A New Noreudesmane-type Sesquiterpenoid from Alpinia oxyphylla

Experimental

General Procedures. IR spectra were recorded on a JASCO FT-IR 4100 spectrophotometer (Jasco, Japan). Optical rotations were measured using a JASCO DIP-1000 polarimeter (Jasco, Japan). The NMR spectra were recorded on Bruker ADVANCE III 400 MHz and ADVANCE 500 MHz (Bruker, Germany) spectrometers. The HR-ESI-MS spectra were performed on maXis 4G mass spectrometer (Bruker, Germany). Preparative HPLC was performed using a Waters 515 HPLC Pump with a Waters 2996 Photodiode-array detector and YMC J'sphere ODS-H80 column (4 μm, 150 × 20 mm, USA). Column chromatography was perform-ed using a silica gel (70-230 mesh, Merck) and Lichroprep RP-18 (40-63 μm, Merck). TLC was performed using aluminum plates precoated with Kieselgel 60 F254 (Merck).

Plant Materials. The dried fruits of A. oxyphylla were purchased from Kyungdong herbal market, Seoul, Korea, in March 2011. The plant material was identified by Kyong Soon Lee, Emeritus Professor, Chungbuk National University. A voucher specimen (CBNU-11AO) was deposited at the Herbarium of the College of Pharmacy, Chungbuk National University, Korea.

Extraction and Isolation. Dried fruits of A. oxyphylla (3 Kg) were extracted with three times MeOH at room temper-ature. After filtration and evaporation of the solvent under reduced pressure, the combined methanol extract (470 g) was suspended in water (1.5 L), and partitioned with n-hexane, CH2Cl2 and EtOAc to afford extracts of n-hexane (66.3 g), CH2Cl2 (156.1 g), EtOAc (24.6 g) and water layer, respectively. The CH2Cl2-soluble extract (156.1 g) was sub-jected to a silica gel column chromatography with a solvent system (n-hexane:CH2Cl2 = 2:1 to CH2Cl2:MeOH = 1:1) to give six fractions (AOC1 - AOC6). Fraction 1 (35.5 g) was separated over a silica gel column with a solvent system (n-hexane:CH2Cl2 = 5:1 to CH2Cl2:MeOH = 1:1) to give seven subfractions (AOC1-1 - AOC1-7). AOC1-4 (8 g) was chromatographed on a silica gel column using a gradient of CH2Cl2:MeOH (1:0 to 0:1) to obtain ten subfractions. AOC1-4-7 (3 g) was purified by a silica gel column chromato-graphy with a gradient of CH2Cl2:MeOH (1:0 to 0:1) to afford compounds 10 (251.3 mg) and 2 (1 g). Compound 3 (103 mg) was obtained from AOC1-4-7 by recrystallization in MeOH. AOC1-5 (5 g) was subjected to a MCI gel MPLC with a gradient of H2O:acetone (1:0 to 0:1) to afford five subfractions (AOC1-5-1 - AOC1-5-5). AOC1-5-3 (106 mg) was separated by preparative HPLC with a gradient of MeCN:H2O (1:5 to 1:0) to afford compounds 1 (7 mg) and 14 (3 mg). Fraction 2 (5 g) was subjected to a RP gel MPLC using a gradient of MeOH:H2O (3:7 to 1:0) to yield seven subfractions (AOC2-1 - AOC2-7). AOC2-3 (300 mg) was separated by using preparative HPLC with a gradient of MeCN:H2O (1:5 to 1:0), resulting in the isolation of compounds 4 (2.1 mg), 5 (5.2 mg), 8 (10 mg), and 13 (3.7 mg). AOC2-4 (350 mg) was purified by using preparative HPLC with a gradient of MeCN:H2O (1:5 to 1:0) to yield compounds 9 (3 mg), 11 (1.1 mg) and 16 (3 mg). AOC2-5 (300 mg) was also purified by using preparative HPLC with gradient of MeCN:H2O (2:5 to 1:0) to yield compound 7 (4 mg). AOC2-6 (215 mg) was separated by using preparative HPLC with gradient of MeCN:H2O (2:5 to 1:0) to yield compounds 12 (5 mg) and 15 (4 mg). Fraction 4 (26.1 g) was chromatographed on a silica gel column eluted with a solv-ent system (n-hexane:CH2Cl2 = 2:1 to CH2Cl2:MeOH = 1:1) to give four fractions (AOC4-1 - AOC4-4). AOC4-1 (3 g) was subjected to a RP gel MPLC using a gradient of H2O: MeCN (1:0 to 4:6) to yield ten subfractions (AOC4-1-1 - AOC4-1-10). AOC4-1-5 (100 mg) was purified by using preparative HPLC with gradient of MeCN:H2O (2:5 to 5:5) to yield compound 6 (6.5 mg).

4-Methoxy-oxyphyllenone A (1): Yellow gum; +59.0 (c 0.1, MeOH); IR (KBr) νmax 3271, 1647 cm−1; 1HNMR (500 MHz, CD3OD) and 13C NMR (125 MHz, CD3OD), see Table 1; HR-ESI-MS m/z: 225.1485 [M+H]+ (calcd. for C13H21O3, 225.1491).

Measurement of NO Production and Cell Viability Assay. The nitrite concentration in the medium was deter-mined as an indicator of NO production according to the Griess method previously described.23 Briefly, RAW 264.7 cells were seeded into 96-well tissue culture plates at a density of 2 × 105 cells/mL, and stimulated with 1 μg/mL of LPS in the presence or absence of compounds. After incubation at 37 °C and 5% CO2 atmosphere for 24 h, 100 μL of cell-free supernatant was mixed with 100 μL of Griess reagent containing equal volumes 0.2% (w/v) sulfanilamide in 5% (w/v) phosphoric acid and 0.2% (w/v) of N-(1-naphthyl)ethylenediamine solution to determine nitrite pro-duction. The absorbance was measured at 540 nm by a microplate reader. The remaining cells after Griess assay were used for viability with the CCK (Dojindo, Tokyo, Japan)-based colorimetric assay.