Received date: December 11, 2014; Accepted date: January 09, 2015; Published date: January 12, 2015
Citation: Wu XH, Mi C, He Y, Wang SQ, Zhang J, et al. (2015) Polyphenols from the Rhizomes of Potentilla freyniana. Med chem 5:015-020. doi:10.4172/2161-0444.1000237
Copyright: © 2015 Wu XH, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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A new polyphenol, Potentillanin A (1), together with two known compounds (2–3), was isolated from the chloroform soluble fraction of Potentilla freyniana. The structure of Potentillanin A (1) was elucidated by spectroscopicmethods.
Potentilla freyniana; Potentillanin A; Polyphenols; Spectroscopic methods
The rhizomes of Potentilla freyniana Borum in traditional Chinese medicine (TCM) are a source of Chinese folk drug “Wei-ling-Cai”, and are supposed to be effective as relieving pain and anti-inflammatory in folklore medicine . It’s curative effect is well and adverse reaction is little. In the previous paper, only β-sitosterol and daucosterol were reported from this plant . In the current research, a new polyphenol Potentillanin A (1), together with known compounds (2–3) was isolated from the rhizomes of P. freyniana. The structure of 1 was elucidated mainly by NMR techniques. Herein, we report the isolation and structure elucidation of these polyphenols.
General experimental procedures
IR spectra were recorded with a Perkin-Elmer 577 spectrometer as KBr pellet. NMR spectra were recorded with a Bruker AM-400 spectrometer with TMS as an internal standard. EI-MS (70eV) was carried out with a Finnigan MAT 95 mass spectrometer. CD spectra were recorded on a JASCO J-810 spectropolarimeter. All solvents used were of analytical grade (Shanghai Chemical Plant). Silica gel(200 – 300 mesh) C18 reversed-phase silica gel (150 – 200 mesh, Merck) etc. were used for column chromatography, and pre-coated silica gel GF254 plate (QingDao Marine Chemical Plant) was used for TLC.
The rhizomes of Potentilla freynianawere collected in July 2005 from Enshi County of Hubei Province, People's Republic of China, and identified by Prof. Changgong Zhang, College of Pharmacy, Tongji Medical Center, Huangzhong University of Science and Technology. A specimen (DFZ0120) was deposited in the College of Pharmacy, Tongji Medical Center, Huangzhong University of Science and Technology.
Extraction and isolation
The air-dried rhizomes of P. freyniana (5.0 kg) were ground and extracted with 95% ethanol(10 × 5 L) at room temperature. The ethanol extract was concentrated under vacuum to leave a residue, which was suspended in H2O (3 L) and extracted with Petroleum ether (3 × 3 L), CHCl3 (3 × 3 L), EtOAc (3 × 3 L), and n-BuOH (3 × 3 L), sequentially. A part of the CHCl3 extract (20 g) was subjected to a silica gel column chromatography eluting with gradient solvents of Petroleum ether– Acetone (15:1 – 1:1, and then pure Acetone) to afford four fractions (Fr. 1 – 4). Fraction 2 was chromatographed over silica gel eluting with CHCl3-EtOAc (8:1) to yield 15 mg of 1 (0.0003 %, w/w) (Rf = 0.5, developed with CHCl3-EtOAc (6:1) ). Fraction 3 was chromatographied over silica gel eluting with CHCl3-Acetone (5:1) to afford 2 (20 mg, 0.0004 %, w/w) and 3 (35 mg, 0.0007 %, w/w).
Potentillanin A (1) C11H14O5, an amorphous powder, [α] D 20: +79.0° (MeOH, c 0.20). CD (c 0.0038, MeOH), IR(KBr): νmaxcm–1: 3438, 2251, 1653, 1027. 1H-NMR (400 MHz) and 13C-NMR (100 MHz) (Table 1). EI-MS (70eV): m/z: 227 (2), 226 (40), 180 (15), 152 (10), 139 (100), 84 (50), 66 (65); positive HREIMS : m/z 226.0839 [M]+ (C11H14O5, Calcd 226.0841).
|NO||δC||δH, Multi, J (Hz)|
|2||99.1||4.87 (d, 2.4)|
|4||23.9||2.42 (2H, m)|
|6||95.9||5.89 (d, 1.6)|
|8||94.9||5.68 (d, 1.6)|
|2’||15.6||1.08 (t, 6.8)|
Table 1: 1H-NMR (400 MHz) and 13C-NMR (100 MHz) spectral data of 1 (in DMSO-d6).
Potentillanin A (1), an amorphous powder, showed molecular formula of C11H14O5 determined on the basis of positive HREIMS at m/z 226.0839 [M]+ (Calcd 226.0841) with 5o of unsaturation. Eleven carbon signals including one methyl, two methylenes, four methines, four quaternary carbons were evident from the 13.C-NMR spectra of 1 (Table 1). The IR spectrum showed absorptions at 3438, 1653, and 1027 cm–1 representing the existence of hydroxyl, benzene ring and ether linkage group, respectively. In the 13C-NMR spectrum, one oxygenated methylene (δ 63.5, C-1’), one ketal carbon (δ 98.1, C-2), one oxygenated methine carbon (δ 63.1, C-3) and three oxygenated quaternary carbons (δ 156.7, C-5; δ 157.0, C-7; δ 152.7, C-9). A benzenering and the presence of a cyclic system accounted for 5o of the unsaturation. The 1H-NMR spectrum (in DMSO-d6) of 1 (table 1) displayed one methyl signal at 1.08 (t, J=6.8, CH3-2’), two oxygenated methylene protons at δ 3.59 and δ 3.68 (m, CH2-1’), one ketal carbon proton at δ 4.87 (d, J=2.4, H-2), one oxygenated methine proton at δ 3.74 (m, H-3), two methylene protons at δ 2.42 (m, CH2-4), two methine protons at δ 5.89 (d, J=1.6, H-6) and δ 5.68 (d, J = 1.6, H-8). The coupling and oxygenated patterns revealed by 1H-NMR were consistent with the functional groups indicated by the above 13C-NMR analyses.
Analysis of the 1H-NMR, 13C-NMR and HSQC spectra of 1 enabled the assignment of all the protons to the bonding carbons. The HMBC correlations and planar structure of 1 was outlined as Figure 1.
The structure is similar to character of a flavan-3-ol, and its CD spectrum(Figure 2) is consistent with that of a flavan-3-ol. It showed a strong positive effect near 270 nm, and a negative effect near 290 nm. Analysis of the CD spectrum, the stereochemical structure was fit to be (2R, 3S) refered to . Thus, the structure of 1 was unambiguously elucidated as (2R, 3S) - 2 - ethoxy - 3,5,7 - trihydroxy - 3,4 - dihydro - Benzopyran (1).
The two known polyphenols were successively identified as 2 refered to , and 3 refered to  on the basis of EI-MS, 1H-NMR and 13C-NMR data. The compounds 2 and 3 were isolated from this plant for the first time.
Special thanks are due to the Analytical Center, Huazhong University of Science and Technology for recording UV, MS, CD and NMR spectra.
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