Research On Ligusticum Chuanxiong Protecting Rice From The Injury Of S-metolachlor

Currently, it is an important way for development of pesticides that chemical compounds obtained from natural product are directly developed as new pesticides or structurally modified in an attempt to develop new compounds with higher activities.L. chuanxiong belonged to Apiaceae is well-known in Traditional Chinese Medicine, which disperses blood stasis and is used extensively for the treatments of cardiovascular and cerebrovascular diseases, headache and menstrual disorders. It is also proved that L. chuanxiong could reverse the effect on rice caused by chloroacetamides in our lab. Hence, purpose of this paper was to obtain extract from L. chuanxiong by CO2-SFE and separate active compounds from the extract by HSCCC, which could protect rice from the injury of S-metolachlor. Finally, mode of action of active compounds as saferners was studied.1Active extract from L. chuanxiong by CO2-SFE.Extract was achieved to4.45%in extraction ratio by CO2-SFE under optimized condtions. The optimized process was to extract L. chuanxiong under temperature of70℃and pressure of35MPa for2.5h. Furthermore, the quality control of extract was conducted in terms of main active compounds Z-ligustilide and senkyunolide A, which were quantified by17.85%and40.58%respectively.2Laboratory or field determination of activities of extract from L. chuanxiong.In laboratory experiment, extract significantly protected rice from the damage of S-metolachlor. The level of Shoots height was totally recovered to that of the untreated and the level of roots length was close to that of the untreated after extract treatment in agar medium. Meanwhile, the level of shoots height was close to that of the untreated after extract treatment in soil-based medium.The results of field experiments verified that S-metolachlor at ratio of60g/hm2or90g/hm2obviously inhibited the rice growth during entire period of rice growth. Extract could totally reverse the effect which caused by S-metolachlor at60g/hm2, with the reduced capability of reversing the effect on rice caused by S-metolachlor at90g/hm2. In contrast, overdose of extract could produce harm to rice. Results of the final rice yields verified that the highest rice yield was achieved after the detoxification of60g/hm2metolachlor by240g/hm2extact. and less achieved from the untreated due to the competitive growth of weeds.Results demonstrated S-metolachlor effectively controlled barnyard grass with90%at60g/hm2and95%at90g/hm2in control efficacy. Extract and feclorim didn't significantly influenced barnyard grass control.3Separation and identification of active compounds from extractThe targeted peaks1-4from extract was separated in a run of HSCCC by the appropriate solvent system which was n-hexane/ethyl acetate/ethanol/water [5:4:3:2(v/v)], corresponding to the K values of0.18,0.50,2.01and3.40separately. Among the compounds1-4, compounds1and2needed for further purification after analysis of HPLC and GC-MS. The other compounds3and4were identified as Z-ligustilide and senkyunolide A, corresponding to the molecule weight of190and192, respectively. The slight difference was found between C8and C9in bonding of compounds3and4which both belong to phthalide.4Bioassay of separated compounds.In laboratory experiment, protective effect on rice by Z-ligustilide was better than that by senkyunolide A. The level of shoots height was totally recovered to that of the untreated and the level of roots length was close to that of the untreated after Z-ligustilide treatment in agar medium. Meanwhile, the level of shoots height was close to that of the untreated after extract treatment in soil-based medium.5Mode of action of Z-ligustilide protecting rice against S-metolachlor.Z-ligustilide could enhance the ability for rice plants to detoxify S-metolachlor by increasing GST activities in plants, subsequently leading to reversion of effect on rice cause by S-metolachlor. GST activities in roots or shoots from S-metolachlor-treated rice seedlings presented no significant difference from the untreated control, while rice growth was severly inhibited by S-metolachlor. After detoxification of herbicide by Z-ligustilide ranging from1-4mg/L, GST activities of roots and shoots were increased, positively correlated to recoveries in roots and shoots. However, GST activities in roots or shoots maintained the highest level after detoxification treatment of more than4mg/L Z-ligustilide, on the contrary, recoveries in roots and shoots were reduced.Further study was focused on mRNA of OsGSTU2in rice roots and shoots analyzed by Real-time PCR. Results showed that there were significant difference in expression level of OsGSTU2mRNA in roots and shoots between the untreated, the S-metolachlor-treated and combined treatment, suggesting expression level of OsGSTU2mRNA was positively correlated to GST activities.