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Plant diseases seriously affect crop yield and quality and are difficult to control. Marine natural products (MNPs) have become an important source of drug candidates with new biological mechanisms. Marine natural product essramycin (1) was found to have good anti-tobacco mosaic virus (TMV) and anti-phytopathogenic fungus activities for the first time. A series of essramycin derivatives were designed, synthesized, and evaluated for their bioactivity. Most of these compounds exhibited antiviral effects that are greater than that of the control ribavirin. Compounds 7e and 8f displayed antiviral activities that are greater than that of ningnanmycin (the most widely used antiviral agent at present), thus emerging as novel antiviral lead compounds. As the lead compound, 7e was selected for further antiviral mechanism research. The results indicated that 7e could inhibit virus assembly and promote 20S disk protein aggregation. Fungicidal activity tests against 14 kinds of phytopathogenic fungi revealed that essramycin analogues displayed broad-spectrum fungicidal activities. Compound 5b displayed more than 50% inhibition rate against most of the 14 kinds of phytopathogenic fungi at 50 μg/mL. The current research lays a solid foundation for the application of essramycin alkaloids in crop protection.

We present herein an easy way to prepare novel responsive hydrogels by simply doping lanthanide complexes into a polymer hydrogel, poly(2-acrylamido-2-methyl-1-propanesulfonicacid) (PAMPSA). The resulting hybrid hydrogels can be readily processed into a range of shapes. Both the on-off luminescence switching and the healable properties are simultaneously achieved in the resulting responsive hybrid hydrogels. They exhibit effectively self-healing performance without any external stimulus and reversible "on-off" luminescence switching triggered by exposure to acid-base vapor. The key to this on-off luminescence switching behavior is that the protonation of the organic ligands compete with full coordination to Ln(3+) and that incomplete coordination affects the luminescence yield. The high proton strength in the resulting hydrogels makes the doped lanthanide complexes unstable, and ammonia (or triethylamine) vapor can dramatically decrease the proton strength through neutralization, driving the full coordination of the ligand to Ln(3+).

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