Sprogøe Kennett, Staerk Dan, Jäger Anna K, Adsersen Anne, Hansen Steen Honoré, Witt Matthias, Landbo Anne-Katrine R, Meyer Anne S, Jaroszewski Jerzy W
Department of Medicinal Chemistry, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
J Nat Prod. 2007 Sep;70(9):1472-7. doi: 10.1021/np0702741. Epub 2007 Sep 7.
The hyphenated technique, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-SPE-NMR), has been applied for rapid identification of novel natural products in crude extracts of Hubertia ambavilla and Hubertia tomentosa. The technique allowed full or partial identification of all major extract constituents and demonstrated the presence of unusual quinic acid derivatives containing the (1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl residue that exhibit strongly coupled ABXY patterns, the parameters of which were obtained by spin simulations. Using homo- and heteronuclear 2D NMR data acquired in the HPLC-SPE-NMR mode, complete structure determination of three new natural products, i.e., 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quinic acid (1), its 2-hydroxy derivative (2), and 3,5-di-O-caffeoyl-4-O-[(4-hydroxyphenyl)acetyl]quinic acid (3), was performed. Finally, targeted isolation of 1 was achieved by SPE fractionation and preparative HPLC, followed by evaluation of its antioxidant and antimicrobial activity. In contrast to chlorogenic acid and 3,5-di-O-caffeoylquinic acid, which act as antioxidants, compound 1 proved at the same conditions to possess prooxidant activity in an assay evaluating the oxidation of human low-density lipoprotein induced by Cu(2+).
联用技术，即高效液相色谱-固相萃取-核磁共振光谱法（HPLC-SPE-NMR），已被应用于快速鉴定安巴胡氏木（Hubertia ambavilla）和绒毛胡氏木（Hubertia tomentosa）粗提物中的新型天然产物。该技术能够对所有主要提取物成分进行全部或部分鉴定，并证明存在含有(1-羟基-4-氧代环己-2,5-二烯基)乙酰基残基的异常奎尼酸衍生物，这些衍生物呈现出强耦合的ABXY模式，其参数通过自旋模拟获得。利用在HPLC-SPE-NMR模式下采集的同核和异核二维核磁共振数据，完成了三种新天然产物的结构确定，即3,5-二-O-咖啡酰基-4-O-[(1-羟基-4-氧代环己-2,5-二烯基)乙酰基]奎尼酸（1）、其2-羟基衍生物（2）和3,5-二-O-咖啡酰基-4-O-[(4-羟基苯基)乙酰基]奎尼酸（3）。最后，通过固相萃取分级分离和制备型高效液相色谱法实现了对1的靶向分离，随后评估了其抗氧化和抗菌活性。与作为抗氧化剂的绿原酸和3,5-二-O-咖啡酰基奎尼酸相比，在评估铜(2+)诱导的人低密度脂蛋白氧化的试验中，化合物1在相同条件下被证明具有促氧化活性。
