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Molecules 2017, 22(8), 1308; doi:10.3390/molecules22081308

Characterization of Proanthocyanidin Oligomers of Ephedra sinica

Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
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Received: 14 July 2017 / Revised: 27 July 2017 / Accepted: 3 August 2017 / Published: 6 August 2017
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Abstract

Ephedra sinica, an important plant in Chinese traditional medicine, contains a complex mixture of proanthocyanidin oligomers as major constituents; however, only the minor components have been chemically characterized. In this study, oligomers with relatively large molecular weights, which form the main body of the proanthocyanidin fractions, were separated by adsorption and size-exclusion chromatography. Acid-catalyzed degradation in the presence of mercaptoethanol or phloroglucinol led to the isolation of 18 fragments, the structures of which were elucidated from their experimental and TDDFT-calculated ECD spectra. The results indicated that (−)-epigallocatechin was the main extension unit, while catechin, the A-type epigallocatechin–gallocatechin dimer, and the A-type epigallocatechin homodimer, were identified as the terminal units. Among the degradation products, thioethers of gallocatechin with 3,4-cis configurations, a B-type prodelphinidin dimer, a prodelphinidin trimer with both A- and B-type linkages, and a prodelphinidin dimer with an α-substituted A-type linkage were new compounds. In addition, a phloroglucinol adduct of an A-type prodelphinidin dimer, a doubly-linked phloroglucinol adduct of epigallocatechin, and a unique product with a flavan-3-ol skeleton generated by the rearrangement of the aromatic rings were also isolated. View Full-Text
Keywords: Ephedra sinica; proanthocyanidin; oligomer; thiolysis; phloroglucinolysis; TDDFT; ECD Ephedra sinica; proanthocyanidin; oligomer; thiolysis; phloroglucinolysis; TDDFT; ECD
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MDPI and ACS Style

Orejola, J.; Matsuo, Y.; Saito, Y.; Tanaka, T. Characterization of Proanthocyanidin Oligomers of Ephedra sinica. Molecules 2017, 22, 1308.

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