The Sakaguchi test is a chemical test used to detect presence of arginine in proteins. It is named after the Japanese food scientist and organic chemist, Shoyo Sakaguchi (1900&ndash;1995) who described the test in 1925. The Sakaguchi reagent used in the test consists of 1-Naphthol and a drop of sodium hypobromite. The guanidino (–C group in arginine reacts with the Sakaguchi reagent to form a red-coloured complex.