Influence of Molecular Weight Fractions Isolated from Roasted Malt on the Enzyme Activities of NADPH−Cytochrome c−Reductase and Glutathione-S-transferase in Caco-2 Cells

Abstract

In the present study, water-soluble nonenzymatic browning products (melanoidins) formed in roasted malt were separated, quantified, and investigated for their effects on detoxifying mechanisms in intestinal Caco-2 cells. The melanoidins were prepared from roasted malt by hot water extraction, and the water-soluble compounds were separated into different molecular weight (MW) fractions by gel filtration chromatography. By monitoring the effluent at 300 nm, seven molecular fractions I-VII were consecutively collected, revealing that approximately 2.3% of the water-soluble compounds had mean MWs between 10000 and 30000 Da. Thus, the bulk of water-soluble malt melanoidins consisted of MW > 30000 Da, among which approximately 58% showed mean MWs between 60000 Da and 100000 Da, whereas approximately 32% exhibited mean MWs of 200000 Da. Biotransformation enzyme activities of NADPH-cytochrome c-reductase (CCR) and glutathione-S-transferase (GST) were analyzed in Caco-2 Cells after 48 h of exposure to the different MW fractions. The low MW fraction of 10000 Da was most effective in activating the CCR and the GST activities (+122 and +33% vs control, respectively). The majority of the mid molecular weight compounds tested showed an activating effect on CCR activity and an inhibitory effect on GST activity. These effects were most pronounced for compounds of up to 70000 Da and >200000 Da but less distinct for fractions of an average molecular weight of 100000 Da.

Five years of research on health risks and benefits of Maillard reaction products: An update

“…Melanoidin fractions of different molecular weights prepared from roasted malt by hot water extraction followed by gel filtration chromatography were demonstrated to modulate the CCR and GST activity in human intestinal Caco-2 cells. Again, the LMW fraction of 10 kDa was most effective in enhancing the CCR and the GST activity (+ 122% and + 33% vs. control, respectively) [27].…”

“…Effects on the chemopreventive potential Induction of chemopreventive enzymes in in vitro and in vivo systems by model and food melanoidin mixtures [5,11,26,27] as well as by novel, chemically identified compounds [28,29,30].…”

Melanoidins produced by the Maillard reaction: Structure and biological activity

“…More recent reports, however, have indicated that melanoidins include a LMW fraction, too (Cosovic et al, 2010;Faist, Lindenmeier, Geisler, Erbersdobler, & Hofmann, 2002;Glosl et al, 2004). In real foods, most of the melanoidins have been shown to be HMW compounds.…”

“…It is known that MRPs contain high concentrations of Ne-carboxymethyllysine (CML), a compound known to induce CCR and inhibit GST Faist, Lindenmeier et al, 2002), which may partially explain the effects of melanoidin fractions on CCR and GST . However, this xenobiotic enzyme-modulating activity cannot be entirely explained by the presence of CML, as it seems various reaction products formed during the heat-treatment of food and model systems, such as MRPs and native polyphenols, also contribute to this effect, which could help to explain the discrepancies in the above investigations.…”

Coordinated induction of GST and MRP2 by cAMP in Caco-2 cells: Role of protein kinase A signaling pathway and toxicological relevance

“…Total cellular membranes were prepared by differential centrifugation as described (García et al, 2001) and resuspended in 100 μl of 0.3 M sucrose (with protease inhibitors). In order to evaluate GST protein content and activity, cytosolic fractions from Caco-2 cells were obtained by ultracentrifugation as described previously (Faist et al, 2002).…”