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ENZYMIC OXIDATION OF SIMPLE DIPHENOLS AND FLAVONOIDS BY ORANGE JUICE EXTRACTS
Author(s) -
BRUEMMER JOSEPH H.,
ROE BONGWOO
Publication year - 1970
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1970.tb12117.x
Subject(s) - chemistry , quinone , benzoquinone , hydroquinone , menadione , enzyme , oxidase test , reductase , biochemistry , organic chemistry
SUMMARY: Extracts of orange juice vesicles oxidized p‐hydroquinone (HQ) and o‐dihydroxyphenylalanine (DOPA) with O 2 . Most of the oxidase activity was associated with a particulate fraction that sedimented at 100,000 × g. Sonic disruption of the particulates followed by chromatography on DEAE‐cellulose increased specific activities with both substrates. The partially purified enzyme oxidized numerous naturally occurring o‐diphenols and o‐methoxyphenols. Acidic media below pH 4 and heating above 70°C destroyed most of the oxidase activity. KCN, diethyl‐dithiocarbamate and 8‐hydroxyquinoline but not EDTA inhibited the oxidase. The partially purified enzyme reduced benzoquinone and oxidized the reduced form of nicotinamide‐dinucleotide (NADH). Ubiquinone, a benzoquinone derivative, but not menadione or vitamin K 1 , naphthoquinone derivatives, could replace benzoquinone in the oxidation of NADH. Ubiquinone, benzoquinone and similar p‐quinones may function in the orange as the oxidation‐reduction couple between NADH‐quinone reductase and diphenol oxidase.