19-Hydroxyprostaglandin B2 as an internal standard for on-line extraction-high-performance liquid chromatography analysis of lipoxygenase products

Variable recovery of polar compounds is a potential pitfall in the on-line extraction-reversed-phase HPLC analysis of lipoxygenase products. Therefore, the addition of a polar internal standard to biological samples, which permits the assessment of the recovery of the polar components in individual samples, appears to be essential. 19-Hydroxyprostaglandin (PG) B2 was found to be a suitable compound for this application. It was easily prepared from deproteinized human semen by base-catalyzed dehydration of 19-hydroxy-PGE2, and purified in a single step by reversed-phase HPLC. Similarly to PGB2, already used as internal in HPLC, 19-hydroxy-PGB2 has excellent chemical stability and carries a strong uv chromophore that enables detection at 280 nm. Most importantly, it is eluted just prior to the polar arachidonic acid metabolites 20-hydroxy- and 20-carboxy-leukotriene B4, 12-oxo-dodecatrienoic acid and the lipoxines A and B. The measurement of the ratio of PGB2 and 19-hydroxy-PGB2 used in combination as internal standards in HPLC analysis of lipoxygenase products, provides a simple and reliable way to assess sample to sample recovery of the polar components when using on-line extraction procedures.