Natural (iso)flavonoids have been recently reported to inhibit cyclic nucleotide phosphodiesterases (PDEs) and induce vasorelaxation, albeit the results described in the literature are discordant. ...The cGMP-selective isoform PDE-5A, in particular, represents the target of sildenafil and its analogues in the treatment of erectile dysfunction (ED) and pulmonary hypertension by promoting relaxation in vascular smooth muscle through the activation of the NO/cGMP pathway. We undertook this study to verify if osajin and pomiferin, two natural prenylated isoflavones and major constituents of Maclura pomifera extracts previously investigated for their anticancer, antibacterial and antidiabetic properties, show inhibitory activity on PDE-5A. These two isoflavones were isolated from the plant extracts and then synthetically modified to obtain a set of semi-synthetic derivatives with slight and focused modifications on the natural scaffold. The compounds were at first screened against PDE-5A in vitro and, based on the encouraging results, further tested for their relaxant effect on isolated rat artery rings. Computational docking studies were also carried out to explore the mode of interaction with the target protein. The obtained data were compared to the behaviour of the well-known PDE-5A inhibitor sildenafil. Our results demonstrate that semi-synthetic derivatives of osajin and pomiferin show an inhibitory effect on the isolated enzyme that, for some of the compounds, is accompanied by a vasorelaxant activity. Based on our findings, we propose the here described isoflavones as potential lead compounds for the development, starting from natural scaffolds, of a new class of PDE-5A inhibitors with vasorelaxant properties.
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Although spiral computed tomography (CT) is being used increasingly as the first-line imaging procedure in the diagnostic workup of patients with clinically suspected pulmonary embolism (PE), the ...diagnostic value of negative findings, at least when using the four-detector row scanners, is still controversial. A total of 702 consecutive patients with clinical symptoms suggestive of PE underwent four-slice CT. Patients with negative findings received the determination of D-dimer. Those with positive D-dimer underwent further diagnostic workup to confirm or rule out the diagnosis of PE. Those with negative D-dimer were followed-up to 6 months to detect the development of symptomatic venous thromboembolism (VTE). The CT test was interpreted as negative in 536 patients (76.3%). These patients had the D-dimer determination, which was positive in 279 and negative in the remaining 257 patients. Of the former, PE subsequently was documented in 55 patients (19.7%). Of the latter, symptomatic VTE in the follow-up period developed in three patients (1.17%; 95% confidence interval, 0.24 to 3.38%). In conclusion, when using the four-detector row, the negative predictive value of CT findings in patients with clinically suspected PE and positive D-dimer is low. In contrast, it is safe to withhold anticoagulation from patients with negative findings and negative D-dimer.
