[56] Physical chemistry, stability, and handling of prostaglandins E2, F2α, D2, and I2: A critical summary

This chapter discusses the physical chemistry, stability, and handling of prostaglandins E2, F2α, D2, and I2. The molecular configuration of crystalline PGE2 has been assessed by X-ray diffraction and appears to have the α (C-1 -C-7) chain and β (C-13- C-20) chain well separated. In solution, PGE2 may or may not assume what is termed the “hairpin configuration,” where the two side chains are closely and specifically aligned through hydrophobic interactions. This side-chain alignment is most prominent in protic media. For PGF2,, a very similar prostaglandin, circular dichroism behavior (change in absorption between right and left circularly polarized light as a function of wavelength) shows progressive changes as one goes from pH 4 aqueous buffer to 95% ethanol to butanol and finally to acetonitrile. It is found that Stability of PGE2 methyl ester is superior to that of PGE2 in ethanol. Other prostaglandins, however, have been found to have poorer stability. These include 17-phenyl-PGE2 and PGE1-alcohol. These latter two prostaglandins have significant changes in side-chain structure that may decrease chain-chain interaction. Prostaglandins are extremely potent materials. For this reason precautions must be taken in handling them. Handling of these substances should ideally be done in a confined area, such as a fume hood. Prostaglandins that are oils or that are in solution should not contact the skin. Protective gloves should be worn when handling these materials.