Cytotoxic ent-kaurane diterpenoids from Isodon macrophyllus

Design, Synthesis, and Anticancer Activity of Novel Enmein-Type Diterpenoid Derivatives Targeting the PI3K/Akt/mTOR Signaling Pathway

The enmein-type diterpenoids are a class of anticancer ent-Kaurane diterpnoids that have received much attention in recent years. Herein, a novel 1,14-epoxy enmein-type diterpenoid 4, was reported in this project for the first time. A series of novel enmein-type diterpenoid derivatives were also synthesized and tested for anticancer activities. Among all the derivatives, compound 7h exhibited the most significant inhibitory effect against A549 cells (IC50 = 2.16 µM), being 11.03-folds better than its parental compound 4. Additionally, 7h exhibited relatively weak anti-proliferative activity (IC50 > 100 µM) against human normal L-02 cells, suggesting that it had excellent anti-proliferative selectivity for cancer cells. Mechanism studies suggested that 7h induced G0/G1 arrest and apoptosis in A549 cells by inhibiting the PI3K/AKT/mTOR pathway. This process was associated with elevated intracellular ROS levels and collapsed MMP. In summary, these data identified 7h as a promising lead compound that warrants further investigation of its anticancer properties.

Screening and Capability Assessment of Tyrosinase Inhibitors in Isodon excisoides by Ultrafiltration Coupled with UHPLC-Q-TOF-MS and Molecular Docking Technology

Tyrosinase inhibitors can alleviate the harm to the liver caused by tyrosinase. How to effectively screen out natural tyrosinase inhibitors becomes a focus. In this study, Isodon excisoides was first extracted with the ultrasound optimized by response surface methodology. Then, a method combined ultrafiltration with ultra-liquid chromatography mass spectrometry (UHPLC/MS) was built to screen and identify tyrosinase inhibitors. The binding energies of active ingredients to tyrosinase were calculated by molecular docking. The reliability of the results was validated by the IC₅₀ of enzyme inhibition assay. As a result, the binding energies of 7 components including excisanin B, lasiokaurin, rabdophyllin G, rabdoserrin B, rabdosin D, rabdosinate and weisiensin were lower than that of resveratrol. It was indicated that these components had high tyrosinase inhibitory activity. The IC₅₀ values of lasiokaurin and excisanin B were 177 and 142 μmol/mL, which were less than that of resveratrol (183 μmol/mL). It showed that this way was simple, rapid, reliable and effective, which provided a new strategy to screen natural bioactive compounds from plants.

Diterpenoids from Isodon rubescens and their nitric oxide production inhibitory activity

Six new ent-kaurane diterpenoids, isodonrubescins A-F (1-6), together with twenty-five known ent-kaurane diterpenoids (7-31), a known ent-atisane diterpenoid (32), and two known ent-abietane diterpenoids (33-34), were isolated from Isodon rubescens. Their structures were established by means of extensive MS and NMR data analysis. Among the all isolates, compound 7 was found in a natural product for the first time, and ent-atisane diterpenoid was discovered from I. rubescens in Hubei Province, P. R. China for the first time. Furthermore, all the isolated compounds were tested for their NO production inhibitory activity in LPS stimulated RAW264.7 cells. Compounds 7-9, 12, 13, 16, and 17 displayed NO production inhibitory activities with IC50 values ranging from 1.36 to 18.25 μM, respectively.