Pseudostellaria heterophylla is used in China not only as a functional food but also as an herb to tonify the spleen, enhance immunity, and treat palpitation. Our previous investigation showed that a fraction enriched in glycosides obtained from the roots of P. heterophylla possessed pronounced protective effects on H9c2 cells against CoCl2-induced hypoxic injury. However, the active compounds responsible for the observed effects were still unknown. In the current investigation, pseudosterins A–C (1–3), three new alkaloids with a 1-ethyl-3-formyl-β-carboline skeleton, together with polydatin, have been isolated from the active fraction. Their structures were elucidated on the basis of spectroscopic analysis and quantum chemical calculations. The four compounds showed cardioprotective effects against sodium hydrosulfite-induced hypoxia-reoxygenation injury in H9c2 cells, with the three alkaloids being more potent. This is also the first report of alkaloids with a β-carboline skeleton isolated from P. heterophylla as cardioprotective agents. 相似文献
The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component. However, the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible. We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode. Numerical simulation shows that it can be focused into a sharper focal spot of 0.125λ2 without additional apodizations or filters. The beam quality describing the purity of longitudinally polarized component is up to 86%. 相似文献
A fast analytical method for the simultaneous determination of fumonisin B1 (FB1) and fumonisin B2 (FB2) in corn using a novel QuEChERS method and LC–MS–MS was developed and validated. Samples were extracted with methanol–water (3:1 v/v) by means of ultrasonic extraction. The extract was purified with a novel modified QuEChERS method. Firstly, FB1 and FB2 in the extract were retained with primary secondary amine (PSA). Then, FB1 and FB2 were released from PSA with 1.0 % formic acid in methanol. The final eluate was diluted with water, and analyzed by LC–MS–MS on a Waters Acquity BEH C18 column with 0.1 % formic acid in water/methanol as mobile phase with gradient elution. Mean recoveries of 83.5–102.4 % with CVs of 3.6–10.5 % were obtained at fortification levels of 2, 50 and 1,000 μg kg−1. The limit of quantification was 2.0 μg kg−1.