Detection of 8-epi prostaglandin F(2α) in an extract of epidermal secretion of the catfish from the Arabian Gulf

We provide herein mass spectrometric evidence for the existence of F₂ isoprostanes in an epidermal secretion of the catfish from the Arabian Gulf. The compounds were extracted, purified by thin layer chromatography (TLC) and derivatized into the pentafluorobenzyl trimethylsilyl (PFB-TMSi) derivatives and quantified using SIM-negative ion gas chromatography-mass spectrometry based on the addition of tetradeuterated 8-epi PGF(2α) as internal standard prior to sample workup. Freshly collected secretions from the male catfish contained 5.63 and 4.17 ng/ml (two determinations) and from the female catfish 3.60 and 3.81 ng/ml (two determinations) of free 8-epi PGF(2α). The level of these compounds increases approximately 8-fold upon storage of the extract at -20°. In view of the potent reported actions of F₂ isoprostanes on vasoconstriction and as thromboxane receptor antagonists, the presence of isoprostanes in the catfish secretions may contribute to the reported ulcer healing properties of these secretions.