Corinthian Currants Promote the Expression of Paraoxonase-1 and Enhance the Antioxidant Status in Serum and Brain of 5xFAD Mouse Model of Alzheimer's Disease.

Paraoxonase-1 (PON1), a serum antioxidant enzyme, has been implicated in Alzheimer's disease (AD) pathogenesis that involves early oxidative damage. Corinthian currants and their components have been shown to display antioxidant and other neuroprotective effects in AD. We evaluated the effect of a Corinthian currant paste-supplemented diet (CurD), provided to 1-month-old 5xFAD mice for 1, 3, and 6 months, on PON1 activity and levels of oxidation markers in serum and the brain of mice as compared to a control diet (ConD) or glucose/fructose-matched diet (GFD). Administration of CurD for 1 month increased PON1 activity and decreased oxidized lipid levels in serum compared to ConD and GFD. Longer-term administration of CurD did not, however, affect serum PON1 activity and oxidized lipid levels. Furthermore, CurD administered for 1 and 3 months, but not for 6 months, increased PON1 activity and decreased free radical levels in the cortex of mice compared to ConD and GFD. To probe the mechanism for the increased PON1 activity in mice, we studied the effect of Corinthian currant polar phenolic extract on PON1 activity secreted by Huh-7 hepatocytes or HEK293 cells transfected with a PON1-expressing plasmid. Incubation of cells with the extract led to a dose-dependent increase of secreted PON1 activity, which was attributed to increased cellular PON1 expression. Collectively, our findings suggest that phenolics in Corinthian currants can increase the hepatic expression and activity of antioxidant enzyme PON1 and that a Corinthian currant-supplemented diet during the early stages of AD in mice reduces brain oxidative stress.

Mechanistic insight into the capacity of natural polar phenolic compounds to abolish Alzheimer's disease-associated pathogenic effects of apoE4 forms.

Polar phenols found in plant foods have been suggested to act protectively against pathogenic processes underlying Alzheimer's disease (AD), such as oxidative stress. The major risk factor for AD is apolipoprotein E4 (apoE4) and apoE4 forms can affect AD-related processes. It was shown previously that the hereditary apoE4 mutant apoE4[L28P], as well as the apoE4 fragment apoE4-165, induce neuronal oxidative stress. The effect of polar phenols on AD-related pathogenic functions of apoE4 forms is largely unexplored. The aim was to examine the effect of Corinthian currant polar phenolic extract and specific polar phenols resveratrol, quercetin, kaempferol and epigallocatechin gallate on AD-related functions of apoE4 forms. The polar phenolic extract and the individual compounds restored the viability of human neuroblastoma SK-N-SH cells in the presence of lipoprotein-associated apoE4[L28P] and prevented changes in cellular redox status. Furthermore, resveratrol, quercetin, kaempferol and epigallocatechin gallate prevented redox status changes induced by Aß42 uptake in SK-N-SH cells treated with lipid-free apoE4[L28P] or apoE4-165. Investigation of the molecular mechanism of action of these polar phenols showed that resveratrol prevented cellular Aß42 uptake via changes in cell membrane fluidity. Interestingly, kaempferol prevented cellular Aß42 uptake by apoE4[L28P], but not by apoE4-165, due to a modulating effect on apoE4[L28P] secondary structure and stability. The action of quercetin and epigallocatechin gallate could be attributed to free radical-scavenging or other protective activity. Overall, it is shown for the first time that natural compounds could modify the structure of apoE4 forms and ameliorate AD-related pathogenic effects of apoE4 forms.

Corinthian currants finishing side-stream: Chemical characterization, volatilome, and valorisation through wine and baker's yeast production-technoeconomic evaluation.

The industrial currants finishing generates a considerable amount of side-stream (FSS) with great potential for biotechnological exploitation. The chemical composition of FSS generated from the premium quality Vostitsa currants was studied. Its use for wine making (at low temperatures, using both free and immobilized yeast) combined with baker's yeast production (with minor nutrient supplementation), is also proposed. Analysis showed that FSS has a rich volatilome (including Maillard reaction/lipid degradation products), increased antioxidant capacity, and total lipid and phenolic contents, compared to the marketable product (currants). However, acidity levels and the presence of specific volatiles (such as acetate esters and higher alcohols) may be indicative of microbial spoilage. The wines made from FSS were methanol free and contained higher levels of terpenes (indicating hydrolysis of bound forms) and fermentation-derived volatiles, compared to FSS. A preliminary technoeconomic analysis for integrated wine/baker's yeast industrial production, showed that the investment is realistic and worthwhile.

Water-soluble vitamin content of sun-dried Corinthian raisins (Vitis vinifera L., var. Apyrena).

BACKGROUND: Corinthian raisins are dried vine products, representing approximately 3% of the world dried vine fruit production. The majority of Corinthian raisin production is of Greek origin. Studies on the B-group vitamin content of Corinthian raisins produced in Greece as well as on the effect of region and cultivation altitude on the B-group vitamin content are absent in the literature. RESULTS: Corinthian raisin vitamin content was evaluated by reversed-phase high-performance liquid chromatography after acid and enzymatic hydrolysis in terms of raisin subcategory, i.e. regions of cultivation, crop-to-crop variations, and cultivation altitude. Eight vitamers from five different vitamins were identified and quantified in Corinthian raisins. Vitamin B3 (0.77-2.82 g × 10-2 × kg-1 ) was found to predominate, followed by B6 (0.27-0.37 g × 10-2 × kg-1 ), B1 (0.19-0.22 g × 10-2 × kg-1 ), and B2 (0.10-0.15 g × 10-2 × kg-1 ). B9 content was up to 7.1 g × 10-5 × kg-1 . Minor differences were observed among regions of cultivation, cultivation altitude and crop-to-crop variations. CONCLUSION: This study revealed the presence of several water-soluble vitamins in Corinthian raisins that, together with other health-promoting micronutrients present in the product, further reinforce its place as part of a healthy diet. © 2019 Society of Chemical Industry.

Corinthian raisins (Vitis vinifera L., var. Apyrena) antioxidant and sugar content as affected by the drying process: a 3-year study.

BACKGROUND: Corinthian raisins or Corinthian currants are dried grape products that account for approximately 3% of dried vine fruit production worldwide. Greece is the major Corinthian raisin producer. In this study Corinthian raisins were produced by applying two traditional drying methods, i.e. sun and shade drying. The drying process effect on the raisin phytochemical and sugar content was assessed; samples obtained over three consecutive crops were evaluated to prevail over climatic condition variations. RESULTS: Total phenolic, flavanol, and anthocyanin content were higher in Corinthian raisins dried under shade as compared with the sun-dried ones; individual anthocyanidin-3-O-glucosides were also qualitatively and quantitatively higher under shade drying in most cases. Differences were observed in Corinthian raisin phytochemical content among the crop years evaluated. The drying process applied did not discriminatively affect the sugar content of Corinthian raisin. CONCLUSION: Drying under shade was proven superior to sun drying with respect to Corinthian raisin phytochemicals and could be considered as an appealing drying method for the production of dried raisins and perhaps other dried fruits. © 2018 Society of Chemical Industry.

Anthocyanins content and antioxidant capacity of Corinthian currants (Vitis vinifera L., var. Apyrena).

Corinthian currants are dried vine products used in the Mediterranean diet. Currant is produced almost exclusively in Southern Greece; three commercial subcategories are recognised, i.e. Vostizza, Gulf, and Provincial. Thirty-five batches of Corinthian currants obtained over two crop years and belonging to the several subcategories, were evaluated in terms of total and individual anthocyanins, total phenolics and antioxidant capacity. Variations were observed among batches, cultivation regions, and subcategories with respect to the studied parameters. Up to five anthocyanidin-3-O-glucosides were identified and quantified in currants for the first time. Overall, Vostizza currants presented the higher total anthocyanins content and the lower total phenolics content and antiradical activity; reducing power showed no differentiation among currants subcategories and crop years studied. Though the contribution of currants to the daily anthocyanin intake is rather low, the combined presence of other phenolics as well, makes this product a source of hydrophilic antioxidants.