p-Hydroxymandelic acid

p-Hydroxybenzoylformic acid and (R)-(-)-p-hydroxymandelic acid, two antifungal compounds isolated from the liquid culture of the ectomycorrhizal fungus Pisolithus arhizus

Two antifungal compounds isolated from the liquid culture medium of Pisolithus arhizus were identified as p-hydroxybenzoylformic acid and (R)-(-)-p-hydroxymandelic acid and given the trivial names pisolithin A and pisolithin B, respectively. The efficacy of the compounds to inhibit the germination of conidia of Truncatella hartigii was compared with that of commercially available structural analogues, and a comparable range of effectiveness for 50% germination inhibition (GI50) of conidia was recorded. The commercially available synthetic compounds (R)-mandelic acid, benzoylformic acid, and racemic p-hydroxymandelic acid, had GI50 values of 82, 72, and 59 micrograms/mL, respectively, as compared with the natural compounds pisolithin A, 67 micrograms/mL, and pisolithin B, 71 micrograms/mL. Two synthetic S enantiomers of mandelic acid, (S)-mandelic acid and (S)-(+)-p-hydroxymandelic acid, were the most effective compounds, with GI50 values of 31 and 33 micrograms/mL, respectively. A sodium salt of mandelic acid had no activity below 500 micrograms/mL. Pisolithin A and pisolithin B were compared with polyoxin D for inhibition of hyphal growth, as measured by protein estimation. Both pisolithin A and B measured higher levels of putative extractable protein than polyoxin D, but less mycelial wet weight was measured. It is suggested that the pisolithins caused a disruption of cell turgor. A measurement of mycelial dry weights of phytopathogens, incubated with the commercially available analogues, benzoylformic acid and racemic p-hydroxymandelic acid, indicated that benzoylformic acid was either more effective than, or as effective as, racemic p-hydroxymandelic acid or nystatin in arresting fungal growth.(ABSTRACT TRUNCATED AT 250 WORDS)

p-Hydroxymandelic acid--a key intermediate in the metabolism of DL (plus or minus)-phenylalanine by Aspergillus niger

The enzymatic oxidation of p-hydroxymandelic acid to p-hydroxybenzoic acid

Determination of p-hydroxymandelic acid enantiomers in urine by high-performance liquid chromatography with electrochemical detection

High-performance liquid chromatography (HPLC) with electrochemical detection using a chiral ligand-exchange column was developed for the enantioselective determination of p-hydroxymandelic acid (HMA), a metabolite of synephrine, with high sensitivity. A good linear relationship between current ratio and amount was noted for 0.5-500 pmol HMA, with a correlation coefficient of 0.999 for each HMA enantiomer. The relative standard deviation (R.S.D.) was 1.6% at 100 pmol d-HMA and 2.2% at 100 pmol l-HMA. The detection limit of each HMA enantiomer was 0.5 pmol (signal to noise ratio, S/N = 3). By this method, HMA in Citrus unshiu and in urine following the ingestion of C. unshiu was determined. Although no HMA was found in c. unshiu, d- and l-HMA were present in urine after the ingestion of C. unshiu. The time courses of HMA and conjugated synephrine enantiomers excreted in urine following the ingestion of C. unshiu for 24 h could be monitored. This method should prove applicable to the study of synephrine metabolism.

Normal excretion of m-hydroxymandelic acid in hypertensive patients

o-Hydroxymandelic acid (OHMA), m-hydroxymandelic acid (MHMA) and p-hydroxymandelic acid (PHMA) were measured in the urine of 42 normotensive and 54 hypertensive patients. Patients having high urinary MHMA levels were all found to be ingesting medications containing m-synephrine (phenylephrine). These patients also had high levels of urinary m-synephrine which was excreted as the glucuronide. When patients ingesting m-synephrine were excluded from the analysis, no significant differences were observed between the two groups for the urinary excretion of OHMA, MHMA and PHMA.