Hoonjeong Kwon

Evaluation of aloin and aloe-emodin as anti-inflammatory agents in aloe by using murine macrophages.

The aloe ingredients responsible for physiological effects and the concentrations required to exert their biological activities are not fully understood. This study compares the anti-inflammatory effects of aloin and aloe-emodin with other polyphenols. Our results demonstrated that aloe-emodin dose-dependently inhibited inducible nitric oxide synthase (iNOS) mRNA expression and nitric oxide (NO) production at 5–40 μM. In addition, the levels of cyclooxygenase-2 (COX-2) mRNA and prostaglandin E2 (PGE2) production were suppressed by 40 μM aloe-emodin. Aloin also suppressed the production of NO at 5–40 μM, although it did not suppress PGE2 production. The present results indicate that aloin and aloe-emodin possibly suppress the inflammatory responses by blocking iNOS and COX-2 mRNA expression. The anti-inflammatory effect of aloe-emodin was comparable to that of kaempferol and quercetin, indicating aloe-emodin as a possible key constituent responsible for the anti-inflammatory activity of aloe.

Determination of ethyl carbamate in some fermented Korean foods and beverages

Ethyl carbamate has been associated with cancer for several decades. It is mainly found in fermented foods and beverages. In view of the importance of fermented foods in the Korean diet and the significant level of ethyl carbamate expected, we determined ethyl carbamate concentrations in some of the staple food items and estimated the daily intake for the Korean population. Ethyl carbamate in commercial samples of kimchi, soy sauce, vinegar, soybean paste, and alcoholic beverages were determined by gas chromatography-mass spectrometry/selective ion monitoring (GC-MS/SIM). Homemade soy sauce and kimchi were also analysed. The maximum ethyl carbamate concentrations observed were 73 μg/kg in soy sauce, 7.9 μg/kg in soybean paste, 2.5 μg/l in vinegar, 16.2 μg/kg in kimchi and 15.4 μ/l in Korean traditional alcoholic beverages. Combining these values with the average daily food intake data, we estimated that the maximum daily exposure of Korean population to ethyl carbamate is 2.8 μg/day, which is not a negligible amount considering the ‘virtually safe dose’ derived by animal experiment ranges between 1.2 and 4.8 μg/day. It would be desirable to closely monitor ethyl carbamate levels in Korean foods and to find ways to reduce the daily intake.

Dietary aloin, aloesin, or aloe-gel exerts anti-inflammatory activity in a rat colitis model

AIMS Aloe has been a very popular folk remedy for inflammation-related pathological conditions despite the lack of studies reporting its efficacy in vivo. The present study evaluated the anti-inflammatory effects of aloe components (aloin, aloesin and aloe-gel) known to be biologically active in the rat model of colitis. MAIN METHODS Male Sprague Dawley rats were fed experimental diets for 2 weeks before and during the induction of colitis. Drinking water containing 3% dextran sulfate sodium (DSS) was provided for 1 week to induce colitis. At the end of the experimental period, clinical and biochemical markers were compared. KEY FINDINGS Plasma leukotriene B(4) (LTB(4)) and tumor necrosis factor-α (TNF-α) concentrations were significantly decreased in all groups supplemented with aloe components compared to the colitis control group (p<0.05). Animals fed both a 0.1% and 0.5% aloesin supplemented diet showed colonic myeloperoxidase (MPO) activities which were decreased by 32.2% and 40.1%, respectively (p<0.05). Colonic mucosa TNF-α and interleukin-1ß (IL-1β) mRNA expressions were significantly reduced in all animals fed aloin, aloesin, or aloe-gel (p<0.05). SIGNIFICANCE Dietary supplementation of aloe components ameliorates intestinal inflammatory responses in a DSS-induced ulcerative colitis rat model. In particular, aloesin was the most potent inhibitor. Further studies are required for a more complete understanding of the specific mechanism of the action of these supplements.

Estimation of daily exposure to 4-hydroxy-2-alkenals in Korean foods containing n-3 and n-6 polyunsaturated fatty acids

4-Hydroxy-2-alkenals are cytotoxic aldehydes generated from the oxidation of n-3 and n-6 polyunsaturated fatty acids. The compounds have shown various biological effects via Schiff base adducts or Michael addition adducts at levels higher than physiological ones. To assess human exposure to 4-hydroxy-2-alkenals in the diet, 4-hydroxy-2-alkenals in vegetable oils, fish and shellfish were monitored using GC/MS/SIM. 2001 National Health and Nutrition Survey (2002) data were employed for the dietary intake pattern. The Korean daily exposure to 4-hydroxy-2-alkenals, excluding a possible one from fried food, was 4.3 µg day−1, constituted of 1.6 µg 4-hydroxy-2-hexenal (HHE) and 2.7 µg 4-hydroxy-2-nonenal (HNE). It was calculated that Koreans could be additionally exposed to more than 11.8 µg day−1 4-hydroxy-2-alkenal from fried foods. Thus, the combined exposure would be 16.1 µg day−1, which corresponds to 0.3 µg kg−1 body weight day−1 for a 60 kg Korean adult. In spite of the biological toxicity of 4-hydroxy-2-alkenals, the risk for human could not be quantified due to the lack of a virtually safe dose of the compounds. However, considering the basal level of 4-hydroxy-2-alkenals in many tissues, the present value from the diet may not pose a significant risk for human health.

Estimated intakes of isoflavones and coumestrol in Korean population

The dietary intakes and sources of isoflavones and coumestrol were estimated for each age group of Koreans based on data from the Korean Nutrition Survey conducted in 1998. For quantitative data on the levels of isoflavones and coumestrol, our previous study monitoring phytoestrogens in 220 Korean leguminous foodstuffs was employed and the median value for each food was adopted. The total isoflavones and coumestrol intake per capita was estimated as 23.3 mg/day, which constituted 14.2 mg daidzein, 6.7 mg genistein, 0.9 mg glycitein, 1.0 mg formononetin, 0.2 mg biochanin A, and 0.3 mg coumestrol. The top five foods arrowroot, soybean paste, tofu, soybean, and soybean sprout contributed to 88.2% of isoflavone intake, with the corresponding intake from each food being 8.3 mg/day, 4.9 mg/day, 2.6 mg/day, 2.5 mg/day, and 2.0 mg/day, respectively. Starting at age 3–6, the contributions of fermented soy products to the isoflavones intakes were around 30%. Soybean sprout was a major source of coumestrol intake in Koreans. Slight differences in the preference of these foods were observed among the various age groups. As regards the total isoflavone intakes, the highest value was 33.6 mg/day for people age 30–49, followed by age 50–64 (26.4 mg/day), 20–29 (21.0 mg/day), ≥65 (18.8 mg/day), 1–2 (14.5 mg/day), 7–12 (12.4 mg/day), 13–19 (10.1 mg/day), and 3–6 (8.9 mg/day). The intake levels are likely to be exceeded in groups who have preferably consumed high phytoestrogen-containing foods such as soy-protein-based infant formula and arrowroot.

4-hydroxy-2-alkenals in polyunsaturated fatty acids-fortified infant formulas and other commercial food products.

4-Hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE) were determined using selected ion-monitoring gas chromatography-mass spectrometry (GC-MS) in 56 kinds of commercially available PUFA-fortified foods including infant formulas and baby foods. HHE and HNE, each specifically coming from the oxidation of n-3 and n-6 polyunsaturated fatty acids (PUFA), were observed at <10–77 and 41–132 µg kg–1 in the infant formulas (n = 12) and at <10–52 and 36–116 µg kg–1 in the baby foods (n = 7), respectively. 4-Hydroxy-2-alkenals in infant formulas and baby foods were further determined at 10 and 30 days after opening in an attempt to examine the time dependence of the levels of 4-hydroxy-2-alkenals. The values of HHE and HNE had increased appreciably to <10–220 and 79–792 µg kg–1 in infant formulas and to <10–112 and 135–572 µg kg–1 in baby foods, respectively, at 10 days and decreased, although statistically not significant, in most of the tested samples after 30 days, which suggested that the reactive compounds might interact with other constituents like proteins in the samples to form adducts or be decomposed with time. Based on the current study, it was calculated that 3-month to 1-year-old babies maintained exclusively on these commercially available PUFA-fortified infant formulas or baby foods could be exposed to a maximum of 20.2 µg kg–1 body weight day–1 of 4-hydroxy-2-alkenals, which is two orders of magnitude higher than the exposure of Korean adults estimated in a previous study of the authors’ (2005). The present study may trigger future studies investigating the physiological influence of 4-hydroxy-2-alkenals originating from the diet on man at an early stage of development.

Distribution of Seven N-Nitrosamines in Food

N-nitrosamines, which are classified as carcinogens by IARC and US EPA, can be easily found in various foods. They are reaction products between nitrogen oxide and secondary amines, but can also be generated during fermentation. Ever since the 1960s, when nitrite, used as a preservative in processed meats, was suspected to generate N-nitrosamines, the usage of the food additive has been debated. However, the benefit of nitrite in food supply could not be ignored and the risk-benefit analysis has become a key issue in the use of the additive. For a risk analysis, an accurate estimation of the hazardous material is necessary; therefore, analytical methods for nitrosamines have continuously evolved from the 1950s. Solid supported liquid-liquid extraction and solid phase extractions have replaced the distillation for the clean-up steps, and tandem mass spectrometry is employed for higher selectivity and sensitivity. In the present study, for a better estimation of N-nitrosamine intake, the total diet study samples were prepared for the N-nitrosamines analysis. In order to obtain the most sensitive results, a partial preparation procedure was developed and modified for different food matrices. Among seven N-nitrosamines (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, N-nitrosopiperidine, N-nitrosopyrrolidine, and N-nitrosomorpholine) analyzed in the present study, N-nitrosodiethylamine has shown the highest detection rate in agricultural foods, while N-nitrosodimethylamine has appeared most frequently in livestock and fishery food products. The concentration of N-nitrosodimethylamine was the highest in seasoning.

Simultaneous determination of 4-hydroxy-2-alkenals, lipid peroxidation toxic products

Lipid peroxidation has been associated with cell injury and possible carcinogenecity, for the products can damage cellular membrane and DNA. Among the products formed from lipid peroxidation, 4-hydroxy-2-alkenals are the major components and have been suggested to play a role in cellular toxicity. However, the difficulties of the quantification due to their strong reactivity during laboratory procedures hinder the exposure measurement of the compounds. A novel detection method based on the conversion of 4-hydroxy-2-alkenals to stable diols and to subsequent ortho -esters has been developed. Simultaneous detection in a sensitive single-ion monitoring mode by GC/MS was carried out, monitoring m/z 129, which was the common fragment ion for the ortho -esters derived from 4-hydroxy-2-alkenals. The proposed method was used to quantify 4-hydroxy-2-nonenal in oils and in oxidized arachidonic acid.

Intestinal absorption of aloin, aloe-emodin, and aloesin; A comparative study using two in vitro absorption models

Aloe products are one of the top selling health-functional foods in Korea, however the adequate level of intake to achieve desirable effects are not well understood. The objective of this study was to determine the intestinal uptake and metabolism of physiologically active aloe components using in vitro intestinal absorption model. The Caco-2 cell monolayer and the everted gut sac were incubated with 5-50 µM of aloin, aloe-emodin, and aloesin. The basolateral appearance of test compounds and their glucuronosyl or sulfated forms were quantified using HPLC. The % absorption of aloin, aloe-emodin, and aloesin was ranged from 5.51% to 6.60%, 6.60% to 11.32%, and 7.61% to 13.64%, respectively. Up to 18.15%, 18.18%, and 38.86% of aloin, aloe-emodin, and aloesin, respectively, was absorbed as glucuronidated or sulfated form. These results suggest that a significant amount is transformed during absorption. The absorption rate of test compounds except aloesin was similar in two models; more aloesin was absorbed in the everted gut sac than in the Caco-2 monolayer. These results provide information to establish adequate intake level of aloe supplements to maintain effective plasma level.

Estimated Dietary Intake of Thiocyanate from Brassicaceae Family in Korean Diet

Glucosinolate, sulfur-containing organic anions bonded to glucose, is found in plants including the family of Brassicaceae. Glucosinolate is hydrolyzed by myrosinase and produces various by-products that possess biological activities. Among the decomposed products, thiocyanate is known for its adverse effects on thyroid metabolism due to competition with iodine. This is of concern in that Korean dietary habits consist of consumption of large amounts of Brassicaceae vegetables such as cabbage and radishes, which may be correlated with high incidence of thyroid dysfunction. Thus, quantification of thiocyanate in Brassicaceae vegetables was performed by hydrolysis and spectrophotometrical detection. Average daily intake of Brassicaceae vegetables was obtained from the Third Korea National Health and Nutrition Examination Survey (KNHANES III), 2005—Nutrition Survey and from The Vegetable Production Statistics, 2007. Average daily intake of thiocyanate through Brassicaceae vegetables in Korea was estimated to be 16.3 μmol SCN−/d/person. When this was compared to published animal studies, average thiocyanate intake per person was lower than doses required to produce adverse effects. However, further studies may be warranted to ensure safety with sufficient margins of safety.