Displaying publications 1 - 20 of 114 in total

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  1. 1H NMR based pharmacometabolomics analysis of urine identifies metabolic phenotype of clopidogrel high on treatment platelets reactivity in coronary artery disease patients
    Amin AM, Sheau Chin L, Teh CH, Mostafa H, Mohamed Noor DA, Sk Abdul Kader MA, et al.
    J Pharm Biomed Anal, 2017 Nov 30;146:135-146.
    PMID: 28873361 DOI: 10.1016/j.jpba.2017.08.018
    Clopidogrel high on treatment platelets reactivity (HTPR) has burdened achieving optimum therapeutic outcome. Although there are known genetic and non-genetic factors associated with clopidogrel HTPR, which explain in part clopidogrel HTPR, yet, great portion remains unknown, often hindering personalizing antiplatelet therapy. Nuclear magnetic resonance (1H NMR) pharmacometabolomics analysis is useful technique to phenotype drug response. We investigated using 1H NMR analysis to phenotype clopidogrel HTPR in urine. Urine samples were collected from 71 coronary artery disease (CAD) patients who were planned for interventional angiographic procedure prior to taking 600mg clopidogrel loading dose (LD) and 6h post LD. Patients' platelets function testing was assessed with the VerifyNow® P2Y12 assay at 6h after LD. Urine samples were analysed using 1H NMR. Multivariate statistical analysis was used to identify metabolites associated with clopidogrel HTPR. In pre-dose samples, 16 metabolites were associated with clopidogrel HTPR. However, 18 metabolites were associated with clopidogrel HTPR in post-dose samples. The pathway analysis of the identified biomarkers reflected that multifactorial conditions are associated with clopidogrel HTPR. It also revealed the implicated role of gut microbiota in clopidogrel HTPR. Pharmacometabolomics not only discovered novel biomarkers of clopidogrel HTPR but also revealed implicated pathways and conditions.
    Matched MeSH terms: Platelet Aggregation Inhibitors/therapeutic use*; Platelet Aggregation Inhibitors/urine*
  2. 2020 Asian Pacific Society of Cardiology Consensus Recommendations on the Use of P2Y12 Receptor Antagonists in the Asia-Pacific Region
    Tan JW, Chew DP, Abdul Kader MAS, Ako J, Bahl VK, Chan M, et al.
    Eur Cardiol, 2021 Feb;16:e02.
    PMID: 33708263 DOI: 10.15420/ecr.2020.40
    The unique characteristics of patients with acute coronary syndrome in the Asia-Pacific region mean that international guidelines on the use of dual antiplatelet therapy (DAPT) cannot be routinely applied to these populations. Newer generation P2Y12 inhibitors (i.e. ticagrelor and prasugrel) have demonstrated improved clinical outcomes compared with clopidogrel. However, low numbers of Asian patients participated in pivotal studies and few regional studies comparing DAPTs have been conducted. This article aims to summarise current evidence on the use of newer generation P2Y12 inhibitors in Asian patients with acute coronary syndrome and provide recommendations to assist clinicians, especially cardiologists, in selecting a DAPT regimen. Guidance is provided on the management of ischaemic and bleeding risks, including duration of therapy, switching strategies and the management of patients with ST-elevation and non-ST-elevation MI or those requiring surgery. In particular, the need for an individualised DAPT regimen and considerations relating to switching, de-escalating, stopping or continuing DAPT beyond 12 months are discussed.
    Matched MeSH terms: Platelet Aggregation Inhibitors
  3. A review of the effects of ticagrelor on adenosine concentration and its clinical significance
    Akkaif MA, Ng ML, Sk Abdul Kader MA, Daud NAA, Sha'aban A, Ibrahim B
    Pharmacol Rep, 2021 Dec;73(6):1551-1564.
    PMID: 34283374 DOI: 10.1007/s43440-021-00309-0
    BACKGROUND: Ticagrelor is an oral antiplatelet drug that can reversibly bind to the platelet P2Y12 receptor. Ticagrelor is metabolized mainly by CYP3A4 and produces a rapid blood concentration-dependent platelet inhibitory effect. Unlike other P2Y12 receptor antagonists, many clinical features of ticagrelor are not related to P2Y12 receptor antagonism.

    PURPOSE: This review aims to gather existing literature on the clinical effects of ticagrelor after inhibiting adenosine uptake.

    METHODOLOGY: The current study reviewed literature related to the effects of ticagrelor on adenosine metabolism. The review also examined the drug's biological effects and clinical characteristics to see how it could be used in a clinical setting.

    RESULTS: Many studies have shown that ticagrelor can inhibit equilibrative nucleoside transporter 1 (ENT1). This inhibition leads to intracellular adenosine uptake, increased adenosine half-life and plasma concentration levels and an enhanced adenosine-mediated biological effect.

    CONCLUSIONS: Based on the studies reviewed, it was found that ticagrelor essentially inhibits adenosine absorption of adenosine into cells through ENT1, which increases the concentration in the blood and subsequently increases the protection of the heart muscle by adenosine. It also prevents platelet aggregation, and extends the biological effects of coronary arteries. Moreover, it leads to a lower mortality rate in acute coronary syndrome (ACS) patients.

    Matched MeSH terms: Platelet Aggregation Inhibitors/pharmacology
  4. An investigation of the antiplatelet effects of succinobucol (AGI-1067)
    Houston SA, Ugusman A, Gnanadesikan S, Kennedy S
    Platelets, 2017 May;28(3):295-300.
    PMID: 27681689 DOI: 10.1080/09537104.2016.1218456
    Succinobucol is a phenolic antioxidant with anti-inflammatory and antiplatelet effects. Given the importance of oxidant stress in modulating platelet-platelet and platelet-vessel wall interactions, the aim of this study was to establish if antioxidant activity was responsible for the antiplatelet activity of succinobucol. Platelet aggregation in response to collagen and adenosine diphosphate (ADP) was studied in rabbit whole blood and platelet-rich plasma using impedance aggregometry. The effect of oxidant stress on aggregation, platelet lipid peroxides, and vascular tone was studied by incubating platelets, washed platelets or preconstricted rabbit iliac artery rings respectively with a combination of xanthine and xanthine oxidase (X/XO). To study the effect of succinobucol in vivo, anaesthetized rats were injected with up to 150 mg/kg succinobucol and aggregation measured in blood removed 15 mins later. Succinobucol (10-5-10-4M) significantly attenuated platelet aggregation to collagen and ADP in whole blood and platelet-rich plasma. X/XO significantly increased aggregation to collagen and platelet lipid peroxides and this was reversed by succinobucol. Addition of X/XO to denuded rabbit iliac arteries caused a dose-dependent relaxation which was significantly inhibited by succinobucol. In vivo administration up to 150 mg/kg had no effect on heart rate or mean arterial blood pressure but significantly inhibited platelet aggregation to collagen ex vivo. In conclusion, succinobucol displays anti-platelet activity in rabbit and rat blood and reverses the increase in platelet aggregation in response to oxidant stress.
    Matched MeSH terms: Platelet Aggregation/drug effects*; Platelet Aggregation Inhibitors/pharmacology*
  5. Fulltext Anti-inflammatory and antiplatelet activities of plasma are conserved across twelve mammalian species
    Ahmed S, Gul S, Idris F, Hussain A, Zia-Ul-Haq M, Jaafar HZ, et al.
    Molecules, 2014;19(8):11385-94.
    PMID: 25090125 DOI: 10.3390/molecules190811385
    Human plasma inhibits arachidonic acid metabolism and platelet aggregation. This helps human form a haemostatic control system that prevents the progress of certain aggregatory or inflammatory reactions. Whether this property of plasma is unique to human or extends to other species is not well known. It is speculated that this protective ability of plasma remains evolutionarily conserved in different mammals. In order to confirm this, the effect of plasma from 12 different mammalian species was investigated for its inhibitory potential against arachidonic acid metabolism and platelet aggregation. Metabolism of arachidonic acid by cyclooxygenase and lipoxygenase pathways was studies using radio-immuno assay and thin layer chromatography while platelet aggregation in the plasma of various mammals was monitored following turbedmetric method in a dual channel aggregometer. Results indicate that inhibition of AA metabolism and platelet aggregation is a common feature of plasma obtained from different mammalian species, although there exists large interspecies variation. This shows that besides human, other mammals also possess general protective mechanisms against various aggregatory and inflammatory conditions and this anti-inflammatory property of the plasma is evolutionarily conserved in mammalian species. The most likely candidates responsible for these properties of plasma include haptoglobin, albumin and lipoproteins.
    Matched MeSH terms: Platelet Aggregation/drug effects; Platelet Aggregation Inhibitors/pharmacology*
  6. Antiphospholipid Antibody-Mediated Thrombotic Mechanisms in Antiphospholipid Syndrome: Towards Pathophysiology-Based Treatment
    Islam MA, Alam F, Sasongko TH, Gan SH
    Curr Pharm Des, 2016;22(28):4451-69.
    PMID: 27229722
    Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by a persistently high titer of antiphospholipid antibodies (aPLs). In addition to pregnancy morbidity, arterial and/or venous thrombosis is another clinical feature of APS. Regardless of the type of APS, the thrombi formed by the induction of aPLs can lead to deep vein thrombosis, pulmonary embolism, myocardial infarction, stroke and gangrene. Although the concept of APS was introduced approximately 32 years ago, its thrombogenic pathophysiology is still unclear. Therefore, patients are treated with anticoagulant and/or antiplatelet regimens just as in other thrombotic disorders even though the thrombotic pathophysiology is mainly aPLs-mediated. In this review, we provided an update of the cellular, auto-immune and genetic factors known to play important roles in the generation of thrombi. Current successful regimens are also outlined along with potential emerging treatment strategies that may lead to the optimum management of thrombotic APS patients.
    Matched MeSH terms: Platelet Aggregation Inhibitors/therapeutic use
  7. Antiplatelet activity of aporphine and phenanthrenoid alkaloids from Aromadendron elegans Blume
    Jantan I, Raweh SM, Yasin YH, Murad S
    Phytother Res, 2006 Jun;20(6):493-6.
    PMID: 16619347
    Six aporphine and one phenanthrenoid alkaloids isolated from Aromadendron elegans Blume were investigated for their ability to inhibit arachidonic acid (AA), collagen and ADP induced platelet aggregation in human whole blood. The antiplatelet activity of the compounds was measured in vitro by the Chrono Log whole blood aggregometer using an electrical impedance method. Of the compounds tested, (-)-N-acetylnornuciferine, (-)-N-acetylanonaine and 1-(N-acetyl-N-methylamino)ethyl-3,4,6-trimethoxy-7-hydroxyphenanthrene showed strong inhibition on platelet aggregation caused by all three inducers. (-)-N-acetylanonaine was the most effective antiplatelet compound as it inhibited both arachidonic acid, collagen and ADP-induced platelet aggregation with IC(50) values of 66.1, 95.1 and 80.6 microm, respectively.
    Matched MeSH terms: Platelet Aggregation/drug effects*; Platelet Aggregation Inhibitors/isolation & purification*
  8. Fulltext Antiplatelet aggregation and platelet activating factor (PAF) receptor antagonistic activities of the essential oils of five Goniothalamus species
    Moharam BA, Jantan I, Ahmad Fb, Jalil J
    Molecules, 2010 Aug;15(8):5124-38.
    PMID: 20714290 DOI: 10.3390/molecules15085124
    Nine essential oils, hydrodistilled from different parts of five Goniothalamus species (G. velutinus Airy-Shaw, G. woodii Merr., G. clemensii Ban, G. tapis Miq. and G. tapisoides Mat Salleh) were evaluated for their ability to inhibit platelet aggregation in human whole blood using an electrical impedance method and their inhibitory effects on platelet activating factor (PAF) receptor binding with rabbit platelets using 3H-PAF as a ligand. The chemical composition of the oils was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The bark oil of G. velutinus was the most effective sample as it inhibited both arachidonic acid (AA) and ADP-induced platelet aggregation with IC(50) values of 93.6 and 87.7 microg/mL, respectively. Among the studied oils, the bark oils of G. clemensii, G. woodii, G. velutinus and the root oil of G. tapis showed significant inhibitory effects on PAF receptor binding, with IC(50 )values ranging from 3.5 to 10.5 microg/mL. The strong PAF antagonistic activity of the active oils is related to their high contents of sesquiterpenes and sesquiterpenoids, and the individual components in the oils could possibly produce a synergistic effect in the overall antiplatelet activity of the oils.
    Matched MeSH terms: Platelet Aggregation/drug effects*; Platelet Aggregation Inhibitors/pharmacology*
  9. Antiplatelet therapy in diabetic ischemic stroke patients: associated factors and outcomes
    Hassan Y, Al-Jabi SW, Aziz NA, Looi I, Zyoud SH
    Int J Clin Pharmacol Ther, 2011 Oct;49(10):605-13.
    PMID: 21961485 DOI: 10.5414/cp201574
    BACKGROUND: Patients with diabetes mellitus (DM) are more prone to develop atherosclerotic complications including stroke. Moreover, as a primary and secondary prevention of stroke, antiplatelet therapy is recommended by clinical guidelines for patients with DM.

    AIMS: This study aimed to determine the prevalence of antiplatelet therapy use prior to current stroke in diabetic ischemic stroke patients, to examine the factors associated with the use of this important therapy and to assess the impact of the previous use of antiplatelet therapy on ischemic stroke outcomes.

    METHODS: An observational study of diabetic acute ischemic stroke patients attending a Malaysian hospital during a 1-year period was carried out. Demographic information, risk factors, previous antiplatelet use and variables used to assess stroke outcomes were collected from medical records.

    RESULTS: Overall, 295 diabetic stroke patients were analyzed. The prevalence of previous antiplatelet use among diabetic patients was 38.3%. The independent variables associated with the previous use of antiplatelet medication were previous stroke attack (p < 0.001) and ischemic heart disease (p < 0.001). Better outcomes as measured by a minor Glasgow Coma Scale at admission (p = 0.032), and a higher Modified Barthel index at discharge (p = 0.027) were observed among patients on previous antiplatelet therapy.

    CONCLUSION: Our data suggest that antiplatelet therapy is under prescribed among such diabetic stroke patients, particularly in primary prevention. Effective methods to increase antiplatelet use and to enhance the adherence of clinical practice guidelines should be considered at the national and community level.
    Matched MeSH terms: Platelet Aggregation Inhibitors/therapeutic use*
  10. Fulltext Antiplatelet treatment for acute secondary prevention of non-cardioembolic minor stroke / transient ischaemic attack: an update for the acute physician
    Krishnan K, Law ZK, Minhas JS, Bath PM, Robinson TG, Sprigg N, et al.
    Clin Med (Lond), 2022 Sep;22(5):449-454.
    PMID: 36507812 DOI: 10.7861/clinmed.2021-0597
    Acute stroke is the leading cause of disability in the UK and a leading cause of mortality worldwide. The majority of patients with ischaemic stroke present with minor deficits or transient ischaemic attack (TIA), and are often first seen by patient-facing clinicians. Urgent evaluation and treatment are important as many patients are at high risk of major vascular events and death within hours to days after the index event. This narrative review summarises the evidence on four antiplatelet treatments for non-cardioembolic stroke prevention: aspirin, clopidogrel, dipyridamole and ticagrelor. Each of these drugs has a unique mechanism and has been tested as a single agent or in combination. Aspirin, when given early is beneficial and short-term treatment with aspirin and clopidogrel has been shown to be more effective in high-risk TIA / minor stroke. This review concludes by highlighting gaps in evidence, including scope for future trials that could potentially change clinical practice.
    Matched MeSH terms: Platelet Aggregation Inhibitors/therapeutic use
  11. Fulltext Asia-Pacific working group consensus on non-variceal upper gastrointestinal bleeding: an update 2018
    Sung JJ, Chiu PW, Chan FKL, Lau JY, Goh KL, Ho LH, et al.
    Gut, 2018 10;67(10):1757-1768.
    PMID: 29691276 DOI: 10.1136/gutjnl-2018-316276
    Non-variceal upper gastrointestinal bleeding remains an important emergency condition, leading to significant morbidity and mortality. As endoscopic therapy is the 'gold standard' of management, treatment of these patients can be considered in three stages: pre-endoscopic treatment, endoscopic haemostasis and post-endoscopic management. Since publication of the Asia-Pacific consensus on non-variceal upper gastrointestinal bleeding (NVUGIB) 7 years ago, there have been significant advancements in the clinical management of patients in all three stages. These include pre-endoscopy risk stratification scores, blood and platelet transfusion, use of proton pump inhibitors; during endoscopy new haemostasis techniques (haemostatic powder spray and over-the-scope clips); and post-endoscopy management by second-look endoscopy and medication strategies. Emerging techniques, including capsule endoscopy and Doppler endoscopic probe in assessing adequacy of endoscopic therapy, and the pre-emptive use of angiographic embolisation, are attracting new attention. An emerging problem is the increasing use of dual antiplatelet agents and direct oral anticoagulants in patients with cardiac and cerebrovascular diseases. Guidelines on the discontinuation and then resumption of these agents in patients presenting with NVUGIB are very much needed. The Asia-Pacific Working Group examined recent evidence and recommends practical management guidelines in this updated consensus statement.
    Matched MeSH terms: Platelet Aggregation Inhibitors/therapeutic use*
  12. Association of CYP2C19*2 polymorphism with clopidogrel response and 1-year major adverse cardiovascular events in a multiethnic population with drug-eluting stents
    Tan SSN, Fong AYY, Mejin M, Gerunsin J, Kong KL, Chin FYY, et al.
    Pharmacogenomics, 2017 08;18(13):1225-1239.
    PMID: 28745576 DOI: 10.2217/pgs-2017-0078
    BACKGROUND: Patients undergoing elective percutaneous coronary intervention (PCI) with drug-eluting stents (DES) who have impaired clopidogrel response, have a higher risk of subsequent major adverse cardiovascular events (MACE).

    AIM OF THE STUDY: To establish the relationship between CYP2C19 genotype, clopidogrel responsiveness and 1-year MACE.

    MATERIALS & METHODS: Aspirin/clopidogrel responses were assessed with Multiplate Analyzer and CYP2C19*2 allele by SpartanRx.

    RESULTS: A total of 42.0% carried ≥1 CYP2C19*2 allele. Prevalences of aspirin and clopidogrel high on-treatment platelet reactivity (HPR; local cutoffs: 300 AU*min for aspirin and 600 AU*min for clopidogrel) were 11.5% and 19.8% respectively. In multivariate ana-lysis, clopidogrel HPR was found to be an independent predictor for 1-year MACE (adj HR: 3.48, p = 0.022 ).

    CONCLUSION: Having clopidogrel HPR could be a potentially modifiable risk factor guided by phenotyping.

    Matched MeSH terms: Platelet Aggregation Inhibitors/adverse effects*; Platelet Aggregation Inhibitors/therapeutic use
  13. Attenuation of Thrombosis by Crude Rice (Oryza sativa) Bran Policosanol Extract: Ex Vivo Platelet Aggregation and Serum Levels of Arachidonic Acid Metabolites
    Wong WT, Ismail M, Tohit ER, Abdullah R, Zhang YD
    Evid Based Complement Alternat Med, 2016;2016:7343942.
    PMID: 27800004
    Background. Vascular occlusion or thrombosis was often attributed to uncontrolled platelet activation. Influence of sugarcane policosanol extract on platelet was reported but little was known of rice bran policosanol, particularly its mechanisms of actions on platelet activities. Objective. Antiplatelet mechanisms of rice bran policosanol extract (RBE) were studied using hyperlipidemic Sprague Dawley rats. Ex vivo platelet aggregation, platelet count (PC), bleeding time (BT), and coagulation time were assayed. Serum eicosanoids and other aggregation-related metabolites levels were quantified. Design. Rats were divided into 6 groups for comparisons (vehicle control Tween 20/H2O, high dose policosanol 500 mg/kg, middle dose policosanol 250 mg/kg, low dose policosanol 100 mg/kg, and positive control aspirin 30 mg/kg). Results. Low dose 100 mg/kg of RBE inhibited aggregation by 42.32 ± 4.31% and this was comparable with the effect of 30 mg/kg aspirin, 43.91 ± 5.27%. Results showed that there were no significant differences in PC, BT, and coagulation time among various groups after RBE treatment. Serum thromboxane A2 was attenuated while prostacyclin level increased upon RBE treatment. Conclusions. RBE reduced ex vivo ADP-induced platelet aggregation without giving adverse effects. No changes in full blood count suggested that rice bran policosanol did not disturb biological blood cell production and destruction yet it reduced aggregation through different mechanisms.
    Matched MeSH terms: Platelet Aggregation
  14. Availability and affordability of cardiovascular disease medicines and their effect on use in high-income, middle-income, and low-income countries: an analysis of the PURE study data
    Khatib R, McKee M, Shannon H, Chow C, Rangarajan S, Teo K, et al.
    Lancet, 2016 Jan 2;387(10013):61-9.
    PMID: 26498706 DOI: 10.1016/S0140-6736(15)00469-9
    BACKGROUND: WHO has targeted that medicines to prevent recurrent cardiovascular disease be available in 80% of communities and used by 50% of eligible individuals by 2025. We have previously reported that use of these medicines is very low, but now aim to assess how such low use relates to their lack of availability or poor affordability.
    METHODS: We analysed information about availability and costs of cardiovascular disease medicines (aspirin, β blockers, angiotensin-converting enzyme inhibitors, and statins) in pharmacies gathered from 596 communities in 18 countries participating in the Prospective Urban Rural Epidemiology (PURE) study. Medicines were considered available if present at the pharmacy when surveyed, and affordable if their combined cost was less than 20% of household capacity-to-pay. We compared results from high-income, upper middle-income, lower middle-income, and low-income countries. Data from India were presented separately given its large, generic pharmaceutical industry.
    FINDINGS: Communities were recruited between Jan 1, 2003, and Dec 31, 2013. All four cardiovascular disease medicines were available in 61 (95%) of 64 urban and 27 (90%) of 30 rural communities in high-income countries, 53 (80%) of 66 urban and 43 (73%) of 59 rural communities in upper middle-income countries, 69 (62%) of 111 urban and 42 (37%) of 114 rural communities in lower middle-income countries, eight (25%) of 32 urban and one (3%) of 30 rural communities in low-income countries (excluding India), and 34 (89%) of 38 urban and 42 (81%) of 52 rural communities in India. The four cardiovascular disease medicines were potentially unaffordable for 0·14% of households in high-income countries (14 of 9934 households), 25% of upper middle-income countries (6299 of 24,776), 33% of lower middle-income countries (13,253 of 40,023), 60% of low-income countries (excluding India; 1976 of 3312), and 59% households in India (9939 of 16,874). In low-income and middle-income countries, patients with previous cardiovascular disease were less likely to use all four medicines if fewer than four were available (odds ratio [OR] 0·16, 95% CI 0·04-0·57). In communities in which all four medicines were available, patients were less likely to use medicines if the household potentially could not afford them (0·16, 0·04-0·55).
    INTERPRETATION: Secondary prevention medicines are unavailable and unaffordable for a large proportion of communities and households in upper middle-income, lower middle-income, and low-income countries, which have very low use of these medicines. Improvements to the availability and affordability of key medicines is likely to enhance their use and help towards achieving WHO's targets of 50% use of key medicines by 2025.
    FUNDING: Population Health Research Institute, the Canadian Institutes of Health Research, Heart and Stroke Foundation of Ontario, AstraZeneca (Canada), Sanofi-Aventis (France and Canada), Boehringer Ingelheim (Germany and Canada), Servier, GlaxoSmithKline, Novartis, King Pharma, and national or local organisations in participating countries.
    Matched MeSH terms: Platelet Aggregation Inhibitors/economics; Platelet Aggregation Inhibitors/supply & distribution; Platelet Aggregation Inhibitors/therapeutic use
  15. Benzophenones and xanthones from Garcinia cantleyana var. cantleyana and their inhibitory activities on human low-density lipoprotein oxidation and platelet aggregation
    Jantan I, Saputri FC
    Phytochemistry, 2012 Aug;80:58-63.
    PMID: 22640928 DOI: 10.1016/j.phytochem.2012.05.003
    Three benzophenones, 2,6,3',5'-tetrahydroxybenzophenone (1), 3,4,5,3',5'-pentahydroxybenzophenone (3) and 3,5,3',5'-tetrahydroxy-4-methoxybenzophenone (4), as well as a xanthone, 1,3,6-trihydroxy-5-methoxy-7-(3'-methyl-2'-oxo-but-3'-enyl)xanthone (9), were isolated from the twigs of Garcinia cantleyana var. cantleyana. Eight known compounds, 3,4,5,3'-tetrahydroxy benzophenone (2), 1,3,5-trihydroxyxanthone (5), 1,3,8-trihydroxyxanthone (6), 2,4,7-trihydroxyxanthone (7), 1,3,5,7-tetrahydroxyxanthone (8), quercetin, glutin-5-en-3β-ol and friedelin were also isolated. The structures of the compounds were elucidated by spectroscopic methods. The compounds were investigated for their ability to inhibit low-density lipoprotein (LDL) oxidation and platelet aggregation in human whole blood in vitro. Most of the compounds showed strong antioxidant activity with compound 8 showing the highest inhibition with an IC₅₀ value of 0.5 μM, comparable to that of probucol. Among the compounds tested, only compound 4 exhibited strong inhibitory activity against platelet aggregation induced by arachidonic acid (AA), adenosine diphosphate (ADP) and collagen. Compounds 3, 5 and 8 showed selective inhibitory activity on platelet aggregation induced by ADP.
    Matched MeSH terms: Platelet Aggregation/drug effects*; Platelet Aggregation Inhibitors/isolation & purification; Platelet Aggregation Inhibitors/pharmacology; Platelet Aggregation Inhibitors/chemistry
  16. Biomolecular interaction of a platelet aggregation inhibitor, 3,4-methylenedioxy-β-nitrostyrene with human serum albumin: multi-spectral and computational characterization
    Kabir MZ, Roslan AA, Ridzwan NFW, Mohamad SB, Tayyab S
    J Biomol Struct Dyn, 2020 Jun;38(9):2693-2703.
    PMID: 31271347 DOI: 10.1080/07391102.2019.1640133
    Molecular interaction of the 3,4-methylenedioxy-β-nitrostyrene (MNS), an inhibitor of platelet aggregation with the main transport protein, albumin from human serum (HSA) was explored using absorption, fluorescence and circular dichroism (CD) spectroscopy in combination with in silico analyses. The MNS-HSA complexation was corroborated from the fluorescence and absorption spectral results. Implication of static quenching mechanism for MNS-HSA system was predicted from the Stern-Volmer constant, KSV-temperature relationship as well as the bimolecular quenching rate constant, kq values. Stabilization of the complex was affirmed by the value of the binding constant (Ka = 0.56-1.48 × 104 M-1). Thermodynamic data revealed that the MNS-HSA association was spontaneously driven mainly through hydrophobic interactions along with van der Waal's interaction and H-bonds. These results were well supported by in silico interpretations. Far-UV and near-UV CD spectral results manifested small variations in the protein's secondary and tertiary structures, respectively, while three-dimensional fluorescence spectra displayed microenvironmental fluctuations around protein's fluorophores, upon MNS binding. Significant improvement in the protein's thermostability was evident from the temperature-stability results of MNS-bound HSA. Binding locus of MNS, as identified by competitive drug displacement findings as well as in silico analysis, was found to be located in subdomain IIA (Sudlow's site I) of the protein.Communicated by Ramaswamy H. Sarma.
    Matched MeSH terms: Platelet Aggregation
  17. Blood compatibility of human amniotic membrane compared with heparin-coated ePTFE for vascular tissue engineering
    Kakavand M, Yazdanpanah G, Ahmadiani A, Niknejad H
    J Tissue Eng Regen Med, 2017 06;11(6):1701-1709.
    PMID: 26190586 DOI: 10.1002/term.2064
    Amniotic membrane (AM), a placenta-derived natural biomaterial, has several characteristics which make it a potential substitute for blood vessels. However, there are no reports on the effects of the AM on blood components. The aim of this study was to evaluate the blood compatibility of the epithelial and mesenchymal surfaces of the amnion for potential use in vascular tissue engineering. The activation of intrinsic and extrinsic pathways of the clotting system, haemolysis and platelet adhesion were studied and the results were compared with heparin-coated expanded polytetrafluoroethylene (ePTFE) as a standard synthetic vascular graft. Prothrombin time (PT), activated partial thromboplastin time (aPTT), clotting time (CT) and haemolysis (%) tests showed that both the epithelial and mesenchymal sides of the AM are haemocompatible. Platelet aggregation and P-selectin production from the platelets showed that the epithelial surface of the AM has less induction of platelet activation than ePTFE. The results of scanning electron microscopy (SEM) demonstrated that platelets in contact with ePTFE had a higher rate of adhesion than with the epithelial and mesenchymal surfaces of the AM. Moreover, the morphological distribution of the platelets showed that the majority of platelets were round, while a large number of cells on ePTFE were dendritic. These results suggest that the AM which contains epithelial and mesenchymal stem cells has appropriate haemocompatibility to be employed in vascular tissue engineering, especially as a vein substitute. Copyright © 2015 John Wiley & Sons, Ltd.
    Matched MeSH terms: Platelet Aggregation
  18. CYP2C19 Genotype-Guided Antiplatelet Therapy Among Asian Patients with Ischaemic Stroke
    Kow CS, Zaihan AF, Hasan SS
    Clin Drug Investig, 2021 01;41(1):115-116.
    PMID: 33237558 DOI: 10.1007/s40261-020-00985-5
    Matched MeSH terms: Platelet Aggregation Inhibitors
  19. CYP2C19 and PON1 polymorphisms regulating clopidogrel bioactivation in Chinese, Malay and Indian subjects
    Chan MY, Tan K, Tan HC, Huan PT, Li B, Phua QH, et al.
    Pharmacogenomics, 2012 Apr;13(5):533-42.
    PMID: 22462746 DOI: 10.2217/pgs.12.24
    AIM, MATERIALS & METHODS: We investigated the functional significance of CYP2C19*2, *3, *17 and PON1 Q192R SNPs in 89 consecutive Asian patients on clopidogrel treatment and the prevalence of functionally significant polymorphisms among 300 Chinese, Malays and Asian Indians.
    Matched MeSH terms: Platelet Aggregation/drug effects; Platelet Aggregation/genetics; Platelet Aggregation Inhibitors/administration & dosage; Platelet Aggregation Inhibitors/pharmacokinetics*; Platelet Aggregation Inhibitors/pharmacology; Platelet Aggregation Inhibitors/therapeutic use
  20. CYP2C19 genotypes and their impact on clopidogrel responsiveness in percutaneous coronary intervention
    Mejin M, Tiong WN, Lai LY, Tiong LL, Bujang AM, Hwang SS, et al.
    Int J Clin Pharm, 2013 Aug;35(4):621-8.
    PMID: 23661171 DOI: 10.1007/s11096-013-9783-y
    BACKGROUND: Cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms are more common in Asian populations and have been associated with diminished antiplatelet response to clopidogrel. In this era of 'personalised medicine', combining genotyping and phenotyping as a strategy to personalise antiplatelet therapy warrants further exploration.

    OBJECTIVE: This study aimed to investigate the prevalence and impact of CYP2C19*2, *3 and *17 genotypes on clopidogrel responsiveness in a multiethnic Malaysian population planned for percutaneous coronary intervention.

    SETTING: Between October 2010 and March 2011, a total of 118 consecutive patients planned for percutaneous coronary intervention were enrolled in Sarawak General Hospital, Borneo. All patients received at least 75 mg aspirin daily for at least 2 days and 75 mg clopidogrel daily for at least 4 days prior to angiography.

    METHOD: Genotyping for CYP2C19*2 (rs4244285, 681G > A), *3 (rs4986893, 636G > A) and *17 (rs11188072, -3402C > T) alleles were performed by polymerase chain reaction-restriction fragment linked polymorphism method. Whole blood ADP-induced platelet aggregation was assessed with multiple electrode platelet aggregometry (MEA) using the Multiplate Analyzer.

    MAIN OUTCOME MEASURES: The distribution of CYP2C19*2, *3 and *17 among different ethnic groups and the association between genotype, clopidogrel responsiveness and clinical outcome were the main outcome measures.

    RESULTS: The highest prevalence of poor metabolisers (carriers of at least one copy of the *2 or *3 allele) was among the Chinese (53.7 %), followed by the Malays (26.9 %), Ibans (16.4 %) and other races (3.0 %). Poor metabolisers (PMs) had the highest mean MEA (303.6 AU*min), followed by normal metabolisers (NMs) with 270.5 AU*min and extensive metabolisers (EMs) with 264.1 AU*min (p = 0.518). Among poor responders to clopidogrel, 65.2 % were PMs and NMs, respectively, whereas none were EMs (p = 0.350). Two cardiac-related deaths were reported.

    CONCLUSION: There was a diverse inter-ethnic difference in the distribution of CYP2C19 polymorphism. The findings of this study echo that of other studies where genotype appears to have a limited impact on clopidogrel responsiveness and clinical outcome in low-risk patients.

    Matched MeSH terms: Platelet Aggregation/drug effects; Platelet Aggregation Inhibitors/administration & dosage; Platelet Aggregation Inhibitors/pharmacology; Platelet Aggregation Inhibitors/therapeutic use*
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