Antiplatelet and Anticoagulant Effects of Diterpenes Isolated from the Marine Alga,Dictyota menstrualis

Cardiovascular diseases represent a major cause of disability and death worldwide. Therapeutics are available, but they often have unsatisfactory results and may produce side effects. Alternative treatments based on the use of natural products have been extensively investigated, because of their low toxicity and side effects. Marine organisms are prime candidates for such products, as they are sources of numerous and complex substances with ecological and pharmacological effects. In this work, we investigated, through in vitro experiments, the effects of three diterpenes (pachydictyol A, isopachydictyol A and dichotomanol) from the Brazilian marine alga, Dictyota menstrualis, on platelet aggregation and plasma coagulation. Results showed that dichotomanol inhibited ADP- or collagen-induced aggregation of platelet-rich plasma (PRP), but failed to inhibit washed platelets (WP). In contrast, pachydictyol A and isopachydictyol A failed to inhibit the aggregation of PRP, but inhibited WP aggregation induced by collagen or thrombin. These diterpenes also inhibited coagulation analyzed by the prothrombin time and activated partial thromboplastin time and on commercial fibrinogen. Moreover, diterpenes inhibited the catalytic activity of thrombin. Theoretical studies using the Osiris Property Explorer software showed that diterpenes have low theoretical toxicity profiles and a drug-score similar to commercial anticoagulant drugs. In conclusion, these diterpenes are promising candidates for use in anticoagulant therapy, and this study also highlights the biotechnological potential of oceans and the importance of bioprospecting to develop medicines.     

骆驼尿辅助治疗疾病的研究进展

尿是人类和脊椎动物为了新陈代谢的需要,经由泌尿系统及尿路排出体外的液体排泄物。近年来,骆驼尿液因具有广泛的医疗作用而引起广泛关注。在中东地区,其主要用于对疾病的辅助治疗,包括发烧、感冒甚至癌症。研究表明,骆驼尿液中含有一些独特的生物化学成分,如刀豆氨酸可在不同肿瘤中表现出细胞毒性和抗肿瘤活性。且研究证实骆驼尿液具有抗菌、保肝、抗肿瘤和抗血小板活性等重要作用,极具研究价值。文章主要介绍了骆驼尿液中的有效生物化学成分,并对骆驼尿液在各种疾病中的医药作用进行详细阐述,为今后对骆驼尿液的进一步研究提供理论依据。     

野菊花抗血小板聚集有效成分的筛选

以野菊花为材料,顺次用石油醚、氯仿、乙酸乙酯、正丁醇、水抽提,抽提物终浓度相当于1g草药/ml,对5μmol/L ADP诱导的血小板聚集分别抑制30.8±20.2％、49.3±29.4％、51.9±22.8％、43.5±18.0％、13.7±1.6％。野菊花乙酸乙酯抽提物抑制5μmol/L ADP诱导的血小板聚集IC_(50)=1mg/ml。乙酸乙酯抽提物用硅胶柱制备分离得C1、C2、C3、C4、C5、C6六种结晶,经TLC检识分别为一个斑点。定性分析知为基黄酮化合物。在0.5mg/ml浓度下,对2μmol/L ADP诱导的血小板聚集后三种物质分别抑制78.9％、85.3％、83.5％。     

Detection of antiplatelet antibody: comparison of platelet immunofluorescence,agglutination, and immunoinjury tests using rabbit antiequine platelet serum

Immunofluorescence, tube agglutination, and platelet factor-3 immunoinjury tests for detecting antiplatelet antibody were compared using a heterologous system of equine platelets and rabbit antiequine platelet serum. Platelet immunofluorescence tests were performed using paratormaldehyde-fixed platelets in suspension as well as in air-dried smears on glass slides (solid phase). Bright homogeneous, membranous, specific fluorescence was seen in both assays with anti-immunoglobulin G (IgG) and protein G fluorescein isothiocynate conjugates (FITC-conjugates). Protein A conjugate gave nonspecific fluorescence irrespective of normal or antiserum treatment. Anti-IgG and protein G conjugates in suspension immunofluorescence tests with the same antiserum yielded antibody titers of 1:1024 and 1:128, respectively. Similarly, respective titers of 1:512 and 1:64 were obtained with solid phase immunoassay. Platelet suspension assay was slightly better than the solid phase assay. These observations indicated that anti-IgG was more sensitive than protein G in detecting antiplatelet antibody by fluorescence microscopy, while protein A was ineffective because of its nonspecificity. Chloroquine treatment of platelets failed to reduce the nonspecific fluorescence. Platelet agglutination and platelet factor-3 tests were relatively less sensitive to detect equine antiplatelet antibody.     

Effects of aspirin dose escalation on platelet function and urinary thromboxane and prostacyclin levels in normal dogs

Established “low” aspirin dosages inconsistently inhibit platelet function in dogs. Higher aspirin dosages consistently inhibit platelet function, but are associated with adverse effects. The objectives of this study were to use an escalation in dosage to determine the lowest aspirin dosage that consistently inhibited platelet function without inhibiting prostacyclin synthesis. Eight dogs were treated with five aspirin dosages: 0.5 mg/kg q24h, 1 mg/kg q24h, 2 mg/kg q24h, 4 mg/kg q24h and 10 mg/kg q12h for 7 days. Utilizing aggregometry and a whole‐blood platelet function analyzer (PFA‐100), platelet function was evaluated before and after treatment. Urine 11‐dehydro‐thromboxane‐B₂ (11‐dTXB₂) and 6‐keto‐prostaglandin‐F_1α (6‐keto‐PGF_1α), were measured. Compared to pretreatment, there were significant post‐treatment decreases in the maximum aggregometry amplitude and increases in the PFA‐100 closure times for all dosages expect 0.5 mg/kg q24h. There was no difference in amplitude or closure time among the 2 mg/kg q24h, 4 mg/kg q24h, and 10 mg/kg q12h dosages. Compared to pretreatment values, there was a significant decrease in urinary 11‐dTXB₂‐to‐creatinine and 6‐keto‐PGF_1α‐to‐creatinine ratios, but there was no dose‐dependent decrease for either metabolite. An aspirin dosage of 2 mg/kg q24h consistently inhibits platelet function without decreasing prostacyclin synthesis significantly more than lower aspirin dosages.