Kequan Zhou

Antioxidant rich grape pomace extract suppresses postprandial hyperglycemia in diabetic mice by specifically inhibiting alpha-glucosidase.

BackgroundPostprandial hyperglycemia is an early defect of type 2 diabetes and one of primary anti-diabetic targets. Treatment of postprandial hyperglycemia can be achieved by inhibiting intestinal α-glucosidase, the key enzyme for oligosaccharide digestion and further glucose absorption. Grape pomace is winemaking byproduct rich in bioactive food compounds such as phenolic antioxidants. This study evaluated the anti-diabetic potential of two specific grape pomace extracts by determining their antioxidant and anti-postprandial hyperglycemic activities in vitro and in vivo.MethodsThe extracts of red wine grape pomace (Cabernet Franc) and white wine grape pomace (Chardonnay) were prepared in 80% ethanol. An extract of red apple pomace was included as a comparison. The radical scavenging activities and phenolic profiles of the pomace extracts were determined through the measurement of oxygen radical absorbance capacity, DPPH radical scavenging activity, total phenolic content and flavonoids. The inhibitory effects of the pomace extracts on yeast and rat intestinal α-glucosidases were determined. Male 6-week old C57BLKS/6NCr mice were treated with streptozocin to induce diabetes. The diabetic mice were then treated with vehicle or the grape pomace extract to determine whether the oral intake of the extract can suppress postprandial hyperglycemia through the inhibition of intestinal α-glucosidases.ResultsThe red grape pomace extract contained significantly higher amounts of flavonoids and phenolic compounds and exerted stronger oxygen radical absorbance capacity than the red apple pomace extract. Both the grape pomace extracts but not the apple pomace extract exerted significant inhibition on intestinal α-glucosidases and the inhibition appears to be specific. In the animal study, the oral intake of the grape pomace extract (400 mg/kg body weight) significantly suppressed the postprandial hyperglycemia by 35% in streptozocin-induced diabetic mice following starch challenge.ConclusionThis is the first report that the grape pomace extracts selectively and significantly inhibits intestinal α-glucosidase and suppresses postprandial hyperglycemia in diabetic mice. The antioxidant and anti-postprandial hyperglycemic activities demonstrated on the tested grape pomace extract therefore suggest a potential for utilizing grape pomace-derived bioactive compounds in management of diabetes.

Chelating and radical scavenging activities of soy protein hydrolysates prepared from microbial proteases and their effect on meat lipid peroxidation

Three commercial microbial proteases, neutral protease from Bacillus subtilis (NP), validase from Aspergillus oryze (Val), and alkaline protease from Bacillus licheniformis (AP), were investigated for producing antioxidant hydrolysates from soy protein. The resulting hydrolysates were fractioned by sequential ultrafiltration and their antioxidant properties were examined. All the 12 hydrolysate fractions showed noticeable oxygen radical absorbance capacity (ORAC) but significantly varied from 23.8 to 83.8 micromol Trolox equivalents (TE)/g. The hydrolysates also possessed significantly different 1,1-diphenyl-2-picrylhydrazyl (DPPH()) scavenging activities and transition metal chelating activities. Three fractions with strong antioxidant activities, NP-F1, Val-F1, and AP-F3, were incorporated into ground beef to determine their dose-response on lipid peroxidation during 15-day storage. AP-F3 and NP-F1 but not Val-F1 significantly reduced meat lipid peroxidation by 20.1% and 12.9%, respectively. Our results suggested that the commercial microbial proteases such as B. subtilis and B. licheniformis could be used to produce effective antioxidant hydrolysates from food proteins.

Effects of grape pomace antioxidant extract on oxidative stress and inflammation in diet induced obese mice.

Norton grape is one of the most important wine grapes in Southern and Midwestern states and generates massive pomace byproducts. The objective of this study is to characterize the antioxidant compounds and activity in Norton grape pomace extract (GPE) and further assess the potential health promoting properties of Norton GPE using an animal disease model. The total phenolic content and anthocyanins in Norton GPE were 475.4 mg of gallic acid equiv/g and 156.9 mg of cyanidin 3-glucoside equiv/g, respectively. Catechin and epicatechin in GPE were 28.6 and 24.5 mg/g, respectively. Other major antioxidants in GPE included quercetin (1.6 mg/g), trans-resveratrol (60 μg/g), gallic acid (867.2 μg/g), coutaric acid (511.8 μg/g), p-hydroxybenzoic acid (408.3 μg/g), and protocatechuic acid (371.5 μg/g). The antioxidant activity of GPE was evaluated by oxygen radical absorbance capacity (ORAC) and was 4133 μmol of Trolox equiv/g. Male diet-induced obese (DIO) mice were randomly divided to three treatment groups (n = 12): a normal diet (ND group), a high fat diet (HF group), and the high fat diet supplemented with GPE (HFGPE group). After 12-week treatment, mice in the high fat diet groups gained 29% more weight than the ND group. The GPE supplementation (estimated 250 mg/kg bw/d) lowered plasma C-reactive protein levels by 15.5% in the high fat diet fed mice (P < 0.05), suggesting a potential anti-inflammatory effect by dietary GPE. However, dietary GPE did not improve oxidative stress in DIO mice as determined by plasma ORAC, glutathione peroxidase, and liver lipid peroxidation. The results showed that GPE contained significant antioxidants and dietary GPE exerted an anti-inflammatory effect in diet induced obesity.

Optimizing the Extraction of Phenolic Antioxidants from Peanut Skins Using Response Surface Methodology

Peanut skins are a byproduct of peanut blanching operations and contain high levels of phenolic antioxidants. The effect of solvent type (methanol MeOH, ethanol EtOH, and water), concentration (0, 30, 60, 90%), temperature (30, 45, 60 degrees C), and time (10, 20, 30 min) on total phenolic content (TPC), oxygen radical absorbance capacity (ORAC) level, and resveratrol content of peanut skins was investigated. Response surface methodology was used to estimate the optimum extraction conditions for each solvent. EtOH extracts had the highest TPC followed by MeOH and water. The maximum predicted TPC under the optimized conditions (30.8%, 30.9 degrees C, 12 min) was 118 mg of gallic acid equivalents (GAE)/g of skins. MeOH extracts had the highest ORAC activity of 2149 micromol of TE/g followed by EtOH and water under the optimized conditions of 30% MeOH, 52.9 degrees C and 30 min. Resveratrol was identified in MeOH extracts but was not found in samples extracted with EtOH or water.

Potential Anticancer Properties of Grape Antioxidants

Dietary intake of foods rich in antioxidant properties is suggested to be cancer protective. Foods rich in antioxidant properties include grape (Vitis vinifera), one of the worlds largest fruit crops and most commonly consumed fruits in the world. The composition and cancer-protective effects of major phenolic antioxidants in grape skin and seed extracts are discussed in this review. Grape skin and seed extracts exert strong free radical scavenging and chelating activities and inhibit lipid oxidation in various food and cell models in vitro. The use of grape antioxidants are promising against a broad range of cancer cells by targeting epidermal growth factor receptor (EGFR) and its downstream pathways, inhibiting over-expression of COX-2 and prostaglandin E2 receptors, or modifying estrogen receptor pathways, resulting in cell cycle arrest and apoptosis. Interestingly, some of these activities were also demonstrated in animal models. However, in vivo studies have demonstrated inconsistent antioxidant efficacy. Nonetheless, a growing body of evidence from human clinical trials has demonstrated that consumption of grape, wine and grape juice exerts many health-promoting and possible anti-cancer effects. Thus, grape skin and seed extracts have great potential in cancer prevention and further investigation into this exciting field is warranted.

Dietary Supplementation of Grape Skin Extract Improves Glycemia and Inflammation in Diet-Induced Obese Mice Fed a Western High Fat Diet

Dietary antioxidants may provide a cost-effective strategy to promote health in obesity by targeting oxidative stress and inflammation. We recently found that the antioxidant-rich grape skin extract (GSE) also exerts a novel anti-hyperglycemic activity. This study investigated whether 3-month GSE supplementation can improve oxidative stress, inflammation, and hyperglycemia associated with a Western diet-induced obesity. Young diet-induced obese (DIO) mice were randomly divided to three treatment groups (n = 12): a standard diet (S group), a Western high fat diet (W group), and the Western diet plus GSE (2.4 g GSE/kg diet, WGSE group). By week 12, DIO mice in the WGSE group gained significantly more weight (24.6 g) than the W (20.2 g) and S groups (11.2 g); the high fat diet groups gained 80% more weight than the standard diet group. Eight of 12 mice in the W group, compared to only 1 of 12 mice in the WGSE group, had fasting blood glucose levels above 140 mg/dL. Mice in the WGSE group also had 21% lower fasting blood glucose and 17.1% lower C-reactive protein levels than mice in the W group (P < 0.05). However, the GSE supplementation did not affect oxidative stress in diet-induced obesity as determined by plasma oxygen radical absorbance capacity, glutathione peroxidase, and liver lipid peroxidation. Collectively, the results indicated a beneficial role of GSE supplementation for improving glycemic control and inflammation in diet-induced obesity.

Selective Growth Inhibition of Human Breast Cancer Cells by Graviola Fruit Extract In Vitro and In Vivo Involving Downregulation of EGFR Expression

The epidermal growth factor receptor (EGFR) is an oncogene frequently overexpressed in breast cancer (BC), and its overexpression has been associated with poor prognosis and drug resistance. EGFR is therefore a rational target for BC therapy development. This study demonstrated that a graviola fruit extract (GFE) significantly downregulated EGFR gene expression and inhibited the growth of BC cells and xenografts. GFE selectively inhibited the growth of EGFR-overexpressing human BC (MDA-MB-468) cells (IC50 = 4.8 μg/ml) but had no effect on nontumorigenic human breast epithelial cells (MCF-10A). GFE significantly downregulated EGFR mRNA expression, arrested cell cycle in the G0/G1 phase, and induced apoptosis in MDA-MB-468 cells. In the mouse xenograft model, a 5-wk dietary treatment of GFE (200 mg/kg diet) significantly reduced the protein expression of EGFR, p-EGFR, and p-ERK in MDA-MB-468 tumors by 56%, 54%, and 32.5%, respectively. Overall, dietary GFE inhibited tumor growth, as measured by wet weight, by 32% (P < 0.01). These data showed that dietary GFE induced significant growth inhibition of MDA-MB-468 cells in vitro and in vivo through a mechanism involving the EGFR/ERK signaling pathway, suggesting that GFE may have a protective effect for women against EGFR-overexpressing BC.

Effects of chitosan-essential oil coatings on safety and quality of fresh blueberries.

UNLABELLED Chitosan coating plus different essential oils was developed and applied to fresh blueberries in order to find more natural treatments to preserve fresh fruit quality and safety during postharvest storage. Studies were 1st performed in vitro where wild-type Escherichia coli and Penicillium digitatum were grown in suitable media, and then subjected to 6 essential oils. Three compounds, carvacrol (CAR), cinnamaldehyde (CIN), and trans-cinnamaldehyde (ECIN) had high antimicrobial capacity and were selected for an in vivo study for postharvest storage of blueberries. The selected essential oils, 0.5% each, were added into a chitosan solution and coated on fresh blueberries. After storage at 5, 10, and 20 °C for various days, fruit firmness and microbial populations were evaluated. The chitosan coating substantially decreased bacteria and yeasts/molds on the fruit, and all 3 essential oils added to the antimicrobial activities. Further dosage experiments showed that the antimicrobial activity remained even when lowering CAR concentration to 0.1% and ECIN to 0.2%. Chitosan, CAR, and ECIN also maintained fruit firmness. Our results suggest that chitosan coatings containing essential oils are effective in extending the shelf life of fresh blueberries. PRACTICAL APPLICATION Blueberries are high-value fruit with strong antioxidant capacity and other health-promoting benefits. However, microbial food safety is an increasing concern, and decay and softening limits their storability. A combination of ≥ 0.1% CAR or ≥ 0.2% ECIN with a chitosan coating effectively reduced softening of fresh berries and decay by inhibiting microbial growth.

Production and functional characterisation of antioxidative hydrolysates from corn protein via enzymatic hydrolysis and ultrafiltration.

Corn protein was hydrolysed by three microbial proteases and further separated by sequential ultra-filtration to 12 hydrolysate fractions which were investigated for free radical scavenging capacity and chelating activity. The oxygen radical absorbance capacity (ORAC) of the hydrolysates varied significantly between 65.6 and 191.4μmoles Trolox equivalents (TE)/g dried weight with a small peptide fraction (NP-F3) produced by neutral protease (NP) possessing the highest antioxidant activity. The 1,1-diphenyl-2-picrylhydrazyl radical (DPPH()) scavenging activities of the hydrolysate fractions also varied significantly between 18.4 and 38.7μmoles TE/g. Two fractions (AP-F2 and AP-F3) produced by alkaline protease (AP) showed the strongest activity. However, no significant difference was detected on the chelating activity of the fractions. NP-F3, AP-F2, and AP-F3 were incorporated into ground beef to determine their effects on lipid oxidation during 15-day storage period. NP-F3 was the only fraction that inhibited lipid oxidation at both 250 and 500μg/g levels by as much as 52.9%.

Three new anti-proliferative Annonaceous acetogenins with mono-tetrahydrofuran ring from graviola fruit (Annona muricata).

Bioassay-guided fractionation of the fruit powder of graviola (Annona muricata) yielded three novel compounds: muricins J, K, and L. The compounds are all C35 Annonaceous acetogenins with a mono-tetrahydrofuran ring and four hydroxyls. Their structures were elucidated by spectral methods and chemical modification after isolation via chromatographic techniques and HPLC purification. These three acetogenins demonstrated an antiproliferative against human prostate cancer PC-3 cells.