黄龙山白桦桦木醇与桦木酸含量研究

为了阐明黄龙山白桦不同生境、不同径级、不同器官桦木醇与桦木酸含量，系统采集了陕北黄土高原黄龙山林场阳坡、阴坡、林缘、孤立木4种生境下的白桦不同径级植株的树皮、树枝和树叶样品，采用超声波辅助提取法提取样品，用高效液相色谱法测定了不同生境、不同径级白桦各器官桦木醇、桦木酸含量。结果表明：（1）不同生境下白桦各器官桦木醇、桦木酸含量均存在显著差异（P＜0.05），白桦树皮中桦木醇与桦木酸含量、白桦树枝中桦木酸含量在4种生境下均表现为阴坡＞孤立木＞林缘＞阳坡，白桦树叶中桦木醇与桦木酸含量及树枝中桦木醇含量均表现为阴坡＞林缘＞孤立木＞阳坡，总体来看阴坡生境下白桦各器官桦木醇与桦木酸含量都是最高的。（2）在白桦各器官中，桦木醇、桦木酸含量均表现为树皮＞树枝＞树叶。（3）不同生境下白桦各器官桦木醇、桦木酸含量随着胸径的增大均先增大后减小，均在第Ⅱ径级即胸径10.1~20 cm达到最大。研究认为，阴坡生境有利于白桦各器官积累桦木醇、桦木酸；白桦各器官中桦木醇含量较高，桦木酸含量比较低，而以桦木酸为原料的生物制剂已进入临床应用阶段，因此，以桦木醇为原料制取桦木酸是解决桦木酸在天然植物中含量低、提取困难的有效途径；对白桦各器官的采收应注意把握时机，于白桦生长到胸径10.1~20 cm时为最佳采收期。

Contents of Betulin and Betulinic Acid of Betula platyphylla in Huanglong Mountain

Collected the birch barks,branches and leaves of plant samples in four habitats of sunny slope,shady slope,forest edge and isolated trees in different diameters of Betula platyphylla in Huanglong mountain forest farm of northern Shaanxi Province in loess plateau,to illustrate the variation of betulin and betulinic contents.The samples extracted by ultrasonic assisted extraction,and used an accurate HPLC method to detect betulin and betulinic acid contents in different habitats and different diameters.The result indicated that there was a great variation between different habitats,and it was showed concretely as follows: (1) The contents of betulin and betulinic acid in barks and the contents of betulinic acid in branches ranged from high to low as shady slope,isolated trees,forest edge and sunny slope.The contents of betulin and betulinic acid in leaves and the contents of betulin in branches ranged from high to low as shady slope,forest edge,isolated trees and sunny slope.(2) The contents of betulin and betulinic acid in various organs of birch from high to low as bark,branch,leaf.(3) The betulin and betulinic acid contents of the different organs in different habitats increased first and then decreased with the increasing DBH of the trees,and the top value was observed in the DBH of 10.1-20 cm.The research suggested that shady habitat conducive to the accumulation of betulin and betulinic acid in various organs;the content of betulin in different organs of B.platyphylla is higher and the content of betulinic acid in different organs is lower,and betulin as raw material to prepare betulinic acid is an effective way to solve the betulinic acid in low levels of natural plants and difficult to extract;Attentions should be pay to grasp the opportunity of the organs of B.platyphylla,it is better to collect when the DBH of birch grows to 10.1-20 cm.