Aporphine and phenanthrene alkaloids with antioxidant activity from the roots of Stephania tetrandra
Graphical abstract
Introduction
Stephania tetrandra S. Moore (Menispermaceae) is a traditional Chinese medicinal plant, and its roots are used for treatment of rheumatalgia, dropsy, dysuria, and eczema [1]. Previous phytochemical investigations on this plant revealed that alkaloids were the main constituents [[2], [3], [4], [5], [6], [7]], including bisbenzylisoquinoline alkaloids, aporphine alkaloids, phenanthrene alkaloids, and protoberberine alkaloids. Some of these compounds showed the anti-acetylcholinesterase [6], anti-inflammatory [8], anti-hyperglycemic [9], antioxidant [10], and anticancer activities [11,12]. As part of our work to study traditional Chinese medicine, an investigation was performed on the roots of Stephania tetrandra. The crude extract exhibited significant antioxidant activity. Therefore, the chemical constituents in the active portions and their antioxidant activity were investigated. This led to the isolation of 15 alkaloids (Fig. 1), including three new aporphine alkaloids, two new phenanthrene alkaloids and 10 known analogues. Herein, the isolation, structural elucidation, and bioactivity evaluation of these compounds are reported.
Section snippets
General experimental procedures
UV spectra were obtained in MeOH on a JASCO V-650 spectrophotometer (JASCO, Japan). Optical rotations were measured using a JASCO P-2000 automatic digital polarimeter (JASCO, Japan). ECD spectra were tested on a JASCO J-815 spectrometer (JASCO, Japan). Melting points were recorded on an XT5B microscope melting point apparatus (Beijing Keyi Electro-optical Instrument Factory, China). IR spectra were measured by a Nicolet 5700 spectrometer (Thermo Fisher Scientific, USA). The NMR data were
Results and discussion
Compound 1 was obtained as colorless crystals. The IR spectrum suggested the presence of amidic (1641 cm−1) functionality. Its molecular formula was determined to be C21H21O5N by the HRESIMS ion at m/z 368.1486 [M + H]+ (calcd for C21H22O5N, 368.1492), implying 12 degrees of unsaturation. In addition, a weak ion peak at m/z 309.1117 was observed due to loss of (N-COCH3 + H) from the molecular. These data indicated that the amidic functionality was in the shape of N-acetyl group. The 1D NMR data
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was financially supported by Chinese Academy of Medical Sciences (CAMS) Initiative for Innovative Medicine [CAMS-12M-1-010], the State Key Laboratory of Bioactive Substance and Function of Natural Medicines [No. GTZA201803], and the Drug Innovation Major Project [2018ZX09711001-008-009].
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2023, PhytochemistryCitation Excerpt :The HMBC correlations of 10-OCH3, 1-OCH3, and 2-OCH3 for 5, suggested that the three methoxy groups were attached to C-1, C-2, and C-10, respectively. According to the literature, the optical rotations of the aporphine alkaloids were mainly affected by the chirality at the C-6a position (Chaichompoo et al., 2021; Chen et al., 1997; da Silva et al., 2016; Wang et al., 2020b). The optical rotation of 5 was [α] = +109 (c = 0.10, MeOH), suggesting that the relative configuration at C-6a was S* (da Silva et al., 2016).
<sup>13</sup>C NMR spectroscopic data of aporphine alkaloids
2023, Alkaloids: Chemistry and BiologyCitation Excerpt :Natural source: Stephania tetrandra85Unlabelled Image 13C NMR (150 MHz, CDCl3)85: (E): 142.9 (C-1), 126.6 (C-1a), 126.2 (C-1b), 152.0 (C-2), 111.9 (C-3), 130.9 (C-3a), 29.8 (C-4), 36.2 (C-5), 54.2 (C-6a), 38.7 (C-7), 129.0 (C-7a), 119.8 (C-8), 111.5 (C-9), 150.0 (C-10), 144.5 (C-11), 119.7 (C-11a), 62.1 (1-OCH3), 56.3 (2-OCH3), 56.2 (10-OCH3), 162.0 (CHO). 13C NMR (150 MHz, CDCl3)85: (Z): 143.2 (C-1), 127.0 (C-1a), 126.7 (C-1b), 151.8 (C-2), 111.6 (C-3), 129.8 (C-3a), 31.1 (C-4), 42.1 (C-5), 49.9 (C-6a), 35.2 (C-7), 129.7 (C-7a), 120.1 (C-8), 111.6 (C-9), 149.7 (C-10), 144.4 (C-11), 119.6 (C-11a), 62.1 (1-OCH3), 56.3 (2-OCH3), 56.2 (10-OCH3), 162.2 (CHO).