Elena Verzelloni

Antiglycative and neuroprotective activity of colon-derived polyphenol catabolites

SCOPE Dietary flavonoids and allied phenolic compounds are thought to be beneficial in the control of diabetes and its complications, because of their ability to inhibit oxidative stress, protein glycation and to act as neuroprotectants. Following ingestion by humans, polyphenolic compounds entering the large intestine undergo extensive metabolism by interaction with colonic microbiota and it is metabolites and catabolites of the parent compounds that enter the circulatory system. The aim of this study was to investigate the inhibitory activity of some colonic microbiota-derived polyphenol catabolites against advanced glycation endproducts formation in vitro and to determine their ability, at physiological concentrations, to counteract mild oxidative stress of cultured human neuron cells. METHODS AND RESULTS This study demonstrated that ellagitannin-derived catabolites (urolithins and pyrogallol) are the most effective antiglycative agents, whereas chlorogenic acid-derived catabolites (dihydrocaffeic acid, dihydroferulic acid and feruloylglycine) were most effective in combination in protecting neuronal cells in a conservative in vitro experimental model. CONCLUSION Some polyphenolic catabolites, generated in vivo in the colon, were able in vitro to counteract two key features of diabetic complications, i.e. protein glycation and neurodegeneration. These observations could lead to a better control of these events, which are usually correlated with hyperglycemia.

Effect of dietary melanoidins on lipid peroxidation during simulated gastric digestion: their possible role in the prevention of oxidative damage.

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(2+) 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.

From balsamic to healthy: Traditional balsamic vinegar melanoidins inhibit lipid peroxidation during simulated gastric digestion of meat

In this work traditional balsamic vinegar (TBV) melanoidins were characterized for chemical composition and antioxidant activity and their anti-peroxidative effect during an in vitro gastric digestion of turkey meat was studied. The most important constituents of TBV melanoidins were carbohydrates (51% w/w) of which glucose (35% w/w) and fructose (10% w/w) are the main representatives, hydroxymethylfurfural (7.2% w/w), phenolic groups (4.6% w/w) and proteins (1.2% w/w). The antioxidant capacity of melanoidins was studied, measuring lipid hydroperoxides and secondary lipoxidation products formed during in vitro gastric digestion of turkey meat. The most important mechanisms in their antioxidant activity resulted radical scavenging and Fe(2+)-chelating activities. Pepsin inhibiting ability has been excluded. TBV melanoidins were also able to bind heme under gastric conditions potentially preventing its absorption and prooxidant and cytotoxic effects. Our results support the idea that TBV melanoidins may have a role in oxidative damage prevention. Fe(2+)-chelating and heme-binding activities as well as mechanisms of antioxidant activity of TBV melanoidins were also compared with coffee, barley coffee and dark beer melanoidins.

The Type and Concentration of Milk Increase the in Vitro Bioaccessibility of Coffee Chlorogenic Acids

Coffee with different types and concentrations of milk was digested with pepsin (2 h) and pancreatin (2 h) to simulate gastropancreatic digestion. Chlorogenic acids (CGAs) were determined by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry in ultrafiltrate (cutoff 3 kDa) to evaluate their bioaccessibility. After digestion, bioaccessible CGAs decreased from 80.2 to 53.0 and 69.5 μmol/200 mL in coffee without milk and coffee-whole milk, respectively. When whole, semiskimmed, skimmed, or diluted milk were present, the increase in bioaccessibility was dependent on fat content (r = 0.99, p < 0.001). No relationship was observed between bioaccessibility and proteins, carbohydrates, and calcium content. The addition of milk to coffee caused an immediate decrease in the bioaccessibility due to CGAs binding to proteins. After digestion, 86-94% of bound CGAs remained in the high molecular weight fraction. Casein bound 5-caffeoylquinic acid with high affinity (K(D) of 37.9 ± 2.3 μmol/L; n = 0.88 ± 0.06).

Sugar conversion induced by the application of heat to grape must.

Two lots of the grape Trebbiano cultivar were harvested from the same vineyard 15 days apart, and their musts were cooked in an open stainless steel pan directly heated by fire; the kinetics of formation or disappearance of key constituents was then monitored for at least 16 h. From an engineering standpoint, the vessel behaved like a nonisothermal batch reactor in which the volume of the grape must necessarily decreased while its composition changed profoundly as a result of chemical reactions. Brix, total titratable acids, acetic acid, malic acid, lactic acid (d and l), pH, water activity, 5-HMF, and phenolic and radical-scavenging compounds were proposed as markers of the extent of cooking for which water vaporization and sugar degradation were identified as the two main driving factors. Acid-catalyzed dehydration was hypothesized as the predominant mechanism for sugar degradation, assuming a direct role of water vaporization; however, contributions of Maillard degradation pathways and other parallel reversible reactions were also hypothesized. Fractional conversion of 5-HMF and radical-scavenging compounds were proposed as quantitative markers for the extent of sugar degradation at, respectively, the early and advanced stages of cooking. Selectivity indices were also proposed as a performance criterion to design cooking processes in relation to sugar degradation.

Pomegranate ellagitannins inhibit α-glucosidase activity in vitro and reduce starch digestibility under simulated gastro-intestinal conditions

Abstract Pomegranate extract was tested for its ability to inhibit α-amylase and α-glucosidase activity. Pomegranate extract strongly inhibited rat intestinal α-glucosidase in vitro whereas it was a weak inhibitor of porcine α-amylase. The inhibitory activity was recovered in an ellagitannins-enriched fraction and punicalagin, punicalin, and ellagic acid were identified as α-glucosidase inhibitors (IC50 of 140.2, 191.4, and 380.9 μmol/L, respectively). Kinetic analysis suggested that the pomegranate extract and ellagitannins inhibited α-glucosidase activity in a mixed mode. The inhibitory activity was demonstrated using an in vitro digestion system, mimicking the physiological gastro-intestinal condition, and potatoes as food rich in starch. Pre-incubation between ellagitannins and α-glucosidase increased the inhibitory activity, suggesting that they acted by binding to α-glucosidase. During digestion punicalin and punicalagin concentration decreased. Despite this loss, the pomegranate extract retained high inhibitory activity. This study suggests that pomegranate ellagitannins may inhibit α-glucosidase activity in vitro possibly affecting in vivo starch digestion.

Relationship between the chemical composition and the biological activities of food melanoidins

The relationship between the chemical composition and the biological activities of food melanoidin-rich fractions was investigated. Melanoidin-rich fractions were extracted using ultrafiltration (a 10 kDa cut-off) from coffee, barley coffee, dark beer, and traditional balsamic vinegar. All the food melanoidin-rich fractions were formed mainly of carbohydrates, phenolic compounds, and proteins. In dark beer, barley coffee, and traditional balsamic vinegar melanoidins, glucose was the most abundant sugar incorporated into melanoidins. Coffee melanoidins contained the largest amount of phenolic groups, followed by traditional balsamic vinegar melanoidins. The radical scavenging, Fe2+-chelating, and heme binding abilities of food melanoidins were investigated under gastric conditions. The melanoidinrich fraction extracted from coffee was the most active, showing the highest radical scavenging, Fe2+-chelating, and heme binding activities, compared to barley coffee, dark beer, and traditional balsamic vinegar. The radical scavenging and Fe2+-chelating abilities were assigned to the phenolic groups present in food melanoidins.