目的 分离纯化银杏Ginkgo biloba叶中的双黄酮类成分，考察银杏叶变黄前后黄酮类成分质量分数的变化。方法 从自然脱落的银杏叶中提取分离双黄酮类成分，对其乙醇提取物的二氯甲烷部位进行了分离，通过硅胶柱色谱和半制备液相方法对目标成分进行制备，采用HPLC法对银杏叶中的双黄酮进行了测定。结果 分离的4个化合物分别为去甲银杏双黄酮、银杏双黄酮、异银杏双黄酮和金松双黄酮。对变黄前后银杏叶中4种双黄酮进行测定，结果表明，自然黄叶前3周内，银杏叶中双黄酮量逐渐降低，质量分数差别达30%左右。结论 HPLC法可用作银杏叶中双黄酮的测定，方法简便、可靠，能用于银杏叶的质量控制。同时，制备条件可对快速制备双黄酮对照品提供依据。

Objective To purify the biflavonoids from Ginkgo biloba leaves and determine their contents in the leaves collected in different periods. Methods Dichloromethane fraction of ethanol extract was used to purify biflavonoids through silica gel column and semi-preparative HPLC. The contents of four biflavonoids were simultaneously determined using RP-HPLC. Results According to the reported 1H-NMR data, four compounds were identified as bilobetin (LB-1), ginkgetin (LB-2), isoginkgetin (LB-3), and sciadopitysin (LB-4). Content determination demonstrated that the biflavonoids accumulation decreased as the leaves collected from the beginning to the end of September, and the content difference can be as large as 30%. Conclusion RP-HPLC method can be used in the quantitative determination of biflavonoids in G. biloba leaves. The semi-preparative condition can be used in the purification of biflavonoids from G. biloba leaves. The contents of four biflavonoids could be decreased significantly when the leaves turned yellow, which provides the useful information for the collection of G. biloba leaves. However, the mechanism and the accumulation of other kinds of compounds need further study.

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