Maresins (MaRs) are biosynthesized from DHA by macrophages through the action of 12-LOX, which catalyzes the oxygenation of DHA to 14-hydroperoxidocosahexaenoic acid (14-HpDHA) (Rodriguez and Spur 2020a). This is followed by reduction to 13S, 14S-epoxy-maresin, which is further modified in human macrophages to produce MaR1 (Deng et al. 2014) and conversion of 13S, 14S-epoxy-maresin by soluble epoxide hydrolase to produce MaR2 (Deng et al. 2014). Maresins, like the many other SPM members mentioned, have anti-inflammatory, protective and healing-promoting properties. In a study using a murine model of respiratory distress syndrome, and initial in vivo production of MaR1was detected during platelet-neutrophil interactions, and its levels increased significantly within 2 hours and peaked at 24 hours (Dalli et al. 2013c). Measurement of 17-HDHA in tissue is used as a marker for the level of activation of the MaR production pathway (Wang et al. 2015). Maresin-like lipid mediators MaR-L1 and MaR-L2 are produced by white blood cells and platelets and rescue the reparative function of macrophages damaged by diabetes (Hong et al. 2014). Total synthesis of MaRs has not yet been reported.