The new santanolides, arbusculin-A, -B and -E, have been isolated from Artemisia arbuscula Nutt. ssp. arbuscula: and the closely related colartin (11,13-dihydroarbusculin-A) has been found in A. tripartita Gray ssp. rupicola Beetle. These four lactones appear to represent early stages near the origin of the biosynthetic pathway of formation of compounds of this class. © 1969.