Flavonoids as potential anti-platelet aggregation agents: from biochemistry to health promoting abilities

Cardiovascular ailments are the number one cause of mortalities throughout the globe with 17.9 million deaths per year. Platelet activation and aggregation play a crucial role in the pathogenesis of arterial diseases, including acute coronary syndrome, acute myocardial infarction, cerebrovascular transient ischemia, unstable angina, among others. Flavonoids-rich plant extracts are gaining interest for treating the heart-related problems due to safe nature of these herbal extracts. Consumption of plant-food-derived bioactives, particularly flavonoids, has shown antithrombotic, and cardiovascular protective effects due to its anti-platelet activity. Preclinical and clinical trials have proven that flavonoid-rich plant extracts are protective against the cardiac ailments through anti-platelet aggregation activity. This review aims to highlight the anti-platelet aggregation potential of flavonoids with a key emphasis on the therapeutic efficacy in humans. The mechanism of flavonoids in preventing and treating cardiovascular diseases is also highlighted based on preclinical and clinical experimental trials. Further studies are the need of time for exploring the exact molecular mechanism of flavonoids as anti-platelet aggregation agents for treating heart-related problems.

Anticancer molecular mechanisms of oleocanthal

Cancer is among the leading causes of mortality worldwide. Current cancer therapies are associated with serious side effects, which further damage patients' health. Therefore, the search for new anticancer agents with no toxic effects on normal and healthy cells is of great interest. Recently, we and other groups have demonstrated that oleocanthal (OLC), a phenolic compound from extra virgin olive oil, exhibits antitumor activity in various tumor models. However, the underlying mechanisms and intracellular targets of OLC remain to be completely elucidated. This review summarizes the current advancers concerning the anticancer activity of OLC, with particular emphasis on the molecular signaling pathways modulated by this compound in different tumor cell types. The major mechanisms of action of OLC include modulation of the apoptotic pathway, the HGF/c-Met pathway, and the signal transducer and activator of transcription 3 signaling pathway, among others. Furthermore, OLC has synergistic effects with anticancer drugs in vitro. Also discussed are OLC bioavailability and its concentration in olive oil. Data summarized here will represent a database for more extensive studies aimed at providing information on molecular mechanisms against cancer induced by OLC.

Platelet Oxidative Stress and its Relationship with Cardiovascular Diseases in Type 2 Diabetes Mellitus Patients

Enhanced platelet activation and thrombosis are linked to various cardiovascular diseases (CVD). Among other mechanisms, oxidative stress seems to play a pivotal role in platelet hyperactivity. Indeed, upon stimulation by physiological agonists, human platelets generate and release several types of reactive oxygen species (ROS) such as O2 -, H2O2 or OH-, further amplifying the platelet activation response via various signalling pathways, including, formation of isoprostanes, Ca2+ mobilization and NO inactivation. Furthermore, excessive platelet ROS generation, incorporation of free radicals from environment and/or depletion of antioxidants induce pro-oxidant, pro-inflammatory and platelet hyperaggregability effects, leading to the incidence of cardiovascular events. Here, we review the current knowledge regarding the effect of oxidative stress on platelet signaling pathways and its implication in CVD such as type 2 diabetes mellitus. We also summarize the role of natural antioxidants included in vegetables, fruits and medicinal herbs in reducing platelet function via an oxidative stress-mediated mechanism.

Flavonoids and Platelet-Derived Thrombotic Disorders

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Thrombotic disorders are characterized by an increase in the probability of the formation of unnecessary thrombi that might be due to the activation of the coagulation cascade or the circulating platelets. Platelets or thrombocytes play an essential role in hemostasis but abnormal platelet function leads to the development of a number of cardiovascular complications, including thrombotic disorders. Under pathological conditions, platelets are associated with the development of different thrombotic disorders, including atherosclerosis, arterial thrombosis and stroke, deep venous thrombosis and pulmonary embolism; therefore, platelets are the target of a number of anti-thrombotic strategies. Flavonoids, a large group of polyphenols ubiquitously expressed in fruits and vegetables that have attracted considerable attention because of their benefits in human health, including the reduction of the risk of cardiovascular disease. Flavonoids have been reported to reduce platelet activity by attenuating agonist-induced GPIIb/IIIa receptor activation, mobilization of intracellular free Ca2+, granule exocytosis, as well as activation of different signaling molecules such as mitogen- activated protein kinases or phospholipases. This review summarizes the current studies concerning the modulation of platelet activation by flavonoids, giving especial attention to those events associated to thrombotic disorders.

Medicinal Plants with Antiplatelet Activity

Blood platelets play an essential role in the hemostasis and wound-healing processes. However, platelet hyperactivity is associated to the development and the complications of several cardiovascular diseases. In this sense, the search for potent and safer antiplatelet agents is of great interest. This article provides an overview of experimental studies performed on medicinal plants with antiplatelet activity available through literature with particular emphasis on the bioactive constituents, the parts used, and the various platelet signaling pathways modulated by medicinal plants. From this review, it was suggested that medicinal plants with antiplatelet activity mainly belong to the family of Asteraceae, Rutaceae, Fabaceae, Lamiaceae, Zygophyllaceae, Rhamnaceae, Liliaceae, and Zingiberaceae. The antiplatelet effect is attributed to the presence of bioactive compounds such as polyphenols, flavonoids, coumarins, terpenoids, and other substances which correct platelet abnormalities by interfering with different platelet signalization pathways including inhibition of the ADP pathway, suppression of TXA2 formation, reduction of intracellular Ca(2+) mobilization, and phosphoinositide breakdown, among others. The identification and/or structure modification of the plant constituents and the understanding of their action mechanisms will be helpful in the development of new antiplatelet agents based on medicinal plants which could contribute to the prevention of thromboembolic-related disorders by inhibiting platelet aggregation. Copyright © 2016 John Wiley & Sons, Ltd.

Platelet signalling abnormalities in patients with type 2 diabetes mellitus: a review

The hyperactivation of platelets is involved in the cardiovascular complications associated with type 2 diabetes mellitus. Altered platelet behavior contributes to the angiopathies associated with diabetes. A number of mechanisms involved in platelet activation are altered in diabetes. Platelets from type 2 diabetic patients show an enhanced endogenous reactive oxygen species production and a reduced antioxidant capability, which increase the activity of several tyrosine kinases, such as the Bruton's tyrosine kinase, MAP kinases or proteins of the SRC family. Oxidative stress is also involved in the abnormal intracellular calcium homeostasis observed in platelets from type 2 diabetics, including an enhanced resting cytosolic calcium concentration and calcium release and entry in response to agonists. Moreover, diabetes alters the bioavailability of nitric oxide in platelets. Basal nitric oxide synthase activity is reduced in homogenates of platelets obtained from patients with type 2 diabetes mellitus. The study of these abnormalities might be helpful in the development of new pharmacological strategies to reduce platelet activation in type 2 diabetes mellitus.

Antiaggregant effects of Arbutus unedo extracts in human platelets

Platelet hyperaggregability plays a pivotal role in the pathogenesis of cardiovascular diseases. Thrombin evokes aggregation through Ca(2+) mobilization, tyrosine phosphorylation and generation of reactive oxygen species (ROS). We have investigated the antiaggregant properties of Arbutus unedo extracts in human platelets. Changes in cytosolic Ca(2+) concentration and intracellular oxidants production were registered by espectrofluorimetry using fura-2 and dichlorodihydrofluorescein, respectively, platelet aggregation was assessed by aggregometry and protein tyrosine phosphorylation was detected by Western blotting. Platelet treatment with increasing concentrations (0.015-1.5mg/mL) of crude aqueous, ethyl acetate or diethyl ether extracts reduced platelet aggregation evoked by thrombin (0.5 U/mL) and show a potent ROS scavenger activity, preventing thrombin-evoked endogenous generation of ROS. Treatment with Arbutus unedo extracts did not alter thrombin-evoked Ca(2+) release from the intracellular stores but reduced store-operated Ca(2+) entry induced by thrombin or by selective depletion of the two Ca(2+) stores in platelets, the dense tubular system and the acidic stores. In addition, platelet treatment with extracts reduced both basal and thrombin-stimulated protein tyrosine phosphorylation. We conclude that Arbutus unedo extracts show antiaggregant actions due to attenuation of Ca(2+) mobilization, ROS production and protein tyrosine phosphorylation and might be used for the treatment and/or prevention of cardiovascular diseases.

Inhibition of Rat Platelet Aggregation byUrtica dioica Leaves Extracts

Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was undertaken to investigate the effects of different extracts of Urtica dioica leaves on platelet aggregation. Rat platelets were prepared and incubated in vitro with different concentrations of the tested extracts and aggregation was induced by different agonists including thrombin (0.5 U/mL), ADP (10 microm), epinephrine (100 microm) and collagen (5 mg/mL). The crude aqueous extract inhibited thrombin-induced platelet aggregation in a dose-dependent manner. At 1 mg/mL, the percent inhibition was 17.1 +/- 4.2%. Soxhlet extraction of the plant leaves with different successive solvents showed that the ethyl acetate extract exhibited the most antiaggregant effect with an inhibition of 76.8 +/- 6.1% at 1 mg/mL. Flavonoids isolated from the plant leaves, produced a strong inhibitory effect on thrombin-induced platelet aggregation with an IC(50) of 0.25 +/- 0.05 and 0.40 +/- 0.04 mg/mL for genins and heterosidic flavonoids, respectively. Flavonoids also markedly inhibited platelet aggregation induced by ADP, collagen and epinephrine. It is concluded that Urtica dioica has an antiplatelet action in which flavonoids are mainly implicated. These results support the traditional use of Urtica dioica in the treatment and/or prevention of cardiovascular disease.

Platelet anti-aggregant property of some Moroccan medicinal plants

It is known that blood platelets may present some dysfunction linked to cardiovascular pathologies such as arterial hypertension. The aim of this work is to examine the in vitro anti-aggregant effect of five medicinal plants among which three were reported as antihypertensive in oriental Morocco: Arbutus unedo (Ericaceae), Urtica dioïca (Urticaceae), and Petroselinum crispum (Apiaceae). The two other plants were Cistus ladaniferus (Cistaceae) and Equisetum arvense (Equisetaceae). The results obtained showed that all extracts produced a dose-dependent inhibition of thrombin and ADP-induced aggregation. The calculated IC50 (half-maximal inhibition of thrombin and ADP-induced aggregation) was found to be identical in all plant extracts while Urtica dioïca had a higher IC50 value. The effect of plants could be related in part to the polyphenolic compounds present in their extracts suggesting their involvement in the treatment or prevention of platelet aggregation complications linked to cardiovascular diseases. Phytochemical separation must be carried out to identify the active principles responsible for the anti-aggregant effect and elucidate their mechanisms of action.