Development Of Aqueous Solutions(AS) Formulation Based On A Herbicidal Extract From Sapindus Mukorossi Gaertn

China is rich in Sapindus mukorossi Gatren resources,which is mainly distributed in the south of China.The extract of S.mukorossi has been found to possess many biological properties,such as antiviral,antibacterial and antitumor activities,which is widely used in medicine chemicals and other fields.According to the previous studies,the extract of S.mukorossi shows herbicidal activity.Up to now,its main active ingredients are still unknown.There are few reports on the development of plant-based herbicides based on the active components from S.mukorossi and its field efficacy.Therefore,the vacuum extraction method of total saponins from S.mukorossi fruits was optimized,the extract of S.mukorossi fruits was separated by macroporous resin and thin layer chromatography.Meanwhile,bio-guided fractionation and identification of active component from S.mukorossi extract were performed by thin layer chromatography and high-resolution mass spectrometer.Furtherly,A plant-based herbicide with S.mukorossi extract as an active ingredient was developed,and its field efficacy was investigated.The aim of this study was to develop a new plant-based herbicide,and provide research basis for the high value utilization of S.mukorossi resources.The main results are as follows:?1?The vaccum extraction method of S.mukorossi saponins was optimized.Based on single factor experiments and orthogonal design,the optimized extraction method was as follows:extraction temperature 60?,extraction time 1 h and the solid-to-liquid ratio 1:14?g:m L?.Under these conditions,the extraction rate of total saponins in S.mukorossi fruits was15.34%.The vaccum extraction method was proved to be superior to the other methods,such as high-speed homogenate extraction,ultrasonic extraction and water extraction methods.?2?Based on bioassay guided strategy,the extract was further fractionated by macroporous resin column chromatography with combination of ethanol and water as eluent.The herbicidal activity of the extract was evaluated by water agar medium method.The 70%ethanol fraction exhibited strong herbicidal activity against Trifolium pratense with EC₅₀values of 0.028 g/L,while the EC₅₀value of crude extract of S.mukorossi was 0.186 g·L^-1.The EC₅₀value of alachlor as positive control aginst T.pratense was 0.004 g·L^-1.The major compound of the active fraction was identified as saponins using thin-layer chromatography method.Separation of the 70%ethanol fraction by TLC method led to six fractions?F1-F6?.The fraction F1 showed the highest herbicidal activity against T.pratense with EC₅₀value of0.017 g·L^-1.The main active compound in fraction F1 was identified as sapindoside B.Its formula was C₄₆H₇₄O₁₆and molecular weight was 882.?3?A plant-based herbicide was developed based on the extract of S.mukorossi fruits.The70%ethanol fraction,as an active ingredient,was selected for formulation preparation.An optimized aqueous solution?AS?formulation was prepared,which composed of 70%ethanol fraction?20%,g/v?,emulsifier?4%,g/v?,water?73%,v/v?and antifreeze?3%,v/v?.Evaluation of physical properties of the developed formulation?including the dilution stability and the stability at low temperature and thermal storage?were carried out.The testing results met the requirements of the national standard.?4?The filed experiment of 20%S.mukorossi extract AS formulation against weeds was carried out in a carrot?Daucus carota L.?field.One chemical herbicide,33%pendimethalin EC was selected as a positive control.The AS formulation and chemical herbicide pendimethalin were sprayed at pre-emergence stage.The S.mukorossi extract AS formulation at a dose of 1500 g a.i./ha showed a significantly pre-emergence inhibition to the broad-leaf weeds,with over 88%against P.oleracea,C.album and C.bursa-pastoris,respectively.The AS formulation at 1500 g a.i./ha significantly reduced the fresh weight of all broad-leaved weeds at 40 day after treatment and the control effects were above 75%.However,the control effect on the narrow-leaved weed S.viridis was poor?below 50%?.In brief,20%S.mukorossi extract AS formulation gave good control of weeds in carrot,without any phytotoxic effect on carrot seedlings.In summary,the vaccum extraction method of total saponins of S.mukorossi was optimized and developed.A plant-based herbicide was developed with the 70%ethanol fraction as an active ingredient,which was prepared and successfully applied in carrot field for weed control.In addition,the herbicidal active compounds were identified as triterpenoid saponins.These results provide technical support for the application of S.mukorossi resources to plant-based herbicides.