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Isolation of Two New Meroterpenoids from Sargassum siliquastrum
Isolation of Two New Meroterpenoids from Sargassum siliquastrum
Bulletin of the Korean Chemical Society. 2014. Sep, 35(9): 2867-2869
Copyright © 2014, Korea Chemical Society
  • Received : April 24, 2014
  • Accepted : May 30, 2014
  • Published : September 20, 2014
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About the Authors
Jung-Im Lee
Division of Marine Environment and Bioscience, Korea Maritime and Ocean University, Busan 606-791, Korea
Byung Ju Park
Busan Science High School, Busan 604-828, Korea
Hojun Kim
Division of Marine Environment and Bioscience, Korea Maritime and Ocean University, Busan 606-791, Korea
Youngwan Seo
Ocean Science & Technology School, Korea Maritime and Ocean University, Busan 606-791, Korea

Abstract
Keywords
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Experimental
General Experimental Procedures . NMR spectra were recorded in CD 3 OD on a Varian Mercury 300 spectrometer. 1 H and 13 C NMR spectra were measured using standard Varian pulse sequence programs at 300 MHz and 75 MHz, respectively. Optical rotations were taken on a Perkin-Elmer polarimeter 341 using a 5 cm cell. All chemical shifts were recorded with respect to residual CD 3 OD peaks. Mass spectra were obtained at the Korean Basic Science Institute, Seoul, Korea. HPLC was performed using a Dionex P580 isocratic pump equipped with a Shodex RI detector. All solvents used were spectral grade or were distilled from glass prior to use.
1H and13C NMR data for compounds2and3isolated fromSargassum siliquastrum
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Measured in CDCl3 at 300 and 75 MHz, respectively. Assignments were aided by 1H gDQCOSY, TOCSY, DEPT, gHMQC, and gHMBC experiments.
Plant Material . The brown alga Sargassum siliquastrum was collected by hand in February 2007, along the shore of Cheju Island, Korea and identified by Dr. Jee Hee Kim. A voucher specimen (No J07-11) was deposited at the Division of Marine Environment & Bioscience, Korea Maritime University, Korea.
Extraction and Isolation . Shade-dried samples of S . siliquastrum were ground to powder and extracted successively for 24 h with a mixture (1:1) of acetone-CH 2 Cl 2 (2 L × 2) and MeOH (2 L × 2). The combined crude extract (59.6 g) was evaporated under reduced pressure and then the residue was partitioned between CH 2 Cl 2 and water. The organic layer was further partitioned between 85% aq. MeOH and n -hexane, and the aqueous layer was fractionated with n -BuOH and H 2 O. The resulting four fractions were evaporated to dryness in vacuo , to yield n -hexane (7.8 g), 85% aq. MeOH (8.7 g), n -BuOH (3.3 g), and water (41.9 g) fractions, respectively. The 85% aq. MeOH fraction was separated into six subfractions by C 18 (YMC-GEL ODS-A, 12 nm, S-75 mm) reversed-phase vacuum flash chromatography eluting with stepwise gradient mixtures of MeOH and water (50%, 60%, 70%, 80%, and 90% aq. MeOH, and 100% MeOH). Fraction 6 was separated by reversed-phase HPLC (ODS-A, 73% aq. MeOH) to give 6 subfractions (6-1~4), in order of elution. Subfraction 6-1 was further separated by reversedphase HPLC (ODS-A, 75% aq. CH 3 CN) to give 3 (5.5 mg). Subfraction 6-2 was also further separated by reversed-phase HPLC with 78% aq. CH 3 CN to yield 1 (3.5 mg) and 2 (3.3 mg).
Sargachromanol J (1) : A colorless gum;
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: +27.27° ( c 0.13, MeOH); IR (NaCl): ν max = 3350, 1711 cm −1 ; 1 H and 13 C NMR, see Tables 7 and Tables 8; HREIMS m/z 430.3080 [M] + (calcd for C 27 H 42 O 4 , 430.3083).
Sargachromanol Q (2) : A colorless gum;
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: +42.86° ( c 0.73, MeOH); IR (NaCl): ν max = 3350, 1621 cm −1 ; UV (MeOH) λ max (log ε) 224 (3.86) nm; 1 H and 13 C NMR, see Tables 7 and Tables 8; HREIMS m/z 428.2915 [M] + (calcd for C 27 H 40 O 4 , 428.2927).
Sargachromanol R (3) : A colorless gum;
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: +12.67° ( c 0.12, MeOH); IR (NaCl): ν max = 3350, 1682, 1620 cm −1 ; UV (MeOH) λ max (log ε) 237 (3.77) nm; 1 H and 13 C NMR, see Table 6; HREIMS m/z 424.2609 [M] + (calcd for C 27 H 38 O 3 , 424.2614).
Cell Cytotoxicity : Cytotoxic levels of the isolated compounds on cultured cells were measured using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay [6b], which is based on the conversion of MTT to MTT-formazan by mitochondrial enzyme. The cells were grown in 96-well plates at a density of 5 × 10 3 cells/well. After 24 h, cells were washed with fresh medium and treated with different concentrations of samples. After incubation for 48 h, the cells were rewashed and incubated with 100 μL of MTT (1 mg/mL) for 4 h. Finally, 150 μL of DMSO was added to solubilize the formed formazan crystals. The amount of formazan was determined by measuring the absorbance at 540 nm using a multidetection microplate fluorescence spectrophotometer synergy HT (Bio-Tek instruments Inc., Winooski, VT). Relative cell viability was determined by the amount of MTT converted into formazan. Viability of cells was quantified as a percentage compared with the control, and dose response curves were developed.
Acknowledgements
Mass spectral data were kindly provided by Korea Basic Science Institute. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2012R1-A1A2002851) and is the outcome of a Manpower Development Program for Marine Energy by the Ministry of Land, Transport and Maritime Affairs (MLTM).
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