M-hydroxyphenylacetic Acid Research Articles

Synthesis and evaluation of novel N1-acylated 5-(4-pyridinyl)indazole derivatives as potent and selective haspin inhibitors

Protein kinase dysregulation was strongly linked to cancer pathogenesis. Moreover, histone alterations were found to be among the most important post-translational modifications that could contribute to cancer growth and development. In this context, haspin, an atypical serine/threonine kinase, phosphorylates histone H3 at threonine-3 and is notably overexpressed in various common cancer types. Herein, we report novel 5-(4-pyridinyl)indazole derivatives as potent and selective haspin inhibitors. Amide coupling at N1 of the indazole ring with m-hydroxyphenyl acetic acid yielded compound 21 with an IC50 value of 78 nM against haspin. This compound showed a meaningful selectivity over 15 of the most common off-targets, including Clk 1–3 and Dyrk1A, 1B, and 2. The most potent haspin inhibitors 5 and 21 effectively inhibited the growth of the NCI-60 cancer cell lines, further emphasizing the success of our scaffold as a new selective lead for the development of anti-cancer therapeutic agents.

A mixture of quercetin 4′-O-rhamnoside and isoquercitrin from Tilia americana var. mexicana and its biotransformation products with antidepressant activity in mice

Ethnopharmacological relevanceThe aerial parts of Tilia americana var. mexicana (Malvaceae, formerly Tiliaceae) or “sirimo” are used in Mexican traditional medicine for the relief of mild symptoms of mental stress, commonly referred to as "nerve diseases". Individuals use this plant to fall asleep, to calm states of nervous excitement, headaches, mood disorders, and general discomfort. Recent studies indicated that fractions standardized in their flavonoid content possess antidepressant activity in behavioral assays in mice.The present study aims to focus on the evaluation of the antidepressant effect of the mixture of two flavonoids (FMix), and its interaction with serotonergic drugs. Also, the pharmacological effect of the products of the metabolism of aglycone, quercetin, was evaluated in mice subjected to forced swimming test (FST) and open field test (OFT). Materials and methodsA methanol-soluble extract obtained from leaves of Tilia americana was fractionated in an open column chromatographic separation. One of the fractions contained FMix wich is constituted of the mixture of quercetin 4′-O-rhamnoside (1, 47%) y isoquercitrin (2, 53%). The mice were divided into the several following groups: FMix (0.01, 0.1, 0.5, 1.0, and 2 mg/kg); FMix (1.0 mg/kg) and agonist DOI (2.0 mg/kg); FMix (1.0 mg/kg) and antagonist ketanserin (KET, 0.03 mg/kg) of 5-HT2A receptors; FMix (1.0 mg/kg) and selective agonist 8-OH-DPAT (8-OH, 0.01 mg/kg); FMix (1.0 mg/kg) and antagonist WAY100635 (WAY, 0.5 mg/kg) of 5HT1 receptors; Phloroglucinol (PHL); 3,4-dihydroxy-phenyl acid (DOPAC); p-hydroxyphenyl acetic acid (p-HPAA); and m-hydroxyphenyl acetic acid (m-HPAA) were tested in FST or OFT. ResultsFMix induced dependent-dose antidepressant activity and, at the highest dose administered, a sedative effect was also observed. The 8-OH-DPAT, or the DOI, or the KET combination with FMix (1.0 mg/kg) induced a higher antidepressant effect than compounds alone; there was no effect exerted with WAY. The activity on OFT increased only with the FMix and KET combination. At the same time, the products of the aglycone metabolism of quercetin, that is, DOPAC and p-HPAA, decreased the immobility time of the mice in FST at 1.0 mg/kg, and a dose-curve was formed for these. ConclusionThe antidepressant effect of FMix could depend, at least in part, on the degradation products of quercetin and with a possible action mode through interaction with the serotoninergic system.

Secondary metabolites of rice sheath blight pathogen Rhizoctonia solani Kühn and their biological activities

Eight compounds were isolated from the fermentation cultures of rice sheath blight pathogen Rhizoctonia solani Kühn. They were identified as ergosterol (1), 6β-hydroxysitostenone (2), sitostenone (3), m-hydroxyphenylacetic acid (4), methyl m-hydroxyphenylacetate (5), m-hydroxymethylphenyl pentanoate (6), (Z)-3-methylpent-2-en-1,5-dioic acid (7) and 3-methoxyfuran-2-carboxylic acid (8) by means of physicochemical and spectroscopic analysis. Among them, 2, 3, 5–8 were isolated from R. solani for the first time. All the compounds were evaluated for their biological activities. 4–6 and 8 showed their inhibitory activities on the radical and germ elongation of rice seeds. 1, 4 and 7 showed moderate antibacterial activity to some bacteria. 4, 7 and 8 exhibited weak inhibitory activities on spore germination of Magnaporthe oryzae. 8 showed moderate antioxidant activity with the 1,1-diphenyl-2-picryhydrazyl (DPPH) and β-carotene-linoleic acid assays. This is the first time to reveal compounds 5, 6 and 8 from rice sheath blight pathogen R. solani to have in vitro phytotoxic activity.

The role of the tissues and gut flora in the metabolism of [14C]homoprotocatechuic acid in the rat and rabbit.

Abstract The fate of orally administered [carboxy-14C]3, 4-dihydroxyphenylacetic (homoprotocatechuic) acid has been studied in normal and neomycin-treated rats and rabbits. In normal rats about 93% of the dose (0·1 g/kg) is excreted in 13 days after dosing, although 80% is excreted in the urine within 2 days. In neomycin-treated rats 100% of the 14C is excreted in 13 days, 95% being in the urine within 2 days. The urinary metabolites in 44 hr in normal rats were unchanged homoprotocatechuic acid (55% of the dose), homovanillic acid (19%), m-hydroxyphenylacetic acid (6·5%) and p-hydroxyphenylacetic acid (1·4%). In neomycin-treated rats, homoprotocatechuic acid (70%) and homovanillic acid (22%) were found but the other two metabolites were virtually absent. In normal and neomycin-treated rabbits, the 14C was excreted in the urine almost quantitatively in 9 days. The same metabolites as in rats were excreted, but there was more m-hydroxybenzoic acid (14%) and less homovanillic acid (6%). In neomycin-treated rabbits the excretion of m- and p-hydroxyphenylacetic acids was suppressed. In the rat, the metabolism of homoprotocatechuic acid, as far as methylation, dehydroxylation and decarboxylation (Scheline, 1967) is concerned, is qualitatively similar to that of protocatechuic acid (Dacre & Williams, 1968). In the rabbit, however, there is little, if any, decarboxylation. Whilst methylation is a reaction of the tissues, dehydroxylation and decarboxylation appear to be carried out by gut micro-organisms.

Inhibition of advanced glycation end product formation on collagen by rutin and its metabolites

Several lines of evidence suggest that rutin, flavonoid in fruits and vegetables, or one of its metabolites may effectively modulate advanced glycation end product (AGE) formation. Following ingestion, rutin forms metabolites that include 3,4-dihydroxyphenylacetic acid (3,4-DHPAA), 3,4-dihydroxytoluene (3,4-DHT), m-hydroxyphenylacetic acid (m-HPAA), 3-methoxy-4-hydroxyphenylacetic acid (homovanillic acid, HVA) and 3,5,7,3′,5′-pentahydroxyflavonol (quercetin). We studied the effects of rutin and its metabolites on the formation of AGE biomarkers such as pentosidine, collagen-linked fluorescence, N ε-carboxymethyllysine (CML) adducts, glucose autoxidation and collagen glycation, using an in vitro model where collagen I was incubated with glucose. Rutin metabolites containing vicinyl dihydroxyl groups, i.e., 3,4-DHT, 3,4-DHPAA and quercetin, inhibited the formation of pentosidine and fluorescent adducts, glucose autoxidation and glycation of collagen I in a dose-dependent manner, whereas non-vicinyl dihydroxyl group-containing metabolites, i.e., HVA and m-HPAA, were much less effective. All five metabolites of rutin effectively inhibited CML formation. In contrast, during the initial stages of glycation and fluorescent AGE product accumulation, only vicinyl hydroxyl group-containing rutin metabolites were effective. These studies demonstrate that rutin and circulating metabolites of rutin can inhibit early glycation product formation, including both fluorescent and nonfluorescent AGEs induced by glucose glycation of collagen I in vitro. These effects likely contribute to the beneficial health effects associated with rutin consumption.

Transepithelial Transport of Microbial Metabolites of Quercetin in Intestinal Caco-2 Cell Monolayers

m-Hydroxyphenylacetic acid (mHPA), 3,4-dihydroxyphenylacetic acid (DHPA), and 4-hydroxy-3-methoxyphenylacetic acid (HMPA) are major microbial metabolites of quercetin. After administration of quercetin to human subjects, these metabolites are readily detected in blood and urine. mHPA, DHPA, and HMPA are thought to exert protective biological activity within the body due to their antioxidant properties. However, very little work has been published concerning their absorption. I have examined the absorption characteristics of the quercetin metabolites in Caco-2 cells by a coulometric detection method using HPLC-ECD. All of them exhibited nonsaturable transport in Caco-2 cells up to 30 mM, whereas HMPA and mHPA also showed proton-coupled polarized absorption. The proton-coupled directional transport of HMPA and mHPA was inhibited by the substrate of the monocarboxylic acid transporter (MCT). A considerable amount of apically loaded HMPA and mHPA was taken up and transported through to the basolateral side, while almost all of the apically loaded DHPA was retained on the apical side. Furthermore, the transepithelial flux of DHPA was inversely correlated with the paracellular permeability of Caco-2 cells, although those of HMPA and mHPA were almost constant. These results indicate that transport of DHPA was mainly via paracellular diffusion, although HMPA and mHPA were absorbed to some extent by the MCT.

Chocolate intake increases urinary excretion of polyphenol-derived phenolic acids in healthy human subjects

Proanthocyanidins, the most abundant polyphenols in chocolate, are not depolymerized in the stomach and reach the small intestine intact, where they are hardly absorbed because of their high molecular weight. In vitro and in vivo studies using pure compounds as substrates suggest that proanthocyanidins and the related catechin monomers may be degraded into more bioavailable low-molecular-weight phenolic acids by the microflora in the colon. The aim of the study was to estimate the amounts of phenolic acids formed by the microflora and excreted in the urine of human subjects after consumption of polyphenol-rich chocolate. After consumption of a polyphenol-free diet for 2 d and a subsequent overnight fast, 11 healthy subjects (7 men and 4 women) consumed 80 g chocolate containing 439 mg proanthocyanidins and 147 mg catechin monomers. All urine was collected during the 24 h before chocolate consumption and at 3, 6, 9, 24, and 48 h after chocolate consumption. Aromatic acids were identified in urine by gas chromatography-mass spectrometry and were quantified by HPLC-electrospray ionization tandem mass spectrometry. Chocolate intake increased the urinary excretion of the 6 following phenolic acids: m-hydroxyphenylpropionic acid, ferulic acid, 3,4-dihydroxyphenylacetic acid, m-hydroxyphenylacetic acid, vanillic acid, and m-hydroxybenzoic acid. The antioxidant and biological effects of chocolate may be explained not solely by the established absorption of catechin monomers but also by the absorption of microbial phenolic acid metabolites.

Gut flora and the origin of some urinary aromatic phenolic compounds

The concentration of several phenolic acids and alcohols was measured in urine from germ-free and specific pathogen-free (SPF) rats before and after inoculation with faecal microorganisms, and from conventional rats before and after gut sterilization. The rate of excretion of benzoic acid, phenylacetic acid, and m- and p-hydroxyphenylpropionic acid in the germ-free animals was markedly increased after inoculation. Some acids showed no increase, including the endogenously generated homovanillic, vanilmandelic and p-hydroxyphenyllactic acids. Most others sought showed a small but significant increase. Some of the compounds excreted by the germ-free animals may have been in the food pellets, either as such or as precursors. The pattern was somewhat different in the SPF rats. The excretion of p-hydroxyphenylpropionic, p-hydroxyphenylacetic and m-hydroxyphenylacetic acids was initially much higher than in the germ-free animals and their excretion decreased after inoculation, presumably because of an altered pattern of gut flora. This work quantifies the effect of gut flora in the formation of some of the more important phenolic acids found in rat urine.

Effects of monoamine oxidase inhibitors on the acid metabolites of some trace amines and of dopamine in the rat striatum

The effects of the administration of selective and non-selective inhibitors of monoamine oxidase (MAO) on the concentrations of three trace acid metabolites [phenylacetic acid (PAA); m-hydroxyphenylacetic acid (mHPAA); and p-hydroxyphenylacetic acid (pHPAA)] and of an acid metabolite of dopamine [3,4-dihydroxyphenylacetic acid (DOPAC)] in the rat striatum were determined. Administration of brofaromine (1−100 mg/kg, s.c.) a type AMAO inhibitor, dose-dependently decreased DOPAC and mHPAA levels. pHPAA levels were decreased by 100 mg/kg brofaromine, but PAA levels were unaffected. Doses of deprenyl of less than 100 mg/kg, i.p., had no effect on any of the acids, while 100 mg/kg decreased DOPAC, mHPAA and pHPAA but not PAA levels. Clorgyline, pargyline and tranylcypromine treatment decreased the levels of DOPAC, mHPAA and pHPAA but not PAA. Administration of α-monofluoromethyldopa, an inhibitor of aromatic amino acid decarboxylase, decreased the levels of all four acids. It was concluded that deamination of the respective parent amine by type A MAO is primarily responsible for the synthesis of DOPAC and mHPAA, but that another pathway contributes to pHPAA synthesis. It appears that either PAA arises predominantly independently from the actions of MAO or that its removal via transport or further metabolism regulates its concentration.

Conjugation of phenylacetic acid and m- and p-hydroxyphenylacetic acids in the rat striatum

Two factors that might regulate the levels of the trace acids, phenylacetic acid (PAA), m-hydroxyphenylacetic acid (mHPAA) and p-hydroxyphenylacetic acid (pHPAA) in the rat striatum were investigated: first, formation of conjugates of these acids and second, transport out of the brain by a probenecid-sensitive system. The presence of conjugates of these acids was investigated by subjecting homogenates of rat striatum to hydrolysis. The concentrations of PAA were increased ten-fold by hydrolysis, pHPAA increased two-fold, and mHPAA was unaffected. These findings coupled with the failure of pargyline to decrease free or total PAA levels suggest that conjugation of PAA is an important factor regulating free PAA levels. The transport inhibitor, probenecid, increased the concentrations of free mHPAA, free pHPAA and the total concentrations of all three acids indicating that all three trace acids can be removed from the rat brain by a transport system.

Studies on pathogenesis of Rhizoctonia solani in beans: an evaluation of the possible roles of phenylacetic acid and its hydroxy derivatives as phytotoxins

All isolates of Rhizoctonia solani used in this study, when grown in Weinhold medium supplemented with phenylalanine, accumulated phenylacetic acid (PAA) and its ortho-, meta- and para-hydroxy derivatives in culture. Major metabolites which accumulated were PAA and m-hydroxyphenylacetic acid ( m-OH-PAA). However, the accumulation in vitro of total phenylacetic acid derivatives by isolates of R. solani was not related to their pathogenicity and/or virulence. On the contrary, the non-pathogenic and weakly virulent isolates of R. solani produced the highest quantities of PAA-derivatives per unit weight of mycelium in comparison to the highly virulent isolates. The phenylacetic acid derivatives used in this investigation, when bioassayed at high concentrations, caused inhibition of growth of tomato and bean seedlings. The most active compounds were PAA and dl-α-methoxy-phenylacetic acid (MeO-PAA). However, when m-OH-PAA was assayed at low concentrations there was a stimulation of seedling growth. In addition, when m-OH-PAA solutions were injected into bean hypocotyls or into tobacco leaves they never caused necrotic lesions or symptoms resembling those caused by R. solani on beans. These results indicate that PAA-derivatives are not directly involved in pathogenesis of R. solani in beans.

Determination of free and total phenylacetic and p- and m-hydroxyphenylacetic acids in human urine by liquid chromatography with fluorimetric detection

A highly sensitive and rapid liquid chromatographic method for the determination of free and total phenylacetic and p- and m-hydroxyphenylacetic acids in human urine is described. After extraction of urine with diethyl ether, these acids and phenylpropionic acid (internal standard) are converted into the corresponding fluorescent derivatives by treatment with 3-bromomethyl-6,7-dimethoxy-1-methyl-2(1 H)-quinoxalinone in the presence of potassium hydrogen carbonate and 18-crown-6 in acetonitrile. The derivatives are separated on a reversed-phase column (Radial-Pak Cartridge C 18) with aqueous 65% (v/v) methanol and detected fluorimetrically. The detection limits for phenylacetic and p- and m-hydroxyphenylacetic acids are 5, 30 and 100 fmol, respectively, at a signal-to-noise ratio of 5 in a 20-μl injection volume. This sensitivity permits precise determination of the free and total acids in 20 μl of normal human urine.

TREATMENT OF HYPERPHENYLALANINEMIA V WITH TETRAHYDROBIOPTERIN (BH4) AND NEUROTRANSMITTER (NT) PRECURSORS

In a 9 month infant with the spinal fluid (CSF) NT abnormalities of biopterin synthesis defect we compared treatment with:BH4 high (20 mg/kg/d) dose only; BH4 low (3 mg/kg/d), moderate (10 mg/kg/d) or high dose with the NT precursors dopa/carbidopa (10/1 mg/kg/d) and 5-hydroxytryptophan (5 mg/kg/d); and NT precusors with phenylalanine (phe) restricted diet. Over 4 months we evaluated clinical status, CSF biopterin, CSF NT major metabolites homovanilic acid (HVA), 5-hydroxyindolacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol, and CSF NT minor metabolites 3,4-dihydroxy-phenylacetic acid, vanilmandelic acid, m-hydroxyphenylacetic acid (MHPAA), p-hydroxyphenylacetic acid (PHPAA) and indolacetic acid (IAA). Few control values for CSF biopterin and NT major metabolites and none for minor metabolites are known in children. Clinically the patient was well on NT precursors with or without BH4 and deteriorated on BH4 only. Liver enzymes, which were elevated at 4 months on BH4 only, remained normal and blood phe was in good control. CSF biopterin increased to at or above normal with moderate or high dose BH4 but virtually no response of HVA or 5-HIAA independent of NT precursors was seen. BH4 at any but low dose altered the IAA/5-HIAA ratio and BH4 at any dose increased PHPAA but not MHPAA. In this patient, the first in which NT minor metabolites have been measured on BH4, the CSF major metabolites could be maintained at normal levels only with NT precursors but BH4 modified the patterns of minor metabolites.

Effects of various antipsychotic drugs upon the striatal concentrations of para‐hydroxyphenylacetic acid and meta‐hydroxyphenylacetic acid in the mouse

The endogenous concentrations of p- and m-hydroxyphenylacetic acid in the mouse caudate nucleus were determined by a gas chromatographic or a gas chromatographic-mass spectrometric technique and the concentrations were about 30 and 11 ng g-1 respectively. The subcutaneous administration of (+)-butaclamol (1 mg kg-1), haloperidol (5 mg kg-1), molindone (100 mg kg-1), sulpiride (50 mg kg-1) or chlorpromazine (20 mg kg-1) increased the concentration of mouse striatal p- and m-hydroxyphenylacetic acid; the effects were observed at 2 h after drug administration. Lower doses of chlorpromazine (2 mg kg-1), haloperidol (0.2 mg kg-1) and molindone (2 mg kg-1) did not affect p- or m-hydroxyphenylacetic acid concentrations. The time course for the concentration changes produced by chlorpromazine (20 mg kg-1) revealed that the formation of the metabolites occurred within 30 min after its administration and that their efflux from the caudate nucleus took at least 4 h for p-hydroxyphenylacetic acid and more than 8 h for m-hydroxyphenylacetic acid. Promethazine and (-)-butaclamol which have chemical structures related to chlorpromazine or (+)-butaclamol respectively but which lack antipsychotic activity, produced no effect on striatal p- or m-hydroxyphenylacetic acid concentrations. The results suggest that antipsychotic drugs increase the utilization of mouse striatal p- and m-tyramine and that after use the amines are metabolized by monoamine oxidase to form p- or m-hydroxyphenylacetic acid. The synthesis of the acid metabolites occurs within 30 min after chlorpromazine administration and their efflux from the caudate nucleus takes from 4-8 h.

Estimation of the p and m isomers of hydroxyphenylacetic acid in mouse brain by a gas chromatographic procedure: their regional distribution and the effects of some drugs.

The mouse brain contains 12.5 and 4.1 ng/g of p- and m-hydroxyphenylacetic acids, respectively. The hydroxyphenylacetic acids were isolated by chromatography on DEAE-Sephadex A-25 and quantitated as their pentafluoropropionyl and hexafluoropropanol esters by use of a gas chromatograph equipped with an electron-capture detector. The highest concentrations of p- or m-hydroxyphenylacetic acids were observed in the caudate nuclei (27.9 and 8.7 ng/g, respectively) and olfactory tubercles (20.2 and 5.3 ng/g, respectively). The identities of the p- and m-hydroxyphenylacetic acids were further confirmed as a consequence of the reductions observed following monoamine oxidase inhibition or the increases observed in the appropriate acid following the parenteral administration of p- or m-tyramine.

Plasma concentrations of p- and m-hydroxyphenylacetic acid and phenylacetic acid in humans : Gas chromatographic—high-resolution mass spectrometric analysis

Conjugated and unconjugated phenylacetic acid and m- and p-hydroxyphenylacetic acid have been determined in the plasma of normal, healthy subjects after fasting, consumption of a meal and ingestion of deuterium-labelled amine precursors, by high-resolution gas chromatography—high-resolution mass spectrometry with selected ion monitoring of their trifluoroethyl-pentafluoropropionyl derivatives. We observed that all three conjugated acids are higher in fasting than in non-fasting subjects, and unconjugated phenylacetic acid was lower. Ingestion of deuterium-labelled amine precursors resulted in the appearance in the blood of the correspondingly labelled acids, a peak in the concentrations being reached about 1 h after consumption. Conjugated and unconjugated acids as expected increased following the consumption of a meal. Unconjugated phenylacetic acid was significantly higher in females than in males. Most values tended to increase with age, with male unconjugated and conjugated m-hydroxyphenylacetic acid and female conjugated phenylacetic and m-hydroxyphenylacetic acids increasing significantly.

Longitudinal urinary excretion of some “trace” acids in a human male

Conjugated and unconjugated urinary levels of phenylacetic acid (PAA), m-hydroxyphenylacetic acid ( m-HPA) and p-hydroxyphenylacetic acid have been determined for 24-h urine samples obtained from a single healthy male over a 28-day period. Gas chromatographic—electron-capture and mass spectrometric—integrated ion current techniques incorporating appropriate internal standards were used. The average urinary excretion values obtained were (in mg/24 h): PAA unconjugated 0.67, conjugated 96.6; m-HPA unconjugated 7.3, conjugated < 0.1; p-HPA unconjugated 22.4, conjugated < 1.2. Following the ingestion of appropriate deuterated amino acid precursors the expected urinary deuterated trace acids were identified and quantitated; in the case of deuterated phenylethylamine, m-HPA and p-HPA as well as PAA were identified and quantitated. This is the first evidence of phenylethylamine hydroxylation in the human. The longitudinal excretion of the trace acids was compared with that of the trace amines.

The metabolism of l- m-tyrosine in man

Oral doses of deuterated or undeuterated l- m-tyrosine (5 mg/kg) were given to four normal subjects. The level of the amino acid in the blood was measured at intervals following the load. Urine samples were analyzed for metabolites derived from l- m-tyrosine. The majority of the load was metabolized to m-hydroxyphenylacetic acid but m-hydroxymandelic acid and 3,4-dihydroxyphenylacetic acid were also detected. Low circulating levels of m-tyrosine in the plasma suggest that most of the load is held due to a first pass effect somewhere in the enterohepatic system and that this portion of the load is not in equilibrium with the plasma m-tyrosine. It is postulated that the metabolism of a compound such as m-tyrosine may give further insight into the deficiencies of the phenylalanine hydroxylating system found in the various phenotypes of phenylketonuria.

Metabolism of m-tyrosine in the rat

In order to study the metabolism of m-tyrosine, 14C-labeled m-hydroxyphenyl compounds were synthesized. After intraperitoneal administration of dl-[2- 14C] m-tyrosine, most of the radioactivity was eliminated via the urinary route. The radiolabeled metabolites have been investigated quantitatively. The major metabolites found were: m-tyramine, m-hydroxyphenylacetic acid, m-hydroxyphenylpyruvic acid and m-hydroxymandelic acid. In addition, two unidentified conjugates of m-hydroxyphenylacetic acid and m-tyramine were found. The metabolic fates of the d- and l-isomers of m-tyrosine were investigated comparatively. Results from the in vivo and in vitro experiments on the metabolism of [ 14C] m-hydroxyphenyl compounds demonstrate that decarboxylation is the key step in the metabolism of m-tyrosine, and that liver, kidney and brain have the enzymes necessary to account for the major m-tyrosine metabolites.

Metabolism of 3, 4-dihydroxyphenylalanine, its metabolites and analogues in vivo in the rat: urinary excretion pattern.

The metabolism and interrelationships of orally and intraperitoneally administered L-dopa, related amino acids and their metabolites have been studied 2. Amino acids were decarboxylated. N-Methyldopa formed dopamine but not epinine. D-Dopa was absorbed from the intestine and metabolized by a series of reactions which resulted in greater decarboxylation than was observed after L-dopa. Transamination was a minor pathway. 3. m-Hydroxylated phenylpyruvic acids were poorly reduced, but vanilpyruvic acid was reduced fairly readily. Lactic acids were largely unchanged. Lactic and pyruvic acids formed phenylethylamines and their metabolites. Small amounts of phenylpyruvic acids may be decarboxylated to phenylacetic acids. 4. Glycine conjugates were formed from phenylacetic acids, a partially reversible change 3,4-Dihydroxyphenylacetic acid was metabolized to homovanillic and m-hydroxyphenylacetic acids, especially when given orally. Little 3-hydroxy-4-methoxyphenylacetic acid was oxidized to 3,4-dihydroxyphenylacetic acid but some increase in m-hydroxyphenylacetic acid excretion was observed. 5. 2-Phenylethanol analogues were largely converted to the corresponding acids. 3,4-Dihydroxyphenylethanol was partially m-O-methylated before oxidation. 6. beta-Phenylethylamine analogues were oxidized mainly to phenylacetic acids. but a variable amount of analogous phenylethanol was also formed, especially from m-tyramine. Dopamine was O-methylated, a process not readily reversible. It was also p-dehydroxylated following oral and intraperitoneal administration but not after oral neomycin; biliary excretion of amines may be involved in this sequence of events. N-Methylated amines were oxidized less readily than the parent amine. 7. Differences in route of administration resulted in quantitative changes in degradation pathways, an effect deriving, to some extent, from p-dehydroxylation and O-methylation in the gut.