Some Characteristics of Eggplant and Avocado Polyphenolases

Abstract

SUMMARY Eggplant polyphenolase oxidized chlorogenic acid much faster than it did any other substrate. In contrast, the substrate oxidized most rapidly by the avocado preparation was nordi‐hydroguaiaretic acid (NDGA), followed by catechin and catechin. Resorcinol was a moderately effective competitive inhibitor ( K t = 0.02 M ), whereas hydroquinone ( K t = 0.005 M ) was a slightly less potent noncompetitive inhibitor. All the chlorides tested depressed eggplant polyphenolase activity to a similar but limited extent. The copper‐chelating agents 1‐phenyl‐2‐thiourea and sodium diethyldithio‐carbamate were powerful inhibitors; the former ( K t = 0.01m M ) was shown to act non‐competitively.