In addition to previously reported dimeric hydrolyzable tannins, woodfordins A, B, C and oenothein B, three new trimeric and a tetrameric hydrolyzable tannins (woodfordins D, E, oenothein A, and woodfordin F) have been isolated from an Indonesian crude drug called "Sidowaya" [dried flowers of Woodfordia fruticosa (Lythraceae)]. Oenothein A was also isolated from Oenothera biennis (Onagraceae). They were found to have macrocyclic structures, like oenothein B (1) and woodfordin C (2). Their structures, 4, 14, 5, and 15, having a woodfordinoyl group as one of the structural units connecting monomers, were established based on the spectroscopic analyses and chemical degradation. The host-mediated anti-tumor activity of various types of oligomeric hydrolyzable tannins was also examined. Among the screened oligomeric hydrolyzable tannins, which can be structurally classified into four types, only the oligomers composed of tellimagrandin I (12) and its galloyl analog, such as oenothein B and woodfordin C, exhibited potent activity.