Note: A new 1,5-seco grayanotoxin fromRhododendron decorum

Abstract A new minor 1,5-seco-5-oxo-grayanotoxin named grayanotoxin XXI (1), together with three known grayanotoxins, grayanotoxins I, IV and VIII, has been isolated from the leaves of Rhododendron decorum (Ericaceae). The structure of the new compound (1) was determined on the basis of spectroscopic data. Keywords: Grayanotoxin XXIRhododendron decorumEricaceae Acknowledgements We are grateful to the National Natural Science Foundation of China (Project No. 30170104) for financial support.