Lack of involvement of polyphenol oxidase in ortho-hydroxylation of phenolic compounds in mung bean seedlings

Complete elimination of polyphenol oxidase activity in hypocotyls and leaves of developing mung bean ( Vigna radiata L. Wilczek cv. Berkin) seedlings by tentoxin had no effect on the content of the ortho-hydroxylated flavonoids delphinidin and rutin. Tentoxin completely eliminated polyphenol oxidase-mediated ortho-hydroxylation of p -coumaric acid to caffeic acid. Despite this, tentoxin had no effect on caffeic acid derivative contents in the seedlings. High performance liquid chromatography profiles indicated that elimination of polyphenol oxidase had no effect on either the quality or the quantity of soluble phenolic compounds, These data strongly indicate that polyphenol oxidase is not involved in metabolism of phenolic compounds in developing plant tissues.