Elsevier

Fitoterapia

Volume 129, September 2018, Pages 150-153
Fitoterapia

Two new polyketides from the roots of Stemona tuberosa

https://doi.org/10.1016/j.fitote.2018.06.025Get rights and content

Abstract

Two polyketides, stemonones A (1) and B (2) with new skeletons, were isolated from the roots of Stemona tuberosa. Their absolute structures were fully characterized by comprehensive spectroscopic analyses and comparison of experimental electronic circular dichroism (ECD) spectra with calculated ones. The plausible biosynthetic pathways for 1 and 2 were also proposed. Anti-inflammatory assay confirmed that the two compounds showed moderate inhibitory effects on β-glucuronidase release in rat polymorphonuclear leukocytes (PMNs) induced by platelet-activating factor.

Introduction

The genus Stemona (Stemonaceae) comprising approximately 25 species is widely distributed in the warm areas of East Asia, with seven species occurring in China [1]. The roots of Stemona tuberosa, known as “Baibu” in traditional Chinese medicine (TCM), were listed in the 2015 edition of Chinese Pharmacopeia and has long been prescribed as insecticidal and antitussive medications [[2], [3], [4]]. Previous phytochemical investigations on S. tuberosa have led to the isolation of alkaloids, stilbenoids, sterols, lignans, and glycerin monoesters [[5], [6], [7], [8]]. Pharmacological studies have proven that the antimicrobial activities of S. tuberosa could be attributed to stilbenoids [9]. Though some Stemona alkaloids could relieve cough bronchitis and tuberculosis, the effective constituents with antitussive activity have not been studied too much [10, 11].

As a continuation of our research for new bioactive principles from TCM, the EtOH extract of the roots of S. tuberosa was intensively investigated in the current study. Two new polyketides, stemonones A (1) and B (2) (Fig. 1) incorporating unprecedented skeletons, were obtained and structurally characterized on the basis of comprehensive spectroscopic analyses. Both compounds were evaluated for anti-inflammatory activity by measuring their inhibitory effects on β-glucuronidase release in rat polymorphonuclear leukocytes (PMNs) induced by platelet-activating factor. Herein, we present the isolation, structural elucidation and anti-inflammatory testing of the two interesting compounds.

Section snippets

General experimental procedures

Optical rotation data were recorded on a Rudolph VI digital polarimeter (Rudolph Research Analytical, USA). IR spectra were obtained using a Nicolet 5700 FT-IR spectrometer. NMR experiments were performed on a Bruker AVANCE DRX600 NMR spectrometer (Bruker BioSpin Corporation, Switzerland) with residual solvent peaks as standards (CDCl3 δH 7.26; δC 77.16). ESIMS were acquired on an Agilent 6460 Triple Quad LC/MS spectrometer (Agilent Technologies, USA). HRESIMS were measured on an Agilent

Results and discussion

Compound 1 was obtained as white amorphous powder. Its molecular formula was established as C16H20O4 based on the HRESIMS peak at m/z 277.1435 [M + H]+, corresponding to seven degrees of unsaturation. The IR absorption bands at 1703 and 1636 cm−1 indicated the presence of an α,β-unsaturated ketone. The 1H NMR data (Table 1) showed signals of a 1,2-disubstituted benzene ring at δH 6.85 (1H, d, J = 8.1 Hz, H-3), 6.91 (1H, dd, J = 7.6, 7.3 Hz, H-5), 7.15 (1H, dd, J = 7.3, 1.7 Hz, H-6) and 7.22

Conflict of interest

The authors declare that there are no conflicts of interest with this work.

Acknowledgments

This work was financially supported by Natural Science Foundation of China (21772065, 81673527), Shandong Provincial Natural Science Foundation (ZR2017MH019, JQ201721), National Key Research Project (2017YFC1702702), Shandong Provincial Key Research Project (2017GSF19115, 2018GSF118158), Shandong Talents Team Cultivation Plan of University Preponderant Discipline (No. 10027), and the Science Foundation of University of Jinan (XKY1608).

References (13)

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