Decomposition of leukotriene C4.
Before the structures of leukotrienes C, D, and E were elucidated slow-reacting substance of anaphylaxis was known to be highly unstable and particularly labile in solutions of acidic pH. The chemical reactivity of the sulfidopeptide leukotriene has been observed during the spontaneous degradation of this molecule in aqueous solution. At acidic pH, the tendency of these molecules to degrade as well as to absorb to glass surfaces can be reversed by addition of methanol. In addition, the degradation of leukotriene C4 (LTC4) induced by ferrous iron was shown to be inhibited by ethylenediaminetetra-acetic acid (lmM). While methanol prevented acid degradation of LTC4, it enhanced the Fe++-induced degradation. Fast atom bombardment mass spectrometry and ultraviolet spectroscopy were used to partially characterize the degradation products as well as the autodecomposition induced by acid. Two products observed were oxidized by incorporation of one atom of oxygen and formation of the sulfoxides and 15-hydroxy LTC4. Several products were characterized by the addition of the elements of hydrogen peroxide and formation of a conjugated diene at the expense of the conjugated triene moiety. The facile degradation of the sulfidopeptide leukotrienes suggests that purification of these species may be necessary before they are used in pharmacologic studies or as tools for radioimmunoassay.