Optimization Of Ultrasonic Extraction Conditions Of Allelochemicals From Sedum Spectabile Flower And Allelopathic Effect To Three Weeds

Finding new leading compounds from plant sources is one of the important ways to research on the biological pesticide. Allelochemicals, which are non-nutritive substances mainly produced as plant secondary metabolites or decomposition products of microbes, produce stimulation or inhibition to other creatures, including themselves. Therefore, allelochemicals are one kind of bioactive substances having a bright prospect application. Sedum spectabile is a ground-cover plant used for afforestation, it’s characters of natural growth reflect potential allelopathic effect. This article studied the allelopathic effects of aqueous extracts and methanol extracts of Sedum spectabile different parts, including root, stem, leaves and flower, on seeds germination and seedling growth of weeds by means of bioassay in laboratory. This paper further studied Sedum spectabile flower which has higher allelopathy, it includes the optimum conditions of ultrasonic wave-assisted extraction technology, preliminary separation, identification by gas chromatography-mass spectrometry (GC-MS), allelopathic active substances of Sedum spectabile flower were isolated and identified, then tested allelopathic activity of five potential allelochemicals, The main conclusions were followed as:1. Aqueous extracts and methanol extracts of root, stem, leaves and flower of Sedum spectabile respectively showed allelopathic effects on Trrifolium repens L, and the degree of influence is of difference. The flower showed the strongest inhibition synthesis effect, water and methanol all can extract allelochemicals of Sedum spectabile flower effectively. Allelopathic effect of different parts of Sedum spectabile had characteristics with double concentration effects, which is low-promoting and high-repressing.2. The result of optimization of the ultrasonic extraction conditions showed facters that influence allelopathy of extracts were in order of methanol concentration, ultrasonic time, solid-liquid ratio, extraction temperature. The optimal extraction conditions are as follows:The volume fraction of methanol concentration is 70%, the extraction temperature is 45 ℃, the extraction time is 160 min, and the ratio liquid to solid is 1:30 (W/V). Under the optimized conditions, a good result was got.3. Allelochemicals of Sedum spectabile flower were extracted under the optimized conditions, then organic solvent extraction was carried out to make a preliminary separation. After biological testing from different extraction phases. The result showed the order of allelopathic effect of different phases:Methylene chloride phase> Ethyl acetate phase> n-butanol phase> Petroleum ether phase> aqueous phase. Using GC-MS to detect and identify the organic compounds contained in methylene chloride phase, the result showed the mainly compounds were esters, phenols, organic acids, ketones and hydrocarbons,18 kinds of compounds were identified.4. Selecting 5 potential allelochemicals based on GC-MS detection results, biological testing was conducted to determine their allelopathic effects. The result showed the activity of 5 potential allelochemicals is different, all compounds, except 1,2-benzenedicarboxylic acid dibutyl ester, can inhibit 3 weeds, and Trrifolium repens L is the most sensitive.