Capsicum oleoresin

Capsaicin is the active ingredient in capsicum oleoresin that confers the molecule its biological actions. It induces central sensitization to cause pain and depolarizes nociceptors to increases their cytosolic free Ca2+ concentration. It is a highly selective agonist and activator at the transient receptor potential vanilloid subfamily member 1 (TRPV1) receptors expressed in afferent neuronal C fibers and some Aδ fibers. The aliphatic tail of capsaicin interacts with the channel via nonspecific Van der Waals forces, while hydrogen bonds between its vanillyl “head” and amide “neck” with residues of glutamic acid E571 and T551 of the channel, respectively, confers specificity for ligand binding. Binding and local activation of these receptors lead to increased influx of calcium ions and nerve depolarization. Signal propagation to the central nervous system causes local heat, stinging, and/or itching sensations. Prolonged activation of TRPV1 receptors results in loss of receptor functionality, causing impaired local nociception for extended periods due to desensitization and inactivation of sensory neurons. It is thought that the activation of TRPV1 receptors is the main mechanism of action of capsaicin. Capsaicin also induces a local depletion of substance P, which is a neuropeptide involved in visceral pain signalling; however this effect in the relief of pain remains controversial.