Pseudotutin previously isolated from Coriaria japonica A. GRAY was revealed to be a molecular compound consisting of equimolar tutin (2) and a new related sesquiterpene lactone, corianin (3). Corianin was also isolated together with coriamyrtin (1), tutin (2) and coriatin (4), from Loranthus parasiticus MERR., a parasitic plant that grows on the twigs of Coriaria sinica MAXIM. The structure of corianin was elucidated on the basis of nuclear magnetic resonance and chemical evidence. The previously proposed structure (4) for coriatin was also substantiated.