Exploration of the Mechanism for Self-Emulsion Polymerization of Amphiphilic Vinylpyridine

A rare self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine) (4VP) when polymerized in water with a hydrophilic initiator that results in the production of monodisperse polymeric nanoparticles in a single step. This behavior mimics the behavior obtained with the more commonly reported amphiphilic block copolymers. The synthesis and self-assembly of homopolymer nanoparticle from 4VP without the use of any cross-linker, stabilizing agent, surfactant, or polymeric emulsifier are described along with fundamental aspects of the mechanism of this polymerization. This facile and robust procedure enabled the production of highly monodisperse P4VP nanoparticle with a tunable size ranging from 80 to 445 nm. For the first time, we have investigated the growth mechanism of these polymeric nanoparticles to clarify the mechanism of polymeric nanoparticle formation. This work also provides direct visible evidence through transmission electron microscopy (TEM) images at the nanometer scale, which helps in obtaining a better understanding of the mechanism of self-assembly. The effect of temperature on the size of the polymeric nanoparticles was also examined along with the effect of initiator, monomer, and solvent concentrations. We therefore report a versatile and scalable process for the production of monodisperse polymeric nanoparticles, which we call self-emulsion polymerization (SEP)

Neuroprotective Xanthones from the Root Bark of <i>Cudrania tricuspidata</i>

Seventeen new prenylated xanthones (<b>1</b>–<b>17</b>) were isolated from an ethyl acetate-soluble extract of root bark of <i>Cudrania tricuspidata</i> together with 17 previously identified xanthones. The structures of the new compounds were elucidated by spectroscopic methods. Six new compounds (<b>3</b>, <b>7</b>, <b>8</b>, <b>9</b>, <b>15</b>, and <b>16</b>) and six known compounds (<b>18</b>–<b>23</b>) showed neuroprotective effects against 6-hydroxydopamine-induced cell death in human neuroblastoma SH-SY5Y cells, with EC₅₀ values of 0.7–16.6 μM

Chemical Constituents Isolated from the Root Bark of <i>Cudrania tricuspidata</i> and Their Potential Neuroprotective Effects

Seventy-five compounds, including 21 new compounds (<b>1</b>–<b>21</b>), were isolated from the root bark of <i>Cudrania tricuspidata</i>. The structures of the isolated compounds were elucidated by interpretation of their spectroscopic data. All isolated compounds were evaluated for their neuroprotective effects against 6-hydroxydopamine (6-OHDA)-induced cell death, and nine compounds had activities with EC₅₀ values of 1.9–30.2 μM. The 75 isolated compounds along with 34 previously reported xanthones were tested also for neuroprotective effects against the 1-methyl-4-phenylpyridinium ion (MPP⁺) and oxygen glucose deprivation (OGD)-induced cell death. Three compounds were active against MPP⁺-induced cell death with EC₅₀ values of 0.2–10.3 μM, and 23 compounds were active in the OGD model with EC₅₀ values of 2.9–35.5 μM