Naturally Occurring Food Toxicants: Phenolic Substances of Plant Origin Common in Foods

Abstract

Publisher Summary The risks to humans of serious poisonous effects caused by natural phenols present in normal foods consumed under usual circumstances seem vanishingly small, as determined by experiment, as well as common sense and long-term observation. Conclusions involving evolution obviously are speculative, but some putative relationships appear worthy of discussion to clarify the durability of animal life and the threat of plant toxins generally or of phenols particularly. Phenols are probably the most important group of substances, useful in chemotaxonomic differentiation among plant species. Plants have evolved toxins to combat herbivores, but herbivores have also evolved to tolerate or avoid plant toxins. Phenol itself, and other small phenols, such as catechol, the cresols, guaiacol, orcinols, and pyrogallol, are commonly considered to be industrial chemicals. Gallic acid is widely distributed in plants, but the concentration is usually very low. The flavonoids contribute color, flavor, and processing characteristics important in food. The most often cited effect of phenols that is discussed in this chapter is the inhibition of catechol-O-methyltransferse (COMT) and competition for methyl groups by phenols that serve as a substrate for this enzyme. The chapter discusses that many plants contain secondary metabolites toxic or deterrent to members of the animal kingdom attempting to feed on them. Plant phenols that are highly toxic to animals are rarely found. The phenols that occur widely in plants or in large amounts in common food plants have very low acute oral toxicity and most are also of low toxicity when given parenterally.