Tubiferal A, a backbone-rearranged triterpenoid lactone isolated from the myxomycete Tubifera dimorphotheca, possessing reversal of drug resistance activity

Tubiferal A, a novel rearranged triterpenoid lactone, has been isolated from field-collected fruit bodies of the myxomycete, Tubifera dimorphotheca, and its structure elucidated by spectral data. Tubiferal A () possesses a 9,10-secocycloartan-16,21-olide skeleton, and this new compound exhibited a reversal effect of vincristine (VCR) resistance (more than 4-fold) against VCR-resistant KB cell lines. Tubiferal B (), corresponding to the seco acid of was also isolated, but showed no comparable activity.