HPLC determination of D-glucaric acid in human urine

Determination of D-glucaric acid and/or D-glucaro-1,4-lacton in different apple varieties through hydrophilic interaction chromatography

d-Glucaric acid (GA) derivatives exhibit anti-cancerogenic properties in vivo in apples, but quantitative information about these derivatives is limited. Hydrophilic interaction-based HPLC with ultraviolet detection or mass spectrometry was developed to quantify GA and/or D-glucaro-1,4-lacton (1,4-GL) in apples. Although the formation of 1,4-GL from GA could be the prerequisite to exert biological effects in vivo, only a small portion of GA (<5%) was identified and converted to 1,4-GL in the rat stomach. The 1,4-GL content in apples ranged from 0.3 mg/g to 0.9 mg/g, and this amount can substantiate health claims associated with apples. The amount of 1,4-GL was 1.5 times higher in Gala and the ratio of 1,4-GL to GA was lower in Green Delicious apples than those in the other varieties. Our findings suggested that the variety and maturity of apples at harvest are factors that determine 1,4-GL content.

Cloning and characterization of uronate dehydrogenases from two pseudomonads and Agrobacterium tumefaciens strain C58

Uronate dehydrogenase has been cloned from Pseudomonas syringae pv. tomato strain DC3000, Pseudomonas putida KT2440, and Agrobacterium tumefaciens strain C58. The genes were identified by using a novel complementation assay employing an Escherichia coli mutant incapable of consuming glucuronate as the sole carbon source but capable of growth on glucarate. A shotgun library of P. syringae was screened in the mutant E. coli by growing transformed cells on minimal medium containing glucuronic acid. Colonies that survived were evaluated for uronate dehydrogenase, which is capable of converting glucuronic acid to glucaric acid. In this manner, a 0.8-kb open reading frame was identified and subsequently verified to be udh. Homologous enzymes in P. putida and A. tumefaciens were identified based on a similarity search of the sequenced genomes. Recombinant proteins from each of the three organisms expressed in E. coli were purified and characterized. For all three enzymes, the turnover number (k(cat)) with glucuronate as a substrate was higher than that with galacturonate; however, the Michaelis constant (K(m)) for galacturonate was lower than that for glucuronate. The A. tumefaciens enzyme was found to have the highest rate constant (k(cat) = 1.9 x 10(2) s(-1) on glucuronate), which was more than twofold higher than those of both of the pseudomonad enzymes.

Production of glucaric acid from a synthetic pathway in recombinant Escherichia coli

A synthetic pathway has been constructed for the production of glucuronic and glucaric acids from glucose in Escherichia coli. Coexpression of the genes encoding myo-inositol-1-phosphate synthase (Ino1) from Saccharomyces cerevisiae and myo-inositol oxygenase (MIOX) from mice led to production of glucuronic acid through the intermediate myo-inositol. Glucuronic acid concentrations up to 0.3 g/liter were measured in the culture broth. The activity of MIOX was rate limiting, resulting in the accumulation of both myo-inositol and glucuronic acid as final products, in approximately equal concentrations. Inclusion of a third enzyme, uronate dehydrogenase (Udh) from Pseudomonas syringae, facilitated the conversion of glucuronic acid to glucaric acid. The activity of this recombinant enzyme was more than 2 orders of magnitude higher than that of Ino1 and MIOX and increased overall flux through the pathway such that glucaric acid concentrations in excess of 1 g/liter were observed. This represents a novel microbial system for the biological production of glucaric acid, a "top value-added chemical" from biomass.

Development of a method for the quantification of D-glucaric acid in different varieties of grapefruits by high-performance liquid chromatography and mass spectra

Grapefruits were found to contain D-glucaric acid, which has anticancer properties. In the present investigation, a method has been developed for the quantification of D-glucaric acid in grapefruit by high-performance liquid chromatography (HPLC) using a simple isocratic mobile phase with detection at 210 nm. Grapefruit samples were homogenized, centrifuged and filtered through a 0.45 microm membrane and injected into a HPLC system. The developed method was used for the quantification of D-glucaric acid in nine widely used grapefruit varieties. Furthermore, the identity of D-glucaric acid was confirmed by mass spectra. Seasonal variation of D-glucaric acid within the individual varieties were also measured in fruits harvested during November, February and May. The overall trend of D-glucaric acid level was increased from early to late season fruits. The developed method has a sensitivity of D-glucaric acid as low as 0.05 microg with an accuracy and precision >95%. This method was found to be simple, fast, accurate and reproducible. Moreover, the identity of D-glucaric acid was confirmed by mass spectra. Additionally, the labor intensity and cost of sample preparation were greatly reduced as compared to reported methods. This is the first report on quantification of D-glucaric acid in different varieties of grapefruits from three harvesting sessions.

Biomarker measurements in a coastal fish-eating population environmentally exposed to organochlorines

The Lower North Shore region of the St. Lawrence River is home to a fish-eating population that displays an unusually high body burden of several organochlorines, including polychlorinated biphenyls (PCBs) and dioxin-like compounds (DLCs). We measured biomarkers indicative of liver enzyme induction and investigated the relationship with organochlorine body burden in adult volunteers from this population. We determined plasma concentrations of PCBs and chlorinated pesticides by high-resolution gas chromatography (HRGC) with electron capture detection. DLC concentrations were measured by the dioxin-receptor chemically activated luciferase expression (DR-CALUX) assay and in a subset of participants, by HRGC/high-resolution mass spectrometry. We measured cotinine, d-glucaric acid, and porphyrins in morning urine samples and determined liver CYP1A2 activity in vivo using the caffeine breath test. Neither DLC concentrations as measured by the DR-CALUX nor PCB-153 concentrations, the latter representing total PCB exposure, were correlated with biomarkers of effects. Smoking (morning urinary cotinine concentration) was positively related to CYP1A2 activity as measured by the caffeine breath test (p < 0.01). Liver CYP1A2 activity was in turn negatively correlated with PCB-105:PCB-153 and PCB-118:PCB-153 congener ratios (p < 0.05). Hence, despite the relatively high body burden of PCBs and DLCs in this population, only smoking had a significant correlation with biomarkers of hepatic enzyme induction. Our data are consistent with smoking-induced liver CYP1A2 activity altering heme metabolism and increasing the biotransformation of mono-ortho PCB congeners.