Using human leukocytes and platelets, Hong et al. found that incubating docosahexaenoic acid (DHA) with a mixture of human cytochrome P450 enzymes (CYP1A2, 2C8, 2C9, 2D6, 2E1 and 3A4) formed 14(R)-hydroxy-docsosahexaenoic acid (14(R)-HDHA), the precursor to maresin-like mediator 2 (MaR-L2) (Hong et al. 2014). There is no data to indicate which one or ones of these CYPs mediate this event under physiological conditions. CYP inhibition diminishes the formation of 14(R)-HDHA, confirming CYP determines 14(R)-hydroxylation (Hong et al. 2014). The CYP mixture also formed 22-hydroxy-docosahexaenoic acid (22-HDHA) by ω-oxidation (not shown here). Although the CYP mixture also catalysed the formation of 14(S)-HDHA, the amount formed is minor compared to that formed by 12-lipoxygenase (Hong et al. 2014).