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

The fate of oral doses (0·1 g/kg) of [carboxy-14C]3, 4-dihydroxybenzoic (protocatechuic) acid in normal and neomycin-treated rats has been studied. In normal rats about 72% of the dose of 14C is excreted in 7 days (about 64% in urine and 8% in faeces) whereas in neomycin-treated rats 99% is excreted (87% in urine and 12% in faeces). In normal rats, the radioactive metabolites found in the urine excreted in 24 hr after dosing were protocatechuic acid (36%), vanillic acid (21%), m-hydroxybenzoic acid (2·1%), p-hydroxybenzoic acid (1·2%) and m-methoxybenzoic acid (2%). After neomycin-treatment protocatechuic acid (55%) and vanillic acid (22%) were found, but the other three were virtually absent. Incubation of [14C]protocatechuic acid with rat intestinal contents yielded 14CO2 and small amounts of m- and p-hydroxybenzoic acid. When [14C]protocatechuic acid was injected intraperitoneally into biliary cannulated rats about 13% appeared in the bile mainly as the 4-O-glucuronide of vanillic acid. It is concluded that, whilst the conjugation and methylation of protocatechuic acid occurs in the tissues of the rat, the dehydroxylation and decarboxylation of the acid is carried out by the gut micro-organisms.

Metabolism of vanillin and related substances in the rat

Intraperitoneal administration of vanillin (4-hydroxy-3-methoxybenzaldehyde) to rats gave rise to a number of urinary products, chief among which was vanillic acid, in both free and conjugated forms. Other metabolites were conjugated vanillin, conjugated vanillyl alcohol, and catechol (pyrocatechol). Catechol continued to be formed even after treatment of the animals with neomycin and streptomycin for 72 hours before the vanillin was administered. Besides vanillin, the following exogenous compounds were shown to be sources of urinary catechol: protocatechuic aldehyde, protocatechuic acid, vanillic acid, and guaiacol. Noradrenalone, adrenalone, and isoprenalone were not precursors. Treatment of rats with disulfiram, an inhibitor of aldehyde oxidase, before the administration of vanillin resulted in a decrease in the proportion of vanillic acid formed and an increase in that of vanillyl alcohol. Disulfiram also interfered with the formation of catechol from guaiacol.

Total urinary catechol excretion in cardiovascular and other clinical conditions

Although colorimetry (method of Shaw) permits neither a differentiation of epinephrine and norepinephrine nor their separation from other catechols, it reveals the total urinary catechol excretion, including those portions which were inactivated in the body. No significant abnormalities were found in arterial hypertension, in congestive heart failure, after myocardial infarction and during emotional stress. Thoracolumbar sympathectomy depressed total catechol excretion temporarily. In renal uremia, the regularly demonstrable elevation of the blood catechols was paralleled by a diminution of the conjugated catechols in the urine. It appears to be due to renal retention.

The urinary output of catechol derivatives including adrenaline in normal individuals, in essential hypertension, and in myocardial infarction

Based on Shaw's specific test, the adrenaline content of the urine of some normal individuals was considerably higher than has been reported by those using the von Euler technic (adsorption at an alkaline pH, elution and bioassay). One patient with myocardial infarction showed highly significant amounts on four occasions. The marked elevation in the Kroneberg-Schümann catechol ratio for hypertension patients as compared with normals, reported by these authors, was not confirmed by our findings. In three cases of myocardial infarction the ratio was elevated. Our ratios for normals confirm the original work.

Identification of urinary metabolites of human subjects exposed to o-dichlorobenzene

o-Dichlorobenzene (o-DCB) has adverse effects on the liver and kidney in animals. It also causes some irritation to the eyes and the upper respiratory system in humans. This study aimed to identify urinary metabolites of human subjects exposed to o-DCB. Urine samples were collected from three male workers exposed to o-DCB and were analyzed using a gas chromatograph-mass spectrometer. 2,3- and 3,4-dichlorophenols and 3,4- and 4,5-dichlorocatechols were detected in all the samples. Some amounts of the four metabolites were presumably present as conjugates, because they increased after heating with hydrochloric acid.