Antioxidant activities of phenolic extracts from fourteen different types of fresh grapes were investigated by measuring the inhibition of human low-density lipoprotein (LDL) oxidation in vitro. The inhibition of LDL oxidation ranged from 22% to 60% at 10 μM gallic acid equivalents (GAE) of total phenols and from 62% to 91% at 20 μM GAE. The antioxidant activities were thus comparable to those previously found for wines. The relative LDL antioxidant activity correlated with the concentration of total phenols (r = 0.89, p < 0.01), with the level of anthocyanins (r = 0.56, p < 0.05) and flavonols (r = 0.54, p < 0.05) in the grape extracts as analyzed by high-performance liquid chromatography (HPLC). When seed crushing and longer extraction times were employed, high amounts of flavan-3-ols and hydroxybenzoates were extracted. With these extracts relative LDL antioxidant activity correlated highly with the levels of flavan-3-ols (r = 0.86, p < 0.01), total phenols (r = 0.79, p < 0.05), and hydroxybenzoates (r = 0.77, p < 0.05). Keywords: LDL oxidation; flavonoids; hydroxycinnamates; anthocyanins; flavan-3-ols; flavonols; HPLC

Cocoa consumption suppressed ADP- or epinephrine-stimulated platelet activation and platelet microparticle formation. Cocoa consumption had an aspirin-like effect on primary hemostasis.

Oxidative modification of low-density lipoprotein (LDL) is believed to play a crucial role in atherogenesis. The antioxidant activity of hydroxycinnamic acids typically present in fruits was investigated in vitro using a human LDL oxidation assay. The o-dihydroxy compounds caffeic, caftaric, chlorogenic, and neochlorogenic acids had highest antioxidant activities and inhibited LDL oxidation from 86 to 97% at 5 µM. Ferulic and fertaric acids had lower antioxidant activities, and p-coumaric and p-coutaric acids had the lowest. Differences in antioxidant activity were thus primarily related to the hydroxylation and methylation pattern. The esterification to tartaric acid slightly enhanced the antioxidant activity of p-coumaric and ferulic acids, but esterification of caffeic acid to quinic acid (as in chlorogenic and neochlorogenic acid) had no effect on or slightly decreased antioxidant activity. The observed differences in activities are discussed in terms of structural dissimilarities of the compounds. It is proposed that for the less active hydroxycinnamic acids, p-coumaric and ferulic acids, esterification to tartaric acid may enhance their ability to inhibit LDL oxidation by binding to apolipoprotein B in the LDL particle.

No abstract

No abstract

There is speculation that dietary polyphenols can provide cardioprotective effects due to direct antioxidant or antithrombotic mechanisms. We report in vitro and postingestion ex vivo effects of cocoa procyanidins, a procyanidin-rich cocoa beverage and dealcoholized red wine (DRW) on human platelet activation. In a series of in vitro studies, cocoa procyanidin trimers, pentamers or DRW (3 and 10 micromol/L) were incubated with citrated peripheral whole blood in the presence and absence of platelet agonists. Platelet activation was detected using fluorescent-labeled monoclonal antibodies recognizing the fibrinogen binding conformation of GPIIb-IIIa (referred to herein as PAC-1 binding) and the activation-dependent platelet epitope CD62P (P-selectin). The percentage of CD42a-positive platelets coexpressing PAC-1 binding and/or CD62P was determined by multiparameter flow cytometry. Procyanidin trimers, pentamers and DRW added to whole blood in vitro increased PAC-1 binding and P-selectin expression. In contrast, procyanidin trimers, pentamers and DRW inhibited the platelet activation in response to epinephrine. The effects on platelet activation of cocoa beverage and DRW consumption were also studied in healthy subjects. Citrated blood was obtained before and 2 and 6 h after the ingestion of a cocoa beverage, a caffeine-containing beverage, DRW or water. Platelet activation was measured by flow cytometry. The consumption of DRW did not affect the expression of activation-dependent platelet antigens, either unstimulated or after ex vivo activation with epinephrine. However, the consumption of DRW increased PAC-1 binding in response to 100 micromol/L ADP ex vivo. Cocoa consumption reduced platelet response to agonists ex vivo. The ingestion of water had no effect on platelet activation, whereas a caffeine-containing beverage augmented the response of platelets to epinephrine. In summary, select cocoa procyanidins and DRW added to whole blood in vitro increased expression of platelet activation markers in unstimulated platelets but suppressed the platelet activation response to epinephrine. In contrast, cocoa consumption suppressed unstimulated and stimulated platelet activation in whole blood. This suppressive effect observed on platelet reactivity may explain in part the reported cardioprotective effects of dietary polyphenols.

Epidemiological studies and clinical trials consistently indicate that vitamin K has a positive effect on bone mineral density and decreases fracture risk. Typical dietary intakes of vitamin K are below the levels associated with better BMD and reduced fracture risk; thus issues of increasing dietary intakes, supplementation, and/or fortification arise. To effectively address these issues, large-scale, intervention trials of vitamin K are needed. The effects of coumarin-based anticoagulants on bone health are more ambiguous, with retrospective studies suggesting that long-term therapy adversely affects vertebral BMD and fracture risk. Anticoagulants that do not affect vitamin K metabolism are now available and make clinical trials feasible to answer the question of whether coumarins adversely affect bone. The research suggests that at a minimum, clinicians should carefully assess anticoagulated patients for osteoporosis risk, monitor BMD, and refer them to dietitians for dietary and supplement advice on bone health. Further research is needed to make more efficacious decisions about vitamin K intake, anticoagulant therapy, and bone health.

Plant-derived phenolic compounds possess antioxidant activity that may be applicable to such diverse areas as human health and the preservation of food lipids. The potential antioxidant activities of a variety of plant phenolics were investigated using human aortic endothelial cells (HAEC) to mediate the oxidation of low-density lipoprotein (LDL). Carnosic acid, carnosol, and rosmarinic acid, present in rosemary extract, and thymol, carvacrol, and zingerone, present in thyme, origanum, and ginger, were individually incubated with HAEC and LDL for 12 h. The extent of oxidation was determined spectrophotometrically by measuring absorbance (at 234 nm) of conjugated dienes. All antioxidants produced dose-dependent inhibition of LDL oxidation. Their relative antioxidant activities decreased in the order carnosol > carnosic acid ≈ rosmarinic acid >>> thymol > carvacrol > zingerone. The antioxidant activity of these plant phenolics in the HAEC system suggests that they may have potential benefits in human health. Keywords: LDL oxidation; rosemary; plant phenolics; human aortic endothelial cells; antioxidants