33 卷 2 期 结构化学 (JIEGOU HUAXUE) Vol. 33, No. 2 2014.2 Chinese J. Struct. Chem. 199 203 Isolation and Identification of 5,3,4 -Trihydroxy-7-methoxyflavanone from Artemisia sphaerocephala Kraschen 1 WANG Yong a QING Wei-Xia b LI Lin-Xi a ZHAO Dong-Bao a LIU Xiu-Hua a2 a (Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China) b (Medical College, Henan University, Kaifeng 475004, China) ABSTRACT 5,3,4 -Trihydroxy-7-methoxyflavanone was isolated from Artemisia sphaerocephala Kraschen and characterized by 1 H-NMR, 13 C-NMR, EI-MS, IR, UV spectra, and singlecrystal X-ray diffraction. The title compound crystallizes in orhtorhombic space group Pca2 1, with a = 14.393(3), b = 5.1629(12), c = 36.919(9) Å, V = 2743.4(11) Å 3, Z = 8, M r = 302.27, D c = 1.464 g/cm 3, F(000) = 1264, μ = 0.113 mm -1, S = 1.015, (Δ/σ) max = 0.000, the final R = 0.0757 and wr = 0.1809. Structural analysis indicates the title compound consists of two 5,3,4 -trihydroxy- 7-methoxyflavanone enantiomers in a well-defined arrangement within the crystal lattice, which constructs a three-dimensional network by means of multiple O H O hydrogen bonds. Keywords: 5,3,4 -trihydroxy-7-methoxyflavanone, Artemisia sphaerocephala Kraschen, isolate, crystal structure 1 INTRODUCTION Artemisia sphaerocephala is abundant in the provinces of Gansu, Shanxi, Ningxia and the Inner Mongolia autonomous region in China [1]. In traditional Chinese medicine, including Tibetan medicine, the plants are used to cure the diseases of parotitis, tonsillitis, turgescence and tumefaction, but no investigation has been reported regarding their chemical constituents. In order to discover bioactive principles, the chemical constituents from the whole plant of Artemisia sphaerocephala were investigated. In our systematic studies of active metabolites, we have isolated a new triterpenoid saponin and two new phenolic compounds from ethanol extracts of this plant [2-3]. In addition, several flavonoids were obtained. Flavonoids commonly occur in natural plants as metabolite and several bioactivities have been reported, such as anti-free radical anti-bacterial, anti-mutagenic and anti-tumor activities [4-7]. Herein, we have isolated and identified 5,3,4 -trihydroxy- 7-methoxyflavanone for the first time from Artemisia sphaerocephala Kraschen as colorless crystals. The isolated compound was fully characterized by means of 1 H-NMR, 13 C-NMR and EI-MS as well as X-ray crystallographic studies. To our knowledge, its crystal structure has not been reported up to now. 2 EXPERIMENTAL Received 11 December 2012; accepted 8 December 2013 (CCDC 778613) 1 This work was supported by the Science and Technology Agency of Henan Province (112102310305) and the International Cooperation Program of Henan Province (No. 092102310282) 2 Corresponding author. E-mail: wywang228@163.com
WANG Y. et al.: Isolation and Identification of 5,3,4 -Trihydroxy- 200 7-methoxyflavanone from Artemisia sphaerocephala Kraschen No. 2 2. 1 Instrument Melting points were determined with a Beijing Keyiecopti Instrument Factory XT5 and uncorrected. 1 H NMR and 13 C NMR spectra were taken with a Bruker AVANCE-400 instrument with DMSO-d 6 as solvent and TMS as the internal standard (chemical shift in ppm). Mass spectra were performed by a Trace DSQ II mass spectrometer. UV absorption spectra were obtained with a U-4100 spectrometer at room temperature. IR spectra were obtained from a solid sample palletized with KBr on Nicolet 170 SXFT-IR spectrometer in the range of 400~4000 cm 1. 2. 2 Extraction and isolation The whole body of the herb of Artemisia sphaerocephala Kraschen was collected from Xinjiang Uygur Autonomous Region in China, in October 2003 and identified by Professor Suo You-Rui, Northwest Institute of Plateau Biology, CAS. Air-dried whole plants (5.1 kg) were ground into powder and extracted with 95% ethanol at room temperature for six times. The concentrated extract was dispersed in water and partitioned successively with petroleum ether, chloroform, EtOAc, and n- BuOH. The EtOAc fraction (100 g) was subjected to silica gel with CHCl 3 :CH 3 OH (10:1) to yield three fractions (frs. 3~5). Fraction 3 (10 g) was subjected to silica gel successively with CHCl 3 :CH 3 OH (120:1, 100:1, 80:1, 60:1 to 40:1) to yield six fractions. 1 H 3 CO 8 7 9 O After a week, the crude title compound was crystallized from the third fraction. After recrystallization from CHCl 3 -CH 3 OH, colorless blocks of (I) arose, with a melting point of 219~220. The molecular formula, C 16 H 14 O 6 (Scheme 1), was established by MS (EI + ) m/z = 302.0. 1 H NMR (400MHz, DMSO-d 6 ) δ: 12.13 (1H, s), 9.11 (1H, s), 9.05 (1H, s), 6.88 (1H, s), 6.76 (2H, s), 6.09(1H, d, J = 2.0 Hz), 6.06(1H, d, J = 2.0 Hz), 5.42 (1H, dd, J = 13.0 Hz, 3.0Hz), 3.78 (3H, s), 3.25 (1H, dd, J = 17.0 Hz, 13.0 Hz), 2.71 (1H, dd, J = 17.0 Hz, 3.0Hz). 13 C NMR δ: 197.0 (C-4), 167.5 (C-7), 163.2(C-5), 162.8 (C-9), 145.7 (C-4'), 145.1 (C-3'), 129.2 (C-1'), 118.0 (C-6'), 115.3 (C-5'), 114.3 (C-2'), 102.6(C-10), 94.5 (C-6), 93.7 (C-8), 78.6 (C-2), 42.1 (C-3), 55.9 (7-OCH 3 ). 1 H-NMR and 13 C NMR spectra are consistent with the previous report of 5,3,4 -trihydroxy-7-methoxyflavanone (Lit. [8] 1 H NMR (400MHz, DMSO-d 6 ) δ: 12.23(1H, s), 9.16(1H, s), 8.98(1H, s), 6.71~ 6.94(3H, m), 6.09(1H, d, J = 1.5 Hz), 6.01(1H, d, J = 1.5 Hz), 5.42(1H, dd, J = 12.3 Hz, 2.2Hz), 3.90(3H, s), 3.24(1H, dd, J = 16.8 Hz, 12.3 Hz), 2.86(1H, dd, J = 16.8 Hz, 2.2Hz). 13 C NMR δ: 196.8 (C-4), 167.4 (C-7), 163.2(C-5), 162.8 (C-9), 145.7 (C-4'), 145.2 (C-3'), 129.3 (C-1'), 117.9 (C-6'), 115.4 (C-5'), 114.4 (C-2'), 102.6(C-10), 94.6 (C-6), 93.8 (C-8), 78.6 (C-2), 42.1 (C-3), 55.8 (7-OCH 3 ). m.p: 215~216 ). OH 3' OH 2' 4' 2 5' 1' 6' 6 5 10 4 3 OH O Scheme 1. Molecular structure of the title compound 2. 3 X-ray crystallography Intensity data were collected at 296 K on a Bruker APEX-II diffractometer equipped with graphitemonochromated MoKα radiation (λ = 0.71073 Å)
2014 Vol. 33 结构化学 (JIEGOU HUAXUE)Chinese J. Struct. Chem. 201 using the φ and ω scan technique. The structure was solved by direct methods with SHELXS-97 program [9]. Refinements were done by full-matrix leastsquares on F 2 with SHELXL-97 [10]. All non-hydrogen atoms were refined anisotropically. Crystal data for 1: crystal sizes 0.22mm 0.18mm 0.11mm, F(000) = 1264, T = 296(2) K, 2.21 θ 25.00, measured reflections: 12476, independent reflections: 4713 with R int = 0.0671, the final R = 0.0757, wr = 0.1809 (w = 1/[(σ 2 (F 2 o ) + (0.1024P) 2 + 0.0000P], 2 where P = (F o + 2F 2 c )/3), S = 1.015, (Δ/σ) max = 0.000, (Δρ) max = 0.219 and (Δρ) min = 0.161 e/å 3. The selected bond lengths and bond angles are given in Table 1. Table 1. Selected Bond Lengths (Å) and Bond Angles (º) for 1 Bond Dist. Bond Dist. Bond Dist. O(1) C(1) 1.346(8) O(9) C(23) 1.470(2) C(5) C(6) 1.380(10) O(2) C(2) 1.384(7) O(10) C(25) 1.255(8) C(7) C(8) 1.371(10) O(3) C(11) 1.387(7) O(11) C(31) 1.354(8) C(8) C(9) 1.477(9) O(3) C(7) 1.500(8) O(12) C(29) 1.358(8) C(9) C(10) 1.398(10) O(4) C(9) 1.252(7) O(12) C(32) 1.438(9) C(10) C(11) 1.425(10) O(5) C(15) 1.319(8) C(1) C(2) 1.349(9) C(10) C(15) 1.434(10) O(6) C(13) 1.360(8) C(1) C(6) 1.361(10) C(11) C(12) 1.360(9) O(6) C(16) 1.438(10) C(2) C(3) 1.385(8) C(12) C(13) 1.365(9) O(7) C(17) 1.403(9) C(3) C(4) 1.424(10) C(13) C(14) 1.406(10) O(8) C(18) 1.333(8) C(4) C(5) 1.348(12) C(14) C(15) 1.362(10) O(9) C(27) 1.342(7) C(4) C(7) 1.510(10) Angle Deg Angle Deg Angle Deg O(1) C(1) C(2) 119.8(6) C(2) C(3) C(4) 119.0(7) C(8) C(7) O(3) 111.7(6) O(1) C(1) C(6) 121.4(6) C(5) C(4) C(3) 119.1(7) C(8) C(7) C(4) 119.2(7) C(2) C(1) C(6) 118.7(6) C(5) C(4) C(7) 114.1(8) O(3) C(7) C(4) 102.6(5) C(1) C(2) O(2) 115.7(5) C(3) C(4) C(7) 126.8(8) C(7) C(8) C(9) 116.9(6) C(1) C(2) C(3) 121.1(7) C(4) C(5) C(6) 119.3(8) O(4) C(9) C(10) 122.4(6) O(2) C(2) C(3) 123.1(6) C(1) C(6) C(5) 122.5(7) O(4) C(9) C(8) 120.7(6) 3 RESULTS AND DISCUSSION 3. 1 Structural description Single-crystal X-ray diffraction reveals that the title compound crystallizes in orthorhombic space group Pca2 1, which consists of two enantiomers in a well-defined arrangement within the crystal lattice. The molecular backbone of the title compound is characterized as a three-ring system, including a phenyl ring and a benzopyrone-fused ring (Fig. 1). The C O bond distances range from 1.252(7) to 1.500(8) Å, in which C(9) O(4) (1.252(7) Å) is typical for a C=O double bond. The S(6) ring of O(3)/C(7)/C(8)/C(9)/C(10)/C(11) in I is nonplanar, characterized by a O(3) C(7) C(8) C(9) torsion angle of 47.2(8). Atom C(7) is chiral, but the absolute structure of I could not be established from the present experiment. The dihedral angle between the aromatic ring planes is 79.7. H atoms were treated as riding, with C H distances in the range of 0.93~0.97 Å and O H distances of 0.82 Å. In addition, a considerable number of classic O H O hydrogen bonds are observed between these title compounds (Table 2). Three intramolecular O H O hydrogen bonds help to establish the molecular conformation, both constructing S(6) rings with the O O distances in the range of 2.603(6)~2.684(7) Å, whereas four intermolecular O H O link each other with the O O distances in the range of 2.681(6)~2.917(6) Å gives rise to an infinite three-dimensional network (Fig. 2). Depending on these multiple strong O H O hydrogen bonds involving intermolecular and intramolecular hydrogen bonds, the solid structure of the title compound is further stabilized. 3. 2 IR spectrum IR spectrum of the title compound was performed in KBr disks in a frequency range between 4000 and
WANG Y. et al.: Isolation and Identification of 5,3,4 -Trihydroxy- 202 7-methoxyflavanone from Artemisia sphaerocephala Kraschen No. 2 400 cm 1 (Fig. 3). The absorption around 3378 cm -1 indicated the presence of hydroxyl O H. Compared to free hydroxyl, the ν(o H) vibration frequency has a biggish red shift of about 60 cm -1, the possible major reasons for which may be the influence of multiple strong O H O hydrogen bonds. The absorption vibration at 1637 cm -1 is assigned to the carbonyl stretching vibration (ν(c=o)), which moves to lower wave number owning to the conjugation interaction between the carbonyl group and aromatic ring. The bonds at 1603, 1573, 1499 and 1451 cm -1 are the skeleton vibration of aromatic functional groups. Table 2.Hydrogen Bonds with H A < r (A) + 2.00 Å and <DHA> 110 ( ) D H d(d H) d(h A) <DHA d(d A) A O(1) H(1) 0.82 2.15 144.8 2.860(6) O(7) (x 1/2, y+1, z) O(2) H(2) 0.82 1.90 165.0 2.700(6) O(4) (x 1/2, y, z) O(5) H(5) 0.82 1.89 146.2 2.612(7) O(4) O(7) H(7) 0.82 2.16 152.9 2.917(6) O(1) (x+1/2, y, z) O(7) H(7) 0.82 2.26 112.3 2.684(7) O(8) O(8) H(8) 0.82 1.92 154.3 2.681(6) O(10) (x+1/2, y 1, z) O(11) H(11) 0.82 1.96 134.5 2.603(6) O(10) Fig. 1. Molecular structure of (I), showing the atom-labeling scheme. Hydrogen bonds are shown in the dashed line. Displacement ellipsoids are drawn at the 50% probability level Fig. 2. Three-dimensional structure of (I). Hydrogen bonds are shown in the dashed line
2014 Vol. 33 结构化学 (JIEGOU HUAXUE)Chinese J. Struct. Chem. 203 Fig. 3. IR spectrum of the title compound Fig. 4. UV spectra of the title compound (4.55 10-5 M) ranging from 250 to 500 nm in methanol (A); AlCl 3 solution (B) 3. 3 UV spectrum In order to investigate the solution optical property of the title compound, its UV spectrum is performed in the methanol solution in the absence and presence of AlCl 3, respectively (Fig. 4). Curve A shows the UV spectrum of the title compound in the absence of AlCl 3 (Fig. 4A), which displays two major absorption bands in the region of 500~250 nm, appearing at about 287 nm (band II) and 332 nm (band I), which are associated with the benzoyl moiety (band II) and cinnamoyl system (band I) in the molecules, respectively. In the presence of AlCl 3, the UV spectrum (Fig. 4B) also displays two obvious absorption bands at 309 and 385 nm, which have an evident red shift as compared to curve A. The possible reason may be related to the interactions between the groups 5- hydroxy-4 carbonyl and 3,4 -hydroxy complex with aluminum chloride, respectively. REFERENCES (1) Collection of China Traditional and Herbal Medicine Compilation Group. Collection of China Traditional and Herbal Medicine, Vol. 1. People s Medical Publishing House, Beijing 1983. (2) Li, L. X.; Li, M. J.; Zhao, D. B.; Liu, X. H. A new triterpenoid saponin from Artemisia sphaerocephala. Natural Product Research 2008, 22, 1633 1636. (3) Zhao, D. B.; Li, L. X.; Liu, X. H.; Li, M. J.; Wang, W. L. Two new phenolic compounds from Artemisiasphaerocephala. Chinese Chemical Letters 2007, 18, 551 553. (4) Boots, A. W.; Haenen, G. R.; Bast, A. Health effects of quercetin: from antioxidant to nutraceutical. Eur. J. Pharmacol. 2008, 585, 325 337. (5) Tsuchiya, H.; Sato, M.; Miyazaki, T.; Fujiwara, S.; Tanigaki, S.; Ohyama, M.; Tanaka, T.; Iinuma, M. Comparative study on the antibacterial activity of phytochemical flavanones against methicillin-resistant Staphylococcus aureus. Journal of Ethnopharmacology 1996, 50, 27 34. (6) Cushnie, T. P. T.; Lamb, A. Antimicrobial activity of flavonoids. Int. J. Antimicrob. Agents 2005, 26, 343 356. (7) Cao, G. H.; Sofic, E.; Prior, R. L. Antioxidant and prooxidant behavior of flavonoids: structure-activity relationships. Free Radical Biology and Medicine 1997, 22, 749 760. (8) Zhao, D. B.; Yang, Y. X.; Zhang, W.; Liu, X. H.; Wang, H. Q. Studies on flavonoids from herb of Artemisia ordosica. China Journal of Chinese Materia Medica 2005, 18, 1430 1432. (9) Sheldrick, G. M. SHELXS-97. Program for Solution of Crystal Structures. University of Gottingen, Germany 1997. (10) Sheldrick, G. M. SHELXL-97. Program for Crystal Structure Refinement. University of Gottingen, Germany 1997.