Study On The Content Of Tannin Extract In Four Types Of Quercus Variabilis

Quercus variabils forest is constructive species of the typical zonal vegetation types in warm-temperate deciduous broad-leaved forest.Tannin extract is one of the significant forestry chemical products from Q.variabilis.It has been applied in petroleum,mining industry,chemical engineering,textile,food,medicine agriculture and forestry widely.To illustrate the variation of tannin extract from four types of Q.variabilis,sample-plot survey,controlled experiment in laboratory and statistical analysis were used to study the tannin content and the variation from the four types of Q.variabilis(including thick bark deep crack type,the thick bark shallow crack type,the thin bark deep crack type and the thin bark shallow crack type)on different diameters at breast height.To explain the the tannin content,the variation and to understand the leading ecological factors affecting Q.variabilis tannin extract in different distribution regions(including south slope of Qinling Mountains,north slope of Qinling Mountains,Loess Plateau).To illustrate the suitable technology of ethanol extraction in the tannin from Q.variabilis.The future applications of various tannin extract were prospected.The results of present study provided a theoretical basis for rational development and utilization in tannin resources of Q.variabilis.The main results were as follows:1.With thick bark deep crack type of Q.variabilis valonea as object,the extraction process of Quercus variabilis valonea tannin was optimized,using ethanol was the best extraction medium.This study aimed to illustrate the suitable technology of ethanol extraction in the tannin extract from Q.variabilis.The optimized extraction process for tannin extract were as follows:ethanol concentration of 70%,the liquid ratio of 15:1,extraction temperature of 80? extraction time of 4 hours.The effect of extraction temperature on tannin extraction of valonea from Q.variabilis was the significant and higher than than the other factors,followed by the ratio of smples with ethanol solution and ethanol concentration,the influence of extraction time on tannin extraction was minimum.2.The average tannin content of 2.31%-2.72%was found in the roots of the four types of Q.variabilis,as well as 1.31%?1.72%in the stems,6.32%-6.89%in the leasves,4.49%~4.92%in the branches and 8.17%~8.86%in the barks.The content of tannin in the leaves,branches and barks are much higher than that in the roots and stems obviously.Leaves,branches and barks were suggested as the major raw materials of tannin extract.The significant difference of tannin content was observed among the different organs of the four types of Q.variabilis.In the leaves,branches and barks,the contents of tannin ranged from high to low as the thick bark deep crack type,the thick bark shallow crack type,the thin bark deep crack type,the thin bark shallow crack type.The tannin content in the roots and stems of the four types ranged from high to low as thin the bark deep crack type,the thin bark shallow crack type,the thick bark shallow crack type,the thick bark deep crack type.Because of the tannin contents in the leaves,branches and barks with a high level,the Q.variabilis with the thick bark deep crack type was the best one in the four types for tannin extract.3.The tannin contents of the different organs in the four types augmented with the increasing DBH of the trees,and the top value was observed in the DBH of 20.1~25cm.The DBH and the height of trees affected the tannin contents positively.The suggestion is that the Q.variabilis with DBH above 25cm should be applied fully and efficiently for tannin extraction,or it should be priority for directive cultivation and special protection.4.The results showed that the significant difference of tannin content was observed among the different components in different regions.The tannin content in the 3 different distribution regions ranged from high to low as south slope of Qinling Mountains,north slope of Qinling Mountains and Loess Plateau.The tannin content of valonea of Q.variabilis in the 6 regions was highest,followed by the bark,leaf,branch,the tannin content of root and stem were the lowest.5.Tannin content of different organs of Q.variabilis in 3 different distribution regions(6 sample sites)were analyzed by UV spectrophotometry and the grey correlation degrees with ecological factors were calculated.The results showed that the leading soil factors that influenced tannin content of different organs of Q.variabilis was available nitrogen,available phosphorus,available potassium.Soil organic matter were the main factors affecting the effective component content of tannin extract of Q.variabilis.The positive correlation of tannin content of grapevine organs and these main soil factors was found.The leading climatic factors that affected tannin content of different organs were frost free periods,annual sunshine hours and annual average rainfall.The frost free periods and annual average rainfall was positive correlated with tannin content in different organs of Q.variabilis,the annual sunshine hours was negative correlated with tannin content in different organs of Q.variabilis.The higher frost free periods,higher rainfall,lower sunshine hours,higher organic matter and lower soil nutrients content area was the high priority cultivation area of Q.variabilis tannin extract.