Lightweight, Flexible, and Covalent-Bonding Phenolic Fabric Reinforced Phenolic Ablator for Thermal Insulation and Conformal Infrared Stealth.

Fiber-reinforced phenolic resin aerogel (FRPRA) composite materials are seductive candidates for high-temperature thermal protection owing to their low density, excellent thermostability, and thermal insulation. However, the intrinsic stiffness restricts their further application for high efficiency. We report a homogeneous and chemical bonding strategy for fabricating lightweight and flexible FRPRA with good ablative thermal insulation performance. The compressible (cyclic strain of 60%) and bendable (cyclic strain of 30%) abilities as well as the structural stability during ablation all benefit from the compatibility between the phenolic resin aerogel matrix and the phenolic fiber reinforcement. Additionally, low bulk density and thermal conductivity of 0.20 g cm-3 and 0.043 W m-1 K-1, respectively, endow the composite with efficient thermal insulation capability. With an 8 mm-thick coupon, the temperature of 200 °C can be decreased to 70.6 °C and the temperature around 1200 °C can be camouflaged to 78 °C through combining with the Al panel. The material also enables a conformal stealth of 600 °C based on its bendability. Hence, the composite has potential in applications of both static and dynamic thermal insulation.

Synthesis of novel diosgenyl saponin analogs and evaluation effects of rhamnose moeity on their cytotoxic activity.

Diosgenyl saponins, as a type of natural products derived from plants, are the main active component of traditional chinese medicine. Inspiringly, a large number of natural diosgensyl saponins have been shown to exert excellent toxicity to hepatocellular cancer (HCC) cells. In order to better understand the relationship between the structures and their biological effects, a group of diosgenyl saponins (1-4 as natural products and 5 and 6 as their analogs) were efficiently synthesized. The cytotoxic activity of these compounds was evaluated on human hepatocellular carcinoma (HepG2) cells. Structure-activity relationship studies showed that the pentasaccharide or hexasaccharide saponin analogs were relatively less active than their corresponding disaccharide analogue or dioscin. The extension of 4-branched rhamnose moiety on these saponin does not exhibit significant effect on their cytotoxic activity, which disclosed that a certain number and the linkage mode of rhamnose moieties could influence the cytotoxicity of steroid saponins on HepG2 cells.

Diosgenyl Saponin Inducing Endoplasmic Reticulum Stress and Mitochondria-Mediated Apoptotic Pathways in Liver Cancer Cells.

Diosgenin and diosgenyl saponins as the major bioactive compounds isolated from dietary fenugreek seeds, yam roots, etc. possessed strong antitumor effects. To understand their detailed antitumor mechanisms, a fluorophore-appended derivative of diosgenin [Glc/CNHphth-diosgenin (GND)] was synthesized, starting from diosgenin and glucosamine hydrochloride in overall yields of 7-12% over 7-10 steps. Co-localization of GND with organelle-specific stains, transmission electron microscopy, and relative protein analyses demonstrated that GND crossed the plasma membrane through organic anion-transporting polypeptide 1B1 and distributed in the endoplasmic reticulum (ER), lysosome, and mitochondria. In this process, GND induced ER swelling, mitochondrial damage, and autophagosome and upregulating IRE-1α to induce autophagy and apoptosis. Furthermore, autophagy inhibitor chloroquine delayed the appearance of cleaved poly(ADP-ribose) polymerase and inhibited cleaved caspase 8, which indicated that GND induced autophagy to activate caspase-8-dependent apoptosis. These observations suggested that diosgenyl saponin was a potent anticancer agent that elicited ER stress and mitochondria-mediated apoptotic pathways in liver cancer.