Fast Isolation of Flavonoids from the Endemic Species Nolana ramosissima I.M. Johnst and Its Endothelium-Independent Relaxation Effect in Rat Aorta

The infusion of the desertic plant Nolana ramosissima I.M. Johnst showed vascular smooth muscle relaxation in rat aorta and the presence of several phenolic compounds, which were detected by high resolution UHPLC-Orbitrap-HESI-MS. In addition, five flavonoids were rapidly isolated from a methanolic extract using high-performance counter-current chromatography (HPCCC). The N. ramosissima extract showed endothelium-independent relaxation effect in rat aorta. Sixty-one compounds were detected in the infusion, mainly glycosylated flavonoids, flavanones and several oxylipins, suggesting that a synergistic effect between the compounds in the extracts could be responsible for the relaxation activity. Vascular activity experiments were done in isolated organ bath. In rat aorta, a nitric oxide inhibitor did not prevent the relaxation effects of the extract; however, a selective guanylyl cyclase inhibitor partially blunted this effect. The compound 5,3′-dihydroxy-4′7-dimethoxyflavone presented higher relaxation effect than 100 μg/mL of N. ramosissima extract. The extract and the isolated metabolites from N. ramosissima can show relaxation effects on rat aorta by a mechanism that is independent of the endothelium.

Abstract 029: Photoacoustic Imaging - Novel In Vivo Quantification of Placental Hypoxia in a Mouse Model of Hypertensive Pregnancy

Placental hypoxia/ischemia induces abnormal maternal and neonatal outcomes including preeclampsia and intrauterine growth restriction (IUGR). The ability to accurately determine placental oxygenation in a non-invasive way and in real-time is highly important during pregnancy as it may allow for the early diagnosis of IUGR and preeclampsia. Photoacoustic imaging (PA) is a novel preclinical and emerging clinical tool that combines optical contrast of photoacoustic laser technology with high spatial resolution of ultrasound. PA measures tissue oxygen saturation (sO2) that reflects differences in absorption spectra for oxygenated and deoxygenated hemoglobin. By using photoacoustic features of VEVO LAZR high resolution ultrasound system (VisualSonics) in a three-dimensional mode we investigated the sensitivity and accuracy of PA for placental oxygenation in C57Bl/6 mice at day 14 of gestation. Furthermore, since nitric oxide deficiency is associated with upregulation of circulatory hypoxia markers, C57Bl/6 mice were chronically treated with the nitric oxide inhibitor, L-NAME via osmotic minipumps (50 mg/kg/day; days 13 to 18 of gestation). The comparisons between scanned vs. not scanned uteroplacental units showed that PA had no effect on fetal (scanned: 0.028±0.001 vs. not scanned: 0.03±0.001 g/maternal body weight; p>0.05) or placental (scanned: 0.002±0.003 vs. not scanned: 0.002±0.002 g/maternal body weight; p>0.05) weights in C57Bl/6 mice. Changing inhaled O2 from 100- to 20% resulted on average in 12.5% reduction in total placental sO2. Systolic blood pressures were higher in L-NAME-treated vs. C57Bl/6 mice (215.8±0.8 vs. sham 99.3±4.4 mmHg; p<0.05). L-NAME infusion decreased sO2 in all areas of the placenta: labyrinth (73.6±0.97 vs. 58.6±3.4%, p<0.05), mesometrial triangle (63.0±2.0 vs. 48.9±1.0%, p<0.05), and total placenta (68.2±1.7 vs. 54.4±2.2%, p<0.05). Placental labyrinth had higher sO2 vs. mesometrial triangle area in both L-NAME infused (58.6±3.4 vs. 48.9±1.0%, p<0.05) and in C57Bl/6 (73.6±0.97 vs. 63.0±2.0%, p<0.05) mice reflecting elaborate branching morphology of the labyrinth. Our data suggest that PA imaging can detect regional differences in placental sO2 non-invasively and at different physiological states.