Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

In vitro anti‐HSV‐2 activity and mechanism of action of proanthocyanidin A‐1 from Vaccinium vitis‐idaea

The aim of this study was to investigate the in vitro anti‐HSV‐2 activity and mechanism of action of proanthocyanidin A‐1, a compound isolated from Vaccinium vitis‐idaea Linn (Ericaceae). The results demonstrated that proanthocyanidin A‐1 exhibited anti‐HSV‐2 activity. The IC₅₀ value for the XTT assay was 73.3 ± 14.5 µM and the IC₅₀ and IC₉₀ values for the plaque reduction assay were 41.9 ± 2.0 and 62.8 ± 6.3 µM respectively. Proanthocyanidin A‐1 showed no cell cytotoxic effect at concentrations that blocked HSV‐2 infection, with a CC₅₀ value of 282.1 ± 27.5 µM . The mechanism studies demonstrated that proanthocyanidin A‐1 did not reduce viral infectivity but inhibited viral attachment and penetration and affected the late stage(s) of HSV‐2 infection. It was concluded that proanthocyanidin A‐1 suppressed HSV‐2 infection through many modes of action and thus merits further investigation. Copyright © 2004 Society of Chemical Industry     

Absorption and twenty‐four‐hour metabolism time‐course of quercetin‐3‐O‐glucoside in rats,in vivo

Rats were meal‐fed a semi‐synthetic diet, with or without quercetin 3‐O‐glucoside (Q3G; 100 mg per meal) and groups of three were killed either fasting, or at 2, 5 and 24 post‐feeding. Flavonoids and their metabolites in the diet, stomach contents, small intestinal lumen and mucosa, caecal contents and plasma were determined by LC/MS. Q3G was not hydrolysed in the stomach, but deglycosylation and further metabolism occurred in the small intestinal mucosa. At least 17 flavonoid glucuronides were identified in the lumen and mucosa, with evidence of time‐dependent changes such as de‐ and re‐glucuronidation. Quercetin mono‐sulphate was also detected in the small intestinal contents. Metabolites were still present in tissue and plasma 24 h after feeding. There was also evidence of complex microbial processing of Q3G in the caecal lumen with the appearance of at least one methylquercetin‐mono‐glucuronide, mono‐sulphate unique to this site in the gut, together with phenolic acid derivatives. Intestinal flavonoid metabolism is thus a very complex process in mammals, involving both enterocytes and bacteria. Copyright © 2004 Society of Chemical Industry     

(+)‐Catechin and (−)‐epicatechin levels of concentrated and ready‐to‐drink grape juices through storage

Commercial concentrated Concord (CCJ) and Isabel (CIJ) grapes juices were stored at 4–5 °C while pasteurised ready‐to‐drink juices of the same grape cultivars (PCJ and PIJ) were kept at 20–25 °C under indirect light for 10 months, simulating industrial storage conditions. (+)‐catechin preservation during storage ranged between 63% (PCJ) and 52% (PIJ); (?)‐epicatechin retention was of 32% (CCJ) and 15% (CIJ). Total phenols retention ranged from 93% (CCJ) to 84% (PCJ) and radical scavenging activity (RSA) from 87% (PIJ) to 85% (CCJ and PCJ). Concentrated juices showed higher monomeric flavan‐3‐ols amounts and CCJ depicted superior phenolic contents. PIJ yielded the highest RSA during storage per phenolic unit. Process and storage impacted flavan‐3‐ols and not total phenolics and RSA during 10‐month ageing.