Abstract The effect of tannic acid (TA), gallic acid (GA), propyl gallate (PA) and ellagic acid (EA) on DNA damage in human lymphocytes induced by food mutagens, 3-amino-1-methyl-5 H-pyrido (4,3-b)indole (Trp-P-2) and 2-amino-1-methyl-6-phenylimadazo (4,5-b)pyridine (PhIP), and/or H2O2 was evaluated using single-cell electrophoresis (comet assay). The toxicity of these tested compounds on lymphocytes was not found. These compounds did not cause DNA damage at lower concentration of 0.1-10 µg/ml. At a concentration of 100 µg/ml, TA and GA exhibited slight DNA damage, whereas PA and EA showed no DNA damage. TA and its related compounds decreased the DNA damage induced by Trp-P-2 or PhIP at a concentration of 0.1-10 µg/ml. Moreover, the inhibition of H2O2-induced DNA damage increased with increasing concentrations up to 10 µg/ml. DNA repair enzymes, endonuclease III (Endo III) and formamidopyrimidine-DNA glycoslase (FPG) were used to examine the levels of oxidised pyrimidines and purines in DNA damage induced by H2O2, respectively. All the compounds at 10 µg/ml can reduce the level of FPG sensitive sites. However, only EA inhibited the formation of EndoIII sensitive sites. The results indicate that these compounds can enhance lymphocyte resistance towards DNA damage induced by food mutagens or H2O2. Keywords: Tannic acid; Human lymphocyte; Comet assay; Hydrogen peroxide

Riboflavin is an essential part of the human diet. Although the United States does not have a major problem with a riboflavin deficiency, other regions of the world do. This is especially true for those regions whose main subsistence is rice. To help prevent and control riboflavin deficiencies, many cereal grains are now being fortified with riboflavin. The recommended dietary allowance of riboflavin is 1.1-1.6 mg per day. This value increases slightly for pregnant women, breast feeding women, and athletes. Because riboflavin is an essential part of the diet, it is important to ensure that the minimum requirements for this nutrient are met. By determining the amount of riboflavin in food products, an accurate estimate of daily riboflavin intake can be determined. The AOAC (Association of Official Analytical Chemists) approved microbiological riboflavin assay can be tedious and time consuming. A faster approach to the riboflavin assay would greatly benefit the food industry. By scaling down the assay to microtiter plates both, time and materials can be conserved. Use of microtiter plates would also allow for numerous samples to be assayed simultaneously. The goal for developing the microtiter plate assay is to obtain results more rapidly while maintaining the accuracy and precision of the AOAC ( method 940.33I) tube assay.

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