Capsaicinoid

Capsaicinoids are a group of nitrogen‑containing secondary metabolites produced predominantly in the fruits of Capsicum peppers. They are responsible for the characteristic pungency, or heat, of many chili varieties and are a focus of food, agricultural, and pharmacological research.

Capsaicin is the most abundant capsaicinoid, but several related compounds occur naturally, including dihydrocapsaicin, nordihydrocapsaicin, homocapsaicin, and minor constituents such as nonivamide. The total capsaicinoid content and the ratio of components vary by species, cultivar, fruit maturity, and growing conditions. Pungency is commonly described using the Scoville scale, which reflects capsaicinoid concentration.

Chemically, capsaicinoids are vanillylamide alkaloids featuring a vanillyl group linked to a long-chain fatty acid amide. Capsaicin is the best studied member; others differ by slight saturation or chain length. In peppers, capsaicinoids are produced mainly in the placental tissue and accumulate as the fruit ripens. Biosynthesis involves the convergence of phenylpropanoid and fatty acid pathways.

Physiologically, capsaicinoids activate the transient receptor potential vanilloid 1 (TRPV1) receptor on sensory neurons, generating the sensation of heat and pain. Repeated exposure can desensitize nociceptors, a property exploited in topical analgesics. They have also been investigated for potential anti-obesity, anti-inflammatory, and metabolic effects, though results vary and more research is needed.

Uses and safety: capsaicinoids are widely used to impart heat in foods, seasonings, and sauces, and they feature in self-defense sprays and some topical pain-relief products. Safety considerations include irritation of skin and mucous membranes and potential gastric distress if ingested in excess.