► Grape seed extracts present good affinity to bind to proteins. ► Association strength of tannin–protein interactions changes with tannin structure. ► Samples at harvest have higher ability to bind ...to proteins than at post-veraison. ► Tannin–protein interactions are not the only explanation for the astringency.
The ability of grape seed extracts to bind to bovine serum albumin (BSA) and α-amylase was studied by fluorescence quenching of protein intrinsic fluorescence and nephelometry. The influence of grape seed ripeness on astringency was also evaluated. From the spectra obtained, the modified Sterm–Volmer (Kapp) and the bimolecular quenching constants were calculated. Results showed that grape seed extracts had good affinity for proteins. The association strength of tannin–protein interactions varied with changes in tannin structure associated with the degree of ripeness affecting the binding/quenching process. In all cases studied, higher values of Kapp were obtained in samples at harvest which have greater ability to bind to proteins than have samples at post-veraison time. Nephelometric assays show the same trend as do fluorescence quenching studies. A possible explanation for this is that, as seeds ripen, their tannins increase in molecular mass, which relates to an increase in hydrophobicity of the molecules, and this increases protein affinity. However, that is contrary to the reported decrease in astringency of grape seeds during maturity. This indicates that tannin–protein interactions are not the only explanation for the complex sensations of astringency of grape seeds.
Grape seed polyphenolic extract (GSPE) rich in the flavan-3-ols (+)-catechin and (−)-epicatechin beneficially modulates Alzheimer’s Disease phenotypes in animal models. The parent molecules in the ...extract are converted to a series of methylated and glucuronidated derivatives. To fully characterize these metabolites and establish a robust quantitative assay of their levels in biological fluids, we have implemented a partial synthetic approach utilizing chemical methylation followed by enzymatic glucuronidation. Liquid chromatography/time-of-flight mass spectrometry (LC-TOF-MS) and nuclear magnetic resonance (NMR) spectroscopy were used to assign unequivocal structures to the compounds. An analytical method using solid-phase extraction and LC-MS/MS in selective reaction monitoring mode (SRM) was validated for their quantitation in plasma. These studies provide a basis for improvements in future work on the bioavailability, metabolism, and mechanism of action of metabolites derived from dietary flavan-3-ols in a range of interventions.
The present study aimed to investigate the effects of different levels of dietary supplementation of grape seed extract (GSE) on growth performance, carcass traits and antioxidant status of rabbits ...under heat stress conditions (temperature humidity index 87.5–93.5). Weaned male New Zealand White (NZW) rabbits about 6 weeks old (n = 144, mean body weight 705 g) were randomly allotted to four dietary groups. The Control group was fed a basal diet without GSE; the experimental groups received the basal diet with 100, 200 and 300 mg GSE/kg (Groups 100 GSE, 200 GSE and 300 GSE, respectively). The experimental period lasted for 8 weeks. Compared with other groups, rabbits of Group 300 GSE had the best body weight gain and feed conversion ratio and the lowest mortality. Dietary GSE improved carcass weight, percentage of hot carcass, intestine and edible giblets, while total non-edible parts were reduced (p ≤ 0.05) in comparison with the Control group. In Groups 200 GSE and 300 GSE, plasma total protein, albumin and globulin were increased (p ≤ 0.05). In contrast, all supplementation levels of GSE reduced (p ≤ 0.05) the plasma concentrations of total lipids, total cholesterol, triglycerides and low-density lipoproteins. Antioxidant enzymes of rabbits (superoxide dismutase, catalase, glutathione peroxidase, glutathione transferase) and total antioxidant capacity in blood were increased (p ≤ 0.05) by adding dietary GSE. However, malondialdehyde was reduced (p ≤ 0.001) with increasing GSE levels. Generally, grape seeds can be considered as rich source of phenolic and flavonoid compounds. The results of the study revealed that all tested levels of GSE were useful as a natural protection against heat stress to maintain performance, carcass traits and antioxidant status and could reduce the negative effects of heat stress in rabbits.
Grape seeds full with oil and also rich in hypoglycemic ingredients. This study is to improve the comprehensive utilization of grape seeds and the quality of grape seeds oil. Extract water soluble ...active substances before extracting oil from grape seeds, which show the grape seeds in water soluble extracts containing TP, TC, PC contents, respectively, are 171.1 ± 1.1, 658.8 ± 0.2, 482.3 ± 0.2 (mg GSAE/g). Also we found GSAE samples containing catechin and epicatechin were 44.12 ± 0.21 mg/mL, 111.23 ± 1.29 mg/g, GSAE against α‐glucosidase IC50 was 25.25 ± 0.53 g/mL and GSAE against α‐amylase IC50 was 66.68 ± 1.1 g/mL, both were competitive way, the effects of Inhibitory were obviously better than that of acarbose. In addition, our process guarantee the fat ingredients remained in the grape seeds and not reduce functional components of oil, our study suggests that GSAE can be used to develop functional foods for prevention and treatment of diabetes and its complications.
Practical Application
Grape seeds, by‐products of brewing wines, are rich in polyphenol and other ingredients. The optimized extraction, composition of constituents and hypoglycemic activity were investigated in this study. The results showed that grape seeds were rich in anthocyanins and polyphenols and other active substances, inhibited α‐glucosidase and α‐amylase activity, which provide background and practical knowledge for the deep‐processed products of grape seeds with high added value.
Two procyanidin fractions, namely oligomers and polymers isolated from grape seed methanolic extract were characterized. Phenolic composition and procyanidin purity of these fractions were determined ...by normal-phase and reverse-phase HPLC, thioacidolysis-HPLC, ESI-MS analyses, formaldehyde–HCl precipitation and elemental analysis. Antioxidant activities of these fractions and other well-known antioxidants were measured using xanthine–xanthine oxidase system for generating superoxide radical ({O2-}), the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical method and the Fenton system for generating hydroxyl radical (HO). The results showed that both oligomeric and polymeric procyanidin fractions were highly pure, with the degree of polymerization ranging from 2 to 17–18 and 12 to 32–37, respectively. On the basis of molar concentration, polymeric procyanidins appeared the highest antioxidant activities, followed by oligomeric procyanidins, whereas catechins presented a lower antioxidant activity than its oligomers and polymers. These results indicate that the antioxidant activities of grape seed procyanidins are positively related to their degree of polymerization. Moreover, grape seed procyanidins presented higher antioxidant activities than other well-known antioxidants such as vitamin C, suggesting that grape seed procyanidins might be of interest to be used as alternative antioxidants.
To increase the potential and better exploring of grape seeds that are an important wine-industrial waste, oils of ten traditional Portuguese grape varieties were evaluated in relation to their ...vitamin E content (tocopherols and tocotrienols), fatty acid profile, as well as, antioxidant properties. Our results showed that the grape-seed oils were a good source of γ-tocotrienol (499–1575mg/kg), α-tocopherol (85.5–244mg/kg) and α-tocotrienol (69–319mg/kg). Concerning fatty acid profile, linoleic (C18:2cc), oleic (C18:1), palmitic (C16:0) and stearic (C18:0) acids were the predominant. Grape-seed oils demonstrated to be a good source of polyunsaturated fatty acids (PUFAs) (63.64–73.53%), whereas monounsaturated fatty acid (MUFA) and saturated fatty acid (SFA) ranged between 14.19–21.29% and 11.64–14.94%, respectively. Interesting values of DPPH and ABTS radical scavenging activities were also obtained. This study demonstrated that these seeds may be reused and their oils incorporated in other food products, taking into account the compounds with positive effects on human health that are present in their composition.
► Fatty acid and vitamin E compositions of ten grape-seed oils were determined. ► Grape-seed oils are rich in unsaturated fatty acids and particularly in linoleic acid. ► Grape-seed oils are a good source of γ-tocotrienol, α-tocopherol and α-tocotrienol. ► Grape-seed oils presented interesting DPPH and ABTS radical scavenging activities.
PURPOSE: The aims of this study were to evaluate the antihypertensive effectiveness of different doses of grape seed polyphenols in cafeteria diet-fed hypertensive rats (CHRs) and to establish the ...mechanism involved in the blood pressure (BP) lowering effect of these compounds in this experimental model of metabolic syndrome (MS). METHODS: Male 8-week-old Wistar rats were fed cafeteria or standard (ST) diet for 10 weeks. After this, the antihypertensive effect of a single oral administration of a polyphenol grape seed extract (GSPE) was tested at different doses (250, 375 and 500 mg/kg) in CHRs. BP was recorded before and 2, 4, 6, 8, 24 and 48 h post-administration. The hypotensive effect of GSPE was also proved in ST diet-fed rats. Additionally, in other experiment, CHRs were orally administered 375 mg/kg GSPE. Four hours post-administration, the rats were intraperitoneally administrated 30 mg/kg NG-nitro-L-arginine methyl ester (L-NAME) or 5 mg/kg indomethacin inhibitors of nitric oxide (NO) and prostacyclin synthesis, respectively. BP was recorded initially and 6 h post-administration. RESULTS: GSPE produced a decrease in SBP and DBP, the most effective dose (375 mg/kg) showing an antihypertensive effect in CHRs similar to the drug captopril, and did not affect BP of ST diet-fed rats. The antihypertensive effect was completely abolished by L-NAME and partially inhibited by indomethacin. CONCLUSIONS: GSPE acts as an antihypertensive agent in a rat model of hypertension associated with MS. The change in endothelium-derived NO availability is one of the mechanisms involved in the antihypertensive effect of GSPE in CHRs. Additionally, endothelial prostacyclin contributes to the effect of GSPE on arterial BP.
Grape seed powders, byproducts of either winemaking or grape processing, were prepared from
Vitis vinifera (Merlot and Chardonnay) and
Vitis rotundifolia (Muscadine) species. Water, methanol, acetone ...and ethanol were tested as extractants on Muscadine seed powder. Antioxidant activities of grape seeds and skins were determined as oxygen radical absorbance capacity with phycoerythrin (ORAC
PE) for both grape species. The results indicated that aqueous solutions of ethanol, methanol or acetone were better than a single-compound solvent system for extraction of total phenols from Muscadine seed powder. Antioxidant capacities of Chardonnay, Merlot and Muscadine grape seeds were 638, 345 and 311
μmol Trolox equivalent (TE)/g dry weight in decreasing order
(
P
<
0.05
)
, respectively. (ORAC
PE) values of Chardonnay and Merlot grape skin powders were similar. Total phenol contents of extracts used to determine the antioxidant capacities of grape seeds and skins had a trend similar to (ORAC
PE) values. Our results showed that health functional components of grape skin and seed powders from the tested byproducts of grape/wine industry are comparable to those of fruits and vegetables.
It has been studied whether seeds of the grape varieties Lydia, Isabella, Moldova, Baco, Odesa Black, Cabernet, and the blends N 1 – Muscat Blanc + Noah (50:50), N 2 – Riesling + Chardonnay (50:50), ...and N 3 – Chardonnay + Sukholimansky (50:50) are promising raw materials for fat-and-oil products and cosmetics. The study provides a scientific basis for a technology for manufacturing oils from several grape seed varieties. For seeds from different grape cultivars, appropriate process conditions have been selected to obtain extra virgin oil by cold pressing. The most practical conditions for wet-heat treatment of crushed seeds of the cultivars Cabernet, Moldova, Baco, Odesa Black, and blend N 3 (Chardonnay + Sukholimansky, 50:50) are a temperature of 40 °C and a duration of 10 min. In contrast, seeds of Lydia, Isabella, and blends No. 1 (Muscat Blanc + Noah, 50:50) and N 2 (Riesling + Chardonnay, 50:50) should be treated at the same temperature for 20 min. While extracting oil by pressing, it is recommended to avoid heating the treated crushed seeds (extraction mash) to over 30 °C for more than 5 min. The research results have shown that in the seeds of Lydia, Isabella, Moldova, Baco, Odesa Black, and Cabernet grapes, and those of blends N 1 (Muscat Blanc + Noah, 50:50), N 2 (Riesling + Chardonnay, 50:50), and N 3 (Chardonnay + Sukholimansky, 50:50), the oil content is 14–20 %.
This study was carried out to evaluate the effect of heating and physical conditions of grape seeds on the antioxidant activity of their extracts. Two forms of grape seeds, whole and powdered forms, ...were heated at four different temperatures −50, 100, 150 and 200
°C. After heating, grape seeds were extracted with 70% ethanol (0.1
g grape seed/10
mL of 70% ethanol), and total phenol contents (TPC), radical scavenging activity (RSA) and reducing power of the extracts were determined. Thermal treatment of grape seed increased the antioxidant activity of extracts. The maximum TPC and RSA of whole grape seed extract (WGSE) were achieved when the seeds were heat-treated at 150
°C for 40
min, while that of powdered grape seed extract (PGSE) were at 100
°C for 10
min, and were greater than that of the non-treated control. Also, the reducing powers of WGSE and PGSE slightly increased at the conditions. According to the GC-MS analysis, several low-molecular-weight phenolic compounds such as azelaic acid, 3,4-dihydroxy benzoic acid, and
o-cinnamic acid were newly formed in the WGSE heated at 150
°C for 40
min. There were slight differences in the kinds of phenolic compounds between non-heated and heated GSE. In HPLC analysis, the contents of gallocatechin gallate and caffeine in GSE significantly increased by heat treatment. These results indicated that antioxidant activity of GSE was affected by heating conditions (temperature and time) and physical conditions of grape seeds at the time of heat treatments.
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