Arthrobacter simplex dehydrogenated withaferin A to 4-dehydrowithaferin A but it was not able to dehydrogenate this substrate in position 27.
27-Dehydrowithaferin A was prepared chemically using pyridinium chlorochromate. Whereas 4-dehydrowithaferin A surpassed in
its effect on leukemic P388 cells the original compound and all its dérivates synthesized so far, 27-dehydrowithaferin A was
biologically inactive.