西加云杉木材中单宁的提取、分布及组分

Extraction,distribution and composition of tannin in Picea sitchensis

研究西加云杉木材中植物单宁的提取工艺、分布和组分构成,为木材单宁变色的防治提供参考。采用有机溶剂萃取法,通过单因素试验并结合L9(34)正交试验,优化西加云杉木材中植物单宁的提取工艺;采用香草醛-紫外法测定西加云杉木材内植物单宁在径向(由髓心至树皮方向)和轴向的含量分布;通过定性鉴定试验确定单宁类型,并采用高效液相色谱法测定西加云杉木材中单宁的成分构成及其相对含量。结果表明:西加云杉木材中单宁最佳提取条件为70%(体积分数)乙醇作为提取溶剂,提取温度70℃,提取时间2 h,料液比1∶18(g∶m L),提取次数2次;单宁含量在径向上分布情况为内部心材单宁含量5.440 mg/g,近心边材转换区的心材部分单宁含量最高,平均达10.015 mg/g,心边材转换区部位单宁含量介于心材和边材之间,平均为6.363 mg/g,靠近转换区的边材部位单宁含量最低,平均为4.821 mg/g,近树皮边材含量为6.997 mg/g。西加云杉木材内5种原花青素成分含量存在明显差异,其中儿茶素含量最高,占5种原花青素总量的83.21%,原花青素B2次之。由此可知,有机溶剂法适用于西加云杉木材中单宁的提取;木材中单宁含量径向分布自髓心至树皮整体呈现出先增后减再增、心材大于边材的规律,轴向分布规律表现为下部含量略高于上部,但差异不显著;西加云杉木材内植物单宁类型为缩合单宁,儿茶素为西加云杉木材单宁的主要成分。

The extraction,distribution,and composition of tannin in Picea sitchensis wood were investigated.In this study,six factors,including solvent type,solvent concentration,extraction time,extraction temperature,materialliquid ratio and frequency,were used to explore the optimized tannin extraction process conditions via the L9(34) orthogonal test.The vanillin hydrochloric acid method was used to determine the distribution of tannin in different positions(heartwood,sapwood and transition zone in the radial direction and different heights in the longitudinal direction) of the wood.Qualitative tests were applied to determined tannin type of P.sitchensis.The high-performance liquid chromatography(HPLC) was used to comparatively analyze the composition of tannin in P.sitchensis with five common procyanidins.The results were as follows:the optimum extraction conditions were the ethanol content of70% volume fraction as extraction solvent,extraction temperature of 70℃,extraction time of 2 h,material-liquid ratio of 1:18(g:mL),2 times of extraction.The distribution situation of tannin contents are showed as follows:in the radial direction,the tannin content in the inner of heartwood was 5.440 mg/g,while that in the heartwood next to the transition zone was 10.015 mg/g;the sapwood next to the transition zone had the lowest tannin content of 4.821 mg/g and the sapwood next to the bark was 6.997 mg/g;the content of catechins was the highest,accounting for 83.21% of the total procyanidins,and followed by procyanidins B2,accounting for 14.29%.The organic solvent method is suitable for the extraction of tannin in the P.sitchensis.From the pith to bark,the tannin content increased firstly,then decreased,and increased finally.The tannin content of heartwood was higher than sapwood,and the heartwood next to the transition zone had the highest tannin content,while the sapwood near the transition zone had the lowest tannin content.For the effect of the stem height,the content of lower part was slightly higher than upper part,while there was no significant difference.The tannin type of P.sitchensis was condensed tannins.It is believed that the catechin is the main ingredients,accounting for 59.68% of the total tannin content in P.sitchensis wood.