Colorimetric Determination of Pungent Principles in Radish Root

Abstract

A new colorimetric determination was devised for estimation of isothiocyanate content in radish root (Raphanus sativus L.) juice. Allylthiourea (AU) and trans-4-methylthio-3-butenyl thiourea (MBU) were prepared from allylisothiocyanate and Raphanus sativus L. cv. Aokubi Miyashige Daikon respectively. It was observed that both thiourea derivatives turned blue with 25-fold diluted Grote reagent. In the absorption spectra of the colored solutions of AU and MBU, both peaks were observed at 605nm. After examination of several different conditions, new method based on the colorimetry of thiourea derivatives was established as follows. Each mixture of 1ml AU or 1ml MBU and 4ml modified Grote reagent was incubated at 37•Ž for 45min, and the optical density was determined at 600nm. The absorbancy was proportional to MBU concentration in the range between 20ƒÊg/ml and 200ƒÊg/ml.