Isolation,Identification And Herbicidal Acitivity Of Saponins From Sapindus Mukorossi Gaertn.

Sapindus mukorossi Gaertn.,a deciduous tree of the genus Sapindus,which is mainly distributed in China south of the Yangtze River basin and in the South Central Peninsula,India and Japan.S.mukorossi extract is widely used in pharmaceutical,daily chemical and other fields,which is rich in saponins,a natural nonionic surfactant with various biological activities.Studies have shown that S.mukorossi extract has herbicidal activity,but the active ingredients are not clear yet,and there was no herbicidal activity study on the compound preparation of S.mukorossi extract and pendimethalin.In this study,the S.mukorossi extract was used as the research object.The S.mukorossi saponin components were isolated and identified by high-speed counter-current chromatography（HSCCC）,liquid chromatography-mass spectrometry（LC-MS）,nuclear magnetic resonance（NMR）.Pot culture assay was carried out using the extract of S.mukorossi and the chemical herbicide pendimethalin.Field experiment was performed using the aqueous solution of S.mukorossi extract.This study aims to clarify the herbicidal active components of S.mukorossi and the herbicidal effect of S.mukorossi extracts combined with pendimethalin,and provide a theoretical basis for the high-value utilization of S.mukorossi resources.The main results are as follows:（1）A high-speed countercurrent chromatography separation and purification method for S.mukorossi saponins was established,and compound was successfully isolated and identified,and its herbicidal activity was studied.The optimized high-speed countercurrent chromatography method included that the solvent system was n-hexane﹕ethyl acetate﹕methanol﹕water=1﹕4﹕1﹕4,the flow rate of the mobile phase was 3 m L/min,and the rotation speed was 900 rpm.An active compound was isolated from the 70%ethanol fraction and identified as hederagenin 3-O-β-D-xylopyranosyl-（1→3）-α-L-rhamnopyranosyl-（1→2）-α-L-arabinopyranoside（Compound A）.Its molecular formula is C₄₆H₇₄O₁₆and molecular weight is 882 Da.When compared with 70%ethanol fraction,compound A showed more phytotoxity to the target plant.Therefore,compound A could be one of the effective ingredients.（2）The herbicidal activity of the mixture of S.mukorossi extracts and pendimethalin was evaluated through pot culture assay.Cynodon dactylon L.（monocotyledonous plant）and Trifolium pratense L.（dicotyledonous plant）were used as the target plants,and the concentration of the extract was 300 mg/L,which was mixed with pendimethalin.The fresh weight control efficacy was recorded by 14 and 21 days after treatment.The results showed that when the dosage of pendimethalin was 1/2 of the recommended dose,the fresh weight control effect of pendimethalin was above 90%,indicating that the extract of S.mukorossi had synergistic effect on pendimethalin.Therefore,S.mukorossi extract can be used as a herbicide adjuvant of pendimethalin.The effect of the extract of S.mukorossi was synergistic to reduce the dose of pendimethalin.（3）The filed experiment of the pulp extract formulation against weeds was carried out in a carrot（Daucus carota L.）field.The main weed species in the experimental field contained Eleusine indica（L.）Gaertn.,Cyperus rotundus L.,Acalypha australis L.,and Physalis minima L.One chemical herbicide,33%pendimethalin EC,was selected as a positive control.The pulp extract formulation was set at different doses.The plots were sprayed by the formulation at pre-emergence stage.The data on weed count and weed fresh weight were recorded at 30and 45 days after treatment.The highest weed control efficacy（72.2%）was recorded at a dose of 1500 g a.i./ha.The fresh weight control efficacy was 78.7%by 45 days after treatment at the dose of 1500 g a.i./ha.Among them,the control effect on fresh weight of Acalypha australis L.reached 88.5%at 45 d,which was better than pendimethalin.Thus,the extract of S.mukorossi is suitable for use as a biological herbicide or a herbicide adjuvant.In conclusion,a high-speed countercurrent chromatography separation and purification method for S.mukorossi saponins was established.An active compound was isolated from the70%ethanol fraction and identified.The herbicidal activity of the mixture of S.mukorossi extracts and pendimethalin was evaluated through pot culture assay.The extract of S.mukorossi pulp could be a promising supplement to the synthesized herbicides.The results of this study provide a scientific basis for the application of the extract of S.mukorossi in the field of weed control.