Capsaicin: Its Sources, Isolation, Quantitative Analysis and Applications

Capsaicin is a phenolic compound found in hot peppers and responsible for the characteristic pungent taste and burning sensation. The genus Capsicum includes hot peppers, which is the only genus producing the capsaicin compound. There are more than 32 species of Capsicum reported but five are domesticated, viz. C. annuum, C. chinense, C. baccatum, C. frutescens and C. pubescens. In general, C. chinense and C. frutescens have been reported to have much higher pungency when compared to other species of the genus Capsicum. Capsaicin is only present in the fruits of the Capsicum genus; however, it is not equally distributed in all parts of the fruit. It is mainly concentrated in the placental tissue of the fruit surrounding the seeds. Chemically, capsaicin is 8-methyl-N-vanillyl-6-nonenamide. It belongs to the group of capsaicinoids which also include dihydrocapsaicin, nordihydrocapsaicin, homocapsaicin and homodihydrocapsaicin. Eighty to ninety percent of the total pungency in chilli peppers is contributed by capsaicin and dihydrocapsaicin. Extraction of capsaicinoids from hot peppers starts with selection of appropriate solvents like methanol, ethanol, acetonitrile ether, benzene, dimethyl sulfoxide and acetone. The extraction techniques widely employed are enzymatic, microwave, ultrasound-assisted, Soxhlet, supercritical fluid and pressurized liquid extraction. Major analytical methods for quantification of capsaicinoids include high-performance liquid chromatography (HPLC), gas chromatography and UV spectrophotometry. Calorimetry has also been suggested for the quantification of extracted capsaicinoids after separating them from a chilli pepper by thin-layer chromatography or paper chromatography. Capsaicin finds utility in the food, pharmaceutical and cosmetic industries. Capsaicin consumption is involved in body weight reduction, treating urinary disorders and antioxidant effects. Other pharmaceutical properties of capsaicin include pain alleviation, body temperature control and antimicrobial and anticancer activities.