pubs.acs.org/JAFC © XXXX American Chemical Society J. Agric. Food Chem. XXXX, XXX, 000–000 A DOI:10.1021/jf903701h Effect of Dietary Melanoidins on Lipid Peroxidation during Simulated Gastric Digestion: Their Possible Role in the Prevention of Oxidative Damage DAVIDE TAGLIAZUCCHI,* ELENA VERZELLONI, AND ANGELA CONTE Department of Agricultural and Food Sciences, University of Modena and Reggio Emilia, Via Amendola 2, 42100 Reggio Emilia, Italy The ability of high molecular weight melanoidins extracted from coffee, barley coffee, and dark beer to inhibit lipid peroxidation during simulated gastric digestion of turkey meat has been investigated. Results showed that melanoidins decrease the synthesis of lipid hydroperoxides and secondary lipoxidation products. Coffee melanoidins at 3 mg/mL reversed the reaction and broke down hydroperoxides to concentrations lower than the initial value. Barley coffee and dark beer melanoidins were less effective, and even at 12 mg/mL did not reverse the reaction. The proposed mechanism of action involved Fe 2þ chelating capacity, heme-binding ability, and radical-scavenging activity. Melanoidins were characterized for their content in total proteins, carbohydrates, and phenolics, and the relationship between the chemical composition and the antioxidant activity of dietary melanoidins was investigated. Coffee melanoidins, which contain more phenolics and proteins with respect to the other melanoidins, showed greater antioxidant activity with respect to the other melanoidins tested. KEYWORDS: Food melanoidins; lipid peroxidation; gastric fluid; free radical; antioxidants; turkey meat; heme INTRODUCTION Atherosclerosis and related cardiovascular diseases are the most widespread pathologies in the Western world, where they are the main cause of morbidity and mortality. The molecular mechanism of atherosclerosis is currently unknown, but it is supposed that it could be a multifactorial disease, and several risk factors, including a time-dependent response to arterial injury, low-density and remnant lipoprotein oxidation, and postprandial response to eating, are hypothesized to be involved ( 1 ). Consumption of a meal containing oxidized and oxidizable lipids gives rise to increased plasma levels of lipid hydroper- oxides ( 2 ) that can be incorporated into lipoproteins and thus act as initiators for further lipoprotein oxidation ( 1 , 2 ). Secondary lipoxidation products such as malondialdehyde (MDA) and 4- hydroxynonenal may be absorbed in the gastrointestinal tract and can be involved in the pathogenesis of some cardiovascular diseases ( 3 ). Lipid hydroperoxides and secondary lipoxidation products may be already present in oxidized food but, more interestingly, they may be generated during digestion of highly oxidizable foods such as red meat ( 4 ). Kanner and co-workers suggested that the stomach may act as a “bioreactor”, promoting lipid peroxidation, especially in gastric fluid, which contains dissolved oxygen and has a low pH, and particularly when the meal contains catalysts, such as free iron ions, a free heme group, or heme-containing proteins such as metmyoglobin ( 4 , 5 ). The idea that the gastrointestinal tract is the location for the protective activity of antioxidants was presented by Halliwell et al. ( 6). It has been observed that the consumption of a meal rich in oxidizable fat together with a rich source of antioxidants, such as red wine ( 7 ) or procyanidins ( 8), reduces the absorption of lipid hydro- peroxides and their secondary lipoxidation products as a conse- quence of the antioxidant effect of red wine polyphenols ( 4 , 5 ). Recently, scientific interest in the field of high molecular weight melanoidins has increased because of their varied biological activities and functional properties ( 9 ). Melanoidins are poly- meric brown compounds formed in the last stage of the Maillard reaction, and they are involved in the color, flavor, and texture of thermally treated foods ( 10 ). They are present in some widely consumed foods and beverages such as coffee, dark beer, sweet wine, traditional balsamic vinegar, cocoa, and bread ( 11 -13 ). Some important biological activities of food melanoidins are their antioxidant and chelating activities ( 14 , 15 ) as well as antimicro- bial ( 15 ) and antihypertensive ( 11 , 15 ) activities. Aim of This Work. The aim of this work was to verify the antioxidant effect of high molecular weight melanoidins extracted from coffee, barley coffee, and dark beer during in vitro gastric digestion of turkey meat. For the first time, the protective effect of dietary melanoidins versus lipid peroxidation during simulated gastric digestion was investigated. MATERIALS AND METHODS Materials. Ammonium ferrous sulfate, hemin (HmFe III ), hemoglo- bin, pepsin, 2,6-di-tert-butyl-4-methylphenol (BHT), thiobarbituric acid (TBA), trichloroacetic acid (TCA), 2,4,6-tripyridyl-S-triazine *Corresponding author (telephone þ39-0522-522060; fax þ39- 0522-522053; e-mail davide.tagliazucchi@unimore.it).