Phytochemical Constituents of Salsola komarovii and Their Effects on NGF Induction

Abstract

Five lignan glycosides, seven megastigmane glycosides, and seven phenolic compounds were isolated by repeated column chromatography from the MeOH extract of Salsola komarovii. Their structures were determined to be lariciresinol-9-O-${\beta}$-$\small{D}$-glucopyranoside (1), alangilignoside C (2), conicaoside (3), (+)-lyoniresinol 9'-O-${\beta}$-$\small{D}$-glucopyranoside (4), (8S,8'R,7'R)-9'-[(${\beta}$-glucopyranosyl)oxy]lyoniresinol (5), blumenyl B ${\beta}$-$\small{D}$-glucopyranoside (6), blumenyl A ${\beta}$-$\small{D}$-glucopyranoside (7), staphylionoside D (8), icariside $B_2$ (9), (6R,9S)-3-oxo-${\alpha}$-ionol ${\beta}$-$\small{D}$-glucopyranoside (10), 3-oxo-${\alpha}$-ionol 9-O-${\beta}$-$\small{D}$-apiofuranosyl-($1{\rightarrow}6$)-${\beta}$-$\small{D}$-glucopyranoside (11), blumenol B 9-O-${\beta}$-$\small{D}$-apiofuranosyl-($1{\rightarrow}6$)-${\beta}$-$\small{D}$-glucopyranoside (12), benzyl 6-O-${\beta}$-$\small{D}$-apiofuranosyl-${\beta}$-$\small{D}$-glucopyranoside (13), canthoside C (14), tachioside (15), isotachioside (16), biophenol 2 (17), 2-(3,4-dihydroxy)-phenyl-ethyl-${\beta}$-$\small{D}$-glucopyranoside (18), and cuneataside C (19) by spectroscopic methods. All the isolated compounds 1 - 19 were reported from this source for the first time. Compounds 2, 3 and 6 upregulated NGF secretion to $118.8{\pm}3.6%$, $128.2{\pm}9.3%$ and $111.1{\pm}7.1%$ without significant cell toxicity.

Introduction

Exogenous Nerve growth factor (NGF) has therapeutic potential for neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, and diabetic polyneuropathy and enhances impaired cholinergic neuron system.1 As part of our efforts to search bioactive constituents of Korean medicinal plants, we found that the methanol extract of the aerial parts of Salsola komarovii induce increases in endogenous NGF levels in C6 glioma cells. Salsola species were used for treatments of hypertension, inflammation, cancer, and Alzheimer’s disease.2,3 Previous phytochemical investigations on this genus reported the isolation of flavonoids, alkaloids, coumarins, and sterols.4 However, only few phytochemical studies on S. komarovii have been reported. Thus, we have investigated the bioactive constituents from the aerial parts of S. komarovii. Column chromatographic separation of its MeOH extract led to isolation of five lignan glycosides (1 - 5), seven megastigmane glycosides (6 - 12), and seven phenolic compounds (13 - 19). Their structures were identified by physicochemical and spectroscopic methods. All isolates are here reported for the first time from this plant. Also, we evaluated the effects of isolates (1 - 19) on NGF induction.

 

Experimental

General experimental procedures − Optical rotations were measured on a Jasco P-1020 polarimeter in MeOH. IR spectra were recorded on a Bruker IFS-66/S FT-IR spectrometer. FAB mass spectra were obtained on a JEOL JMS700 mass spectrometer. NMR spectra were recorded on a Varian UNITY INOVA 500 NMR spectrometer operating at 500 MHz (1H) and 125 MHz (13C) with chemical shifts given in ppm (δ). Preparative HPLC was conducted using a Gilson 306 pump with Shodex refractive index detector and Econosil RP-C18 10 μm column (250 × 10 mm). Silica gel 60 (Merck, 70 - 230 mesh and 230 - 400 mesh) and RP-C18 silica gel (YMG GEL ODS-A, 12 nm, S-75 μm) were used for column chromatography. Spots were detected on TLC under UV light or by heating after spraying with 10% H2SO4 in C2H5OH (v/v).

Plant materials – S. komarovii (8 kg) were collected at Jejudo, Korea in September 2011, and the plant was identified by one of the authors (K.R. Lee). A voucher specimen (SKKU-NPL 1211) was deposited at the herbarium of School of Pharmacy in Sungkyunkwan University.

Extraction and isolation – The aerial parts of S. komarovii (8 kg) were extracted three times at room temperature with 80% MeOH and evaporated under reduced pressure to give a residue (384 g), which was dissolved in water (1.8 L) and then succeccively partitioned with n-hexane (20 g), CHCl3 (5 g), EtOAc (7 g), and n-BuOH (38 g). The BuOH fraction (38 g) was separated over an RP-C18 silica gel column (40% MeOH – 100% MeOH) to yield three fractions (B1-B3). Fraction B1 (18.1 g) was chromatographed on a diaion HP-20 column, eluting with a gradient solvent system consisting of 100% water and 100% MeOH, yielded two subfractions (B11 and B12). Fraction B12 (2.1 g) was subjected to Sephadex LH-20 column chromatography eluted with 50% MeOH to give four fractions (B121-B124). Subfraction B123 (215 mg) was separated over a silica gel column [CHCl3-MeOH-Water, 4 : 1 : 0.1] and further purified with an RP-C18 prep. HPLC (20% MeOH) to afford 14 (11 mg, tR = 10.5 min). Subfraction B124 (654 mg) was separated over a silica gel column [CHCl3-MeOH-Water, 6 : 1 : 0.1] and further purified with an RP-C18 prep. HPLC (19% MeOH) to yield 15 (3 mg, tR = 15.7 min), 16 (6 mg, tR = 11.0 min), 17 (7 mg, tR = 14.4 min), 18 (31 mg, tR = 14.1 min), and 19 (10 mg, tR = 20.0 min). Fraction B2 (5.6 g) was separated over a silica gel column [CHCl3-MeOH, 10 : 1 → 2 : 1] to yield nine fractions (B21-B29). Subfraction B26 (75 mg) was subjected to column chromatography using Sep-Pak (30% MeOH) and purified with an RP-C18 prep. HPLC (33% MeOH) to give 9 (3 mg, tR = 13.9 min). Subfraction B28 (353 mg) was separated over an RP-C18 silica gel column (30% MeOH) and purified with an RP-C18 prep. HPLC (10% CH3CN) to afford 1 (5 mg, tR = 12.5 min), 2 (5 mg, tR = 12.3 min), 3 (4 mg, tR = 12.4 min), 6 (17 mg, tR = 17.8 min), and 7 (48 mg, tR = 18.0 min). Subfraction B29 (1.3 g) was subjected to an RP-C18 silica gel column (30% MeOH) to give three fractions (B291-293). Compound 8 was obtained from subfraction B292 by the separation of Sep-Pak [CHCl3-MeOH, 8 : 1] and an RP-C18 prep. HPLC (14% CH3CN). Subfraction B293 was purified with an RP-C18 prep. HPLC (18% CH3CN) to yield 4 (12 mg, tR = 17.1 min), 5 (3 mg, tR = 17.3 min), and 13 (7 mg, tR = 15.7 min). Fraction B3 (8.3 g) was separated by Sephadex LH-20 column (70% MeOH) to yield four fractions (B31-B34). Subfraction B32 (537 mg) was subjected to a silica gel column [CHCl3-MeOHWater, 6:1:0.1] and purified with an RP-C18 prep. HPLC (50% MeOH) to afford 10 (22 mg, Rt = 17.6 min), 11 (11 mg, tR = 22.0 min), and 12 (12 mg, tR = 25.0 min).

Lariciresinol-9-O-β-D-glucopyranoside (1) −White powder, mp : 173 ℃; : +1.84° (c 0.125, MeOH); IR νmax cm−1: 3360, 2946, 2840, 1743, 1375, 1214; FAB-MS m/z: 523 [M + H]+; 1H-NMR (CD3OD, 500 MHz): δ 6.93 (1H, d, J = 1.8 Hz, H-2), 6.80 (1H, d, J = 1.8 Hz, H-2'), 6.76 (1H, m, H-5), 6.75 (1H, m, H-6), 6.71 (1H, d, J = 8.0 Hz, H-5'), 6.65 (1H, dd, J = 8.0, 1.8 Hz, H-6'), 4.74 (1H, d, J = 7.5 Hz, H-7), 4.32 (1H, d, J = 8.0 Hz, H-Glc), 4.05 (1H, m, H-9'), 4.03 (1H, m, H-9), 3.85 (3H, s, 3-OCH3), 3.83 (3H, s, 3'-OCH3), 3.73 (1H, m, H-9), 3.62 (1H, m, H-9'), 2.96 (1H, m, H-7’), 2.77 (1H, m, H-8'), 2.55 (1H, m, H-7'), 2.48 (1H, m, H-8); 13C-NMR (CD3OD, 125 MHz): δ 147.8 (C-3, 3'), 144.6 (C-4, 4'), 134.4 (C-1), 132.5 (C-1'), 121.1 (C-6'), 118.6 (C-6), 114.9 (C-5'), 114.8 (C-5), 112.3 (C-2'), 109.6 (C-2), 103.6 (Glc C-1), 83.00 (C-7), 76.9 (Glc C-5), 76.8 (Glc C-3), 74.00 (Glc C-2), 72.4 (C-9'), 70.5 (Glc C-4), 67.3 (C-9), 61.5 (Glc C-6), 55.2 (3, 3'-OCH3), 50.5 (C-8), 42.7 (C-8'), 32.7 (C-7').

Alangilignoside C (2) − Colorless gum, : +17.7° (c 0.125, MeOH); IR νmax cm−1: 3300, 2905, 1614, 1370, 1210, 1040; FAB-MS m/z: 581 [M − H]−; 1H-NMR (CD3OD, 500MHz): δ 6.65 (2H, s, H-2, 6), 6.50 (2H, s, H-2', 6'), 4.85 (1H, d, J = 6.5 Hz, H-7), 4.31 (1H, d, J = 8.0 Hz, H-1''), 4.08 (1H, m, H-9), 3.99 (1H, m, H-9'), 3.84 (1H, d, J = 12.0 Hz, H-6''), 3.83 and 3.82 (12H, s, 3, 3', 5, 5'-OCH3), 3.75 (2H, m, H-9, 9'), 3.66 (1H, dd, J = 12.0, 4.8 Hz, H-6''), 2.96 (1H, dd, J = 13.0, 5.0 Hz, H-7'), 2.75 (1H, m, H-8'), 2.52 (2H, m, H-7',8); 13C-NMR (CD3OD, 125 MHz): δ 149.1 (C-3', 5'), 149.0 (C-3,5), 134.7 (C-4), 133.7 (C-4'), 133.6 (C-1), 131.7 (C-1'), 105.8 (C-2',6'), 103.5 (C-2,6), 103.1 (Glc C-1), 83.2 (C-7), 76.9 (Glc C-5), 76.8 (Glc C-3), 74.0 (Glc C-2), 72.6 (C-9’), 70.5 (Glc C-4), 67.3 (C-9), 61.5 (Glc C-6), 55.6 (3, 3', 5, 5'-OCH3), 50.6 (C-8), 42.8 (C-8'), 33.1 (C-7').

Conicaoside (3) − Colorless gum, : −19.9° (c 0.125, pyridine); IR νmax cm−1: 3432, 2945, 1601, 1520, 1466, 1240, 1151, 1040; FAB-MS m/z: 575 [M + Na]+; 1H-NMR (pyridine-d5, 500 MHz): δ 7.25 (1H, d, J = 8.0 Hz, H-5'), 7.10 (2H, s, H-2, 6), 7.05 (1H, d, J = 1.8 Hz, H-2'), 6.50 (1H, dd, J = 8.0, 1.8 Hz, H-6'), 5.70 (1H, d, J = 7.0 Hz, H-1''), 5.48 (1H, d, J = 5.0 Hz, H-7), 4.38 (1H, m, H-9'), 4.35 (1H, dd, J = 10.5, 6.0 Hz, H-9), 4.18 (1H, dd, J = 10.5, 7.0 Hz, H-9), 4.10 (1H, t like, J = 7.8 Hz, H-9'), 3.72 (9H, s, 3, 3', 5-OCH3), 3.26 (1H, dd, J = 13.0, 4.0 Hz, H-7'), 3.10 (1H, m, H-8'), 2.85 (1H, m, H-7'), 2.76 (1H, m, H-8'); 13C-NMR (pyridine-d5, 125 MHz): δ 153.1 (C-3,5), 147.8 (C-3'), 144.7 (C-4'), 140.5 (C-1), 134.3 (C-4), 132.3 (C-1'), 120.9 (C-6'), 115.1 (C-5'), 112.2 (C-2'), 104.3 (Glc C-1), 103.5 (C-2, 6), 82.8 (C-7), 77.2 (Glc C-5), 76.7 (Glc C-3), 74.6 (Glc C-2), 72.6 (C-9'), 70.2 (Glc C-4), 61.4 (Glc C-6), 59.4 (C-9), 55.9 (3, 5-OCH3), 55.2 (3'-OCH3), 52.9 (C-8), 42.6 (C-8'), 32.4 (C-7').

Fig. 1.The structures of 1 - 19 from S.komarovii.

(+)-Lyoniresinol-9'-O-β-D-glucopyranoside (4) − Colorless gum, : +39.0° (c 0.125, MeOH); IR νmax cm−1: 3430, 2800, 1605, 1520, 1035; FAB-MS m/z: 583 [M + H]+; 1H-NMR (CD3OD, 500 MHz): δ 6.58 (1H, s, H-6), 6.42 (2H, s, H-2', 6'), 4.20 (1H, d, J = 6.0 Hz, H-7'), 4.28 (1H, d, J = 8.0 Hz, H-1''), 3.90 (1H, m, H-9'), 3.86 (3H, s, 5-OCH3), 3.74 (6H, s, 3', 5'-OCH3), 3.65 (1H, dd, J = 11.0, 6.5 Hz, H-9), 3.54 (1H, m, H-9'), 3.34 (3H, s, 3-OCH3), 2.72 (1H, dd, J = 15.0, 4.5 Hz, H-7), 2.62 (1H, dd, J = 15.0, 11.5 Hz, H-7), 2.08 (1H, m, H-8'), 1.70 (1H, m, H-8'); 13C-NMR (CD3OD, 125 MHz): δ 147.8 (C-3', 5'), 147.5 (C-5), 146.4 (C-3), 138.2 (C-4), 137.7 (C-4'), 133.3 (C-1'), 129.0 (C-1), 125.3 (C-2), 106.7 (C-6), 105.8 (C-2', 6'), 103.7 (Glc C-1), 77.1 (Glc C-5), 76.8 (Glc C-3), 74.0 (Glc C-2), 70.5 (C-9'), 70.3 (Glc C-4), 65.1 (C-9), 61.7 (Glc C-6), 58.9 (3-OCH3), 55.7 (5-OCH3), 55.4 (3', 5'-OCH3), 45.5 (C-8'), 41.6 (C-7'), 39.4 (C-8), 32.6 (C-7).

(8S,8'R,7'R)-9'-[(β-glucopyranosyl)oxy]lyoniresinol (5) − Colorless gum, : −59.0° (c 0.125, MeOH); IR νmax cm−1: 3460, 2805, 1615, 1523, 1041; FAB-MS m/z: 605 [M + Na]+; 1H-NMR (CD3OD, 500 MHz): δ 6.57 (1H, s, H-6), 6.42 (2H, s, H-2', 6'), 4.23 (1H, d, J = 6.5 Hz, H-7'), 4.13 (1H, d, J = 7.5 Hz, H-1''), 3.87 (1H, m, H-9'), 3.87 (3H, s, 5-OCH3), 3.75 (6H, s, 3', 5'-OCH3), 3.56 (1H, dd, J = 11.0, 6.5 Hz, H-9), 3.44 (1H, m, H-9'), 3.35 (3H, s, 3-OCH3), 2.66 (2H, m, H-7), 2.11 (1H, m, H-8'), 1.67 (1H, m, H-8'); 13C-NMR (CD3OD, 125 MHz): δ 147.8 (C-3', 5'), 147.5 (C-5), 146.4 (C-3), 138.3 (C-4), 137.7 (C-4'), 133.5 (C-1'), 129.0 (C-1), 125.1 (C-2), 106.6 (C-6), 106.0 (C-2', 6'), 103.1 (Glc C-1), 77.0 (Glc C-5), 76.8 (Glc C-3), 73.9 (Glc C-2), 70.8 (C-9'), 70.4 (Glc C-4), 65.0 (C-9), 61.5 (Glc C-6), 58.9 (3-OCH3), 55.7 (5-OCH3), 55.4 (3', 5'-OCH3), 45.4 (C-8'), 42.1 (C-7'), 40.1 (C- 8), 32.6 (C-7).

Blumenyl B β-D-glucopyranoside (6) − Colorless gum, : +2.0° (c 0.125, MeOH); FAB-MS m/z: 411 [M+ Na]+; 1H-NMR (CD3OD, 500MHz): δ 5.82 (1H, s, H-4), 4.31 (1H, d, J = 7.5 Hz, H-1'), 3.82 (1H, m, H-9), 3.79 (1H, dd, J = 12.0, 2.0 Hz, H-6'), 3.64 (1H, dd, J = 12.0, 5.5 Hz, H-6'), 2.66 (1H, d, J = 18.0 Hz, H-2), 2.13 (1H, d, J = 18.0 Hz, H-2), 2.04 (3H, d, J = 1.0 Hz, H-13), 1.81 (2H, m, H-7), 1.76 (1H, m, H-8), 1.24 (3H, d, J = 6.5 Hz, H-10), 1.09 (3H, s, H-11), 1.01 (3H, s, H-12); 13C-NMR (CD3OD, 125 MHz): δ 199.8 (C-3), 170.6 (C-5), 125.5 (C-4), 103.2 (C-1'), 78.2 (C-6), 77.2 (C-3'), 77.0 (C-5'), 76.7 (C-9), 74.1 (C-2'), 70.4 (C-4'), 61.6 (C-6'), 49.9 (C-2), 42.0 (C-1), 33.6 (C-7), 31.8 (C-8), 23.2 (C-13), 22.8 (C-12), 21.0 (C-11), 20.9 (C-10).

Blumenyl A β-D-glucopyranoside (7) − Colorless gum, : +34.0° (c 0.125, MeOH); FAB-MS m/z: 409 [M + Na]+; 1H-NMR (CD3OD, 500 MHz): δ 5.96 (1H, d, J = 15.0 Hz, H-7), 5.86 (1H, br s, H-4), 5.72 (1H, dd, J = 15.0, 7.0 Hz, H-8), 4.52 (1H, m, H-9), 4.26 (1H, d, J = 8.0 Hz, H-1'), 3.82 (1H, m, H-9), 3.79 (1H, dd, J = 12.0, 1.5 Hz, H-6'), 3.64 (1H, m, H-6'), 2.61 (1H, d, J = 19.0 Hz, H-2), 2.16 (1H, d, J = 18.0 Hz, H-2), 1.94 (3H, s, H-13), 1.28 (3H, d, J = 6.0 Hz, H-10), 1.09 (3H, s, H-11), 1.01 (3H, s, H-12); 13C-NMR (CD3OD, 125 MHz): δ 200.1 (C-3), 165.9 (C-5), 132.6 (C-7), 132.5 (C-8), 125.9 (C-4), 100.6 (C-1'), 78.8 (C-6), 77.2 (C-3'), 77.0 (C-5'), 73.7 (C-9), 73.4 (C-2'), 70.5 (C-4'), 61.6 (C-6'), 49.6 (C-2), 41.3 (C-1), 23.5 (C-13), 22.4 (C-12), 20.9 (C-11), 18.4 (C-10).

Staphylionoside D (8) − Colorless gum, : −58.0° (c 0.125, MeOH); FAB-MS m/z: 385 [M − H]−; 1H-NMR (CD3OD, 500 MHz): δ 5.83 (1H, s, H-8), 4.44 (1H, d, J = 7.5 Hz, H-1'), 3.86 (1H, dd, J = 12.0, 2.0 Hz, H-6'), 3.67 (1H, dd, J = 12.0, 5.0 Hz, H-6'), 2.37 (1H, ddd, J = 13.0, 4.0, 2.0 Hz, H-4), 2.19 (3H, s, H-10), 2.08 (1H, ddd, J = 13.0, 4.0, 2.0 Hz, H-2), 1.46 (2H, m, H-2,4), 1.39 (3H, s, H-13), 1.38 (3H, s, H-11), 1.15 (3H, s, H-12); 13C-NMR (CD3OD, 125 MHz): δ 210.3 (C-9), 199.6 (C-7), 118.9 (C-6), 101.5 (C-1'), 99.9 (C-8), 76.9 (C-3'), 76.7 (C-5'), 73.9 (C-2'), 71.4 (C-3), 71.2 (C-5), 70.5 (C-4'), 61.6 (C-6'), 48.7 (C-4), 45.5 (C-2), 35.8 (C-1), 31.1 (C-12), 29.6 (C-13), 28.2 (C-11), 25.3 (C-10).

Icariside B2 (9) − Colorless gum, : −96.8° (c 0.125, MeOH); FAB-MS m/z: 385 [M − H]−; 1H-NMR (CD3OD, 500 MHz): δ 7.00 (1H, d, J = 16.0 Hz, H-7), 6.25 (1H, d, J = 15.5 Hz, H-8), 4.39 (1H, d, J = 7.0 Hz, H-1'), 3.89 (1H, m, H-3), 2.43 (1H, m, H-4), 2.28 (3H, s, H-10), 1.73 (1H, m, H-4), 1.66 (1H, m, H-2), 1.38 (1H, m, H-2), 1.20 (3H, s, H-13), 1.18 (3H, s, H-12), 0.98 (3H, s, H-11); 13C-NMR (CD3OD, 125 MHz): δ 199.1 (C-9), 144.1 (C-7), 132.6 (C-8), 101.8 (C-1'), 76.9 (C-3'), 76.7 (C-5'), 73.9 (C-2'), 71.6 (C-3), 70.5 (C-4'), 69.9 (C-6), 67.2 (C-5), 61.6 (C-6'), 44.0 (C-2), 36.9 (C-4), 34.8 (C-1), 28.3 (C- 12), 26.3 (C-11), 24.3 (C-10), 19.0 (C-13).

(6R,9S)-3-Oxo-α-ionol β-D-glucopyranoside (10) − Colorless gum, FAB-MS m/z: 371 [M + H]+; 1H-NMR (CD3OD, 500 MHz): δ 5.88 (1H, br s, H-4), 5.75 (1H, dd, J = 15.0, 9.5 Hz, H-7), 5.57 (1H, dd, J = 15.0, 7.5 Hz, H-8), 4.48 (1H, m, H-9), 4.28 (1H, d, J = 7.5 Hz, H-1'), 3.83 (1H, m, H-6'), 3.62 (1H, m, H-6'), 2.69 (1H, d, J = 9.5 Hz, H-6), 2.46 (1H, d, J = 17.0 Hz, H-2), 2.05 (1H, d, J = 16.5 Hz, H-2), 1.98 (3H, d, J = 1.0 Hz, H-13), 1.29 (3H, d, J = 6.5 Hz, H-10), 1.03 (3H, s, H-12), 0.98 (3H, s, H-11); 13C-NMR (CD3OD, 125 MHz): δ 200.8 (C-3), 164.4 (C-5), 135.9 (C-8), 129.9 (C-7), 125.0 (C-4), 100.6 (C-1'), 77.2 (C-3'), 76.9 (C-5'), 73.8 (C-2’), 73.6 (C-9), 70.6 (C-4'), 61.7 (C-6'), 55.7 (C-6), 48.2 (C-2), 35.9 (C-1), 26.9 (C-12), 26.2 (C-11), 22.7 (C-13), 21.1 (C-10).

3-Oxo-α-ionol 9-O-β-D-apiofuranosyl-(1→6)-β-Dglucopyranoside (11) − Colorless gum, FAB-MS m/z: 501 [M − H]−; 1H-NMR (CD3OD, 500MHz): δ 5.93 (1H, br s, H-4), 5.78 (1H, dd, J = 15.0, 9.5 Hz, H-7), 5.61 (1H, dd, J = 15.0, 7.5 Hz, H-8), 5.04 (1H, d, J = 2.0 Hz, H-1''), 4.46 (1H, m, H-9), 4.31 (1H, d, J = 7.5 Hz, H-1'), 2.73 (1H, d, J = 9.5 Hz, H-6), 2.50 (1H, d, J = 17.0 Hz, H-2), 2.07 (1H, d, J = 16.5 Hz, H-2), 2.01 (3H, d, J = 1.0 Hz, H-13), 1.33 (3H, d, J = 6.5 Hz, H-10), 1.06 (3H, s, H-12), 1.02 (3H, s, H-11); 13C-NMR (CD3OD, 125 MHz): δ 200.3 (C-3), 163.4 (C-5), 135.3 (C-8), 130.2 (C-7), 125.1 (C-4), 111.2 (C-1''), 100.6 (C-1'), 81.2 (C-3''), 77.2 (C-3'), 77.0 (C-2''), 76.9 (C-5'), 73.9 (C-4''), 73.8 (C-2'), 73.6 (C-9), 70.6 (C-4'), 67.7 (C-6'), 55.7 (C-6), 48.4 (C-2), 36.4 (C-1), 26.9 (C-12), 26.2 (C-11), 22.1 (C-13), 20.6 (C-10).

Blumenol B 9-O-β-D-apiofuranosyl-(1→6)-β-Dglucopyranoside (12) − Colorless gum, FAB-MS m/z: 543 [M + Na]+; 1H-NMR (CD3OD, 500 MHz): δ 5.83 (1H, s, H-4), 5.02 (1H, d, J = 2.0 Hz, H-1''), 4.32 (1H, d, J = 7.5 Hz, H-1'), 3.82 (1H, m, H-9), 2.52 (1H, d, J = 18.0 Hz, H-2), 2.13 (1H, d, J = 18.0 Hz, H-2), 2.04 (3H, d, J = 1.0 Hz, H-13), 1.81 (2H, m, H-7), 1.76 (1H, m, H-8), 1.23 (3H, d, J = 6.5 Hz, H-10), 1.15 (3H, s, H-11), 1.02 (3H, s, H-12); 13C-NMR (CD3OD, 125 MHz): δ 199.8 (C-3), 170.6 (C-5), 125.5 (C-4), 110.9 (C-1''), 103.2 (C-1'), 80.8 (C-3''), 78.2 (C-6), 77.2 (C-3'), 77.1 (C-2''), 77.0 (C-5'), 74.0 (C-4''), 76.7 (C-9), 74.0 (C-2'), 70.4 (C-4'), 66.6 (C-6'), 49.9 (C-2), 42.0 (C-1), 33.6 (C-7), 31.8 (C-8), 23.2 (C-13), 22.8 (C-12), 21.0 (C-11), 20.9 (C-10).

Benzyl 6-O-β-D-apiofuranosyl-β-D-glucopyranoside (13) − Colorless gum, FAB-MS m/z: 401 [M − H]−; 1H-NMR (CD3OD, 500 MHz): δ 7.43-7.25 (5H, m, H-2, 3, 4, 5, 6), 5.05 (1H, d, J = 2.5 Hz, H-1''), 4.90 (1H, d, J = 11.5 Hz, H-7), 4.66 (1H, d, J = 12.0 Hz, H-7), 4.32 (1H, d, J = 8.0 Hz, H-1'); 13C-NMR (CD3OD, 125 MHz): δ 137.8 (C-1), 128.1 (C-3, 5), 128.1 (C-2), 127.5 (C-6), 109.7 (C-1''), 102.6 (C-1'), 79.3 (C-3''), 76.9 (C-2''), 76.8 (C-3'), 75.7 (C-5'), 73.8 (C-4''), 73.7 (C-2'), 70.5 (C-4'), 69.4 (C-7), 67.6 (C-5''), 64.4 (C-6).

Canthoside C (14) − Colorless gum, FAB-MS m/z: 435 [M+ H]+; 1H-NMR (CD3OD, 500 MHz): δ 6.76 (1H, d, J = 2.5 Hz, H-2), 6.71 (1H, d, J = 8.0 Hz, H-5), 6.60 (1H, dd, J = 8.0, 2.5 Hz, H-6), 4.98 (1H, d, J = 2.0 Hz, H-1''), 4.70 (1H, d, J = 7.5 Hz, H-1'), 3.76 (3H, s, 3-OCH3) ; 13C-NMR (CD3OD, 125 MHz): δ 151.6 (C-1), 148.1 (C-3), 141.9 (C-4), 114.9 (C-5), 109.8 (C-1''), 108.9 (C-6), 102.9 (C-2), 102.6 (C-1'), 79.3 (C-3''), 76.9 (C-2''), 76.8 (C-3'), 75.7 (C-5'), 73.8 (C-4''), 73.7 (C-2'), 70.5 (C-4'), 67.6 (C-5''), 64.4 (C-6'), 55.4 (5-OCH3).

Tachioside (15) − Colorless gum, FAB-MS m/z: 302 [M + H]+; 1H-NMR (CD3OD, 500 MHz): δ 6.80 (1H, d, J = 3.0 Hz, H-2), 6.73 (1H, d, J = 8.5 Hz, H-5), 6.57 (1H, dd, J = 8.5, 3.0 Hz, H-6), 4.80 (1H, d, J = 7.5 Hz, H-1'), 3.68 (3H, s, 3-OCH3); 13C-NMR (CD3OD, 125 MHz): δ 152.1 (C-4), 149.7 (C-2), 141.2 (C-1), 119.4 (C-6), 106.5 (C-5), 103.2 (C-1'), 100.7 (C-3), 76.9 (C-3'), 76.6 (C-5'), 73.9 (C-2'), 70.3 (C-4'), 61.4 (C-6'), 55.6 (3-OCH3).

Isotachioside (16) − Colorless gum, FAB-MS m/z: 302 [M + H]+; 1H-NMR (CD3OD, 500 MHz): δ 7.02 (1H, d, J = 9.0 Hz, H-5), 6.80 (1H, d, J = 3.0 Hz, H-2), 6.28 (1H, dd, J = 9.0, 3.0 Hz, H-6), 4.80 (1H, d, J = 7.5 Hz, H-1'), 3.7.0 (3H, s, 3-OCH3) ; 13C-NMR (CD3OD, 125 MHz): δ 153.8 (C-4), 150.9 (C-2), 139.9 (C-1), 119.4 (C-6), 106.5 (C-5), 103.2 (C-1'), 100.7 (C-3), 76.9 (C-3'), 76.6 (C-5'), 73.9 (C-2'), 70.3 (C-4'), 61.4 (C-6'), 55.4 (3-OCH3).

Biophenol 2 (17) − Colorless gum, FAB-MS m/z: 339 [M + Na]+; 1H-NMR (CD3OD, 500 MHz): δ 7.10 (1H, d, J = 8.5 Hz, H-5), 6.73 (1H, d, J = 2.0 Hz, H-2), 6.65 (1H, dd, J = 8.5, 2.0 Hz, H-6), 4.69 (1H, d, J = 8.0 Hz, H-1'), 3.69 (2H, t, J = 7.0 Hz, H-8), 2.71 (2H, t, J = 7.0 Hz, H-7); 13C-NMR (CD3OD, 125 MHz): δ 147.2 (C-4), 144.1 (C-3), 135.1 (C-1), 120.2 (C-2), 118.1 (C-5), 116.5 (C-6), 103.6 (C-1'), 77.1 (C-5'), 76.9 (C-3’), 73.9 (C-2'), 70.2 (C-4'), 63.1 (C-8), 61.3 (C-6'), 38.5 (C-7).

2-(3,4-Dihydroxy)-phenyl-ethyl-O-β-D-glucopyranoside (18) − Colorless gum, FAB-MS m/z: 339 [M + Na]+; 1H-NMR (CD3OD, 500MHz): δ 6.73 (1H, d, J = 2.0 Hz, H-2), 6.67 (1H, d, J = 8.0 Hz, H-5), 6.54 (1H, dd, J = 8.0, 2.0 Hz, H-6), 4.28 (1H, d, J = 8.0 Hz, H-1'), 4.02 (1H, m, H-8), 3.69 (1H, m, H-8), 2.76 (2H, m, H-7); 13C-NMR (CD3OD, 125 MHz): δ 144.7 (C-3), 143.3 (C-4), 130.1 (C-1), 119.9 (C-6), 115.7 (C-5), 114.9 (C-2), 102.9 (C-1'), 76.7 (C-3'), 76.5 (C-5'), 73.7 (C-2'), 70.7 (C-4'), 70.2 (C-8), 61.3 (C-6'), 35.2 (C-7).

Cuneataside C (19) − Colorless gum, FAB-MS m/z: 471 [M + Na]+; 1H-NMR (CD3OD, 500 MHz): δ 6.68 (1H, d, J = 2.0 Hz, H-2), 6.67 (1H, d, J = 8.0 Hz, H-5), 6.55 (1H, dd, J = 8.0, 2.0 Hz, H-6), 5.00 (1H, d, J = 3.0 Hz, H-1''), 4.27 (1H, d, J = 7.5 Hz, H-1'), 4.02 (1H, m, H-8), 3.69 (1H, m, H-8), 2.76 (2H, m, H-7); 13C-NMR (CD3OD, 125 MHz): δ 144.7 (C-3), 143.3 (C-4), 130.0 (C-1), 119.9 (C-6), 115.7 (C-5), 114.9 (C-2), 109.6 (C-1''), 103.0 (C-1'), 79.2 (C-3''), 76.6 (C-2''), 75.5 (C-3'), 73.7 (C-5'), 73.6 (C-4''), 70.8 (C-2'), 70.3 (C-8), 67.3 (C-4'), 64.1 (C-5''), 62.9 (C-6'), 35.2 (C-7).

NGF and cell viability assays − C6 glioma cells were used to measure NGF release into the medium.11 C6 cells were purchased from the Korean Cell Line Bank and maintained in DMEM supplemented with 10% FBS and 1% penicillin-streptomycin in a humidified incubator with 5% CO2. To measure NGF content in medium and cell viability, C6 cells were seeded into 24-well plates (1 × 105 cells/well). After 24 h, the cells were treated with DMEM containing 2% FBS and 1% penicillin-streptomycin with 20 μM of each isolated compound for one day. Media supernatant was used for the NGF assay using an ELISA development kit (R&D Systems). Cell viability was assessed by the MTT assay.

 

Results and Discussion

Compounds 1 - 19 were identified as lariciresinol-9-O-β-D-glucopyranoside (1),6 alangilignoside C (2),7 conicaoside C (3),8 (+)-lyoniresinol 9'-O-β-D-glucopyranoside (4),9,10 (8S,8'R,7'R)-9'-[(β-glucopyranosyl)oxy]lyoniresinol (5),11 blumenyl B β-D-glucopyranoside (6),12 blumenyl A β-D-glucopyranoside (7),12 staphylionoside D (8),13 Icariside B2 (9),14 (6R,9S)-3-oxo-α-ionol β-D-glucopyranoside (10),15 3-oxo-α-ionol 9-O-β-D-apiofuranosyl-(1→6)-β-D-glu copyranoside (11),16 blumenol B 9-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (12),16 benzyl 6-O-β-Dapiofuranosyl-β-D-glucopyranoside (13),17 canthoside C (14),18 tachioside (15),19 isotachioside (16),20 biophenol 2 (17),20 2-(3,4-dihydroxy)-phenyl-ethyl-O-β-D-glucopyra noside (18),21 and cuneataside C (19)22 by comparing the 1H-, 13C-NMR, and MS spectral data with the literature values. All the isolated compounds 1 - 19 were reported from this source for the first time. The following describes the structural elucidation of compound 3, which upregulated NGF secretion without significant cell toxicity.

Compound 3 was obtained as a colorless gum. From the FAB-MS (m/z: 575 [M + Na]+) and 1H- and 13C-NMR spectral data, the molecular formula of 3 was deduced to be C27H36O12. The 1H-NMR spectrum showed five aromatic protons at δH 7.25 (1H, d, J = 8.0 Hz), 7.10 (2H, s), 7.05 (1H, d, J = 1.8 Hz), and 6.50 (1H, dd, J = 8.0, 1.8 Hz), three methoxy groups at δH 3.72 (9H, s). The coupling patterns of five aromatic protons suggested the existence of typical 1,3,4-trisubstituted and 1,3,4,5-tetrasubstituted benzene rings. In addition, signals attributable to sugar moiety were observed at δH 5.70 (1H, d, J = 7.0 Hz) and 4.50-4.00 (5H, m) in the 1H-NMR spectrum. The 13C-NMR spectrum demonstrated the presence of 27 carbon signals, consisting of 12 aromatic carbon signals including 5 oxygenated aromatic carbon signals [δC 153.1 (×2), 147.8, 144.7, and 134.3] and three methoxy carbon signals [δC 55.9 (×2), 55.2]. The presence of anomeric carbon signal at δC 104.3 and five oxygenated carbon signals (δ 77.2, 76.7, 74.6, 70.2, and 61.4) suggested the presence of D-glucose (Stephen et al., 1977). The coupling constant (J = 7.0 Hz) of the anomeric proton of D-glucose indicated that it was the β-form.23 Based on the above evidences, the structure of 3 was determined to be conicaoside.8

Table. 1.a C6 cells were treated with 20 μM of compounds 1 - 19. After 24 h, the content of NGF secretion in C6-conditioned media was measured by ELISA, and the cell viability was determined by MTT assay. The level of secreted NGF and viable cells are expressed as percentage of the untreated control. The data shown represent the means ± SD of three independent experiments performed in triplicate. b 6- Shogaol as positive control.

The isolated compounds 1 - 19 were evaluated for their effects on NGF induction using C6 glial cells. As shown in Table 1, compound 5 was stimulants of NGF secretion in C6 cells (127.3 ± 10.3%). However, compound 5 induced significant cytotoxicity (62.9 ± 4.7%) at a concentration of 20 μM. Also, Compounds 2, 3 and 6 increased NGF secretion to 118.8 ± 3.6%, 128.2 ± 9.3% and 111.1 ± 7.1% of untreated control and nomal cell viability (84.5 ± 4.5%, 85.4 ± 18.0 and 104.9 ± 2.0, respectively).

The most potent stimulant of NGF release, conicaoside (3), may have a potential for neuroprotection via inducing NGF secretion and may deserve further investigation as a candidate for regulation of neurodegenerative diseases and diabetic polyneuropathy. The apparent activity of multiple components from this plant suggests the possibility of additive or synergistic effects which merits further investigation.