Bee Lan Lee

Peroxyl radical scavenging capacity, polyphenolics, and lipophilic antioxidant profiles of mulberry fruits cultivated in southern China.

Twenty-seven cultivars of mulberry fruits ( Morus atropurpurea Roxb) were analyzed for their total phenolic content, total anthocyanin content, and peroxyl radical scavenging capacities. The proanthocyanidin contents of the fruit were also quantified using 4-dimethylamino-cinnamaldehyde assay, and characterization was attempted using electrospray ionization mass spectra. The phenolic compounds of mulberry fruits were characterized using HPLC with ESI-MS and diode array detection. Results showed that the content of mulberry fruits varied with different cultivars with total phenolic content, total anthocyanin content, total proanthocyanidin content, and peroxyl radical scavenging capacities ranging from 0.060-0.244, 0.001-0.056, 0.001-0.015, and 0.301-1.728, respectively. Good correlations were observed among the phenolic, anthocyanin, and proanthocyanidin contents and the radical scavenging capacities of mulberry fruits. Mulberry fruits were found to contain low amount of proanthocyanidins. The high total phenolic content of mulberry fruits were mainly contributed by anthocyanins, rutin, and chlorogenic acids. The lipid soluble antioxidants are profiled by an HPLC method developed in-house, and the results of selected mulberry fruits revealed significant amounts of lutein and delta- and gamma-tocopherols but low alpha-tocopherol. Our results provide useful antioxidant nutritional information of a mulberry cultivar that has potential for large scale plantations.

Oxidative burden in prediabetic and diabetic individuals: evidence from plasma coenzyme Q10

Aimu2003 Individuals with diabetes and prediabetes are at risk of vascular injury. However, the exact mechanisms are unclear. The mitochondria mobile electron carrier coenzyme Q10 (CoQ10) is a potent lipophilic antioxidant. We hypothesize that oxidative stress, detectable as changes in plasma CoQ10 concentrations and composition, plays an important role in vascular disease in diabetes.

Coenzyme Q10 and differences in coronary heart disease risk in Asian Indians and Chinese.

Indians or South Asians have been found to be particularly susceptible to coronary heart disease (CHD) in many countries. A novel risk factor for CHD may be coenzyme Q10 (CoQ10). In this study, plasma CoQ10 (including ubiquinol-10, CoQ10H2, and total CoQ10), various lipid parameters, and antioxidant levels were determined in a random sample of Indians and Chinese from the general population of Singapore. The reduced form of coenzyme Q10, CoQ10H2, and total Q10 concentrations in plasma were significantly lower in Indian males than Chinese males. Although no significant differences were found in plasma concentrations of total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL) between the two ethnic groups, the ratios of ubiquinol and total CoQ10 to triglycerides, total cholesterol, and LDL were significantly lower in Indian males than Chinese males. There were no significant ethnic differences in other antioxidant levels, including trans-retinol, alpha-tocopherol, and ascorbic acid. The consistently lower values of coenzyme Q10, especially its reduced form, in Indian males may contribute to the higher susceptibility of this ethnic group to coronary heart disease.

Comprehensive high-performance liquid chromatographic method for the measurements of lipophilic antioxidants in human plasma

Owing to the increasing interest in the health effects of antioxidant micronutrients on chronic diseases, a robust and rapid HPLC method for simultaneous measurement of coenzyme Q(10) (ubiquinone and ubiquinol), vitamin A (all-trans-retinol), vitamin E (tocopherols and tocotrienols) and carotenoids (lutein, zeaxanthin, beta-cryptoxanthin, lycopene and beta-carotene) was developed. Sample preparation and analytical conditions that would affect solubility and stability of these antioxidants were investigated and optimized. The mobile phase used was made up of acetonitrile, methanol, ethanol and tert-butanol without corrosive additives such as ammonium perchlorate and perchloric acid. Our results show that using two C(18) columns coupled with photodiode array, fluorescence and electrochemical detection, a comprehensive spectrum of 16 lipid-soluble antioxidants in 30 microL of plasma could be separated and quantified within 30 min. The chromatographic run time was about 3-fold faster and the sample size was about 5-fold smaller than when assays were performed separately using existing methods. The present method will be useful for dietary habit studies and for antioxidant status investigations.

Monomeric C18 chromatographic method for the liquid chromatographic determination of lipophilic antioxidants in plants

Reversed-phase liquid chromatography was used to determine lipophilic antioxidants in plants using two monomeric C18 columns operated at 30 degrees C and 4 degrees C, with a column-switching technique and acetonitrile-methanol gradient elution. The chromatograms were extracted at different wavelengths using a UV diode array detector (DAD). A wide range of plant antioxidants, including nine carotenoids (neoxanthin, violaxanthin, lutein, zeaxanthin, beta-cryptoxanthin, lycopene, canthaxanthin, alpha-carotene and beta-carotene) together with all-trans-retinol, capsaicin, dihydrocapsaicin, chlorophyll a, and chlorophyll b can be separated within 50 min. Fluorometric detection was applied to quantify trace amounts of six vitamin E analogues (alpha-, delta- and gamma-tocopherols and tocotrienols). The detection limits were 0.2-0.4 microg/g for various xanthophylls and 0.04-0.10 microg/g for vitamin E analogues.

Association of blood lead and homocysteine levels among lead exposed subjects in Vietnam and Singapore

Objectives: Lead and homocysteine are both linked to cardiovascular disease. With this in mind, the authors evaluated the relation between blood lead and homocysteine in people aged 19–66 years in two Asian populations. Methods: This cross-sectional study comprised 183 workers from a lead stabiliser factory in Singapore and 323 workers from a battery factory in Vietnam. Workers were occupationally exposed to lead. Blood lead was analysed using atomic absorption spectrophotometry while plasma homocysteine was measured using high performance liquid chromatography. Results: Chinese subjects had the lowest blood lead levels while the Indians had the highest. Controlling for age, sex and race, an increase of 1 &mgr;g/dl in blood lead was associated with an increase of 0.04 &mgr;mol/l of homocysteine on the log scale. Gender and ethnicity seemed to be strongly associated with the relation between lead and homocysteine. The positive relation between lead and homocysteine among the Vietnamese subjects was significant (Pearson’s ru200a=u200a0.254, p<0.01). When blood lead levels were divided by quartiles, the correlation coefficient between blood lead levels in the 4th quartile and homocysteine among the Vietnamese was higher (ru200a=u200a0.405, p<0.01). Overall, an increase of 1 &mgr;g/dl in blood lead in all the Vietnamese subjects was associated with an increase of 0.05 &mgr;mol/l increase in homocysteine on the log scale. However, in the 4th quartile, the same increase was associated with an increase of 0.41 &mgr;mol/l of homocysteine on the log scale. Conclusions: Blood lead was found to be associated with homocysteine levels in this Asian sample. Although we cannot determine causality from cross-sectional data, it is sensible to consider the probability that this relation could explain one of the mechanisms of the impact of lead on the cardiovascular system. More studies would be needed to confirm this inference.

Caloric restriction prevents oxidative damage induced by the carcinogen clofibrate in mouse liver

Long‐term caloric restriction in rodents is known to decrease levels of oxidative damage, which may contribute to an ‘anti‐ageing’ effect. We show here that a shorter period (10 months) of caloric restriction had only small effects on levels of oxidative DNA and protein damage in the livers of mice, but completely attenuated increased oxidative damage caused by the carcinogen clofibrate. Since clofibrate is thought to exert its actions by increasing oxidative damage, our data suggest that 10 months of caloric restriction can increase the resistance of tissues to agents inducing oxidative stress. This may be an important factor in explaining how caloric restriction decreases cancer incidence.

Urinary homovanillic acid (HVA) and vanillymandelic acid (VMA) in workers exposed to manganese dust

The neurotoxicity of manganese (Mn) is well known, however, the neurochemical effect caused by this metal is less well investigated. In this study, urinary homovanillic acid (HVA) and vanillymandelic acid (VMA), two end products of catecholamine metabolism, were measured in 39 workers chronically exposed to Mn in a manganese smelting plant. The average duration of Mn exposure was 17.4 yr. Nineteen nonexposed workers were also studied. Concentrations of Mn in serum (MnS) and in urine (MnU) were measured by Zeeman graphite furnace atomic absorption spectrophotometry (ZAAS), and HVA and VMA determined by high performance liquid chromatography (HPLC). For Mn-exposed workers, the concentration of MnS was nearly 2.8 times (1.61 ± 0.16 mg/L vs 0.56 ± 0.16 mg/L) and MnU about 4.5 times higher (7.62 ± 0.17 mg/L vs 1.69 ± 0.16 mg/L) than the nonexposed. Although the geometric mean concentration of HVA in exposed workers was similar to that of the nonexposed (3.09 ± 1.39 mg/g ere. vs 2.99 ± 1.40 mg/g cre.), the VMA concentration was significantly higher (3.02 ± 1.43 mg/g cre. vs 2.49 ± 1.58 mg/g cre.,p = 0.033). Multiple regression analysis showed that although there were no correlations between any of these parameters with the duration of exposure to Mn, both HVA and VMA showed significant correlations with increase in MnS and MnU. These data provide evidence that exposure to Mn was associated with measurable increase in catecholamine metabolites. This finding is compatible with recent observations in laboratory animals that Mn interferes with neurochemical metabolism.

Urine phyto-oestrogen metabolites are not significantly associated with risk of type 2 diabetes: the Singapore Chinese health study.

We evaluated the relationship between urine concentrations of phyto-oestrogens (isoflavones and lignans) and risk of incident type 2 diabetes in middle-aged and elderly Chinese residing in Singapore. Urine metabolites of isoflavones and lignans were assayed by HPLC among 564 diabetes cases and 564 matched controls in a case-control study nested within the Singapore Chinese Health Study cohort. Participants were free of diagnosed diabetes, CVD and cancer at morning urine collections during 1999-2004. Cases were participants who reported to have physician-diagnosed diabetes at follow-up visits during 2006-2010, whereas controls were randomly selected among those who remained free of diabetes and were matched to the index cases by age, sex, dialect group and date of urine collection. Conditional logistic regression models were used to calculate OR and 95 % CI with adjustment for potential confounders. The mean age of the participants at the time of urine collection was 59·8 years, and the average interval between urine collection and diabetes diagnosis was 4·0 years. The multivariate-adjusted OR for diabetes were 1·00 (reference), 0·76 (95 % CI 0·52, 1·11), 0·78 (95 % CI 0·53, 1·14) and 0·79 (95 % CI 0·54, 1·15) across quartiles of urine isoflavones (P for trend=0·54), and were 1·00 (reference), 0·87 (95 % CI 0·60, 1·27), 1·10 (95 % CI 0·77, 1·56) and 0·93 (95 % CI 0·63, 1·37) for lignans (P for trend=0·93). The results were similar in men and women, as well as for individual metabolites of isoflavones (genistein, daidzein, glycitin and equol) or lignans (enterodiol and enterolactone). The present study did not find a significant association between urine phyto-oestrogen metabolites and risk of type 2 diabetes in Chinese adults.

Ultra-performance liquid chromatographic assay coupled with two-dimensional separation for spectrometric determination of urinary S-phenylmercapturic acid

A gradient ultra-performance liquid chromatographic (UPLC) assay coupled with the two dimensional separation and diode array detection method was developed to determine S-phenylmercapturic acid (SPMA), a specific urinary metabolite of benzene. Gradient separation was performed on two C18 core–shell columns (2.6 and 1.7 μm, 50 × 2.1 mm i.d.) maintained at 40 and 20 °C. Among various solvents evaluated, dichloromethane which offered >85% recovery rates of both SPMA and D-benzylmercapturic acid (internal standard) was used for extraction. The yield of free-SPMA was maximized by hydrolyzing 200 μL of urine with 20 μL of 6 M HCl prior to dichloromethane extraction. The limit of detection was 1 μg L−1(s/n = 5) and the limit of quantification was 2 μg L−1. Using our method, a correlation of 0.99 was obtained with 10 specimens (range, 1.7 to 182 μg L−1) from the German External Quality Assessment Scheme. Among the 75 non-occupational exposure individuals, 61 (81%) had SPMA levels below the LOQ. Among the 26 male petroleum workers, 5 who were exposed to <0.04 ppm of benzene were found to have SPMA levels below the LOQ. The geometric means obtained from the other 15 non-smokers and 6 smokers who were exposed to <0.5 ppm of benzene were 5.05 and 6.65 μg g−1creatinine, respectively. The proposed method can be useful for occupational benzene exposure surveillance.