Capsaicin: identification, nomenclature, and pharmacotherapy.

OBJECTIVE: To provide a brief overview of the chemical history, analysis, nomenclature, biology, pharmacology, and pharmacotherapy of capsaicin. DATA SOURCES: Chemical Abstracts, Biological Abstracts, and a MEDLINE search were used to identify pertinent literature; selected literature was used in this review. DATA EXTRACTION: Original articles, reviews, and abstracts of articles were used to select material pertinent to the objectives of the review. The volume of material available prohibits comprehensive data extraction.
CONCLUSIONS: A history of the use of Capsicum spp. and the predominant active ingredient, capsaicin, the parent compound of a group of vanillyl fatty acid amides, is presented. Distinct structural differences are noted between this compound and the capsaicinoids, especially the synthetic analog nonivamide, which has appeared as an adulterant in capsaicin-labeled products. Analysis shows that although some of these synthetic analogs eventually may prove to be true natural products, conclusive evidence based on isolation and structure elucidation is still absent after decades of attempted isolation from several potential natural sources. Although the crude, dark oleoresin extract of capsicum contains over 100 distinct volatile compounds and therefore may function in many ways dissimilar to capsaicin, the oleoresin continues to be marketed in products with a high degree of variability in efficacy. Capsaicin as a pure white crystalline material, however, acts specifically by depleting stores of substance P from sensory neurons, and has been successful in the treatment of several painful conditions (e.g., rheumatoid arthritis, osteoarthritis, peripheral neuropathies.