Study of the polymorph of etoposidum

Etoposidum: 4'-demethyl-epipodophyllotoxin-beta-D-ethylidene-pyrano-glucoside or VP-16-213 in trade name is a semisynthetic antineoplastic drug. We found that it has two different kinds of crystal form named crystal A and B, they were crystallized from methanol and ethanol respectively. Their structures were identified by NMR and MS. They have similar infrared spectrum but with repeatable small differences. The powder X-ray diffraction pattern of the two kinds of crystals are quite different. The DSC curve of crystal A is rather smooth but that of crystal B shows abnormal positive and negative peaks. On the other hand, they have the same kind of smooth TGA curves. This fact shows that the positive and negative peaks are not the result of chemical reaction. After heating crystal B in DSC oven at 190 degrees C and 250 degrees C, respectively, their IR spectra showed that the pattern of the first one did not change, but the second one changed to the spectrum of crystal A. This reveals that the positive peak is d