New racemosol derivatives as potent cyclooxygenase (COX) inhibitors

Racemosol (1) and 10-O-demethylracemosol (2), natural products from Bauhinia malabarica Roxb., exhibit potent in vitro anti-inflammatory activities against cyclooxygenase-1 and -2 (COX-1 and -2) enzymes. To investigate the structure-activity relationship (SAR) of these molecules, we prepared and fully characterized 17 derivatives by functionalizing one, two, or all three OH group(s) of 2 (Scheme). Both the size and polarity of the substituents as well as the substitution pattern in compounds 3a-q were found to be critical for anti-inflammatory activity. The orientation of the drugs and their mode of binding were studied by molecular docking based on the known 3D structure of the complex between COX-2 and the drug SC-558. Whereas the monoacetoxy derivative 3h exhibited an equally potent inhibitory activity towards both COX-1 and -2 (Table 1), its diacetoxy congener 3i was slightly more selective toward COX-2. In vivo anti-inflammatory tests showed that 3i and 2 are slightly more active than the reference compound phenylbutazone (Table 2).     

Effects of Cytochrome P450 2C19 and Paraoxonase 1 Polymorphisms on Antiplatelet Response to Clopidogrel Therapy in Patients with Coronary Artery Disease

Clopidogrel is an antiplatelet prodrug that is recommended to reduce the risk of recurrent thrombosis in coronary artery disease (CAD) patients. Paraoxonase 1 (PON1) is suggested to be a rate-limiting enzyme in the conversion of 2-oxo-clopidogrel to active thiol metabolite with inconsistent results. Here, we sought to determine the associations of CYP2C19 and PON1 gene polymorphisms with clopidogrel response and their role in ADP-induced platelet aggregation. Clopidogrel response and platelet aggregation were determined using Multiplate aggregometer in 211 patients with established CAD who received 75 mg clopidogrel and 75–325 mg aspirin daily for at least 14 days. Polymorphisms in CYP2C19 and PON1 were genotyped and tested for association with clopidogrel resistance. Linkage disequilibrium (LD) and their epistatic interaction effects on ADP-induced platelet aggregation were analysed. The prevalence of clopidogrel resistance in this population was approximately 33.2% (n = 70). The frequencies of CYP2C19*2 and *3 were significantly higher in non-responder than those in responders. After adjusting for established risk factors, CYP2C19*2 and *3 alleles independently increased the risk of clopidogrel resistance with adjusted ORs 2.94 (95%CI, 1.65–5.26; p<0.001) and 11.26 (95%CI, 2.47–51.41; p = 0.002, respectively). Patients with *2 or *3 allele and combined with smoking, diabetes and increased platelet count had markedly increased risk of clopidogrel resistance. No association was observed between PON1 Q192R and clopidogrel resistance (adjusted OR = 1.13, 95%CI, 0.70–1.82; p = 0.622). Significantly higher platelet aggregation values were found in CYP2C19*2 and *3 patients when compared with *1/*1 allele carriers (p = 1.98×10⁻⁶). For PON1 Q192R genotypes, aggregation values were similar across all genotype groups (p = 0.359). There was no evidence of gene-gene interaction or LD between CYP2C19 and PON1 polymorphisms on ADP-induced platelet aggregation. Our findings indicated that only CYP2C19*2 and *3 alleles had an influence on clopidogrel resistance. The risk of clopidogrel resistance increased further with smoking, diabetes, and increased platelet count.