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Phenolic Compounds and Triterpenes from the Barks of Diospyros burmanica
Phenolic Compounds and Triterpenes from the Barks of Diospyros burmanica
Natural Product Sciences. 2015. Jun, 21(2): 76-81
Copyright © 2015, The Korean Society of Pharmacognosy
  • Received : October 02, 2014
  • Accepted : January 26, 2015
  • Published : June 30, 2015
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About the Authors
Janggyoo Choi
College of Pharmacy and Research Institute of Pharmaceutical Science, Seoul National University, Seoul, Korea
Jae Youl Cho
Department of Genetic Engineering, Sungkyunkwan University, Suwon 440-746, Korea
Young-Dong Kim
Department of Life Science, Hallym University, Chuncheon 200-702, Korea
Khin Myo Htwe
Popa Mountain Park, Forest Department, Kyaukpadaung Township, Mandalay Division, Myanmar
Woo-Shin Lee
Department of Forest Sciences, Seoul National University, Seoul 151-921, Korea
Jun Chul Lee
College of Pharmacy and Research Institute of Pharmaceutical Science, Seoul National University, Seoul, Korea
Jinwoong Kim
College of Pharmacy and Research Institute of Pharmaceutical Science, Seoul National University, Seoul, Korea
Kee Dong Yoon
College of Pharmacy, The Catholic University of Korea, Bucheon 420-743, Korea
kdyoon@catholic.ac.kr

Abstract
Diospyros burmanica Kurz. is an evergreen deciduous tree distributed in Mandalay of Myanmar, which belongs to the family of Ebenaceae. In Myanmar, it has been used to treat diarrhea, diabetes, diabetes and also as lumbers. In this study, seven flavonoids ( 1 - 7 ), a phenolic compound ( 8 ), and five triterpenes ( 9 - 13 ) were isolated from the barks of D. burmanica and their chemical structures were elucidated. Isolates were identified to be (+)-catechin ( 1 ), (+)-catechin 3- O -α-L-rhamnopyranoside ( 2 ), (+)-catechin 3- O -gallate ( 3 ), (−)-epicatechin ( 4 ), (−)-epicatechin 3- O -gallate ( 5 ), (+)-afzelechin 3- O -α-L-rhamnopyranoside ( 6 ), (+)-2,3- trans -dihydrokaempferol 3- O -α-L-rhamnopyranoside ( 7 ), methyl gallate ( 8 ), lupeol ( 9 ), methyl lup-20(29)-en-3-on-28-oate ( 10 ), β-amyrin ( 11 ), α-amyrin ( 12 ), 3β-hydroxy-D:B-friedo-olean-5-ene ( 13 ) through MS, 1 H NMR and 13 C NMR spectroscopic evidences.
Keywords
Introduction
Diospyros burmanica Kurz (Ebenaceae) is an evergreen deciduous tree distributed in the Mandalay region of Myanmar, and local traditional practitioners have used this plant as a medicinal plant to treat diabetes, diarrhea and dysentery. Over 350 species of genus Diospyros have been known worldwide and many have been used as traditional medicines in the India, Africa and China, 1 and especially D. kaki has well been investigated for its phytochemicals and biological activities. 2 - 6 As for the study of D. burmanica , only a paper has been reported revealing bisnaphtoquinones and naphthol derivatives and their leishmanicidal inhibitory activities. 7 This study focused on the further phytochemical investigation of D. burmanica and led to the isolation of seven flavonoids, a phenolic compound, and five triterpenes.
Experimental
General experimental procedure 1 H NMR and 13 C NMR spectra were obtained on a Bruker AscendTM 500 spectrometer (Bruker, Germany). Mass spectra were recorded by using an Agilent 6530 ESI-QTOF MS (Agilent Technologies, USA) and JEOL JMS-700 spectrometer (JEOL, Japan). A Gilson preparative HPLC system (Gilson, USA) was used to isolate compounds and equipped with a GX-271 liquid handler, binary pumps, and an UV/VIS-155 detector. An MPLC system composed of an IOTA S 300 pump (ECOM, Czech Republic) and a Saphire 600 UV-VIS variable wavelength detector (ECOM, Czech Republic) were used. The preparative HPCCC (Dynamic Extractions, UK) possessed two sets of two bobbins. One bobbin was equipped with an analytical coil (11 mL, 0.8 mm ID), and the other with a preparative coil (492 ml, 4 mm ID). Deionized water was prepared by Millipore Milli-Q water purification system (Millipore, USA), and organic solvents for column chromatography were purchased from Daejung-Chemical and Metals Co. Ltd. (Kyunggi-Do, Korea). Silica gel and reversed-phase silica gel for column chromatography were Kieselgel 60 (230 - 400 mesh, Merck, Germany) and YMC RP-18 resin (YMC, Japan), respectively. HPLC column was YMC-Pack ODS-A (250 × 20 mm, 5 μm, YMC, Japan) and YMC-Pack Ph (250 × 20 mm, 5 μm, YMC, Japan).
Plant material − Barks and leaves of D. burmanica were collected from AKNP of Myanmar in February 2012, and identified by Professor Young-Dong Kim (Hallym University, Chuncheon, Korea). A voucher specimen (CU-2014-2-12) was deposited at the Herbarium of College of Pharmacy, The Catholic University of Korea.
Extraction and isolation − Extraction and isolation - Dried barks (1.3 kg) of D. burmanica were extracted with 100 % MeOH in an ultrasonic bath for (5 L × 2 h × 3 times). After evaporating solvent in vacuo, the methanolic extract (221.5 g) was suspended in water and partitioned sequentially with CH 2 Cl 2 (8.1 g), EtOAc (68.9 g), and n -BuOH (93.9 g). The EtOAc soluble fraction was subjected to silica gel column chromatography (CC) (CHCl 3 : MeOH, 10:1→1:1, v/v) to yield five subfractions (E1~E5). E1 (7.5 g) was subjected to countercurrent chromatography (CCC) with solvent composition of n -hexane-EtOAC-MeOH-water (2:8:2:8, v/v) to yield another five fractions (E1-1~E1-5). Compound 2 (243.7 mg) was purified from E1-1 by silica gel column chromatography (CHCl 3 -MeOH-water, 12:5:1, v/v). Fraction E1-2 was subjected to silica gel CC (CHCl 3 -MeOH-water, 20:5:1, v/v) to give compound 1 (282.9 mg). Fraction E1-3 was chromatographed on silica gel CC (CHCl 3 -MeOH, 5:1, v/v) to give four subfraction (E1-3-1~E1-3-4), and E1-3-2 was purified by RP-HPLC (YMC-Pack Ph, MeOH-water, 25:75, v/v) to give compound 8 (56.5 mg) and 7 (27.3 mg). Compound 3 and 5 were obtained from E1-3-4 through silica gel CC (CHCl 3 -water, 5:1, v/v) and RP-HPLC (YMC-Pack ODS-A, MeOH-water, 30:70, v/v). Compound 4 (1.7 mg) and 6 (7.6 mg) were obtained from E2 through silica gel CC (CHCl 3 -MeOH-water, 15:5:1, v/v) and RP-HPLC (YMC-Pack Ph, MeOH-water, 33:67, v/v). The CH 2 Cl 2 fraction was subjected to silica gel CC (CHCl 3 : MeOH, 50:1 → 5:1; v/v) to provide seven subfractions (M1~M7). M1 was subjected to silica gel CC ( n -hexane-EtOAc, 10:1, v/v) to yield two subfractions (M1-1, M1-2). Compound 10 (12.0 mg) was obtained from M1-1 through RP-HPLC (YMC-Pack ODS-A, MeOH-Water, 95:5, v/v). Compound 11 (3.8 mg), 12 (10.2 mg) and 13 (2.2 mg) was obtained from M1-2 through RP-HPLC (ODS-A, MeOH). Compound 9 (21.5 mg) was obtained from M2 through silica gel CC ( n -hexane-EtOAc, 20:1, v/v) and RP-HPLC (YMC-Pack Ph).
(+)-Catechin (1)
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: +21 ( c 0.2, MeOH); UV (MeOH) λ max 277 nm; ESI-QTOF MS: m/z 291.0866 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 4.56 (1H, d, J = 7.5 Hz, H-2), 3.96 (1H, m, H-3), 2.85 (1H, dd, J = 16.3, 5.3 Hz, H-4eq), 2.50 (1H, d, J = 16.2, 8.0 Hz, H-4ax), 5.85 (1H, d, J = 2.2 Hz, H-6), 5.92 (1H, d, J = 2.2 Hz, H-8), 6.84 (1H, d, J = 2.0 Hz, H-2'), 6.76 (1H, d, J = 8.0 Hz, H-5'), 6.72 (1H, dd, J = 8.0, 2.0 Hz, H-6'); 13 C NMR (CD 3 OD, 125 MHz): δ 83.0 (C-2), 69.0 (C-3), 28.7 (C-4), 157.7 (C-5), 96.4 (C-6), 158.0 (C-7), 95.6 (C-8), 157.1 (C-9), 100.9 (C-10), 132.4 (C-1'), 115.4 (C-2'), 146.4 (C-3'), 146.4 (C-4'), 116.2 (C-5'), 120.2 (C-6')
(+)-Catechin 3-O-α-L-rhamnopyranoside (2)
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: −18.2 ( c 0.5, MeOH); UV (MeOH) λ max 279 nm; ESIQTOF MS: m/z 437.1454 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 4.62 (1H, d, J = 7.7 Hz, H-2), 3.93 (1H, m, H-3), 2.88 (1H, dd, J = 16.2, 8.3 Hz, H-4eq), 2.64 (1H, d, J = 16.1, 8.3 Hz, H-4ax), 5.85 (1H, d, J = 2.2 Hz, H-6), 5.93 (1H, d, J = 2.4 Hz, H-8), 6.84 (1H, d, J = 1.9 Hz, H-2'), 6.76 (1H, d, J = 8.0 Hz, H-5'), 6.72 (1H, dd, J = 8.2, 1.9 Hz, H-6'), 4.29 (1H, d, J = 1.2 Hz, H-1"), 1.25 (3H, d, J = 6.1 Hz, H-6"); 13 C NMR (CD 3 OD, 125 MHz): δ 81.3 (C-2), 76.1 (C-3), 28.1 (C-4), 157.7 (C-5), 95.7 (C-6), 158.1 (C-7), 96.6 (C-8), 157.0 (C-9), 102.3 (C-10), 132.1 (C-1'), 115.2 (C-2'), 146.4 (C-3'), 146.5 (C-4'), 116.3 (C-5'), 120.0 (C-6'), 100.8 (C-1"), 72.2 (C-2"), 72.4 (C-3"), 74.1 (C-4"), 70.5 (C-5"), 18.1 (C-6")
(+)-Catechin 3-O-gallate (3)
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: +8.9 ( c 0.1, MeOH); UV (MeOH) λ max 277 nm; ESI-QTOF MS: m/z 443.2216[M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 5.06 (1H, d, J = 6.1 Hz, H-2), 5.37 (1H, m, H-3), 2.82 (1H, dd, J = 16.5, 5.1 Hz, H-4eq), 2.71 (1H, d, J = 16.5, 6.0 Hz, H-4ax), 5.94 (1H, d, J = 2.2 Hz, H-6), 5.96 (1H, d, J = 2.4 Hz, H-8), 6.84 (1H, s, H-2'), 6.72 (2H, s, H-5', 6'), 6.96 (2H, s, H-2", 6"); 13 C NMR (CD 3 OD, 125 MHz): δ 75.9 (C-2), 71.3 (C-3), 24.5 (C-4), 156.6 (C-5), 96.6 (C-6), 157.7 (C-7), 95.8 (C-8), 158.2 (C-9), 99.8 (C-10), 131.6 (C-1'), 114.6 (C-2'), 146.3 (C-3'), 146.4 (C-4'), 116.4 (C-5'), 119.4 (C-6'), 121.5 (C-1"), 110.3 (C-2", 6"), 146.5 (C-3", 5"), 140.0 (C-4"), 167.7 (- C OO-)
(−)-Epicatechin (4)
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: −38.5 ( c 0.9, MeOH); UV (MeOH) λ max 280 nm; ESI-QTOF MS: m/z 291.1953 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 4.82 (1H, s, H-2), 4.17 (1H, m, H-3), 2.73 (1H, dd, J = 16.5, 2.8 Hz, H-4eq), 2.86 (1H, dd, J = 16.5, 4.9 Hz, H-4ax), 5.91 (1H, d, J = 2.2 Hz, H-6), 5.94 (1H, d, J = 2.2 Hz, H-8), 6.97 (1H, d, J = 1.8 Hz, H-2'), 6.75 (1H, d, J = 8.2 Hz, H-5'), 6.79 (1H, dd, J = 8.4, 1.7 Hz, H-6'); 13 C NMR (CD 3 OD, 125 MHz): δ 80.0 (C-2), 67.7 (C-3), 29.4 (C-4), 157.9 (C-5), 96.0 (C-6), 158.2 (C-7), 96.5 (C-8), 157.5 (C-9), 100.2 (C-10), 132.5 (C-1'), 115.5 (C-2'), 146.1 (C-3'), 146.0 (C-4'), 116.0 (C-5'), 119.5 (C-6')
(−)-Epicatechin 3-O-gallate (5)
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: −12.4 ( c 0.1, MeOH); UV (MeOH) λ max 277 nm; ESI-QTOF MS: m/z 443.2216 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 5.03 (1H, s, H-2), 5.52 (1H, m, H-3), 2.99 (1H, dd, J = 17.3, 4.7 Hz, H-4eq), 2.85 (1H, d, J = 17.3, 2.1 Hz, H-4ax), 5.95 (1H, d, J = 2.4 Hz, H-6), 5.96 (1H, d, J = 2.4 Hz, H-8), 6.93 (1H, d, J = 1.9 Hz, H-2'), 6.69 (1H, d, J = 8.3 Hz, H-5'), 6.81 (1H, dd, J = 8.2, 1.7 Hz, H-6'), 6.95 (2H, s, H-2", 6"); 13 C NMR (CD 3 OD, 125 MHz): δ 78.8 (C-2), 70.1 (C-3), 27.0 (C-4), 157.4 (C-5), 96.7 (C-6), 158.0 (C-7), 96.0 (C-8), 158.0 (C-9), 99.6 (C-10), 131.6 (C-1'), 115.3 (C-2'), 146.1 (C-3'), 146.1 (C-4'), 116.2 (C-5'), 119.5 (C-6'), 121.6 (C-1"), 110.4 (C-2", 6"), 146.5 (C-3", 5"), 139.9 (C-4"), 167.8 (-COO)
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Chemical structures of compounds 1 - 13 from D. burmanica Kurz.
(+)-Afzelechin 3-O-α-L-rhamnopyranoside (6)
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: −83.4 ( c 0.3, MeOH); UV (MeOH) λ max 225, 279 nm; ESI-QTOF MS: m/z 421.2333 [M+H] + ; 1 H-NMR (CD 3 OD, 500 MHz): δ 4.66 (1H, d, J = 7.9 Hz, H-2), 3.94 (1H, m, H-3), 2.65 (1H, dd, J = 16.3, 8.9 Hz, H-4eq), 2.91 (1H, d, J = 15.9, 5.7 Hz, H-4ax), 5.85 (1H, d, J = 2.2 Hz, H-6), 5.94 (1H, d, J = 2.4 Hz, H-8), 7.23 (2H, d, J = 8.5 Hz, H-2', 6'), 6.79 (2H, d, J = 8.5 Hz, H-3', 5'), 4.25 (1H, br s, H-1"), 1.25 (3H, d, J = 6.3 Hz, H-6"); 13 C NMR (CD 3 OD, 125 MHz): δ 81.3 (C-2), 76.4 (C-3), 28.4 (C-4), 157.1 (C-5), 95.6 (C-6), 157.7 (C-7), 96.6 (C-8), 158.1 (C-9), 100.8 (C-10), 131.4 (C-1'), 129.5 (C-2', 6'), 116.2 (C-3', 5'), 158.7 (C-4'), 102.4 (C-1"), 72.1 (C-2"), 72.4 (C-3"), 74.1 (C-4"), 70.5 (C-5"), 18.1 (C-6")
(+)-2,3-trans-Dihydrokaempferol 3-O-α-L-rhamnopyranoside (7)
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: −15.3 ( c 0.5, MeOH); UV (MeOH) λ max 290, 332 nm; ESI-QTOF MS: m/z 435.2365 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 5.14 (1H, d, J = 11.2 Hz, H-2), 4.62 (1H, d, J = 11.2 Hz, H-3), 5.92 (1H, d, J = 2.2 Hz, H-8), 5.89 (1H, d, J = 2.2 Hz, H-6), 7.36 (2H, d, J = 8.8 Hz, H-2', 6'), 6.84 (1H, d, J = 8.8 Hz, H-3', 5'), 4.00 (1H, d, J = 1.4 Hz, H-1"), 1.18 (3H, d, J = 6.2 Hz, H-6"); 13 C NMR (CD 3 OD, 125 MHz): δ 84.0 (C-2), 78.8 (C-3), 196.2 (C-4), 165.7 (C-5), 97.6 (C-6), 164.3 (C-7), 96.4 (C-8), 168.9 (C-9), 102.4 (C-10), 128.8 (C-1'), 130.2 (C-2', 6'), 116.6 (C-3', 5'), 159.6 (C-4'), 102.6 (C-1"), 71.9 (C-2"), 72.3 (C-3"), 73.9 (C-4"), 70.7 (C-5"), 18.0 (C-6")
Methyl gallate (8)
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: + 19.3 ( c 0.3, CHCl 3 ); UV (MeOH) λ max 277 nm; ESI-Q-TOF MS: m/z 185.0443 [M+H] + ; 1 H NMR (CD 3 OD, 500 MHz): δ 7.04 (2H, s, H-2, 6), 3.81 (3H, s, -OMe); 13 C NMR (CD 3 OD, 125 MHz): δ 121.6 (C-1), 110.2 (C-2, 6), 146.6 (C-3, 5), 139.9 (C-4), 169.2 (C=O), 52.4 (-OMe)
Lupeol (9)
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: +31.5 ( c 0.5, CHCl 3 ); ESI-Q-TOF MS: m/z 426.3862 [M+H] + ; 1 H NMR (CDCl 3 , 500 MHz): δ 3.16 (1H, dd, J = 11.5, 5.2 Hz, H-3), 2.35 (1H, m, H-19), 1.90 (1H, m, H-21), 0.77 (3H, s, H-23), 0.81 (3H, s, H-24), 0.92 (3H, s, H-25), 0.94 (3H, s, H-26), 1.01 (3H, s, H-27), 0.74 (3H, s, H-28), 4.54 (1H, m, H-29a), 4.66 (1H, d, J = 2.4 Hz, H-29b), 1.66 (3H, s, H-30); 13 C NMR (CDCl 3 , 125 MHz): δ 39.0 (C-1), 27.6 (C-2), 79.2 (C-3), 39.1 (C-4), 55.5 (C-5), 18.6 (C-6), 34.5 (C-7), 41.1 (C-8), 50.7 (C-9), 37.4 (C-10), 21.2 (C-11), 25.4 (C-12), 38.3 (C-13), 43.1 (C-14), 27.7 (C-15), 35.8 (C-16), 43.2 (C-17), 48.6 (C-18), 48.2 (C-19), 151.2 (C-20), 30.1 (C-21), 40.2 (C-22), 28.2 (C-23), 15.6 (C-24), 16.3 (C-25), 16.2 (C-26), 14.8 (C-27), 18.2 (C-28), 109.5 (C-29), 19.5 (C-30)
Methyl lup-20(29)-en-3-on-28-oate (10)
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: +14.3 ( c 0.35, CHCl 3 ); LRFAB MS: m/z 469 [M+H] + ; 1 H NMR (CDCl 3 , 500 MHz): δ 2.98 (1H, m, H-3), 2.47 (1H, m, H-19), 0.90 (3H, s, H-23), 0.93 (3H, s, H-24), 0.95 (3H, s, H-25), 0.99 (3H, s, H-26), 1.04 (3H, s, H-27), 4.58 (1H, m, H-29a), 4.71 (1H, m, H-29b), 1.66 (3H, s, H-30), 3.65 (3H, s, 28-OC H3 ); 13 C NMR (CDCl 3 , 125 MHz): δ 38.4 (C-1), 26.6 (C-2), 218.2 (C-3), 39.7 (C-4), 56.6 (C-5), 19.7 (C-6), 33.7 (C-7), 42.5 (C-8), 55.0 (C-9), 36.9 (C-10), 21.4 (C-11), 25.6 (C-12), 37.0 (C-13), 47.0 (C-14), 29.7 (C-15), 34.2 (C-16), 47.4 (C-17), 49.9 (C-18), 49.4 (C-19), 150.5 (C-20), 32.1 (C-21), 40.6 (C-22), 30.6 (C-23), 15.8 (C-24), 19.4 (C-25), 16.0 (C-26), 14.7 (C-27), 176.7 (C-28), 109.7 (C-29), 21.1 (C-30), 51.3 (28-O C H 3 )
β-Amyrin (11)
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: +89.2 ( c 0.3, CHCl 3 ); HRFAB MS: m/z 426.3855 [M+H] + ; 1 H NMR (CDCl 3 , 500 MHz): δ 3.20 (1H, dd, J = 10.2, 4.5 Hz, H-3), 5.16 (1H, t, J = 3.6 Hz, H-12), 0.98 (3H, s, H-23), 0.77 (3H, s, H-24), 0.92 (3H, s, H-25), 0.95 (3H, s, H-26), 1.11 (3H, s, H-27), 0.81 (3H, s, H-28), 0.85 (6H, s, H-29, H-30); 13 C NMR (CDCl 3 , 125 MHz): δ 38.8 (C-1), 27.2 (C-2), 79.3 (C-3), 39.0 (C-4), 55.4 (C-5), 18.6 (C-6), 32.9 (C-7), 41.9 (C-8), 47.9 (C-9), 37.2 (C-10), 23.9 (C-11), 121.9 (C-12), 145.4 (C-13), 40.0 (C-14), 28.3 (C-15), 26.4 (C-16), 32.9 (C-17), 47.5 (C-18), 47.1 (C-19), 32.7 (C-20), 35.0 (C-21), 37.4 (C-22), 28.6 (C-23), 15.7 (C-24), 15.8 (C-25), 17.0 (C-26), 26.2 (C-27), 27.5 (C-28), 33.6 (C-29), 23.8 (C-30)
α-Amyrin (12)
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: +51.6 ( c 0.7, CHCl 3 ); HRFAB MS: m/z 426.3856 [M+H] + ; 1 H NMR (CDCl 3 , 500 MHz): δ 3.21 (1H, dd, J = 10.4, 5.1 Hz, H-3), 5.10 (1H, t, J = 3.6 Hz, H-12), 0.98 (3H, s, H-23), 0.76 (3H, s, H-24), 0.93 (3H, s, H-25), 0.99 (3H, s, H-26), 1.05 (3H, s, H-27), 0.78 (3H, s, H-28), 0.78 (3H, s, H-29), 0.89 (3H, s, H-30); 13 C NMR (CDCl 3 , 125 MHz): δ 39.0 (C-1), 27.5 (C-2), 79.3 (C-3), 39.0 (C-4), 55.4 (C-5), 18.6 (C-6), 33.2 (C-7), 40.2 (C-8), 47.9 (C-9), 37.1 (C-10), 23.6 (C-11), 124.6 (C-12), 139.8 (C-13), 42.3 (C-14), 26.8 (C-15), 28.4 (C-16), 34.0 (C-17), 59.3 (C-18), 39.9 (C-19), 39.8 (C-20), 31.5 (C-21), 41.7 (C-22), 28.3 (C-23), 15.9 (C-24), 15.8 (C-25), 17.1 (C-26), 23.5 (C-27), 29.0 (C-28), 17.7 (C-29), 21.6 (C-30)
3β-Hydroxy-D:B-friedo-olean-5-ene (13)
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: +73.1 ( c 0.5, CHCl 3 ); HRFAB MS: m/z 426.3853 [M+H] + ; 1 H NMR (CDCl 3 , 500 MHz): δ 3.50 (1H, m, H-3), 5.66 (1H, m, H-12), 1.08 (3H, s, H-23), 1.17 (3H, s, H-24), 0.88 (3H, s, H-25), 1.13 (3H, s, H-26), 1.04 (3H, s, H-27), 1.19 (3H, s, H-28), 1.02 (3H, s, H-29), 0.98 (3H, s, H-30); 13 C NMR (CDCl 3 , 125 MHz): δ 18.4 (C-1), 28.0 (C-2), 76.6 (C-3), 41.1 (C-4), 141.8 (C-5), 122.3 (C-6), 23.9 (C-7), 47.7 (C-8), 35.1 (C-9), 49.9 (C-10), 34.8 (C-11), 30.6 (C-12), 38.1 (C-13), 39.5 (C-14), 32.3 (C-15), 36.2 (C-16), 30.3 (C-17), 43.3 (C-18), 35.3 (C-19), 28.5 (C-20), 33.3 (C-21), 39.1 (C-22), 29.2 (C-23), 25.7 (C-24), 16.4 (C-25), 18.6 (C-26), 19.8 (C-27), 32.2 (C-28), 32.6 (C-29), 34.7 (C-30)
Results and Discussion
The methanolic extract of D. burmanica was partitioned successively with CH 2 Cl 2 , EtOAc, and n -BuOH. The EtOAc and CH 2 Cl 2 soluble fraction were subjected diverse column chromatography to give six flavan 3-ol derivatives, a dihydroflavonol glycoside, a phenolic compound and five triterpenes. Spectroscopic data of isolates were compared with those of literature values to determin (+)-catechin ( 1 ), 8 (+)-catechin 3-O-α-L-rhamnopyranoside ( 2 ), 8 (+)-catechin 3- O -gallate ( 3 ), 9 (−)-epicatechin ( 4 ), 8 (−)-epicatechin 3- O -gallate ( 5 ), 10 (+)-afzelechin 3- O -α-L-rhamnopyranoside ( 6 ), 11 (+)-2,3- trans -dihydrokaempferol 3- O -α-L-rhamnopyranoside ( 7 ), 12 methyl gallate ( 8 ), 13 lupeol ( 9 ), 14 - 15 methyl lup-20(29)-en-3-on-28-oate ( 10 ), 16 β-amyrin ( 11 ), 17 α-amyrin ( 12 ), 18 3β-hydroxy-D:B-friedo-olean-5-ene ( 13 ). 19 To the best of our knowledge, all isolates were isolated from D. burmanica for the first time.
Compound 1 was obtained as brownish amorphous powder and the molecular formula, C 15 H 14 O 6 , was established by the positive ion mode ESI-QTOF MS (m/z 291.0866 [M+H] + ). The 1 H NMR spectrum showed the signals for 1,3,4-substituted aromatic protons [δ H 6.84 (1H, d, J = 2.0, H-2'), 6.76 (1H, d, J = 8.0, H-5'), 6.72 (1H, dd, J = 8.0, 2.0, H-6')], two meta coupling protons [δ H 5.92 (1H, d, J = 2.2, H-8), 5.85 (1H, d, J = 2.2, H-6)], a methene group [δ H 2.85 (1H, dd, J = 16.3, 5.3, H-4 eq ), 2.50 (1H, dd, J = 16.2, 8.0, H-4ax)] and two methine protons [δ H 4.56 (1H, d, J = 7.5, H-2), 3.96 (1H, m, H-3)]. The 2,3- trans configuration was confirmed from the large J value of H-2 ( J = 7.5 Hz). The 13 C NMR detected 15 carbon signals including twelve aromatic carbons, one oxygenated aliphatic carbon and two aliphatic carbons. Thus, compound 1 was identified as (+)-catechin based on the spectroscopic evidences and comparison of literature values.
Compound 2 was isolated as dark brownish amorphous powder and the molecular formula was deduced to be C 21 H 24 O 10 from its ESI-QTOF MS ion peak at m/z 437.1454 [M+H] + . The 1 H and 13 C NMR spectra showed similar patterns with those of compound 1 except for the sugar moiety. The sugar moiety was elucidated to be α-rhamnopyranoside from the anomeric proton signal at δ H 4.29 (1H, d, J = 1.2, H-1") and six alipathic carbon signals at δ C 100.8 (C-1"), 72.2 (C-2"), 72.4 (C-3"), 74.1 (C-4"), 70.5 (C-5"), 18.1 (C-6"). On the basis of spectroscopic data with comparison of literature values, the structure of compound 2 was determined to be (+)-catechin 3- O -α-L-rhamnopyranoside.
Compound 3 was obtained as dark purple amorphous powder. Its molecular formula was identified as C 22 H 18 O 10 from the positive ion mode ESI-QTOFMS ( m/z 443.2216 [M+H] + ). The 1 H and 13 C NMR spectra was similar to compound 1 (see Experimental) except for the presence of a gallic acid moiety at δ H 6.96 (2H, s, H-2”, 6”) and δ C 121.5 (C-1"), 110.3 (C-2", 6"), 146.5 (C-3", 5"), 140.0 (C-4"), 167.7 (- C OO). The HMBC correlation of δ H 5.37 (H-3) to δ C 167.7 indicated that gallic acid was linked to C-3 of (+)-cathecin. Thus, compound 3 was confirmed to be(+)-catechin 3- O -gallate
Compound 4 was isolated as brown amorphous powder and its molecular formula was determined to be C 15 H 14 O 6 by the positive ion mode ESI-QTOFMS ( m/z 291.1953 [M+H] + ). The 1 H NMR indicated flavan 3-ol moiety including 1,3,4-substitued aromatic proton signals at δ H 6.97 (1H, d, J = 1.8, H-2'), 6.75 (1H, d, J = 8.2, H-5'), 6.79 (1H, dd, J =8.4, 1.7, H-6'), two meta -coupled aromatic proton signals at δ H 5.91 (1H, d, J = 2.2, H-6), 5.94 (1H, d, J = 2.2, H-8) and a methene group at δ H 2.73 (1H, dd, J = 16.5, 2.8, H-4 eq ), 2.86 (1H, dd, J = 16.5, 4.9, H-4ax) and two methine protons at δ H 4.82 (1H, s, H-2), 4.17 (1H, m, H-3). The 2,3- cis configuration was confirmed from the singlet signal of H-2. Based on the spectroscopic evidences and comparison with literature values, compound 4 was determined to be (-)-epicatechin.
Compound 5 was obtained as dark purple amorphous powder showing its molecular as C 22 H 18 O 10 from ESIQTOFMS ( m/z 443.2216 [M+H] + ). The 1 H and 13 C NMR spectra detected (−)-epicathecin skeleton and additionally observed the presence of a gallic acid moiety (see Experimental). The HMBC correation of δ H 5.52 (H-3) to δ C 167.8 revealed that gallic acid was linked to C-3 of (−)-epicatechin. Thus, compound 5 was elucidated as (−)-epicatechin 3- O -gallate.
The molecular formula of compound 6 was determined to be C 21 H 24 O 9 by at m/z 421.2333 [M+H] + ion peak of ESI-QTOFMS spectrum. The 1 H and 13 C NMR spectra displayed similar patterns with those of compound 2 except for the signals of 1,4-substituted aromatic proton signals [δ H 7.23 (2H, d, J = 8.5, H-2', 6'), 6.79 (2H, d, J = 8.5, H-3', 5'); δ C 131.4 (C-1'), 129.5 (C-2', 6'), 116.2 (C-3', 5'), 158.7 (C-4')]. From these spectroscopic data and through comparison with literature values, compound 6 was assigned to be (+)-afzelechin 3- O -α-L-rhamnopyranoside.
Compound 7 was isolated as yellowish amorphous powder and the molecular formula was determined to be C 21 H 22 O 10 by ESI-QTOFMS ion peak at m/z 435.2365 [M+H] + . The 1 H NMR spectrum displayed dihydrokaempferol skeleton including 1,4-substituted aromatic proton signals [δ H 7.36 (2H, d, J = 8.8, H-2', 6'), 6.84 (2H, d, J = 8.8, H-3', 5'), two meta -coupled aromatic protons at δ H 5.92 (1H, d, J = 2.2, H-8), 5.89 (1H, d, J = 2.2, H-6) and two aliphatic proton signals at δ H 5.14 (1H, d, J = 11.2, H-2), 4.62 (1H, d, J = 11.2, H-3). The coupling constant (J = 11.2 Hz) between H-2 and H-3 indicated that 2,3- trans configuration. Furthermore, α-rhamnopyranoside was detected at δ H 4.00 (1H, d, J = 1.4, H-1") and δ C 102.6 (C-1"), 71.9 (C-2"), 72.3 (C-3"), 73.9 (C-4"), 70.7 (C-5"), 18.0 (C-6"). The anomeric proton signal of rhamnose (δ H 4.00) was correlated to δ C 78.8 indicating sugar moiety was attached to C-3 position of dihydrokaempferol moiety. Based on the spectroscopic evidences and comparison with literature values, compound 7 was determined to be (+)-2,3- trans -dihydrokaempferol 3- O -α-L-rhamnopyranoside.
Compound 8 was isolated as dark purple amorphous powder and its molecular formula was established as C 8 H 8 O 5 based on the positive mode of ESI-QTOF MS ( m/z 185.0443 [M+H] + ). The 1 H NMR spectrum showed a singlet at δ H 7.04 (2H, s, H-2, 6), assignable to symmetrical protons at H-2 and H-6, and a methoxy signal at δ H 3.81 (3H, s, -OCH 3 ). The 13 C NMR spectrum also showed six aromatic carbon signals at δ C 121.6 (C-1), 110.2 (C-2, 6), 146.6 (C-3, 5), 139.9 (C-4), a methoxy carbon signal at δ c 52.4 and a carbonyl carbon signal at δc 169.2. Based on above data with the comparison to the literature values, compound 8 was identified as methyl gallate.
Compound 9 was obtained as white amorphous powder, and displayed molecular ion peaks at m/z 426.3862 [M+H] + on the positive ion mode HRFAB-MS showing molecular formula of C 30 H 50 O. The 1 H NMR spectrum exhibited seven methyl groups at δ H 0.77 (3H, s, H-23), 0.81 (3H, s, H-24), 0.92 (3H, s, H-25), 0.94 (3H, s, H-26), 1.01 (3H, s, H-27), 0.74 (3H, s, H-28) and 1.66 (3H, s, H-30), two germinal-coupled vinyl protons at 4.54 (1H, m, H-29a), 4.66 (1H, d, J = 2.4 Hz, H-29b), an oxygenated methine proton signals at δ H 3.16 (1H, dd, J = 11.5, 5.2 Hz, H-3). The 13 C NMR detected thirty carbon signals showing characteristic two vinyl carbons (δ C 151.2, C-20; 109.5, C-29), an oxygenated carbon (δ C 79.2, C-3). Therefore, compound 9 was determined to be lupeol based on the spectroscopic evidences and literature values.
The molecular formula of compound 10 was determined to be C 31 H 48 O 3 by LRFAB-MS. The 1 H NMR spectrum exhibited six methyl groups at δ H 0.90 (3H, s, H-23), 0.93 (3H, s, H-24), 0.95 (3H, s, H-25), 0.99 (3H, s, H-26), 1.04 (3H, s, H-27) and 1.66 (3H, s, H-30), a methoxy group at δ H 3.65 (3H, s, 28-OC H3 ) and two germinal-coupled vinyl protons at 4.58 (1H, m, H-29a), 4.71 (1H, m). In addition, the 13 C NMR observed thirty carbon signals including two vinyl carbons (δ C 150.5, C-20; 109.7, C-29), two carbonyl carbons at δ C 218.2 (C-3) and 176.7 (C-28). From the above spectroscopic data and comparing them with published values, compound 10 was elucidated to be methyl lup-20(29)-en-3-on-28-oate.
Compound 11 was isolated as white amorphous powder, and its molecular formula was determined to be C 30 H 50 O by HR-FABMS spectroscopy. The 1 H NMR showed eight methyl signals at δ H 0.98 (3H, s, H-23), 0.77 (3H, s, H-24), 0.92 (3H, s, H-25), 0.95 (3H, s, H-26), 1.11 (3H, s, H-27), 0.81 (3H, s, H-28), 0.85 (6H, s, H-29, H-30), an oxygenated methine signal at δ H 3.20 (1H, dd, J = 10.2, 4.5 Hz, H-3) and a olefinic proton at δ H 5.16 (1H, t, J = 3.6 Hz, H-12). The 13 C NMR revealed thirty carbons containing two olefinic carbons at δ C 121.9 (C-12), 145.4 (C-13) and an oxygenated carbon at δ C 76.6 (C-3). On the basis of above spectroscopic data and comparing them with published values, compound 11 was identified to be β-amyrin.
The MS, 1 H and 13 C NMR data were close to compound 12 except for the two olefinic carbon signals at δ C 124.6 (C-12), 139.8 (C-13) which was characteristic in ursan skeleton. Thus, compound 12 was determined to be a-amyrin by comparing spectroscopic data with those of published values.
The positive ion mode HRFAB-MS showed pseudomolecular ion peak at m/z 426.3853 [M+H] + for compound 13 giving molecular formula of C 30 H 50 O. The 1 H NMR showed eight methyl signals at δ H 1.08 (3H, s, H-23), 1.17 (3H, s, H-24), 0.88 (3H, s, H-25), 1.13 (3H, s, H-26), 1.04 (3H, s, H-27), 1.19 (3H, s, H-28), 1.02 (3H, s, H-29), 0.98 (3H, s, H-30), an oxygenated methine signal at δ H ): δ 3.50 (1H, m, H-3) and a vinyl proton at δ H 5.66 (1H, m, H-12). In 13 C NMR, thirty carbon resonances were observed including an oxygenated methine carbon at δ C 76.6 (C-3) and two olefinic carbons at δ C 141.8 (C-5), 122.3 (C-6). According to MS, MS, 1 H and 13 C NMR of compound 13 and comparing them with literature values, compound 13 was elucidated as 3β-hydroxy-D:B-friedoolean-5-ene.
Acknowledgements
This work was supported by a National Institute of Biological Resources (NIBR) grant funded by the Korean government (ME).
References
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