Zhang Zhongyi

Continuous cropping obstacle and allelopathic autotoxicity of medicinal plants

In this paper, the concept, mechanism and action mode of allelopathic autotoxicity of medicinal plants were discussed. The study identifies that the basic reason for the continuous cropping obstacles and allelopathic autotoxicity of medicinal plant is the homology of autotoxic-allelochemicals and pharmaceutical active substances.Accordingly, the relationship between the causes of the obstacles and the autotoxicity of allelochemicals in medicinal plants are also analyzed. Comprehensive agronomic methods based on rhizospheric soil microflora systems research using DGGE, T-RFLP and other related techniques are proposed. This reduces the in-

Extraction of resveratrol and emondin from Polygonum cuspidatum by supercritical CO2 with different solubilizers

In order to improve the extraction yields of resveratrol and emondin obtained by supercritical CO2 extraction (SCE), different solubilizers were added in the supercritical CO2 extraction process. Resveratrol and emondin were extracted from Polygonum cuspidatum by SCE with different solubilizers, including bis(2-ethylhexyl) sodium sulfosuccinate (AOT), povidone k-90 (PVP k-90), Poloxamer 188 and Tween 80, at extraction pressure 25 MPa and extraction temperature 50°C. The results show that resveratrol was hardly extracted by SCE with ethanol as modifier, but AOT, PVP k-90, Poloxamer 188 and Tween 80 could enhance the extraction yield of resveratrol significantly, while the yield of emodin was influenced gently by using these solubilizers. Based on the comparison of SCE and heat reflux extraction, the advantage of SCE is less extraction time at lower operating temperature without using large amount of organic solvent. The yields of resveratrol and emondin extraction from P. cuspidatum by SCE can be improved by introducing AOT, PVP k-90 and Poloxamer 188 into supercritical CO2. Key words: Polygonum cuspidatum, resveratrol, emondin, supercritical CO2 extraction, solubilizer.