Capsaicin (C₁₈H₂₇NO₃) is an organic vanilloid with a hydrophobic alkyl tail and a polar amide “head.” Its long nonpolar chain makes it largely nonpolar, so it dissolves easily in oils and organic solvents. The modest polarity of the amide allows slight solubility in water (about 1.3 mg/L), but in practice it’s extracted into oil or ethanol rather than water.

Natural capsaicin is concentrated in the white pith (placenta) and seeds of Capsicum fruits (chili peppers). To extract it, dried/chopped peppers are treated with ethanol (or supercritical CO₂) to pull out the oleoresin. After filtration, rotary evaporation and centrifugation yield a red–orange oily extract rich in capsaicinoids. Concentration is measured on the Scoville scale (dilution tests) or quantified precisely by HPLC.

First isolated in 1816 by German chemist Christian Bucholz, capsaicin has a legacy stretching back to ancient Mesoamerica, where Aztecs and Mayans used peppers for food and medicine. By the 16th century, chili peppers had spread globally—reshaping cuisines in India, China, and Europe—and even inspired early antimicrobial and analgesic remedies.

Today, capsaicin’s heat is harnessed in self-defense pepper sprays, topical analgesics (gels and patches for neuropathic pain), and pest repellents (bird- and mammal-deterrent sprays). Chemistry and law enforcement professionals formulate and test these products, making capsaicin a staple in pharmaceutical, security, and agrochemical industries. School labs can study its properties under proper supervision, but legal restrictions often apply to pepper-spray formulations.

In humans, capsaicin binds the TRPV1 ion channel on sensory neurons, causing Ca²⁺ influx, depolarization, and the sensation of “heat” or “burn.” Repeated exposure can desensitize these neurons—basis for capsaicin creams in treating chronic pain. Organs affected include skin, mucous membranes, and, if ingested, the gastrointestinal tract (can trigger endorphin release). Some birds lack functional TRPV1 in their beaks and are immune, which allows peppers to spread via bird dispersal without seed damage.