Protectins (PDs)
Protectin D1 (PD1), also known as neuroprotectin D1 (NPD1), is derived from DHA. DHA is a component of fish oil and the most important omega-3 PUFA. Like other members of PUFA metabolites specialized pro-resolving mediators class, PD1 exerts potent anti-inflammatory and anti-apoptotic/neuroprotective biological activities (Hong et al. 2003; Bazan 2007). PD1 accumulates in the ipsilateral hemisphere of the brain after focal ischemia and has been shown to take part in wound healing and neuroprotection. 15-LOX can acts 17S-HpDHA to produce the isomers of PD1, 10S, 17S-diHDHA (PDx), which also have pro-resolving activity. PD1 production peaks at 12 hours in a zymosan A-induced rat peritonitis model (Bannenberg et al. 2005).
Other PDs with similar activity include PDX; 20-hydroxy-PD1; and 10-epi-PD1 (Shinohara et al. 2012; Balas and Durand 2016). The activity of 17-epi-PD1, a PD1-like metabolite, has not been reported. It should be noted that Neuroprotectin A and B, the bicyclohexapeptides, are structurally and mechanically different from PDs (Kobayashi et al. 2001). The total synthesis of PDX and PD1 methyl ester epimer was successful (Dayaker et al. 2014; Sanceau et al. 2019).