Study On Polymer-Supported Herbicides Based On Extracts Of Eupatorium Adenophorum Spreng

Botanical pesticides are a kind of safe and environmentally-friendly bio-based pesticides.The active ingredients are natural substances,which are easily decomposed into non-toxic substances after application,and have no pollution to the environment;and the components of plant-derived pesticides are diversified,which make target killers more difficult to develop resistance.As a new form of drug release,sustained-release technology has the advantages of environmental friendliness,good safety and high efficiency.It has outstanding technical advantages and broad application prospects in the fields of medicine and modern agriculture.In this paper,to reduce pesticide toxicity and improve drug efficiency,the active constituents of eupatorium adenophorum spreng?AIEAS?were used as plant-derived herbicides to prepare two kinds of supported sustained-release herbicides,and the main components of AIEAS were systematically investigated.The sustained release properties,toxicity and herbicidal effect of the two supported pharmaceutical preparations.Main tasks as follows:?1?Using absolute ethanol as the extraction solvent,the dry powder of eupatorium adenophorum spreng was continuously extracted,and the active ingredient AIEAS of eupatorium adenophorum spreng was obtained by post-treatment such as rotary steaming and ice water removal.Then the thermostability,main components,herbicidal activity and acute toxicity of the drug were studied.The results showed that the main active ingredients of AIEAS are alkaloids and terpenoids.High-dose AIEAS can effectively inhibit the growth of bermudagrass and foxtail,and the toxicity of AIEAS is 5,and the LD₅₀ is more than2500mg/kg,indicating that AIEAS is a low-toxic drug.?2?PVA-ST/AIEAS sustained-release membrane was prepared by using polyvinyl alcohol?PVA?and starch?ST?as the matrix material and AIEAS as plant-derived herbicide,and the structure and sustained-release properties of the sustained-release membrane were studied.At the same time,a nanofiller-loaded drug sustained-release membrane was prepared by using AIEAS loaded with halloysite nanotubes?HNTs?in order to obtain better sustained-release properties.The results show that the surface and cross section of the composite membrane are almost flat,and HNTs-AIEAS can be uniformly dispersed in the controlled release membrane,indicating that it has good compatibility with the polymer matrix and can achieve nanoscale dispersion.When the PVA-ST sustained-release membrane was leached,the surface of the sustained-release membrane was gradually eroded.However,the degree of dissolution of the PVA/ST matrix decreased during the same period after the addition of HNTs,indicating that HNTs can strengthen the sustained-release membrane skeleton,thereby delaying the leaching of the drug AIEAS.?3?Using AIEAS as a plant-derived herbicide,HPCTS/CMC/AIEAS water-dispersed particles were prepared with hydroxypropyl chitosan?HPCTS?and carboxymethyl chitosan?CMC?as raw materials,and the microscopic morphology,microstructure,particle size distribution and sustained release properties of water-dispersed particles were studied.The results showed that the particle size of the water-dispersed particles before and after drug loading was on the micron level,and the zeta potential of the particles was positive after one-step drug loading and two-step drug loading.The sustained release properties of the HPCTS/CMC/AIEAS complex were investigated by immersion medium method.It was found that the cumulative release of the drug AIEAS gradually increased over time,and the release rate was faster in the first 12 h.After 12 h.The release rate tends to be flat,and the release behavior of AIEAS in both stages is consistent with the Ritger-Peppas model,and the release mechanism is Fick diffusion.