Polyhydroxy (Catecholic) Phenolic Acids—the Formation of m-Hydroxy- and Methoxy-Derivatives in Man

Abstract

A method has been described for the determination of the methoxy group in phenolic compounds. Tannic and 3 : 4-dihydroxybenzoic acids when administered orally to man are excreted in appreciable quantities as 4-hydroxy 3-methoxybenzoic and m-hydroxybenzoic acids.THE present communication is an extension of the studies reported previously1. Human urine contains appreciable quantities of m-hydroxyand 4-hydroxy-3-methoxyphenolic a c i d F . The origin of the m-hydroxy acids has been obscure since they do not occur in nature nor is their source dietary. Paper chromatographic studies suggest that 3 : 4-dihydroxyphenolic derivatives may be dehydroxylated to produce mhydroxyphenyl compounds and also methylated to produce 4-hydroxy 3 -m e t h o~y p h e n y l~~~~~J~.The present paper is concerned with quantitative studies involving the determination of the methoxy group and the colorimetric determination of m-hydroxybenzoic and vanillic acids.

Fagaceae Dumort

“…In contrast, the hydrolyzable tannins, which are mixtures of phenolic amino acids esterifi ed with sugars, are readily hydrolyzed by gut esterases to their constituent phenolics and sugars -for example, gallic acid from gallotannins and ellagic acid from ellagitannins (Singleton Once absorbed, gallic acid is biotransformed to phenolic methoxy and polyhydroxy (catecholic) phenolic acids and conjugated for elimination (Booth et al 1959;Tompsett 1959;Potter and Fuller 1968). Any tannic acid absorbed is probably biotransformed in the liver to phenolic subunits (Gupta and Dani 1987).…”

Detoxication mechanisms in man

“…2 Claims, which require substantiation because of unspecifIc methods, have been made that salicylic acid, m-hydroxybenzoic acid, and tannic acid (a derivative of gallic acid or 3,4,5-trihydroxybenzoic acid) are methylated in man. 76 The conversion of nicotinic acid to Nmethylnicotinamide is an example of Nmethylation in man. G5 C)CONH,…”

The role of the tissues and gut micro-organisms in the metabolism of [14C]protocatechuic acid in the rat. Aromatic dehydroxylation

“…Previous work on protocatechuic acid had shown that it was excreted by rabbits partly unchanged, partly conjugated with glucuronic acid and sulphate (Dodgson & Williams, 1949) and partly methylated to vanillic acid . Tompsett (1959) claimed that in man it was converted to ni-hydroxybenzoic acid. It is now shown that orally administered protocatechuic acid is dehydroxylated to a minor extent to mand phydroxybenzoic acid in rats and that ni-methoxybenzoic acid is also a minor urinary metabolite.…”