyl-2-picrylhydrazyl radical-scavenging assay disclosed quercetin (8), isoquercetin (9), rutin (10), chlorogenic acid (11), and caffeic acid (24) as the major antioxidative constituents in this crude drug.