树皮

Large family of bark boring or wood boring short beaked beetles very destructive to forest and trees .

蛀树皮或蛀木头短嘴的甲壳虫；对森林和数破坏严重。

Any betulaceous tree or shrub of the genus Betula having ''.

桦属的任何一种桦树或灌木，有薄的剥落的树皮。

Any betulaceous tree or shrub of the genus Betula having a thin peeling bark.

桦属的任何一种桦树或灌木，有薄的剥落的树皮。

In addition a simple process was also developed to obtain purified betulin using chloroform / NaOH two-phase solvent extraction.

另外还建立了一种在碱性条件下用氯仿/水溶液混合溶剂来一步纯化白桦树皮中的白桦酯醇的方法。

To harmful microflora white part of birch bark is obliged precisely to betulin.

稳定有害菌群白桦树皮部分恰恰有义务为桦木醇。

The microwave-assisted extraction of betulin from Betula platyphylla Suk. bark was optimized using uniform design.

利用均匀设计法优化了微波辅助提取白桦树皮中桦木醇的工艺。

MATERIAL AND METHODS: Betulin was isolated from dry powder of the bark of silver birch by using ethanol circumfluence, decompress concentration and methanol-chloroform recrystallization.

材料与方法：取一定量的白桦树皮干粉，通过乙醇回流，减压浓缩和甲醇-氯仿重结晶等步骤获得白桦酯醇纯品。

The results showed a betulin yield of 25.43%, a purity of 59.19% was achieved from 1g powder of B. platyphylla bark under the extraction temperature of 72℃, microwave power 67W, and extraction time 100s.

试验结果表明，1g白桦树皮粉末，在提取温度72℃、微波功率67W，提取时间100s的条件下，微波辅助提取的桦木醇收率达到25.43%，纯度达到59.19%。

BACKGROUND ＆ AIM: Betulin is an important triterpene. We investigated the antitumor activity of betulin, extracted from the bark of silver birch.

背景与目的：白桦酯醇是一种重要的三萜类生物活性分子，本文从白桦树皮中提取获得白桦酯醇纯品，然后研究该生物活性分子抑制食管癌细胞的活性。

Furthermore, the ability of betulinic acid to induce apoptosis in melanoma and other cell types and the favoral therapeutic index suggests that betulinic acid is an attractive and promising antitumor agent.

虽然白桦酯酸存在于很多植物种类中，但其普遍含量很低，由于其巨大的研究价值，仅靠植物提取已经不能满足越来越多的研究需求，与白桦酯酸结构很相近的化合物白桦酯醇，在白桦树皮中含量高于10%，而白桦又是北半球数量丰富的树种。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。