The Study On Suppress Rhizoctonia Solani By The Active Ingredient Of White Loropetalum Chinense

Rice sheath blight, widely distributed, is a rice disease which has become the most serious rice disease in the south of China. Chemical pesticides used for a long time not only makes the evident pest resistance, but also bring series of problems, such as toxic residues and environmental pollution, etc. Plant source pesticide has strong bactericidal effect, high efficiency, low toxicity, and eco-friendly and loads of other characteristics. White Loropetalum chinense and active substances of its ethanol extracts which displayed strong inhibition to Rhizoctonia solani were studied in this project. Then, the structure information of active compounds monomer was determined through activity tracking, isolation and identification of compounds monomer. This research provided scientific basis and evidence for exploring new plant pesticides suppressing R solani with independent intellectual property right. Following you can find the main research contents and results:1. Active ingredients of 95% ethanol extraction of Loropetalum chinense were extracted repeatedly with petroleum ether (60-90℃), ethyl acetate and n-butanol. The poison culture medium method was used for determine inhibition activity of extraction to R solani. The antibacterial activity of extraction was tracked progressively in following steps because we separated and purified extracts using silica gel column chromatography, silica gel thin-lay chromatography (TLC), Sephadex LH 20 column, reverse silica gel column. The results showed us that the ethyl acetate portion of Loropetalum chinense could dramatically inhibit R. solani with high inhibition rate (up to 82.34%) when all the components’ concentration was 1 g/1. However, the petroleum ether extraction displayed less inhibition to those microorganisms. The inhibition rate of 1 g/1 ethyl acetate extraction to R. solani was about 84.78% and 100 μg/ml further active component performed approximately 38.13% inhibition rate. Three crystalline compounds were obtained through the Sephadex LH 20 column, reverse silica gel column, which were 18 mg compound 1,8 mg compound 2 and 12 mg compound 3 respectively.2. The structural identification of three crystalline compounds were identified by ultraviolet spectroscopy (UV), infrared spectroscopy (IR), mass spectrometry (MS), NMR spectroscopy (1D-NMR) and 2D NMR spectroscopy (2D-NMR) technologies. The identification results showed that compound 1 was quercetin, compound 2 was catechin and compound 3 was catechin-[7,8-bc]-4β-(3,4-dihydroxyphenyl)-dihydro-2(3H)-pyranone。 Antifungal activity of learned,effect of quercetin on Rhizoctonia solani inhibited,the effective concentration EC50 was 0.0763 g/L.The chemical composition of Loropetalum chinense has been studied previously. However, the reports of activity are few currently and in terms of the inhibition to rice sheath blight fungus is much fewer. The results of this study revealed that Loropetalum chinense has significant biocontrol potential against R solani.