Capsaicin--a literature survey.

Capsicum fruits contain about 0.1 to 1 .O% of capsaicin. Capsaicin forms colorless platelets which have an intensely burning taste (threshold 10 ppm), melt at 63 to 6 5 O C, and boil at 210 to 220OC. It is only sparingly soluble in cold water and is more soluble in boiling water, but readily soluble in organic solvents such as petroleum benzene, alcohol, ether, glacial acetic acid, hot carbon disulfide, and fatty oils. Capsaicin has a maximum U V absorption at 227 and 281 nm.154 The chemical properties of capsaicin have been extensively investigated.30138712731zg, It is weakly acidic and contains a phenol group (Figure 1). It is not precipitated, or only very slightly, by the usual reagents which precipitate alkaloids. The phenol group can be methylated to form methyl capsaicin, a derivative with much less pungency than the parent c o m p o ~ n d . ~ ~ , ~ ~ Its pungency is not destroyed by heating with 2% NaOH solution, but is destroyed by oxidation with KMn04 or K2Cr207. However, the synthetic capsaicin, having a saturated side chain, is not readily 0 ~ i d i z e d . I ~ ~ and Nelson and Dawson”’ clarified the structural formula of capsaicin and found that it is the vanillylamide of dicilenic acid. Its empirical formula is C18H2703N and its molecular weight is 305.40 daltons. In addition to capsaicin, four naturally occurring derivatives have been isolated and 144,146,170