Spatiotemporal response of the optical characteristics of dissolved organic matter to seasonality and land use in tropical island rivers.

Dissolved organic matter (DOM), a pivotal component in the global carbon cycle, plays a crucial role in maintaining the productivity and functionality of aquatic ecosystems. However, the driving factors of variations in the properties of riverine DOM in tropical islands still remain unclear. In this study, the spatiotemporal response of the optical characteristics of riverine DOM to seasonality and land use on Hainan Island in southern China was investigated. Our results revealed that DOM in the rivers of Hainan Island exhibited a relatively high proportion of fulvic acid and demonstrated strong terrestrial sources. The optical properties of DOM exhibited significant variations both seasonally and spatially. Land use exerted a dominant influence on riverine DOM. Specifically, during the wet season, riverine DOM exhibited larger molecular weight, increased chromophoric DOM (CDOM) abundance, and higher Fmax compared to the dry season. Furthermore, riverine DOM influenced by grassland and farmland showed higher CDOM abundance, Fmax, and humification degree in contrast to those impacted by forest and urban. Random forest and correlation analysis results indicated that grassland and farmland enhanced the Fmax of DOM by increasing levels of TP, NO3--N, Chl a, and NH4+-N in the dry season. However, during the wet season, the increased Fmax of DOM induced by grassland and farmland relied on the increments of Chl a and TP concentrations. This study improves our understanding of the spatiotemporal fluctuations of DOM in the rivers of Hainan Island, highlighting the effects of season and land use on DOM. It offers valuable support for improving water quality and contributes to enhancing human comprehension of the global carbon cycle.

Chemoproteomics enables identification of coatomer subunit zeta-1 targeted by a small molecule for enterovirus A71 inhibition.

Human enterovirus A71 (EV-A71) is a significant etiological agent responsible for epidemics of hand, foot, and mouth disease (HFMD) in Asia-Pacific regions. There are presently no licensed antivirals against EV-A71, and the druggable target for EV-A71 remains very limited. The phenotypic hit 10,10'-bis(trifluoromethyl) marinopyrrole A derivative, herein termed MPA-CF3, is a novel potent small-molecule inhibitor against EV-A71, but its pharmacological target(s) and antiviral mechanisms are not defined. Here, quantitative chemoproteomics deciphered the antiviral target of MAP-CF3 as host factor coatomer subunit zeta-1 (COPZ1). Mechanistically, MPA-CF3 disrupts the interaction of COPZ1 with the EV-A71 nonstructural protein 2C by destabilizing COPZ1 upon binding. The destruction of this interaction blocks the coatomer-mediated transport of 2C to endoplasmic reticulum, and ultimately inhibits EV-A71 replication. Taken together, our study disclosed that MPA-CF3 can be a structurally novel host-targeting anti-EV-A71 agent, providing a structural basis for developing the COPZ1-targeting broad-spectrum antivirals against enteroviruses. The mechanistic elucidation of MPA-CF3 against EV-A71 may offer an alternative COPZ1-involved therapeutic pathway for enterovirus infection.

Synthesis of 10,10'-bis(trifluoromethyl) marinopyrrole A derivatives and evaluation of their antiviral activities in vitro.

Flavivirus and enterovirus can emerge unexpectedly in human populations and cause a spectrum of potentially severe diseases or even death. Since effective vaccine is currently unavailable against most of these deadly viruses, antiviral chemical drugs remain in urgent need. To meet this unmet demand, we developed a series of 10,10'-bis(trifluoromethyl) marinopyrrole A derivates bearing various substituents at C5'-positions, which exhibited impressive in vitro activities against flaviviruses (ZIKV, DENV, YFV, JEV) and enteroviruses (EV71, CA6, CA16). The lead compound 10,10'-bis(trifluoromethyl) marinopyrrole A 3 was highly effective against enteroviruses EV71 and CA16 in cultured cells, but with low inhibitory activities against flavivirus. Elaborately modified from compound 3, compounds 32 and 33 with sulfhydryl aliphatic chains were found as promising ZIKV and DENV inhibitor; pyrazine-containing compound 19 is a potent broad-spectrum flavivirus inhibitor; thiophene compound 15 exhibited prominent selective inhibitory effect against JEV-SA14, YFV-17D, in addition to broad-spectrum enterovirus inhibitory effect. These results thus suggest that the 5'-sulfhydryl derivates of 10,10'-bis(trifluoromethyl) marinopyrrole A may be promising lead compounds for the development of novel anti-flavivirus and anti-enterovirus drugs.

The in vivo pharmacokinetics, tissue distribution and excretion investigation of mesaconine in rats and its in vitro intestinal absorption study using UPLC-MS/MS.

1. Mesaconine, an ingredient from Aconitum carmichaelii Debx., has been proven to have cardiac effect. For further development and better pharmacological elucidation, the in vivo process and intestinal absorptive behavior of mesaconine should be investigated comprehensively. 2. An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantitation of mesaconine in rat plasma, tissue homogenates, urine and feces to investigate the in vivo pharmacokinetic profiles, tissue distribution and excretion. The intestinal absorptive behavior of mesaconine was investigated using in vitro everted rat gut sac model. 3. Mesaconine was well distributed in tissues and a mass of unchanged form was detected in feces. It was difficultly absorbed into blood circulatory system after oral administration. The insufficient oral bioavailability of mesaconine may be mainly attributed to its low intestinal permeability due to a lack of lipophilicity. The absorption of mesaconine in rat's intestine is a first-order process with the passive diffusion mechanism.

Asymmetric Synthesis of an Advanced Tetracyclic Framework of (+)-Sarain A.

An asymmetric synthetic approach to a tetracyclic framework of the marine-derived alkaloid (+)-sarain A has been developed. The key steps to constructing the congested diazatricycloundecane core include an asymmetric Diels-Alder cycloaddition, an Ireland-Claisen rearrangement, and an intramolecular aziridination/ring-opening sequence.