中文摘要：

目的 以三年生白桦为试材，研究白桦植株中三萜合成前体及其三萜组分积累变化，并对白桦植株中三萜组分积累消长特征进行分析。方法 利用高效液相色谱仪及紫外分光光度计对白桦枝皮和叶进行总三萜、白桦脂醇和黄酮等8种成分检测。结果 白桦植株枝皮和叶中三萜物质各组分积累特征显著不同。在生长季节（5～9月）枝皮中2, 3-氧化角鲨烯、白桦脂酸、白桦脂醇、齐墩果酸、达玛烯二醇、固醇及总三萜积累高峰基本为7～9月，其中2, 3-氧化角鲨烯量较低，最高为0.067 mg/g（7月），白桦脂酸量达8.34 mg/g，而齐墩果酸量高达37.51 mg/g（9月）；达玛烯二醇量最高为14.18 mg/g，总三萜量达168.17 mg/g（7月）。叶中总三萜量为8月份较高，达126.11 mg/g，而2, 3-氧化角鲨烯、白桦脂醇和齐墩果酸量均极低，甚至未能检测到。枝皮和叶片中黄酮积累高峰分别为5月和8月，其中2个月份质量分数分别为53.02 mg/g和58.49 mg/g。消长分析表明，白桦枝皮和叶中三萜组分积累与总三萜积累规律不相吻合，枝皮总三萜、达玛烯二醇、齐墩果酸、白桦脂酸呈S型曲线，白桦脂醇积累呈倒“V”曲线，且黄酮积累与总三萜积累趋势相反。叶中总三萜和黄酮物质积累趋势相近，达玛烯二醇和2, 3-氧化角鲨烯积累趋势相近。结论 明确了三年生白桦枝条和叶片中三萜及黄酮物质积累、分布特征，为白桦枝条皮和叶中三萜资源的挖掘、可持续利用及代谢调控奠定了基础。

英文摘要：

Objective Using three-year-old birch （Betula platyphylla） as the experimental material to study the changes of the accumulation of triterpenoid precursor and triterpenoid components in birch, and to analyze the fluctuation characteristics of triterpenoid component accumulation. Methods Eight compositions, such as the total triterpene, betulin, flavonoids, etc in twig barks and leaves, were analyzed by HPLC and UV spectrophotometer. Results The accumulative characteristics of each component in triterpenoid substances was significantly different between the twig barks and leaves. During the growing seasons （May—September）, the accumulation of 2, 3-oxidized squalene, betulinic acid, betulin, oleanolic acid, dammarenediol, sterol, and total triterpene reached the peak in July—September. Among these, 2, 3-oxidized squalene had a lower content and its highest content was 0.067 mg/g in July. The content of betulinic acid was 8.34 mg/g, while the content of oleanolic acid reached 37.51 mg/g in September. The highest content of dammarenediol was 14.18 mg/g and the total triterpene content was 168.17 mg/g in July. The higher concentration of total triterpene in the leaves was 126.11 mg/g in August, while the contents of 2, 3-oxidized squalene, betulin, and oleanolic acid were very low and not detected. The accumulated peaks of flavonoids in twig barks and leaves were 53.02 and 58.49 mg/g, respectively in May and August. The fluctuation analysis showed that the accumulation of triterpenoid components did not coincide with that of total triterpene in twig barks and leaves,. The total triterpene, dammarenediol, oleanolic acid, and betulinic acid showed the S-shaped curve in twig barks, and the accumulation of betulin showed the inverted “V” curve, the while trend of flavonoid accumulation was contrary to the total triterpene. The trend of the total triterpene accumulation was similar to that of flavonoids, while the trends of dammarenediol and 2, 3-oxidized squalene accumulation were similar. Conclusion This r