Biosynthesis and biological activities of lipoxin A5 and B5 from eicosapentaenoic acid

[1-14C]-Eicosapentaenoic acid (EPA) was incubated with porcine leukocytes. Three polar metabolites were isolated after RP-HPLC separation in addition to pentaene leukotrienes and mono-hydroxy fatty acids. These compounds display U.V. absorbance with U.V. lambda max at 302 nm with shoulders at 289 and 317 nm which were typical of a conjugated tetraenes. Using an alkaline RP-HPLC solvent system, it was found that these three compounds co-eluted with synthetic standards of lipoxin A5, lipoxin B5 and 5S, 6S, 15S-lipoxin A5 [6-S-LXA5] and were identified accordingly. Their structures were further confirmed by GC/MS analysis. When tested for biological activities, it was found that both lipoxin A5 and lipoxin B5 induce superoxide anion generation in canine neutrophils. Furthermore, LXA5 caused a dose-related contraction of isolated rat tail artery. The biological potency of 5-series lipoxins were similar to those of 4-series.