Three pairs of alkaloid enantiomers from the root of Isatis indigotica

Yufeng Liu; Xiaoliang Wang; Minghua Chen; Sheng Lin; Li Li; Jiangong Shi

doi:10.1016/j.apsb.2016.01.003

Three pairs of alkaloid enantiomers from the root of Isatis indigotica

Acta Pharm Sin B. 2016 Mar;6(2):141-7. doi: 10.1016/j.apsb.2016.01.003. Epub 2016 Feb 11.

Authors

Yufeng Liu¹, Xiaoliang Wang², Minghua Chen³, Sheng Lin², Li Li², Jiangong Shi²

Affiliations

¹ State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China; Department of Pharmacy, Jining Medical University, Jining 272067, China.
² State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
³ State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China; Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.

Abstract

Three pairs of enantiomerically pure alkaloids with diverse structure features, named isatindigoticoic acid A and epiisatindigoticoic acid A [(-)-1 and (+)-1], phaitanthrin A and epiphaitanthrin A [(-)-2 and (+)-2], and isatindopyrromizol A and epiisatindopyrromizol A [(-)-3 and (+)-3], respectively, were isolated from an aqueous extract of the roots of Isatis indigotica. Racemic and scalemic mixtures of these enantiomers were separated by HPLC on a chiral semi-preparative column. Their structures including absolute configurations were determined by extensive spectroscopic analysis in conjunction with the calculation of electronic circular dichroism (ECD) spectra. The enantiomer pairs possess parent structures of 2-oxo-1,2,3,4-tetrahydroquinoline-4-carboxylic acid, indolo[2,1-b]quinazolinone, and 3-thioxohexahydro-1H-pyrrolo[1,2-c]imidazol-1-one, respectively. Except for phaitanthrin A [(-)-2] which the configuration was previously undetermined, these compounds are new enantiomeric natural products.

Keywords: 2-Oxo-1,2,3,4-tetrahydroquinoline-4-carboxylic acid; 3-Thioxohexahydro-1H-pyrrolo[1,2-c]imidazol-1-one; Alkaloid enantiomer; Chiral separation; Cruciferae; Indolo[2,1-b]quinazolinone; Isatis indigotica.