Anti-platelet Aggregation Agents Research Articles

Synthesis and Evaluation of Novel Nitric Oxide-Donating Ligustrazine Derivatives as Potent Antiplatelet Aggregation Agents.

Antiplatelet aggregation agents have demonstrated clinical benefits in the treatment of ischemic stroke. In our study, a series of novel nitric oxide (NO)-donating ligustrazine derivatives were designed and synthesized as antiplatelet aggregation agents. They were evaluated for the inhibitory effect on 5'-diphosphate (ADP)-induced and arachidonic acid (AA)-induced platelet aggregation in vitro. The results showed that compound 15d displayed the best activity in both ADP-induced and AA-induced assays, and compound 14a also showed quite better activity than ligustrazine. The preliminary structure-activity relationships of these novel NO-donating ligustrazine derivatives were discussed. Moreover, these compounds were docked with the thromboxane A2 receptor to study the structure-activity relationships. These results suggested that the novel NO-donating ligustrazine derivatives 14a and 15d deserve further study as potent antiplatelet aggregation agents.

Palmatine Derivatives as Potential Antiplatelet Aggregation Agents via Protein Kinase G/Vasodilator-Stimulated Phosphoprotein and Phosphatidylinositol 3-Kinase/Akt Phosphorylation.

Sixty palmatine (PMT) derivatives were synthesized and evaluated for antiplatelet aggregation taking berberine as the lead, and the structure-activity relationship was first systematically described. Among them, compound 2v showed the best potency in reducing adenosine diphosphate (ADP)-induced platelet aggregation in a dose-dependent manner. It greatly suppressed ADP-induced platelet aggregation, activation, and Akt phosphorylation in vitro and ex vivo after oral administration to mice. It also effectively inhibited carrageenan-induced thrombus formation in the mouse tail and lung, as well as reduced the serum P-selectin level. Compound 2v might simultaneously bind to protein kinase G to improve vasodilator-stimulated phosphoprotein phosphorylation and bind to phosphatidylinositol 3-kinase to inhibit Akt phosphorylation, which synergically reduced platelet aggregation, thereby achieving antithrombotic efficacy. Therefore, PMT derivatives constituted a novel family of antiplatelet aggregation agents with the advantage of a good safety profile, worthy of further investigation.

Macrostachyols A-D, oligostilbenes from Gnetum macrostachyum inhibited in vitro human platelet aggregation

Introduction: Gnetum macrostachyum is a known Thai medicinal plant as a source of bioactive oligostilbenes, which possess platelet inhibitory activities. The study aimed to evaluate the in vitro human platelet aggregation inhibitory activities of macrostachyols A-D (compounds 1-4) isolated from the roots of G. macrostachyum. Methods: The in vitro human platelet aggregation assay was assayed with a 96-well microtiter plate format. The well-known aggregating agents were used to investigate the possible mechanism of inhibition, including adenosine diphosphate (ADP), arachidonic acid (AA), thromboxane A2 analog (U-46619), collagen, thrombin, and thrombin receptor-activating peptide-6 (TRAP-6). Results: Compound 1 was more potent than ibuprofen (positive control) on the adenosine diphosphate- induced platelet aggregation assay (P < 0.05). Compound 3 was more potent than 1, 2, and 4 (P < 0.05), but all active oligostilbenes were less potent than the positive control (P < 0.05) on the arachidonic acid-induced platelet aggregation assay. The oligostilbenes 1, 2, 3, and 4 also displayed the inhibitory effects on the U-46619-induced platelet aggregation. The tetrameric stilbenes 1 was the only compound that exhibited inhibitory effects on thrombin-induced platelet aggregation without TRAP-6 mediated platelet aggregation. Conclusion: The findings revealed the inhibitory effects of oligostilbenes on human platelet aggregation through a target-specific experimental design. It suggests that oligostilbenes from this plant might be applied as antiplatelet aggregation agents in platelet hyperreactivity- related diseases.

Anti-inflammatory, Antiplatelet Aggregation, and Antiangiogenesis Polyketides from Epicoccum sorghinum: Toward an Understating of Its Biological Activities and Potential Applications.

The ethyl acetate extract of an endophyte Epicoccum sorghinum exhibited anti-inflammatory activity at a concentration of <10 μg/mL. By bioassay-guided fractionation, one new compound, named epicorepoxydon A (1), and one unusual bioactive compound, 6-(hydroxymethyl)benzene-1,2,4-triol (6), together with six known compounds, were isolated from E. sorghinum. The structures of all isolates were established by spectroscopic analyses. The relative configuration of 1 was deduced by the NOESY spectrum and its absolute configuration was determined by X-ray single-crystal analysis. The biological activities of all isolates were evaluated using four types of bioassays including cytotoxicity, anti-inflammatory, antiplatelet aggregation, and antiangiogenesis activities. Compounds 4 and 6 showed potent anti-inflammatory activity, compound 2 possessed potent antiplatelet aggregation and antiangiogenesis activities, and compound 6 demonstrated antiangiogenesis activity. This fungal species can cause a human hemorrhagic disorder known as onyalai. In this study, we identified the active components with antiplatelet aggregation and antiangiogenesis activities, which may be related to the hemorrhagic disorder caused by this fungus. Moreover, we proposed a biosynthetic pathway of the isolated polyketide secondary metabolites and investigated their structure–activity relationship (SAR). Our results suggested that E. sorghinum is a potent source of biologically active compounds that can be developed as antiplatelet aggregation and anti-inflammatory agents.

Synthesis, pharmacological evaluation and molecular docking of novel R-/S-2-(2-hydroxypropanamido)-5-trifluoromethyl benzoic acid as dual anti-inflammatory anti-platelet aggregation agents.

R-/S-2-(2-hydroxypropanamido) benzoic acid (R-/S-HPABA), marine-derived anti-inflammatory antiplatelet drugs, were initially synthesised in our group. However, preliminary research showed that R-/S-HPABA were eliminated rapidly because of extensive hydroxylation metabolism of phenyl ring in vivo. In order to reduce significant hydroxylation metabolism to improve pharmacological activity and bioavailability, trifluoromethyl group was incorporated into R-/S-HPABA to synthesise R-/S-2-(2-hydroxypropanamido)-5-trifluoromethyl benzoic acid (R-/S-HFBA), respectively. The purposes of this study were to report the synthesis of R-/S-HFBA and compare the anti-inflammatory antiplatelet effect and pharmacokinetic properties of R-/S-HFBA with those of R-/S-HPABA. Carrageenan-induced rat paw edema assay was used for the evaluation of the anti-inflammatory activity. R-/S-HFBA showed better results in inhibiting edema and were able to prolong the anti-inflammatory effect after carrageenan injection. The antiplatelet aggregation activity of R-/S-HFBA and R-/S-HPABA was studied on arachidonic acid-induced platelet aggregation of rabbit platelet-rich plasma. The aggregation inhibition rate of R-/S-HFBA was significantly (p < 0.05) higher than that of R-/S-HPABA, respectively. Molecular docking study revealed that R-/S-HFBA possess more potent binding affinity with COX-1/COX-2 than R-/S-HPABA, respectively, and that the presence of trifluoromethyl group leads to increase in activity of R-/S-HFBA. R-/S-HFBA also afford more favorable pharmacokinetic properties than R-/S-HPABA, respectively, such as higher Cmax, larger AUC0-∞, and longer t1/2, which, as expected, are more metabolically stable.

Synthesis of Phenyl m-coumarylamide Analogs and Their Anti-platelet Aggregation Activity

Phenyl m-coumarylamide analogs were designed based on phenylpropanoid analogs such as coumaric acid, ferulic acid, and caffeic amide having anti-platelet aggregation activity. They prepared through concise synthetic method. Their anti-platelet aggregation was confirmed using ADP-induced rat platelet by aggregrometer. Compound 1b and 1d having dimethylamine and methoxy group on para-position of phenylamide ring, respectively, exhibit potent inhibitory activity (92.3 and 89.3% at 80 μg/mL). The results suggest that phenyl m-coumrylamide analogs could be used to develop potent anti-platelet aggregation agents.

Identification of active ingredients mediating anti-platelet aggregation effects of BuyangHuanwu decoction using a platelet binding assay, solid phase extraction, and HPLC-MS/MS

BuyangHuanwu decoction (BHD) is widely used as a traditional herbal medicine because of its antithrombotic effect, which is attributed to the inhibition of platelet aggregation; however, its active compounds remain unknown. In this study, we developed a method involving platelet binding, solid-phase extraction, and HPLC-MS/MS for screening BHD compounds with potential anti-platelet aggregation properties. Five compounds showing platelet binding affinity were identified as 6-hydroxykaempferol-di-O-glucoside, paeoniflorin, calycosin-7-O-β-d-glucoside, galloylpaeoniflorin, and formononetin-7-O-β-d-glucoside. The results of anti-platelet aggregation experiments in vitro confirmed that these compounds inhibited adenosine diphosphate-induced platelet aggregation. Our results suggest that a platelet binding assay combined with solid-phase extraction and HPLC-MS/MS is an effective method for screening anti-platelet aggregation agents in traditional Chinese medicines.

Do antiplatelet and anticoagulant drugs modify outcome of patients treated for chronic subdural hematoma? Still a controversial issue.

Anticoagulants (ACs) and antiplatelet aggregation agents (AAAs) seem to be correlated to a higher incidence of chronic subdural hematoma (CSDH) but whether or not they contribute to its recurrence is debated. Few data are available on clinical outcomes and indications for the management of this therapy are not so well defined. We investigated the role of ACs and AAAs in modifying patients' clinical outcomes treated for CSDH, especially for re-bleedings. This retrospective study, enrolled patients treated for CSDH. Patients characteristics were recorded including drugs used (antiplatelet/anticoagulant) and clinical conditions (Modified Rankin Scale [mRS]) upon admission. Patients underwent surgery (burrhole vs. minicraniectomy) with subdural drainage positioning. Clinical/radiological follow-ups were performed at one and six months. Chi-square/Fisher's Exact test were used to compare variables and stepwise backward logistic regression analysis was used for defining their impact on complications, risk of re-bleeding and reoperation. Overall, 230 patients (45 on ACs, 76 on AAAs and nine on both) were enrolled. Higher mRS scores were significantly associated with a higher risk of general complications (OR=3.78, 95% CI: 1.66-8.62, P=0.002), higher risk of rebleeding (OR =15.82, 95% CI: 4.33-57.90, P<0.001) and re-operation (OR=11.39, 95% CI: 3.35-37.56, P<0.0001). No statistically significant association was found between AAAs or ACs and complications or re-bleedings or risk of reoperation. AAAs and ACs alone do not seem to worsen the clinical outcome or increase re-bleedings. mRS may be a predicting factor, since patients with higher scores showed a worse outcome and an increased risk of re-bleeding, general complications and reoperation.

Design, synthesis and biological evaluation of 4-methoxy diaryl isophthalates as antiplatelet agents

A series of 4-methoxy diphenyl isophthalates, which are the isosturctural analogs of picotamide, were designed and synthesized using the concept of isosterism. The structures of these new analogs were characterized by all means of spectroscopy, including 1H NMR, 13C NMR, and MS spectra. In vitro antiplatelet aggregation activities of these compounds were investigated by using Born’s test method. Among the 19 compounds tested for both ADP and collagen inducers, six of them (P216–P219 and P220–P221) were found to exhibit higher activity in vitro antiplatelet aggregation than Picotamide. In particular, the compound P220 bearing a nitrooxyl group showed the highest acitivity 72.1% (induced by collagen) and 72.5% (induced by ADP), with IC50 values of 0.30 μM/L induced by ADP (1.3 μM/L) and LD50 > 2500 mg/kg, could have dual mechanism of action. Evaluation of cytotoxic activity of the compounds against L929 cell line revealed that none of the compounds have significant cytotoxicity. Through the careful analysis of in vitro activity data, the SAR of these compounds was preliminarily deduced. The results of this study showed that 4-methoxy diaryl isophthalates derivatives are potential to become an antiplatelet aggregation agents.

Design, synthesis and evaluation of novel 2-amino-3-(naphth-2-yl)propanoic acid derivatives as potent inhibitors of platelet aggregation

Based upon LX2421, a previously identified antiplatelet aggregation agent, a series of novel 2-amino-3-(naphth-2-yl)propanoic acid derivatives were designed, synthesized and evaluated. Among them, compounds LX14 and LX25 were identified as promising antiplatelet aggregation agents. The in vitro biologic study demonstrated that LX14 can block platelet aggregation induced by four different inducers and displays comparable potency in inhibiting GPIIb/IIIa receptor in comparison with Tirofiban. In addition, LX14 has much lower risk of bleeding than Tirofiban and shows significant antithrombotic activity in vivo. Taking together, the results indicated that LX14 is a promising GPIIb/IIIa receptor antagonist against platelet aggregation worthy of further evaluation.

Synthesis and biological evaluation of n-butylphthalide derivatives as anti-platelet aggregation agents

New analogues of n-butylphthalide (NBP) bearing various lengths of alkyl and different substitution at the two-position of phthalide were designed and synthesised. Preliminary evaluation and prediction of ACD LogP software indicate that the derivatives display significant improvement in water solubility than NBP does. Further biological analysis showed that NBP analogues specifically inhibit platelet aggregation induced by arachidonic acid but have no effect on that induced by adenosine 5-diphosphate. Especially compounds 1 and 3 were stronger than classical anti-platelet drug, aspirin, and equal potent with NBP, respectively. These findings provide an alternative approach to the development of NBP analogues with anti-platelet aggregation activity with good water solubility for the intervention of ischemic stroke.

Anticoagulant therapy is not a risk factor for choroidal haemorrhage

Dear Editor, Jin et al. report the experience of the management of delayed supra-choroidal haemorrhage (DSCH) [1]. Table 1 in their paper lays out the risk factors, procedures, and outcomes, but does not mention usage of anticoagulation and antiplatelet aggregation agents. Based on one patient who is stated to have been on Warfarin, they go on to conclude that Warfarin usage is a major risk factor for DSCH, and also recommend cessation of warfarin for 4 days to allow resynthesis of coagulation factors, and cessation of other antiplatelet agents (such as clopidogrel and ticlopidine) for 2 weeks. We think it is important to point out that clear corneal phacoemulsification under topical anaesthesia can be safely done without stopping warfarin or antiplatelet agents [2, 3]. The American Academy of Ophthalmology’s Preferred Practice Pattern on this subject also states that anticoagulation with warfarin does not significantly increase the risk of choroidal haemorrhage [4,] as was also shown by the British National Cataract Dataset report [5]; and the UK Royal College of Ophthalmologists also does not recommend stopping anticoagulation or antiplatelet agents for cataract surgery, as doing so may increase the risk of stroke and death. [6] We would therefore like to emphasise that stopping anticoagulation or antiplatelet agents for routine phacoemulsification is against available evidence and guidelines, and therefore should not be done, although it is sensible to check that the INR is in the desired therapeutic range as set by the treating physician, and the surgery should be done under topical anaesthesia by an ophthalmologist used to doing the operation with this technique; if need be, sub-Tenon anaesthesia may be used.

Synthesis of N-arylmethyl Substituted Indole Derivatives as New Antiplatelet Aggregation Agents.

A number of N-arylmethyl substituted indole derivatives have been synthesized and their effectiveness against ADP and arachidonic acid induced platelet aggregation in human plasma was determined. The desired compounds were synthesized by reacting the appropriate aniline derivative with isatin (or substituted isatin) to form the corresponding imine structures. The so formed compound was then activated using sodium hydride and reacted with the proper substituted benzyl halides. Among the tested compounds, derivatives 4a, 4c, 4d, 4f-i and 4k were the most potent compounds with satisfactory IC50 values (under 38.5 μM) for inhibition of platelet aggregation induced by arachidonic acid. All indole derivatives without substitution on position 1 of the indole ring, exhibited either weaker activities or were not active at all.

English

Platelet aggregation is one of the major causes of cardiovascular diseases. Our search for bioactive molecules from nature, led to the isolation of betulinic acid (BA) and structural modification of BA to 3&beta;-acetoxybetulinic acid (BAA). Both inhibited blood platelet aggregation induced by thrombin, adenosine diphosphate (ADP) and epinephrine. BAA showed an enhance inhibition of platelet aggregation, in the thrombin-induced platelet aggregation (54.5&plusmn;0.01 at 1 mg/ml, 63.5&plusmn;0.17 at 3 mg/ml and 73.5&plusmn;0.15 at 10 mg/ml; IC50 0.81 mg/ml) which was observed to be significantly (p&lt;0.05) similar to that of the standard aspirin (65.4&plusmn;0.07 at 1 mg/ml, 72.1&plusmn;0.03 at 3 mg/ml and 76.5&plusmn;1.22 at 10 mg/ml; IC50 0.33 mg/ml). The results clearly shows that functional group modification of BA to give BAA led to enhanced activity, hence BAA provides a better option as lead in the search for anti-platelet aggregation agents from nature. Key words: Anti-platelet aggregation, aggregation inducer, Betulinic acid, acetoxybetulinic acid, Melalueca bracteata.

Central and Hemicentral Retinal Vein Occlusion: Role of Anti–Platelet Aggregation Agents and Anticoagulants

Central and Hemicentral Retinal Vein Occlusion: Role of Anti–Platelet Aggregation Agents and Anticoagulants

Triterpenes from the stem bark of Protorhus longifolia exhibit anti-platelet aggregation activity

Two triterpenes were isolated from the chloroform extract of Protorhus longifolia. Theirstructures were established through spectral analysis (nuclear magnetic resonance (NMR), infrared (IR), liquid chromatography mass spectrometry (LC-MS)) as 3-oxo-5α-lanosta-8,24-dien-21-oic acid (1) and 3β-hydroxylanosta-9,24-dien-24-oic acid (2). The two triterpenes were screened for their antioxidant, cytotoxicity, anti-platelet aggregation and anti-inflammatory activity. The antioxidant activity of the compounds was measured using 1,1′-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) free radicals scavenging and reduction potential assays. The cytotoxic effects of the compounds was determined against human embryonic kidney (HEK293) and human hepatocellular carcinoma (HepG2) cell lines, while the acute anti-inflammatory activity was determined using the carrageenan-induced rat paw edema model. The anti-platelet aggregation activity of the compounds was separately investigated on thrombin, adenosine diphosphate (ADP), epinephrine and arachidonic acid induced rat platelet aggregation. Although, both compounds exhibited poor antioxidant activities, they showed good concentration dependent anti-platelet aggregation activity. The highest activity by compound 1 (IC50 of 0.99 mg/ml) was observed on the thrombin-induced platelet aggregation. Compound 2 (3 mg/ml) exhibited anticoagulant activity on whole blood and significantly (P < 0.05) inhibited the acute inflammation of rat paw. The compound also weakly inhibited the growth of HEK293 and HepG2 cells. The triterpenes could be potential pharmacologically active anti-platelet aggregation agents. Key words: Triterpenes, antioxidant, anti-inflammatory, anti-platelet aggregation, cytotoxicity.

Central and Hemicentral Retinal Vein Occlusion: Role of Anti–Platelet Aggregation Agents and Anticoagulants

To investigate systematically the role of anti-platelet-aggregating drugs or anticoagulants in central retinal vein occlusion (CRVO) and hemi-CRVO. Cohort study. Six hundred eighty-six consecutive patients with CRVO (567 patients, 585 eyes) and nonischemic hemi-CRVO (119 patients, 122 eyes). At first visit, all patients had a detailed ophthalmic and medical history (including the use of anti-platelet aggregating drugs or anticoagulants), and comprehensive ophthalmic and retinal evaluation. Visual evaluation was carried out by recording visual acuity, using the Snellen visual acuity chart, and visual fields with a Goldmann perimeter. The same ophthalmic evaluation was performed at each follow-up visit. At the initial visit, CRVO and hemi-CRVO were classified as nonischemic and ischemic. Visual acuity, visual fields, and severity of retinal hemorrhages. All 3 types of CRVO, showed a significantly greater severity of retinal hemorrhages among aspirin users than nonusers (P<0.001). Initial visual acuity and visual fields were significantly worse in aspirin users than nonusers in nonischemic CRVO and hemi-CRVO, but did not differ for ischemic CRVO. Among patients with nonischemic CRVO who initially had 20/60 or better visual acuity, there was a significant association of aspirin use with visual acuity deterioration. The odds ratio of visual acuity deterioration, adjusting for age, diabetes, ischemic heart disease, and hypertension, for aspirin users relative to nonusers was 2.24 (95% confidence interval [CI], 1.14-4.41; P = 0.020). Of those whose macular edema resolved, overall cumulative visual acuity outcome also suggested a higher percentage with deterioration among aspirin users, odds ratio for deterioration of 3.62 (95% CI, 0.97-13.54; P = 0.05) for aspirin users relative to nonusers. For the nonischemic CRVO patients with 20/70 or worse visual acuity at the initial visit, after resolution of macular edema, improvement in visual acuity was less likely in the aspirin users than in nonusers (odds ratio, 0.18; 95% CI, 0.04-0.72; P = 0.016). Findings of this study indicate that, for patients with CRVO and hemi-CRVO, the use of aspirin, other anti-platelet aggregating agents, or anticoagulants was associated with a worse visual outcome and no apparent benefit. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

First total synthesis of antrocamphin A and its analogs as anti-inflammatory and anti-platelet aggregation agents

Naturally occurring antrocamphin A (1) is a potent anti-inflammatory compound from the edible fungus Antrodia camphorata (Taiwanofungus camphoratus), whose wild fruiting body is used as a valuable folk medicine in Taiwan. This study is the first total synthesis of antrocamphin A (1) and its analogs. Their inhibition ability on NO release, superoxide anion generation, elastase release and platelet aggregation are reported herein.

Anticoagulants and antiplatelet agents and the risk of development and recurrence of chronic subdural haematomas

Seventy-one patients from northern Sweden were diagnosed with chronic subdural haematomas (CSDH) and treated at the Department of Neurosurgery at Umeå University Hospital over 12 months. Fifty-four patients with CSDH had a history of head trauma (trauma group), while 17 patients had no previous head trauma (non-trauma group). In the non-trauma group 71% of patients were treated with anticoagulants or antiplatelet aggregation agents (AAA) compared to 18% in the trauma group. Considering only AAA, 59% of the non-trauma patients were treated with these drugs versus 17% of patients in the trauma group. The recurrence rate for all patients was 17%. These findings confirm that the use of anticoagulants and AAA is over-represented in patients with non-traumatic CSDH. In our study, recurrence was not associated with previous use of anticoagulants or AAA.

Screening of anti‐platelet aggregation agents from Panax notoginseng using human platelet extraction and HPLC–DAD–ESI‐MS/MS

Root of Panax notoginseng (Sanqi in Chinese) is a highly valued and commonly used Chinese medicine. It has been widely used for treatment of cardio- and cerebro-vascular diseases. In this study, a method involving human platelet extraction and HPLC-DAD-ESI-MS/MS was developed for screening potential anti-platelet aggregation agents in Sanqi. Five compounds which could interact with human platelets were found, and four were identified as adenosine, guanosine, ginsenoside Rh1, and ginsenoside F1, respectively. The effects on rabbit platelet aggregation induced by arachidonic acid, adenosine diphosphate, and thrombin were also investigated in vitro. The results showed that the nucleosides adenosine and guanosine mainly contributed to the anti-platelet aggregation of Sanqi. The data suggest that human platelet extraction combined with HPLC-DAD-ESI-MS/MS is a useful method for screening anti-platelet aggregation agents from Chinese medicines.