The Facile Preparation of PBA-GO-CuO-Modified Electrochemical Biosensor Used for the Measurement of α-Amylase Inhibitors' Activity.

Element doping and nanoparticle decoration of graphene is an effective strategy to fabricate biosensor electrodes for specific biomedical signal detections. In this study, a novel nonenzymatic glucose sensor electrode was developed with copper oxide (CuO) and boron-doped graphene oxide (B-GO), which was firstly used to reveal rhubarb extraction's inhibitive activity toward α-amylase. The 1-pyreneboronic acid (PBA)-GO-CuO nanocomposite was prepared by a hydrothermal method, and its successful boron doping was confirmed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in which the boron doping rate is unprecedentedly up to 9.6%. The CuO load reaches ~12.5 wt.%. Further electrochemical results showed that in the enlarged cyclic voltammograms diagram, the electron-deficient boron doping sites made it easier for the electron transfer in graphene, promoting the valence transition from CuO to the electrode surface. Moreover, the sensor platform was ultrasensitive to glucose with a detection limit of 0.7 µM and high sensitivity of 906 µA mM-1 cm-2, ensuring the sensitive monitoring of enzyme activity. The inhibition rate of acarbose, a model inhibitor, is proportional to the logarithm of concentration in the range of 10-9-10-3 M with the correlation coefficient of R2 = 0.996, and an ultralow limit of detection of ~1 × 10-9 M by the developed method using the PBA-GO-CuO electrode. The inhibiting ability of Rhein-8-b-D-glucopyranoside, which is isolated from natural medicines, was also evaluated. The constructed sensor platform was proven to be sensitive and selective as well as cost-effective, facile, and reliable, making it promising as a candidate for α-amylase inhibitor screening.

Discovery, Topo I inhibitory activity and mechanism evaluation of two novel cytisine-type alkaloid dimers from the seeds of Sophora alopecuroides L.

Alopecurosines A and B (CMs 1 and 2, respectively) are two novel cytisine-type alkaloid dimers first isolated from the aerial parts of Sophora alopecuroides L. CMs 1 and 2 are new dimeric alkaloids whose piperidine matrine ring is cleaved and connected via the N'-1 bond. Their chemical structures have been confirmed by IR, UV, HR-ESI-MS, and NMR. Preliminary screening shows that they have topoisomerase I (Topo I)-based anti-tumor activity. Their Topo I inhibitory activities and mechanism have been evaluated by agarose gel electrophoresis assay and a molecular docking study. The results show that the inhibition rate of CM 1 is 82.26% at 1 mM concentration and that it exhibits significantly Topo I inhibitory activity. Further research has illustrated that CMs 1 and 2 exert inhibitory activity by stabilising the Topo I-DNA cleavage complex, implying that they have the potential to be developed as novel Topo I inhibitors.