Studies On The Contents Of Polyphenols Extracted From Forest Trees And Their Antifungal Effects

For a long time, the abuse of chemical pesticide has caused a series of public disasters such as environment pollution, poison, toxicities to natural enemy, destroying ecological equilibrium and so called "3R"(Residue, Resistance, Resurgence). So searching replaceable antifungal active substance from plants has great significance. Plant secondary metabolites are the products of interaction of plant and environment, which including primary compounds of terpenes, alkaloids, flavones, steroids, phenols, etc. These compounds build the chemical defense mechanism to resist the predators, pests and pathogens. Among them, phenols is one of the most researched and also most important compound.In the study, experiment materials were the polyphenol crude extraction from the selected plants such as cortex of Dracaena cochinchinensi(Lour.) S.C.Chen, Larix gmelinii, Pinus sylvestris L.var.mongolica, Betula platyphylla, Betula dahurica and Belula alnoides which all were polyphenols richness. The antifungal activities of these materials were investigated and build foundation to develop low poison plant antifungal products. In experiment, polyphenols were extracted by reflux ectraction method which applyed petroleum ether to degrease and methyl alcohol solvent. Phenolic hydroxyl were examined and inspected by colour-developing reaction and the content of total polyphenols was determined by UV-spectrophotometry. Screening test were performed to the antifungal activities of polyphenol extraction by the tube dilution method to the selected ten pathogenic fungus such as Dothiorella gregaria, Rhizoctonia solani, Phyllosticta pirina, and the minimal inhibitory concentration(MIC) were measured. The column chromatography and thin layer chromatography were applyed to separate and analyse cortex extracts of Dracaena cochinchinensi (Lour.) S.C.Chen, which was the mostly effective, and the structures were identified by spectrum data of three compounds (UV, IR,'H-NMR, 13C-NMR and MS).The results were indicated as follows: (1) The phenolic hydroxyl existed in all experimented materials. (2) The content of total polyphenols in the cortex crude extracts of Larix gmelinii was highest, then in the cortex extracts of Dracaena cochinchinensi (Lour.) S. C. Chen and lowest in the cortex crude extracts of Belula alnoides. (3)The content of proanthcyanidin in the cortex crude extracts of Larix gmelinii is highest; then in the cortex extracts of Betula platyphylla.but almost didn't exist in the dragon's blood resin and the cortex EtOAc extracts of Pinus sylvestris L.var.mongolica; (3) From the results, the dragon's blood resin showed distinct antifungal activities. The cortex extracts of Larix gmelinii and Pinus sylvestris var.mongolica also showed well antifungal activities. But the cortex extracts of Betula platyphylla, Betula dahurica and Belula alnoides showed little antifungal activity. (4) Four monomers were acquired from dragon's blood resin. Compared with the literatures, the compound I, II and III were proved that they be loureirin A, Loureirin B and Pterostilbene.