Nonendocannabinoids

Nonendocannabinoids are lipid signaling molecules that are related to the endocannabinoid system but do not function as classical endocannabinoids by directly activating the cannabinoid receptors CB1 and CB2 with high affinity. They are sometimes described as endocannabinoid-like lipids, arising from similar biosynthetic pathways but acting through different targets or mechanisms.

The best-known examples are N-acylethanolamines such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). These compounds do not robustly bind CB1 or CB2, yet they influence signaling related to the endocannabinoid system by engaging other receptors and pathways, including peroxisome proliferator-activated receptor alpha (PPAR-α), transient receptor potential vanilloid 1 (TRPV1), and possibly GPR119. They can also modulate endocannabinoid tone indirectly by affecting enzymes that synthesize or degrade endocannabinoids, such as fatty acid amide hydrolase (FAAH).

Functions attributed to nonendocannabinoids include anti-inflammatory, analgesic, neuroprotective, and metabolic effects observed in preclinical studies. While they can influence cannabinoid signaling, their primary mechanisms often involve non-CB receptors or modulation of endocannabinoid metabolism rather than direct receptor activation.

Terminology and classification vary across the literature. Some authors prefer the term endocannabinoid-like lipids rather than nonendocannabinoids, reflecting their distinct receptor targets and actions. Nonetheless, nonendocannabinoids are generally regarded as part of the broader endocannabinoid system, encompassing enzymes, transporters, and receptors that regulate lipid signaling beyond classical CB1/CB2 agonism.