Notes Bull. Korean Chem. Soc. 2010, Vol. 31, No. 1 227 DOI 10.5012/bkcs.2010.31.01.227 Phytochemical Constituents from the Flowers of Gymnaster koraiensis and Their Cytotoxic Activities in vitro Il Kyun Lee, Ki Hyun Kim, Shi Yong Ryu, † Sang Un Choi, † and Kang Ro Lee * Natural Products Laboratory, College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea * E-mail: krlee@skku.ac.kr † Research Institute of Chemical Technology, Teajeon 305-600 Received September 10, 2009, Accepted November 30, 2009 Key Words: Gymnaster koraiensis, Sesquiterpene glucopyranoside, Polyacetylene, Cytotoxicity HO HO O H O OH H H H HO HO O H O OH H H H H HO HO OH OH OH OH H H H H H H H H (a) (b) Figure 1. Key HMBC ( ) (a) and NOESY ( ) (b) correlations of 1. Gymnaster koraiensis (Nakai) Kitamura (Compositae) is widely distributed in the northern parts of Korea. This indi- genous herb is used as a folk medicine for antitussive and anti- bacterial activities. 1 Previous phytochemical studies on this plant showed the presence of polyacetylenes, and benzofurans. 2,3,4 We have recently reported the isolation of sesquiterpenes and flavonoids from this plant. 5 In a continuing study on this source, we have further isolated two new sesquiterpene glucopyrano- sides (1-2), together with ten known compounds (3-12) by repeated column chromatography of the EtOH extract. Com- pounds 3-12 were identified as gymnasterkoreayne B (3), 3 gymnasterkoreayne E (4), 3 gymnasterkoreayne F (5), 3 1,9(Z), 16-heptadecatriene-4,6-diyne-3,8-diol (6), 3,6 apigenin (7), 7 na- ringenin (8), 8,9 apigenin-3-O-β-D-glucopyranoside (9), 10 quer- cetin-3-O-β-D-glucopyranoside (10), 10 isorhamnetin-3-O-β-D- glucopyranoside (11), 12 apigenin-3-O-β-D-glucuronide (12) 7 by comparing the 1 H-NMR, 13 C-NMR, and mass spectral data with the literature data. Compounds 7-12 were isolated from this plant for the first time. The isolated compounds were tested for their cytotoxicity against four human tumor cell lines in vitro using the SRB assay. Compound 1 was obtained as colorless gum with a molecular formula of C21H36O8 from the [M+Na] + peak at m/z 439.2306 (calcd. for C21H36O8Na : 439.2308) in the positive-ion HRFA- BMS. The IR spectrum indicated that 1 possessed a hydroxyl (3386 cm -1 ) group and a C=C double bond (1650 cm -1 ). In the 13 C-NMR (including DEPT) spectrum, 21 carbon signals appear- ed, which included four methyl carbons at δC = 21.9, 21.9, 21.8 and 9.3, two methylene carbons at δC = 32.6 and 30.8, three oxygenated methine carbons at δC = 81.3, 79.6 and 76.6, two olefinic carbons at δC = 136.4 and 120.6, three methine carbons at δC = 52.1, 51.9 and 28.9, one quaternary carbon at δ C = 42.4, and six signals assignable to the glucose moiety (δ C = 104.6, 78.4, 77.3, 76.1, 72.1, and 63.4). These data indicated that compound 1 was a eudesmane type sesquiterpene gluco- pyranoside. 13 Moreover, the above NMR data, except for the glucose part, were similar to 1β,6β-dihydroxy-7-epi-eudesm- 3-ene isolated from Pluchea dioscoridis. 13 The differences were the chemical shifts at C-1, C-6, and C-9 : δ C-1 = 79.6, δ C-6 = 76.6 and δC-9 = 81.3 in 1, and δC-1 = 76.6, δC-6 = 68.4 and δC-9 = 35.3 in 1β,6β-dihydroxy-7-epi-eudesm-3-ene, 13 implying that 1 was glycosylated at C-6 and oxygenated at C-9. The coupling constant (J = 7.5 Hz) of the anomeric proton at δH = 4.36 of D-glucose was in the β-form. 14 The glycosidic position was established by HMBC, with a long-range correlation observed between H-1′ (δ H = 4.36, d, J = 7.5 Hz) and C-6 (δ C = 76.6) (Figure 1). Thus, the structure of 1 was 1,6,9-trihydroxy-trans- eudesm-3-ene-6-O-β-D-glucopyronoside. The configuration of the hydroxyl group at C-1 was β-form based on the J value (δC = 3.69, dd, J = 11.5, 6.3 Hz) 15,16 and NOESY spectrum (Figure 1). The configurations of hydroxyl groups at C-6 and C-9 were β- and α-forms, respectively, based on the NOESY correlations: the correlation of H-6 with H-5 (not with H-7), and the correlations of H-9 with H-7 and H-14 (Figure 1). The proposed structure of 1 was in accordance with 1 H- 1 H COSY, HMQC, HMBC, and NOESY spectra. Therefore, the structure of 1 was 1β,6β,9α-trihydroxy-trans-eudesm-3-ene-6-O-β-D- glucopyranoside. Compound 2 was obtained as colorless gum with a molecular formula of C21H36O9 from the [M+Na] + peak at m/z 455.2259 (calcd. for C21H36O9Na : 455.2257) in the positive-ion HRFA- BMS. The IR spectrum indicated that 2 possessed a hydroxy (3382 cm -1 ) and a C=C double bond (1658 cm -1 ). The NMR spectra of 2 were similar to those of compound 1, except for an additional oxygenated carbon signal in the 13 C-NMR spectrum of 2; four oxygenated carbon signals (δC 81.1, 80.5, 79.5 and 72.8) exist in 2, with only three oxygenated carbon signals (δC 81.3, 79.6 and 76.6) in 1. The coupling pattern of methyl pro- tons at C-12 and C-13 in the 1 H-NMR spectrum was different [δ H = 1.00 (d), 0.95 (d), J = 6.3 Hz in 1; δ H = 1.36 (s), 1.25 (s) in 2]. The position of the hydroxylated carbon at δC = 72.8 was