Coumarin and spirocyclopentenone derivatives from the leaves and stems of Murraya paniculata (L.) Jack
Graphical abstract
Seven previously undescribed compounds and 14 known coumarins were isolated from Murraya paniculata (L.) Jack. Three compounds showed inhibition against LPS-induced NO production in BV-2 microglial cells.
Introduction
Murraya paniculata (L.) Jack (Rutaceae), is a shrub distributed widely in India, Southeast Asia, and South China. As one of the source plants of Murrayae Folium et Cacumen listed in the Chinese Pharmacopoeia (Chinese Pharmacopoeia Commission, 2015), this herb has been extensively used for the treatment of analgesia, anesthesia, abdominal pain, and rheumatism. This herb is also a main material in Sanjiu Weitai granule, a famous Chinese complex prescription for gastric diseases. Previous chemical and pharmacological studies revealed that many active components, such as flavonoids (Kinoshita and Firman, 1997; Zhang et al., 2011), coumarins (Raj et al., 1976; Imai et al., 1989; Wu et al., 1989), and indole alkaloids (Kinoshita et al., 1989; Wang et al., 2017) were isolated from M. paniculata, and they were reported to have the anti-inflammatory, antioxidant, antimicrobial, anti-diabetic, and antitumor effects (Sayar et al., 2014; Rodanant et al., 2015).
In an ongoing search for more bioactive natural products from M. paniculata, the EtOH extract of the leaves and stems of M. paniculata was investigated and afforded seven previously undescribed compounds (1–5), including five coumarins (1a/1b, 2–4) and a pair of spirocyclopentenone enantiomers (5a/5b), along with 14 known coumarin analogues (6–19). Compound 1a/1b is a pair of coumarin enantiomer mixture containing a 2-oxo-1,3-dioxolane unit and compound 5a/5b is a pair of rare spirocyclopentenone enantiomer mixture. They were separated by chiral HPLC to obtain the optically pure compounds. Herein, the isolation and structural elucidation of the undescribed compounds are reported, along with the biological evaluation of the isolates on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells (see Fig. 1).
Section snippets
Results
(±)-Murpanitin A (1) was obtained as a light yellow oil. Its molecular formula was assigned as C16H14O6 based on the protonated ion at m/z 303.0870 [M + H]+ (calcd for C16H15O6, 303.0869) in the positive HRESIMS, indicating 10 indices of hydrogen deficiency. The UV spectrum showed characteristic absorptions of a coumarin skeleton (λmax 322 nm) and the IR spectrum showed absorption bands for carbonyl (1793, 1731 cm−1) and aromatic ring (1608 cm−1) functionalities. The 1H NMR data (Table 1)
Conclusion and discussion
In this study, seven previously undescribed compounds and 14 known coumarins were isolated and identified from the leaves and stems of M. paniculata. Among the isolated coumarins, (+/−)-Murpanitin A (1a/1b) are a pair of coumarin enantiomers with a 2-oxo-1,3-dioxolane unit in the C-8 side chain. The unique structure of 1a/1b is reported for the first time from natural source and worthy of further investigation. Murpanitins B and C are two coumarins in which their isopentenyl side chains are
General experimental procedures
UV spectra were recorded on a Shimadzu UV-2450 spectrophotometer (Shimadzu Co., Kyoto, Japan). IR spectra were recorded on a Thermo Nicolet Nexus 470 FT-IR spectrometer (MA, USA). Specific optical rotation data were acquired on a Rudolph Autopol III automatic polarimeter (Rudolph Research, Fairfield, New jersey, USA). ECD data were acquired on a JASCO 810 CD spectrophotometer (Jasco Co., Tokyo, Japan). HRESIMS experiments were measured on a Waters Xevo G2 Q-TOF mass spectrometer (Waters Co.,
Acknowledgements
This work was financially supported by National Natural Sciences Foundation of China (Nos. 81973199, 81773864, and 81473106), National Key R&D Program of China(No. 2019YFC1711000) and The Drug Innovation Project of China (No. 2018ZX09711001-008-003).
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