Originally native to South America and cultivated for over 5000 years, these plants from the nightshade family were introduced to Europe and India via the Portuguese. It has a history of use as a fiery spice and as a pain reliever.
Peppers are rich in alkaloids (capsaicin, cartenoid pigments, flavonoids and ascorbic acid). Capsaicin is structurally similar to vanilla, a flavoring agent.
The hotness of chilli peppers is due to a family of compounds called capsaicinoids, which belong to the larger family called vanilloids. The two capsaicinoids most often found in peppers are capsaicin and dihydrocapsaicin. Different concentrations of capsaicinoids are responsible for the varying pungencies of peppers.
Capsaicin, the acrid component probably evolved to protect the pepper from its natural predators.
Capsaicin inhibits the production and release of Substance P. Substance P is an 11 amino acid long neuropeptide that binds with neurokinin receptors in the brain.