Hepoxilins are biologically relevant signalling molecules produced by certain arachidonate 12-lipoxygenase (ALOX12s). Hepoxilin A3 (HXA3) and B3 (HXB3) have been identified, both of which incorporate an epoxide across the C-11 and C-12 double bond, as well as an additional hydroxyl moiety. HXA3 has a C-8 hydroxyl, whereas the HXB3 hydroxyl occurs at C-10. The epoxy moiety is labile and can be hydrolyzed either by a hepoxilin specific epoxide hydrolase (HXEH) or in acidic aqueous solution to form the corresponding diol metabolites trioxilin A3 (TrXA3) and B3 (TrXB3) (Buczynski et al. 2009, Vance & Vance 2008).