From the Merck Index:
1811. Capsaicin.
(E)-N-[(4-Hydroxy-3-methoxyphenyl)methyl]-8-methyl-6-nonenamide; trans-8-methyl-N-vanillyl-6-nonenamide; N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-trans-6-enamide; Axsain (Euroderma); Mioton (Pharmakhim); Zostrix (GenDerm). C18H27NO3; mol wt 305.42. C 70.79%, H 8.91%, N 4.59%, O 15.72%.
Pungent principle in fruit of various species of Capsicum, Solanaceae. Isoln from paprika and cayenne: Thresh, Pharm. J. and Trans. 7, 21 (1876); Micko, Z. Nahr. Genussm. 1, 818 (1898). See Beilstein 13, suppl. I, 322. Early structure study: Nelson, J. Am. Chem. Soc. 42, 597 (1920). Synthesis: Spth, Darling, Ber. 63, 737 (1930); L. Crombie et al., J. Chem. Soc. 1955, 1025; O. P. Vig et al., Indian J. Chem. 17B, 558 (1979). Constitution and biosynthesis: D. J. Bennet, E. W. Kirby, J. Chem. Soc. C 1968, 442. Pharmacology: Molnar et al., Acta Physiol. 35, 369 (1969). Capsaicin is a powerful irritant; initial administration causes intense pain. Prolonged treatment causes insensitivity to painful stimuli and induces selective degeneration of certain primary sensory neurons: G. Jancso et al., Nature 270, 741 (1977); R. Gamse, Arch. Pharmacol. 320, 205 (1982); P. Holzer et al., Neurosci. Letters 31, 253 (1982). Neuronal depletion of substance P, q.v.: T. M. Jessell et al., Brain Res. 152, 183 (1978); T. L. Yaksh et al., Science 206, 481 (1979). Capsaicin pretreatment also induces long-lasting desensitization of airway mucosa to various mechanical and chemical irritants: J. M. Lundberg, A. Saria, Nature 302, 251 (1983). Preliminary clinical evaluation in chronic postherpetic neuralgia: J. E. Bernstein et al., J. Am. Acad. Dermatol. 17, 93 (1987). Reviews: Molnar, Arzneimittel-Forsch. 15, 718 (1965); Walker, Gavern, Mfg. Chem. Aerosol News 39 (6), 35 (1968); R. M. Virus, G. F. Gebhart, Life Sci. 25, 1273 (1979); Y. Monsereenusorn et al., CRC Crit. Rev. Toxicol. 10, 321-339 (1982).
Monoclinic, rectangular plates, scales from petr ether, mp 65 deg. bp0.01 210-220 deg (air-bath temp). uv max: 227, 281 nm (.epsilon. 7000, 2500). Burning taste, one part in 100,000 can be detected by tasting. Practically insol in cold water. Freely sol in alc, ether, benzene, chloroform; slightly sol in CS2.
USE: As a tool in neurobiological research.
THERAP CAT: Topical analgesic.