A New Phenanthraquinone from the Aerial Parts of Cremastra appendiculata
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A NEW PHENANTHRAQUINONE FROM THE AERIAL PARTS OF Cremastra appendiculata
Yu-Peng Li,1 Ya-Ping Chen,1 Ya-Ting Shao,1 Yong-Sheng Tao,1,2* and Rong-Ping Zhang1*
A new phenanthraquinone, 2,6-dihydroxy-8-methoxy-1,4-phenanthraquinone (1), was isolated from the aerial parts of Cremastra appendiculata. The structure of the new compound was determined on the basis of NMR (1D and 2D) and mass spectroscopic analysis. Keywords: Orchidaceae, Cremastra appendiculata, phenanthraquinone. Cremastra appendiculata belongs to the family Orchidaceae. Previous investigations revealed the isolation of bibenzyls and phenanthrenes from the tubers of this plant [1–3]. As part of our ongoing research towards the discovery of new compounds from the Orchidaceae family [4], a new phenanthraquinone, 2,6-dihydroxy-8-methoxy-1,4-phenanthraquinone (1), was isolated from the aerial parts of C. appendiculata, together with five known compounds. Herein, we describe the isolation and structural determination of the new compound 1. Compound 1 was obtained as a deep purple amorphous powder. The molecular formula C15H10O5 was deduced by HR-ESI-MS, suggesting 11 degrees of unsaturation. For PMR, 13C NMR, and HMBC, see Table 1. The PMR, 13C NMR, and DEPT spectral data (Table 1) indicated the presence of a methoxyl group at δH 4.08 (3H, s) and δC 55.7, a 1,2,3,5-tetrasubstituted benzene ring at δ 7.16 (1H, d, J = 2.4 Hz) and 6.92 (1H, d, J = 2.4 Hz) and at δ 108.2 (C-5) and 107.4 (C-7), and another aromatic ring suggested to be of the 1,2,3,4-substitution pattern according to two coupled aromatic protons at δ 8.69 (1H, d, J = 9.0 Hz) and 7.13 (1H, d, J = 9.0 Hz), and at δ 130.9 (C-9) and 122.6 (C-10). In addition, an olefinic proton at δ 7.45 (1H, s) and δ 114.9 (C-3) and two carbonyl groups at δ 181.0 (C-1) and 181.3 (C-4), which compose a quinone unit, were observed, indicating that compound 1 should be a compound of phenanthraquinone [5, 6]. The structure of 1 was further elucidated by 2D NMR techniques (1H–1H COSY, HSQC, HMBC, and NOESY). According to the analysis of PMR, 13C NMR, COSY, and DEPT, we found that the arrangement of all atom orders was in good agreement. The HSQC data indicated the cross peaks between protons and the attached carbons (C-3 and H-3, C-5 and H-5, C-7 and H-7, C-9 and H-9, and C-10 and H-10). The NOE correlations methoxyl/H-7 and H-9 are shown in Fig. 1. The location of the methoxyl group at C-8 and the hydrogen atom at C-3, C-5, and C-7 was further supported by the correlations in the HMBC spectrum (Fig. 1). Thus, the structure of 1 was identified as shown in Fig. 1.
1) School of Pharmaceutical Science and Yunnan Key Laboratory of Pharmacology for Natural Products, Kunming Medical University, 650500, Kunming, P. R. China, fax: +86 871 65922780, e-mail: [email protected]; 2) Department of Journal Editorial of Kunming Medical University, 650500, Kunming, P. R. China, e-mail: [email protected]. Published in Khimiya Prirodnykh Soedinenii, No. 5, September–October, 2020, pp. 677–678. Original article submitted November 20, 20
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