The Allelochemical In Exocarp Of Pecan(Carya Cathayensis Sarg.)and Its Herbicidal Activity Improving

Hickory(Carya cathayensis Sarg.)as a precious nut and woody-oil plant is endemic to China.With the increase of area and yield of hickory in Zhejiang and Anhui provinces,the pollution caused by the leaching of exocarp after raining has become an environmental problem that should not be neglected in the producing area.In order to achieve resource utilization and solve the environmental problems,the techniques of modern instrument analysis and separation detection,guided by bioassay and weed seeds and seedlings as receptor,were used to analyzed the active components in the aqueous extract of hickory exocarp,isolated the main allelochemical,and optimized extract process and condition of the main allelochemical.The modification of chemical structure was adopted to improve the herbicidal activity of the main allelochemical;meanwhile it revealed.These could provide the structure-activity relationship between the structure of allelochemicals and their herbicidal activities.These could provide scientific basis and technical approach for the utilization of hickory exocarp.The main results were as followed:The aqueous extract of hickory exocarp was present with allelopathic activity,and the elution constituent of 4:6(water:ethanol)had the most inhibited effect on weed seed germination and seedling growth.The main allelochemical was 4,8-dihydroxy-1-tetralone(4,8-DHT).The herbicidal activity of pure S-(+)-enantiomer was more effective than the4,8-DHT and R-(+)-enantiomer.The optimal extraction condition of 4,8-DHT by the ultrasonic methods was determined to be on ultrasonic power of 55 w at 60°C for 1 h with50% ethanol.Five analogs of 4,8-DHT including 4-oxo-1,2,3,4-tetrahydronaphthalene-5-hydroxy-1-ethyl benzoate,8-hydroxy-4-(2,3-dyhydroxypropoxy)-1-tetrahydronaphthalene,8-(2,3-dyhydroxy propoxy)-4-hydroxy-1-tetrahydronaphthalene,8-(3-hydroxylpropoxy)-4-hydroxy-1-tetrahydronaphthalene and 8-(2,3-dyhydroxy propoxy)-4-hydroxy-1-tetrahydronaphthalene of4,8-DHT was obtained after structure modification.Among them,the first three structural modifications had more allelopathic herbicidal activity than 4,8-DHT and its S-(+)-enantiomer,which had the potential to develop as new broad-spectrum herbicides.The herbicidal activity of allelochemicals was related to their structures.The herbicidal activity of hydrophilic phenolic hydroxyl groups contained in benzene ring C-4 and C-8 was stronger than that of hydrophobic phenolic hydroxyl groups.The more hydrophilic phenolic hydroxyl group in structure presented stronger herbicidal activity.The structure-activity relationship between the chemical structure and the herbicidal activity enriched the theory of allelopathic herbicidal activity.