Polyphenolic Composition of Rosa canina, Rosa sempervivens and Pyrocantha coccinea Extracts and Assessment of Their Antioxidant Activity in Human Endothelial Cells.

The aim of the present study was the investigation of the antioxidant activity of plant extracts from Rosa canina, Rosa sempervivens and Pyrocantha coccinea. The results showed that the bioactive compounds found at higher concentrations were in the R. canina extract: hyperoside, astragalin, rutin, (+)-catechin and (-)-epicatechin; in the R. sempervirens extract: quinic acid, (+)-catechin, (-)-epicatechin, astragalin and hyperoside; and in the P. coccinea extract: hyperoside, rutin, (-)-epicatechin, (+)-catechin, astragalin, vanillin, syringic acid and chlorogenic acid. The total polyphenolic content was 290.00, 267.67 and 226.93 mg Gallic Acid Equivalent (GAE)/g dw, and the total flavonoid content 118.56, 65.78 and 99.16 mg Catechin Equivalent (CE)/g dw for R. caninna, R. sempervirens and P. coccinea extracts, respectively. The extracts exhibited radical scavenging activity in DPPH and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)•⁺ assays and protection from ROO•-induced DNA damage in the following potency order: R. canina > R. sempervirens > P. coccinea. Finally, treatment with R. canina and P. coccinea extract significantly increased the levels of the antioxidant molecule glutathione, while R. canina extract significantly decreased Reactive Oxygen Species (ROS) in endothelial cells. The results herein indicated that the R. canina extract in particular may be used for developing food supplements or biofunctional foods for the prevention of oxidative stress-induced pathological conditions of endothelium.

Affinity Crystallography Reveals the Bioactive Compounds of Industrial Juicing Byproducts of Punica granatum for Glycogen Phosphorylase.

BACKGROUND: Glycogen phosphorylase (GP) is a pharmaceutical target for the discovery of new antihyperglycaemic agents. Punica granatum is a well-known plant for its potent antioxidant and antimicrobial activities but so far has not been examined for antihyperglycaemic activity. OBJECTIVE: The aim was to examine the inhibitory potency of eighteen polyphenolic extracts obtained from Punica granatum fruits and industrial juicing byproducts against GP and discover their most bioactive ingredients. METHOD: Kinetic experiments were conducted to measure the IC50 values of the extracts while affinity crystallography was used to identify the most bioactive ingredient. The inhibitory effect of one of the polyphenolic extracts was also verified ex vivo, in HepG2 cells. RESULTS: All extracts exhibited significant in vitro inhibitory potency (IC50 values in the range of low µg/mL). Affinity crystallography revealed that the most bioactive ingredients of the extracts were chlorogenic and ellagic acids, found bound in the active and the inhibitor site of GP, respectively.While ellagic acid is an established GP inhibitor, the inhibition of chlorogenic acid is reported for the first time. Kinetic analysis indicated that chlorogenic acid is an inhibitor with Ki=2.5 x 10-3Mthat acts synergistically with ellagic acid. CONCLUSION: Our study provides the first evidence for a potential antidiabetic usage of Punica granatum extracts as antidiabetic food supplements. Although, more in vivo studies have to be performed before these extracts reach the stage of antidiabetic food supplements, our study provides a first positive step towards this process.

Polyphenolic composition of grape stem extracts affects antioxidant activity in endothelial and muscle cells.

The aim of the present study was the assessment of the antioxidant effects of polyphenolic extracts derived from the stems of three Greek grape varieties (Moshomayro, Mavrotragano and Mandilaria) in endothelial (EA.hy926) and muscle (C2C12) cells. We also investigated the effects of the polyphenolic composition on the antioxidant effects of the grape stem extracts. For this purpose, the endothelial and muscle cells were treated with low non-cytotoxic concentrations of the extracts for 24 h in order to assess the effects of the extracts on cellular redox status using oxidative stress biomarkers. The oxidative stress markers were thiobarbituric acid reactive substances (TBARS), protein carbonyl (CARB) levels, reactive oxygen species (ROS) levels and glutathione (GSH) levels. The results revealed that treatment of the EA.hy926 cells with Mandilaria extract significantly decreased the TBARS levels by 14.8% and the CARB levels by 25.9 %, while it increased the GSH levels by 15.8% compared to the controls. Moreover, treatment of the EA.hy926 cells with Mavrotragano extract significantly increased the GSH levels by 20.2%, while it significantly decreased the TBARS and CARB levels by 12.5% and 16.6%, respectively. Treatment of the C2C12 cells with Mandilaria extract significantly decreased the TBARS levels by 47.3 %, the CARB levels by 39.0 % and the ROS levels by 21.8%, while it increased the GSH levels by 22.6% compared to the controls. Moreover, treatment of the C2C12 cells with Mavrotragano significantly decreased the TBARS, CARB and ROS levels by 36.2%, 35.9% and 16.5%, respectively. In conclusion, to the best of our knowledgel, our results demonstrate for the first time that treatment with grape stem extracts at low concentrations improves the redox status of endothelial and muscle cells. Thus, grape stem extracts may be used for developing antioxidant food supplements or biofunctional foods. However, it was also found that the polyphenolic composition of grape stem extracts affects their antioxidant capacity. For example, the results suggested that trans-resveratrol, gallic acid, (+)-catechin, ferulic acid, caffeic acid, quercetin, coumaric acid and kaempferol may be essential for the antioxidant activity of grape stem extracts.

Biochemical and biological assessment of the inhibitory potency of extracts from vinification byproducts of Vitis vinifera extracts against glycogen phosphorylase.

The inhibitory potency of thirteen polyphenolic extracts obtained from vinification byproducts of Greek varieties of Vitis vinifera against glycogen phosphorylase (GP) has been studied by kinetic experiments. GP is an enzyme involved in glucose homeostasis and a molecular target for the discovery of new hypoglycemic agents. Studies have shown that all extracts display significant inhibitory potency for GP in vitro with IC50 values in the range of low µg/mL. X-ray crystallographic analysis of GP crystals soaked with two of these extracts revealed that the most active ingredient is quercetin which binds at novel binding site, distinct from the other known sites of the enzyme. One of the most potent of the studied extracts had also a moderate effect on glycogenolysis in the cellular lever with an IC50 value of 17.35 µg/mL. These results highlight the importance of natural resources in the quest for the discovery of new hypoglycemic agents, while at the same time they can serve as the starting point for their exploitation for antidiabetic usage and the development of novel biofunctional foods.

Anticarcinogenic activity of polyphenolic extracts from grape stems against breast, colon, renal and thyroid cancer cells.

A major part of the wineries' wastes is composed of grape stems which are discarded mainly in open fields and cause environmental problems due mainly to their high polyphenolic content. The grape stem extracts' use as a source of high added value polyphenols presents great interest because this combines a profitable venture with environmental protection close to wine-producing zones. In the present study, at first, the Total Polyphenolic Content (TPC) and the polyphenolic composition of grape stem extracts from four different Greek Vitis vinifera varieties were determined by HPLC methods. Afterwards, the grape stem extracts were examined for their ability to inhibit growth of colon (HT29), breast (MCF-7 and MDA-MB-23), renal (786-0 and Caki-1) and thyroid (K1) cancer cells. The cancer cells were exposed to the extracts for 72 h and the effects on cell growth were evaluated using the SRB assay. The results indicated that all extracts inhibited cell proliferation, with IC50 values of 121-230 µg/ml (MCF-7), 121-184 µg/ml (MDA-MD-23), 175-309 µg/ml (HT29), 159-314 µg/ml (K1), 180-225 µg/ml (786-0) and 134->400 µg/ml (Caki-1). This is the first study presenting the inhibitory activity of grape stem extracts against growth of colon, breast, renal and thyroid cancer cells.

Assessment of polyphenolic content, antioxidant activity, protection against ROS-induced DNA damage and anticancer activity of Vitis vinifera stem extracts.

Grape extracts and wine have been studied widely due to their beneficial effects on human health. However, there are only few studies from grape stems extracts. Therefore, the main objective of the present study was the assessment in stem extracts from Greek Vitis vinifera varieties of the total polyphenolic content (TPC), the identification of the polyphenols present in them, and the evaluation of their antioxidant activity, protection against ROS-induced DNA damage and inhibition of liver (HepG2) and cervical (HeLa) cancer cell growth. The range of the TPC in grape stem extracts was from 345 to 584 mg GAE/g dry weight. Moreover, stem extracts contained different classes of polyphenols as flavonols, flavanols, procyanidins, phenolic acids and stilbenes. In DPPH and ABTS assays, the IC50 values of the stem extracts had an average of 7.8 ± 2.8 and 5.4 ± 2.6 µg/mL respectively. Also, all stem extracts inhibited OH- and ROO-induced DNA damage dose dependent with average IC50 values of 478 ± 217 and 1.15 ± 0.85 µg/mL respectively. Furthermore, stem extracts inhibited at low concentrations the growth of HepG2 and HeLa cancer cells with average IC50 values of 50 ± 12 and 32 ± 16 µg/mL respectively. The above activities of grape stem extracts were comparable to those of seed extracts.