An overview of opioid peptides: Their sources and molecular sequences

Opioid medications have become increasingly prescribed in recent decades due to their sedative and analgesic properties, making them common treatments for pain management. However, prolonged use of these opioids is associated with serious side effects, including respiratory depression, overdose, dependence, and tolerance. In response, research into safer alternatives has focused on opioid-like compounds, particularly endogenous and exogenous opioid peptides, which are produced in the body or derived from the enzymatic digestion of food proteins. These peptides function as neuromodulators, regulating various physiological processes such as pain, emotion, and attachment behavior by interacting with three major G protein-coupled receptors: µ, κ, and δ. Endogenous opioid peptides, such as endorphins, enkephalins, and dynorphins, are generated from precursor molecules through proteolytic cleavage and play key roles in pain modulation and analgesia. Opioid peptides-including both endogenous and exogenous forms from animal or plant sources, as well as synthetic analogs-exhibit complex pharmacology with diverse effects on living systems, often producing complementary or opposing physiological responses. This review highlights significant discoveries regarding the peptide sequences and structural modifications of opioid peptides, emphasizing the need for continued research to fully elucidate their roles in human behavior and their potential as safer therapeutic alternatives to traditional opioids.