1. Capsaicin
Synonyms Axsain; Mioton; Zostrix.
Biological Sources It is the pungent principle present in fruit of various species of Capsicum, namely: Capsicum annuum L. (Family: Solanaceae)-Paprika, Chili, Sweet Peppers; Capsicum frutescens Linn., [Synonyms C. minimum Roxb.]-Bridchilli.
Preparation Capsaicin, the oleoresin from capsicum is prepared by extracting the crushed fruit with either hot acetone or hot ethanol by the method of percolation. The solvent i.e., hot ethanol or acetone is evaporated on an electric-water bath in a fume-cupboard. The resulting residue is once again subjected to successive extraction with cold acetone or ethanol until the residue is free from the pungent odour. The solvent is removed and the capsaicin collected is not less than 8%.
Characteristic Features It has a monoclinic and rectangular plates, or scales from petroleum ether. Its mp is 65°C, bp0.01 210-220°C (air-bath temperature), UVmax 227, 281 nm (ε 7000, 2500). It has a burning taste, one part in 100,000 can be detected easily by tasting. It is practically insoluble in cold water. It is freely soluble ethanol, ether, benzene, chloroform and slightly soluble in CS2.
Chemical Constituents The capsicum contains 8-12% of an oleoresin capsaicin and a red colouring principle known as capsanthin as given below:
However, the pungency of capsaicin is not affected by dilute alkali, but is destroyed almost completely by subjecting it to oxidation with either KMnO4 or K2Cr2O7.
Uses
1. It is used as a tool in neurobiological research.
2. Pretreatment with capsaicin induces long-lasting desensitization of airway mucosa to various mechanical and chemical irritants.
