An inter-laboratory study was performed to evaluate the performance of a method developed for the quantification of enrofloxacin in chicken meat. Liquid-liquid extraction combined with a clean-up procedure based on solid-phase extraction followed by a liquid chromatography-tandem mass spectrometric method was used by three individual laboratories. All the investigated results of calibration curves and limits of quantification were within the acceptable range for regulatory testing of enrofloxacin. The three laboratories received blind a certified reference material to analyze in triplicate and assess using statistical analysis. From the results, no statistical differences were found between the laboratories in the precision of the method. Additionally, all the results of the z-score, which is an indication of fixed interval bias criteria for accuracy from the laboratories, fell within the allowable limits (±2σ). Based on this proficiency testing by inter-laboratory comparisons, the analytical method including the sample preparation step was proven to be applicable.

Polo-like kinase 1 (PLK1) plays crucial roles in various stages of oocyte maturation. Recently, we reported that the peptidomimetic compound AB103-8, which targets the polo box domain (PBD) of PLK1, affects oocyte meiotic maturation and the resumption of meiosis. However, to overcome the drawbacks of peptidic compounds, we designed and synthesized a series of pyrrole-based small-molecule inhibitors and tested them for their effects on the rates of porcine oocyte maturation. Among them, the macrocyclic compound (E/Z)-3-(2,16-dioxo-19-(4-phenylbutyl)-3,19-diazabicyclo[15.2.1]icosa-1(20),6,17-trien-3-yl)propyl dihydrogen phosphate (4) showed the highest inhibitory activity with enhanced inhibition against embryonic blastocyst formation. Furthermore, the addition of this compound to culture media efficiently blocked the maturation of porcine and mouse oocytes, indicating its ability to penetrate the zona pellucida and cell membrane. We investigated mouse oocytes treated with compound 4, and the resulting impairment of spindle formation confirmed PLK1 inhibition. Finally, molecular modeling studies with PLK1 PBD also confirmed the presence of significant interactions between compound 4 and PLK1 PBD binding pocket residues, including those in the phosphate, tyrosine-rich, and pyrrolidine binding pockets. Collectively, these results suggest that the macrocyclic compound 4 may serve as a promising template for the development of novel contraceptive agents.

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The front cover picture shows the inhibition of mouse oocyte maturation from GV to MII stage by the newly synthesized macrocyclic compound (E/Z)‐3‐(2,16‐dioxo‐19‐(4‐phenylbutyl)‐3,19‐diazabicyclo[15.2.1]icosa‐1(20),6,17‐trien‐3‐yl)propyl dihydrogen phosphate (4). Bang et al. synthesized a series of pyrrole‐based macrocyclic small molecules, among which most of the compounds showed good inhibition rates against both porcine and mouse oocyte maturation. In particular, the most active compound, 4, showed a high inhibition rate against oocyte maturation with enhanced inhibition against embryonic blastocyst formation. Treating mouse oocytes with this compound resulted in the impairment of spindles due to polo‐like kinase 1 (PLK1) inhibition. Collectively, these results suggest that the macrocyclic compound 4 may serve as a promising template for the development of novel contraceptive agents. More information can be found in the Full Paper by Suk Namgoong, Nam‐Hyung Kim, Jeong Kyu Bang et al. on page 580 in Issue 8, 2017 (DOI: 10.1002/cmdc.201700048).