Formation of an oxathiolone compound from rutin in acidic mixture of saliva and buckwheat dough: Possibility of its occurrence in the stomach

Buckwheat is used for various foods in the world. The objective of the present study is the determination of the chemical structure of a product formed in the acidic mixture of buckwheat dough and saliva that contains both nitrite and thiocyanate. In the mixture, an oxathiolone derivative of rutin, 5,7-dihydroxy-2-(7-hydroxy-2-oxobenzo[d][1,3]oxathiol-4-yl)-4H-chromen-4-one-3-O-β-rutinoside, was found. This compound seemed to be formed by the hydrolysis of a 2′-thiocyanate derivative of rutin, which was produced by the reaction of thiocyanate with the o-quinone generated by nitrous acid-dependent oxidation of rutin. Importance of the formation of the oxathiolone compound is discussed in relation to scavenging of the toxic quinone in the stomach.