Oxidation of Phenols to Benzoquinones
Oxidation of Phenols to Benzoquinones: Biological Importance
Nature also takes advantage of the property of quinones to reversibly take up electrons during biochemical redox processes. Ubiquinones or coenzyme Q, a group of bioquinones widely distributed in nature, are involved in electron transfer in the respiratory chain in mitochondria. As plastoquinones they are responsible for electron transfer during photosynthesis.
Vitamin E (or α-tocopherol), a phenol widely distributed in plants, apparently takes on various functions in the animal body. Especially important seems to be the function to act as a radical acceptor for peroxy radicals to protect membranes and other oxidation-sensitive molecules. Damage by radicals is also partially responsible for the aging process. Presumably, antioxidants (polyphenols) contained in red wine and the consumption of large amounts of vitamin C are shown to prolong lives.