Insights into stress degradation behavior of gibberellic acid by UHPLC Q-Exactive Orbitrap mass spectrometry

Insight into pyrrolizidine alkaloids degradation and the chemical structures of their degradation products using ultra high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry

Pyrrolizidine alkaloids (PAs), released into the environment by donor plants, are absorbed by crops or transported by animals, posing a global food safety concern. Photolysis is an effective way to eliminate harmful substances in the environment or food. Photolysis happens as PAs move among plants, environment and crops. In this study, we first investigated the photolysis and hydrolysis of 15 PAs and identified their degradation products via ultra-high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry. PAs were degraded under UV radiation but minimally affected by visible light from a xenon lamp, and solvent pH had little impact on their photolysis. PAs were stable in neutral and acidic solutions but degraded by 50% within 24 h in alkaline conditions. The degradation products of PAs were mainly PAs/PANOs isomers and some minor byproducts. Cytotoxicity and computational analysis revealed isomers had similar toxicity, with minor products being less toxic. This study is a precursor for revealing the potential PAs degradation dynamics in the environment and food products, providing a reference for systematic evaluations of potential health and ecological risks of their degradation products.

o-Nitrobenzyl-Based Caged exo-16,17-Dihydro-gibberellin A5-13-acetate for Photocontrolled Release of Plant Growth Regulators

Caged plant growth regulators (caged PGRs) that release bioactive molecules under irradiation are critical in enhancing the efficacy and mitigating the negative environmental effects of PGRs. The synthetically derived plant growth inhibitor exo-16,17-dihydro-gibberellin A5-13-acetate (DHGA5) regulates the development and stress resilience of plants. We report here the conception of novel caged DHGA5 derivatives wherein the photoremovable protecting groups (PRPGs) serve not only to enable light-controlled release but also to protect the carboxyl group during chemical synthesis. Three o-nitrobenzyl-based caged DHGA5 derivatives with different substituents on the nitrobenzyl moiety were obtained and evaluated for their properties in vitro and in vivo. The photolysis half-life values of caged DHGA5 derivatives 7a, 7b, and 7c under a UV lamp were 15.6 h, 1.2 h, and 28.2 h, respectively. Experiments in vivo showed that 0.2 mM of the caged compounds significantly inhibited the growth of the model plant Arabidopsis thaliana and important crop rice in a precise photoactivated form.

Rapid characterization of the potential active metabolites of diacerein in rat plasma based on UHPLC-Q-exactive orbitrap mass spectrometry and molecular docking

Diacerein, a competently semisynthetic diacetyl derivative of anthraquinone, is a nonsteroidal anti-inflammatory drug, which has been used for treating osteoarthritis and preventing vascular diseases. However, previous investigation indicated that diacerein metabolites and its metabolic pathway in vivo was still unclear. In this research, an effective method was established based on ultra-high-performance liquid chromatography coupled with Q-Exactive-Orbitrap mass spectrometer and molecular docking to screen and detect the potential active metabolites of diacerein in rat plasma after oral administration. The data acquisition and processing methods including Full MS-ddMS² combined with parallel reaction monitoring mode, extracted ion chromatogram and diagnostic fragment ions were adopted to detect and identify more infinitesimal and unknown diacerein metabolites in vivo. As a result, a total of 32 metabolites were detected and identified in rat plasma according to retention times, accurate mass, diagnostic fragment ions, and relevant drug biotransformation knowledge, among 31 metabolites were firstly reported in this study. Then, the relevant reactions in vivo such as deacetylation, hydroxylation, methylation, sulfate conjugation, glucuronidation, and their composite reactions, were all detected. Ultimately, the results of molecular docking showed that the metabolites of diacerein might have good affinity with IL-1 receptor in vivo. Among them, the metabolites M21 and M1 have the strongest binding affinity with IL-1 receptors, and could be considered as potential active metabolites of diacerein, which have an efficient effect on exerting pharmacological effects of diacerein in vivo. In conclusion, the study of diacerein metabolites in rat plasma expanded our understanding about the metabolism of diacerein in vivo and provided the significant foundation for further drug efficacy studies.

Kinetics of the photolysis of pyridaben and its main photoproduct in aqueous environments under simulated solar irradiation

The photolytic fate of pyridaben and its main photolysis product was investigated in different aqueous solutions. Results showed that the photolysis of pyridaben followed pseudo first-order kinetics or the hockey-stick model. In buffer solutions, the half-life of pyridaben was the shortest at pH 4, while the degradation rate within 24 h was the highest at pH 9. Humic acids (HA) at concentrations of 1-20 mg L^-1 favored the photolysis of pyridaben while fulvic acids (FA) did not have a significant effect. Nitrate at low concentrations (0.01 mM) accelerated the photolysis and Fe(iii) at high concentrations (0.01 and 0.1 mM) significantly inhibited the photolysis. The photolysis rate of pyridaben in rainwater, tap water, and river water was significantly higher than that in distilled water. The half-lives in distilled water, rainwater, tap water, river water, and pond water were 2.36, 1.36, 1.61, 1.77, and 2.68 h, respectively. Ultra-high-performance liquid chromatography/high-resolution mass spectrometry identified M328 as a photolysis product. The degradation of M328 followed pseudo first-order kinetics in distilled water, buffer solutions and aqueous solutions fortified with HA. The half-lives of M328 were in the range of 7.07-13.95 h. These results are essential for further environmental risk assessment of pyridaben.