State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao SAR 999078, China.
Molecules. 2012 Apr 10;17(4):4236-51. doi: 10.3390/molecules17044236.
Angular-type pyranocoumarins from Peucedani Radix (Chinese name: Qian-hu) have exhibited potential for use on treatment of cancer and pulmonary hypertension. Due to the existence of C-3' and C-4' chiral centers, compounds belonging to this chemical type commonly exist in enantiomers and/or diastereoisomers, which may elicit distinct activities during their interactions with the human body. In the present study, a new method, which combines enzymatic hydrolysis with chiral LC-MS/MS analysis, has been developed to determine the absolute configurations of these angular-type pyranocoumarins. Pyranocoumarins isolated from Qian-hu, their enantiomers, or metabolites were individually incubated with rat liver microsomes. As the common end product from enzymatic hydrolysis of all tested pyranocoumarins, cis-khellactone was collected and its absolute configuration was determined by comparison with (+)-cis-khellactone and (-)-cis-khellactone using chiral LC-MS/MS. The absolute configurations of all tested parent pyranocoumarins were determined by combination of LC-MS/MS, NMR and polarimetric analysis. The results revealed that the metabolite cis-khellactone retained the same absolute configurations of the stereogenic carbons as the respective parent compound. This method was proven to be rapid and sensitive and also has advantages in discriminating single enantiomers and mixtures of optical isomers with different ratios.
角型吡喃香豆素类化合物存在于中药前胡（Peucedani Radix，中文名：前胡）中，具有治疗癌症和肺动脉高压的潜力。由于 C-3'和 C-4'手性中心的存在，该化学类型的化合物通常以对映异构体和/或非对映异构体的形式存在，这可能会在与人体相互作用时产生不同的活性。本研究建立了一种新的方法，将酶解与手性 LC-MS/MS 分析相结合，用于测定这些角型吡喃香豆素的绝对构型。从前胡中分离出的吡喃香豆素、它们的对映异构体或代谢物分别与大鼠肝微粒体孵育。作为所有测试的吡喃香豆素酶解的共同终产物，顺式开马灵被收集，并通过与 (+)-顺式开马灵和 (-)-顺式开马灵进行手性 LC-MS/MS 比较来确定其绝对构型。通过 LC-MS/MS、NMR 和旋光分析相结合，确定了所有测试的母体吡喃香豆素的绝对构型。结果表明，代谢产物顺式开马灵保留了与各自母体化合物相同的手性碳原子绝对构型。该方法快速灵敏，还具有区分单一对映异构体和不同比例的光学异构体混合物的优势。
