Quantitative Structure-Activity Relationship Analysis of Some Thiourea Derivatives with Activities Against HIV-1 (IIIB)

A new crystalline daidzein-piperazine salt with enhanced solubility, permeability, and bioavailability

To overcome the poor solubility, permeability, and bioavailability of the plant isoflavone daidzein (DAI), a novel salt of DAI with anhydrous piperazine (PIP) was obtained based on cocrystallization strategy. The new salt DAI-PIP was characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, and optical microscopy. The results showed that the maximum apparent solubility (Smax) of DAI-PIP increased by 7.27-fold and 1000-fold compared to DAI in pH 6.8 buffer and water, respectively. The peak apparent permeability coefficient (P app ) of DAI-PIP in the Caco-2 cell model was 30.57 ± 1.08 × 10-6 cm/s, which was 34.08% higher than that of DAI. Additionally, compared to DAI, the maximum plasma concentration (Cmax) value of DAI-PIP in beagle dogs was approximately 4.3 times higher, and the area under the concentration-time curve (AUC0-24) was approximately 2.4 times higher. This study provides a new strategy to enhance the dissolution performance and bioavailability of flavonoid drugs, laying a foundation for expanding their clinical applications.

Multivariate statistical analysis methods in QSAR

The emphasis of this review is particularly on multivariate statistical methods currently used in quantitative structure–activity relationship (QSAR) studies.

S-oxygenation of thiocarbamides V: oxidation of tetramethylthiourea by chlorite in slightly acidic media

The reaction between tetramethylthiourea (TTTU) and slightly acidic chlorite has been studied. The reaction is much faster than comparable oxidations of the parent thiourea compound as well as other substituted thioureas. The stoichiometry of the reaction in excess oxidant showed a complete desulfurization of the thiocarbamide to yield the corresponding urea and sulfate: 2ClO2(-) + (Me2N)2C ═ S + H2O → (Me2N)2C ═ O + SO4(2-) + 2Cl(-) + 2H(+). The reaction mechanism is unique in that the most stable metabolite before formation of the corresponding urea is the S-oxide. This is one of the rare occasions in which a low-molecular-weight S-oxide has been stabilized without the aid of large steric groups. ESI-MS data show almost quantitative formation of the S-oxide and negligible formation of the sulfinic and sulfonic acids. TTTU, in contrast to other substituted thioureas, can only stabilize intermediate oxoacids, before formation of sulfate, in the form of zwitterions. With a stoichiometric excess of TTTU over oxidant, the TTTU dimer is the predominant product. Chlorine dioxide, which is formed from the reaction of excess chlorite and HOCl, is a very important reactant in the overall mechanism. It reacts rapidly with TTTU to reform ClO2(-). Oxidation of TTTU by chlorite has a complex dependence on acid as a result of chlorous acid dissociation and protonation of the thiol group on TTTU in high-acid conditions, which renders the thiol center a less effective nucleophile.

Exploring the structural requirements for jasmonates and related compounds as novel plant growth regulators: a current computational perspective

Jasmonates and related compounds have been highlighted recently in the field of plant physiology and plant molecular biology due to their significant regulatory roles in the signaling pathway for the diverse aspects of plant development and survival. Though a considerable amount of studies concerning their biological effects in different plants have been widely reported, the molecular details of the signaling mechanism are still poorly understood. This review sheds new light on the structural requirements for the bioactivity/property of jasmonic acid derivatives in current computational perspective, which differs from previous research that mainly focus on their biological evaluation, gene and metabolic regulation and the enzymes in their biosynthesis. The computational results may contribute to further understanding the mechanism of drug-receptor interactions in their signaling pathway and designing novel plant growth regulators as high effective ecological pesticides.

Quantitative structure-property relationship studies on amino acid conjugates of jasmonic acid as defense signaling molecules

Jasmonates and related compounds, including amino acid conjugates of jasmonic acid, have regulatory functions in the signaling pathway for plant developmental processes and responses to the complex equilibrium of biotic and abiotic stress. But the molecular details of the signaling mechanism are still poorly understood. Statistically significant quantitative structure-property relationship models (r(2) > 0.990) constructed by genetic function approximation and molecular field analysis were generated for the purpose of deriving structural requirements for lipophilicity of amino acid conjugates of jasmonic acid. The best models derived in the present study provide some valuable academic information in terms of the 2/3D-descriptors influencing the lipophilicity, which may contribute to further understanding the mechanism of exogenous application of jasmonates in their signaling pathway and designing novel analogs of jasmonic acid as ecological pesticides.

Current mathematical methods used in QSAR/QSPR studies

This paper gives an overview of the mathematical methods currently used in quantitative structure-activity/property relationship (QASR/QSPR) studies. Recently, the mathematical methods applied to the regression of QASR/QSPR models are developing very fast, and new methods, such as Gene Expression Programming (GEP), Project Pursuit Regression (PPR) and Local Lazy Regression (LLR) have appeared on the QASR/QSPR stage. At the same time, the earlier methods, including Multiple Linear Regression (MLR), Partial Least Squares (PLS), Neural Networks (NN), Support Vector Machine (SVM) and so on, are being upgraded to improve their performance in QASR/QSPR studies. These new and upgraded methods and algorithms are described in detail, and their advantages and disadvantages are evaluated and discussed, to show their application potential in QASR/QSPR studies in the future.