Study Of The Cyclodextrin On The Clathration,Solubilization And Bioactivity Of Herbicides

Cyclodextrin is a kind of ringed oligomers linked by a-1,4-glucosidic bond; cyclodextrin can interact with6,7,8glucose molecules, and is called α-, β-, γ-cyoclodextrin respectively; β-cyoclodextrin (P-CD) has been widely used. Hydroxyproyl-β-cyoclodextrin (HPCD) is a derivative of cyoclodextrin. Cyclodextrin and its derivatives have a cylindric structure of "inner hydrophobic, outer hydrophilic", which can accommodate nonpolar molecule to increase the solubility and bioavailability of nonpolar molecules.Herbicides are chemicals used to kill or decrease the wild grass in fields, nurseries and along roads. The application of herbicides inhibits the growth of weed and alleviates the farm work. It brings firm insurance for the increases of the crop production, the income of farmers and improves their living standard. Heilongjiang province is an important area of crops and commodity grains. In China, it is not only the origin of the application of chemical herbicides, but also the biggest herbicide market. At present, the herbicides used in soybean, corn, sorghum crops involves with chlorimuron ethyl, atrazine. imazethapyr, imazamox, fomesafen, etc. Due to the high efficiency, wide usable range and low cost, chlorimuron ethyl, atrazine and imazethapyr have been widely used in soybean, corn, sorghum, etc. The grain output of Heilongjiang keep increasing for ten years, ranking the first in domestic; all of this owes to the application of herbicides. But the low solubility of these herbicides in water, the low bioavailability and high residues in soil hinders the further application of herbicides. In this paper, cyclodextrms (β-CD and HPCD) are taken as host molecules, and chlorimuron ethyl, atrazine and imazethapyr are taken as guest molecules, the six inclusions of herbicide-cyclodextrin are synthesized. The inclusions have been characterized by UV, FTIR, NMR, XRD, DSC, TG-DTG, SEM, etc. The solubilization of β-CD and HPCD to herbicides is tested by phase solubility experiments; the inclusion ratio and stability constant are also defined; and the bioactivity of the six inclusions has been also studied by indoor bioactivity. The results are summarized as follows:1. Six inclusions of white solids synthesized by herbicides (chlorimuron ethyl, atrazine, imazethapyr) and cyclodextrins (β-CD and HPCD) are prepared by co-solvent, co-precipitation, and ultrasonic method. The recovery ratio of the inclusions is in the range of82%-88%.2. The inclusions are characterized by UV, FTIR, NMR, XRD, XPS, etc. The results show that:there is no change of the maximum wavelength in UV spectra, but the absorption intensity decreases; in the spectra of FTIR,1H NMR,13C NMR, XPS there are characteristic peaks of cyclodextrin and herbicides; the chemical shifts of H atom and C atom change; the binding energy of N, S and Cl change; in the XRD spectrograms, the diffraction peaks of herbicides also change; all of which suggest the formation of new matters rather than physical mixtures. At the same time, the results of TG indicate that the stability of inclusions increases except atrazine-inclusion.3. The solubility, inclusion ratio and stability constant are tested by phase solubility tests. The results show that the solubility of herbicides increases with the increase of cyclodextrin; the solubility effect to three inclusions differs a lot; the solubility of atrazine increases the most; the solubility of imazethapyr increases less and the solubility of chlorimuron ethy increases the least. According to phase solubility curve, the inclusion ratio of6inclusions is all1:1; and the stability of imazethapyr inclusion is higher than that of chlorimuron-ethyl inclusion.In this experiment, corn and barnyard grass are taken as indicator plants and indoor petri dish method is used. The root length, root fresh weight, sprout length, sprout fresh weight and the inhibition rate are all tested. The inhibition effect of6inclusions to corn and barnyard grass differs a lot; the inhibition of HPCD-atrazine is better than that of atrazine; the bioactivity of HPCD-imazethapyr and HPCD-chlorimuron-ethy are worse than that of imazethapyr and chlorimuron-ethy. There is no inhibition of HPCD and β-CD to corn, while the bioactivity of HPCD-cyclodextrin inclusions is higher than that of β-CD.