Study On The Herbicidal Activity Of Sapindus Mukorossi Gaertn

In recent decades, the investigation of the herbicidal activity of plant derived secondary metabolites has drawn the public attention. Natural products not only may be more environmentally acceptable than synthetic pesticides, but also may have novel mechanisms of action different from those of the already known synthetic herbicides. It is of significant importance to isolate and identify new compounds with herbicidal activity from plants. The paper focus on the herbicidal activity of Sapindus mukorossi Gaertn., and systematically isolated the herbicidal compounds from its extracts. The results were as follows:1. Seed germination test(SGT) were used to investigate the herbicide potential of 4 parts of Sapindus mukorossi Gaertn. At the concentration of 10mg/m L, the phytotoxicity of leaves was better than other parts on the growth of the two tested plant species.2. Three solvent were used here to extract leaves to compare their herbicidal activity. The results showed that, at the concentration of 10 mg/m L, the highest inhibitory rate on buds and roots were both from the extract of ethanol.3. Pot experiment were carried out using the extracts of leaves extracted by ethanol. Eight kinds of plant seeds were used as the tested subjects. The results showed that ethanol extracts of Sapindus mukorossi Gaertn leaves had very good herbicidal activity both on buds and roots. Fresh weight reductions of 8 seedlings by treating the stem using ethanol extracts ranged from 14.91% to 27.25% at the concentration of 20mg/m L. The highest fresh weight reduction also could reach 19.06% at the concentration of 10mg/m L. Fresh weight reductions of 8 seedlings by treating the soil using ethanol extracts ranged from 15.93% to 31.15% at the concentration of 20mg/m L. The highest fresh weight reduction also could reach 20.86% at the concentration of 10 mg/m L.4. Ethanol extracts of Sapindus mukorossi Gaertn leaves were suspended with water, then extracted with petroleum ether, ethyl acetate and n-butanol, successively. SGT was used to evaluate the different herbicidal activity of different extracts. The result showed that the petroleum ether phase were of the best herbicidal activity.5. Seven compounds were isolated from Sapindus mukorossi Gaertn by diverse separation methods. The compounds were identified as stearic acid, palmitic acid, lupeol, oleanolic acid, β-sitosterol, stigmasterol, pinitol. Amaranthus retroflexus and Avena fatua L. were used as tested subjects to evaluate the different phytotoxicity of these compounds. Among them the oleanolic acid and pinitol showed strongly herbicidal activity to all the two plant seeds. To further investigate their activity. EC50 of Amaranthus retroflexus and Avena fatua L. seeds were used to assess the inhibitory effects.The EC50 of pinitol to Amaranthus retroflexus were 56.05 μg/m L(buds) and 58.07 μg/m L(roots), that to Avena fatua L were 53.61 μg/m L(buds) and 56.43 μg/m L(roots). The EC50 of oleanolic acid to Amaranthus retroflexus were 61.89 μg/m L(buds) and 66.70 μg/m L(roots), that to Avena fatua L were 58.67 μg/m L(buds) and 59.65 μg/m L(roots).In conclusion, Sapindus mukorossi Gaertn is of good herbicidal activity. It contains various compounds which have good herbicidal activity, such as pinitol and oleanolic acid. So Sapindus mukorossi Gaertn is of certain value for further study.