Ujang Tinggi

Essentiality and toxicity of selenium and its status in Australia: a review

Selenium (Se) is an essential trace element for animals and humans because of its role in an antioxidant enzyme glutathione peroxidase. This enzyme protects cell membranes from damage caused by the peroxidation of lipids. The paper provides an overview of the effects of Se toxicity and deficiency in humans and animals. It is well established that Se deficiency causes health implications in humans and animals. Se is also very toxic and can cause Se poisoning (selenosis) in humans and animals. In Australia, Se deficiency has caused health problem to livestock; however, the problems were eliminated after the introduction of Se supplementation. Se toxicity has also been reported in some regions of Australia as a result of livestock feeding on Se accumulative plant species. The major source of Se is diet, and in many regions of the world the levels of Se in the soils generally reflect the Se status in human populations. In foods, the bioavailability and toxicity of Se depend on its chemical forms. Generally, organic forms of Se are more bioavailable and less toxic than the inorganic forms (selenites, selenates). The Se status in the Australian population and how this is compared with the rest of the world is also discussed.

Selenium: its role as antioxidant in human health

Selenium (Se) is an essential trace element, and its low status in humans has been linked to increased risk of various diseases, such as cancer and heart disease. In recent years, Se research has attracted tremendous interest because of its important role in antioxidant selenoproteins for protection against oxidative stress initiated by excess reactive oxygen species (ROS) and reactive nitrogen species (NOS). The synthesis of selenoproteins requires a unique incorporation of amino acid selenocysteine (Sec) into proteins directed by the UGA codon, which is also a termination codon. Interest in Se research has led to the discovery of at least 30 selenoproteins; however, the biochemical functional roles of some of these selenoproteins are still unknown. Besides in the form of selenoproteins, Se can exist in many different chemical forms in biological materials either as organic Se compounds, such as selenomethionine and dimethylselenide, and inorganic selenites and selenates. In foods, Se is predominantly present as selenomethionine, which is an important source of dietary Se in humans, and also as a chemical form that is commonly used for Se supplements in clinical trials. Concern for potential deficiency diseases associated with low Se status has led to the establishment of the recommended daily requirements for Se in many countries. However, excess Se intakes through supplementation and its potential misuse as health therapy could also pose a risk of adverse health effects if its use is not properly regulated.

Determination of manganese and chromium in foods by atomic absorption spectrometry after wet digestion

Abstract Wet digestion procedures using acid mixtures of HNO 3 /H 2 SO 4 /HClO 4 and HNO 3 /H 2 SO 4 were investigated for their effectiveness for decomposition of food samples prior to determination of manganese (Mn) and chromium (Cr) by flame and Zeeman graphite furnace atomic absorption spectrophotometry. The addition of hydrofluoric acid (HF) to the mixture of HNO 3 /H 2 SO 4 was also investigated for determination of Cr. All the acid mixtures tested were found to be satisfactory, but, for reasons of safety, HNO 3 /H 2 SO 4 was the method of choice. No apparent matrix interferences or losses of analytes were encountered with the method used. Analysis of selected food samples found relatively high levels of Mn and Cr in most cereal products. Meats, dairy products (except for Cr in cheese), vegetables and fruits contained relatively low levels of both elements.

Public Health Risks from Heavy Metals and Metalloids Present in Traditional Chinese Medicines

Out of 247 traditional Chinese medicines (TCM) investigated, a proportion were contaminated with arsenic (5–15%), lead (∼5%), and mercury (∼65%). Some preparations exceeded the tolerable daily intake (TDI) for males and females for arsenic (4 and 5 products, respectively), lead (1 and 2 products), and mercury (5 and 7 products). These exceedances were as high as 2760-fold, which posed a potential danger to public health. As many users are known to self-prescribe, there is a substantial risk of poisoning from the consumption of these contaminated TCM.

B-group vitamin and mineral contents of soybeans during kinema production

Concentrations of several B-group vitamins, determined by high-performance liquid chromatography (HPLC), and minerals, determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), in soybeans during different kinema production stages were compared. After soaking soybeans in water, thiamine (B1) content decreased, whereas riboflavin (B2) content remained unchanged. Cooking had no influence on the B1 content, but it enhanced the level of B2 and niacin (B3). Incubation of beans at 37°C for 48 h, when mixed with Bacillus subtilis, caused an increase in concentration of both B1 and B2. Vitamin B1 levels decreased when either Enterococcus faecium accompanied B subtilis or the temperature was elevated for 18 h fermentation. Traditionally prepared kinema contained 8 mg B1, 12 mg B2, 45 mg B3, 683 mg Ca, 4 mg Cu, 18 mg Fe, 494 mg Mg, 10 mg Mn, 1257 mg P, 2077 mg K, 13 mg Zn and <0·5 mg of Cd, Cr, Pb, Ni and Na per kg dry matter. While the vitamin B1 content was significantly (P<0·05) higher, the contents of vitamins B2 and B3 were significantly (P<0·05) lower in raw soybeans than those in kinema. Mineral concentrations were 3·1–8·3 times higher in raw soybeans than in kinema.

Stable isotope and trace metal compositions of Australian prawns as a guide to authenticity and wholesomeness.

This research has explored the potential of stable isotope and trace metal profiles to distinguish Australian prawns from prawns imported from neighbouring Asian countries. Australian prawns were collected mostly from the Brisbane area. Strong differences in Australian vs. imported prawns were evident from both the isotope and trace element data, with the differences most likely occurring because imported prawns are typically reared in aquaculture facilities and frozen prior to sale in Australia. The aquaculture origins are characterised by comparatively; low δHVSMOW, δ(13)CVPDB values, low concentrations of arsenic, zinc and potassium, and high water contents (>80%). Relatively high arsenic and cadmium contents were found within Australian prawns, but the concentrations did not exceed local human health guidelines.

The selenium content of cell culture serum influences redox-regulated gene expression.

Cell Culture The MDA-MB-231 breast cancer cell line (see Reference 24 in the main text) was cultured in RPMI 1640 medium (Invitrogen, Melbourne, Australia), supplemented with either 10% FBS [either Invitrogen, Lonza (Melbourne, Australia), Quantum (Brisbane, Australia), or 10% serum supreme (Lonza) and 100 μg/mL penicillin (Invitrogen) and 100 μg/mL streptomycin (Invitrogen) in 5% CO2 at 37°C. Media used in transfections did not contain penicillin or streptomycin. All chemicals were purchased from SigmaAldrich (Castle Hill, Australia) unless otherwise specified.

Isotopic and Elemental Composition of Roasted Coffee as a Guide to Authenticity and Origin

This study presents the stable isotopic and elemental compositions of single-origin, roasted coffees available to retail consumers. The δ(13)C, δ(15)N, and δ(18)O compositions were in agreement with those previously reported for green coffee beans. The δ(15)N composition was seen to be related to organic cultivation, reflected in both δ(2)H and δ(18)O compositions. The δ(13)C composition of extracted caffeine differed little from that of the bulk coffee. Stepwise discriminant analysis with jackknife tests, using isotopic and elemental data, provided up to 77% correct classification of regions of production. Samples from Africa and India were readily classified. The wide range in both isotopic and elemental compositions of samples from other regions, specifically Central/South America, resulted in poor discrimination between or within these regions. Simpler X-Y and geo-spatial plots of the isotopic data provided effective visual means to distinguish between coffees from different regions.

Determination of iodine in selected foods and diets by inductively coupled plasma-mass spectrometry*

Iodine is an essential trace element, and its deficiency has caused concern in many countries. Foods are the principal source of iodine, and its levels are generally low. In this study, selected food items were obtained from food market outlets in Brisbane, Australia. Food samples of dietary intakes of selected healthy children in Brisbane, Australia, were also collected for analysis and assessment of iodine nutritional status. In Australia, there has been little study on iodine dietary intakes, particularly in young children. The aims of this study were to provide further information on iodine levels in foods for Australian food composition data, and to estimate the iodine daily intakes of selected healthy children. Food samples were analyzed for iodine concentrations using inductively coupled plasma-mass spectrometry (ICP-MS) after alkaline digestion with tetramethylammonium hydroxide (TMAH), and the method was validated using a certified reference material of nonfat milk (NIST, SRM 1549). The results of this study indicated a wide variation of iodine in foodstuffs, which ranged from <0.02 to 0.101 mg/kg for cereals, 87 to 299 μg/kg for milk, and 86 to 271 μg/kg for cheese products. The study also showed that the daily intakes of iodine in these children (n = 15) varied widely and ranged from 36.9 to 288.1 μg/day (mean ± s.d, 93.1 ± 76.7 μg/day).

Selenium levels in cow's milk from different regions of Australia

Homogenised cows milk samples were collected each season in 1990 and 1991 from 19 selected dairy factories in different regions across Australia. Fresh cows milk samples were also collected every month in 1990 and 1991 from 24 selected dairy farms in Queensland. Selenium (Se) analyses were performed by spectrofluorimetry after complexing with 2,3-diaminonaphthalene. The study found a wide variation of Se levels in homogenised milk from dairy milk factories. Statistical analysis using unpaired t-test showed that Se levels in summer were significantly higher (P < 0.001) than in other seasons. Mean concentrations in summer, autumn, winter and spring for 1990 and 1991 were 23.8 ± 4.6, 20.9 ± 4.4, 20.7 ± 4.2 and 20.6 ± 4.8 μ g/L, respectively. A two-way ANOVA analysis also indicated that regions and season have a significant influence (P < 0.001) on Se levels and that there is an interaction between regions and seasons. High Se levels in each region tend to be associated with high Se levels in summer milk. A wide variation of Se levels was also found in raw milk collected from dairy farms. Mean concentration was 22.0 ± 6.0 μ g/L, with a range of 6.7 to 47.6 μ g/L. When the values of Se levels in homogenised milk for each season were used to estimate the contribution of milk to daily intake of different populations groups, it was found that infants have the highest intake (10.0-12.2 μ g/day) which meets the Australian Recommended Dietary Intake.Homogenised cows milk samples were collected each season in 1990 and 1991 from 19 selected dairy factories in different regions across Australia. Fresh cows milk samples were also collected every month in 1990 and 1991 from 24 selected dairy farms in Queensland. Selenium (Se) analyses were performed by spectrofluorimetry after complexing with 2,3-diaminonaphthalene. The study found a wide variation of Se levels in homogenised milk from dairy milk factories. Statistical analysis using unpaired t-test showed that Se levels in summer were significantly higher (P < 0.001) than in other seasons. Mean concentrations in summer, autumn, winter and spring for 1990 and 1991 were 23.8 +/- 4.6, 20.9 +/- 4.4, 20.7 +/- 4.2 and 20.6 +/- 4.8 micrograms/L, respectively. A two-way ANOVA analysis also indicated that regions and season have a significant influence (P < 0.001) on Se levels and that there is an interaction between regions and seasons. High Se levels in each region tend to be associated with high Se levels in summer milk. A wide variation of Se levels was also found in raw milk collected from dairy farms. Mean concentration was 22.0 +/- 6.0 micrograms/L, with a range of 6.7 to 47.6 micrograms/L. When the values of Se levels in homogenised milk for each season were used to estimate the contribution of milk to daily intake of different populations groups, it was found that infants have the highest intake (10.0-12.2 micrograms/day) which meets the Australian Recommended Dietary Intake.