Our previous study on the secondary metabolites of a For-mosan soft coral Sinularia gibberosa TIXIER-DURIVAULT (Al-cyoniidae) has resulted in the isolation of a series of b-caryophyllene-related metabolites and xeniaphyllane-related metabolites.1—3)Some of these metabolites have been shown to exhibit cytotoxicity toward several caner cell lines.1,3)Our continuing investigation on the chemical constituents of this soft coral has again led to the isolation of one novel norhu-mulene 1, two new norxeniaphyllanes 2 and 3, three new xeniaphyllanes 4—6, and a new xeniaphyllane-derived diter-penoid 7 possessing a rare cyclic peroxyhemiketal (3,6-dihy-dro-1,2-dioxin-3-ol).2,4) We describe herein the isolation, structure elucidation and biological activity of these com-pounds.
The minced bodies of S. gibberosa were extracted exhaus-tively with EtOAc. The combined extract was concentrated under reduced pressure, and the residue was fractionated by open column chromatography on silica gel. The terpenoid-containing fractions (characterized by 1H-NMR measurement
in CDCl3) were selected for further purification, using open column chromatography on silica gel and normal phase HPLC to afford terpenoids 1—7.
Gibberosin N (1) displayed fourteen carbon signals in the 13C-NMR spectrum (Table 1), attributable to two methyls, five sp3methylenes, one sp3methine, one sp2methylene, two sp2methines, and three sp2quaternary carbons. The IR spec-trum displayed absorptions at 3423 and 1653 cm1 for hy-droxy group and carbon-carbon double bond, respectively. The NMR signals at dH 4.14 (dd, J10.4, 4.4 Hz) and dC 74.8 (CH) revealed the presence of a secondary hydroxy group in the molecule. From NMR data (Tables 1, 2) and the presence of hydroxy group, the molecular formula of 1 was suggested to be C14H22O, implying four degrees of unsatura-tion. This was further confirmed from the HR-ESI-MS which showed a ion peak at m/z 189.1641 ([MH2OH]). More-over, two trisubstituted double bonds (dC132.8, C, 130.4, C, 129.2, CH, and 127.1, CH and dH 5.18, dd, J8.4, 7.2 Hz and 4.84, dd, J10.0, 4.4 Hz) and one exocyclic double bond (dC153.2, C and 109.5, CH2and dH5.29, s and 5.09, s) were assigned in the structure. From the above data, 1 was sug-gested to possess a ring. The gross structure of 1 was succes-sively established by the assistance of 1H–1H COSY and HMBC correlations as shown in Fig. 1. The olefinic methyls (dH1.49, s and 1.59, s) attached at C-4 and C-11 were con-firmed by HMBC correlations from H3-13 to C-3, C-4, and C-5 and H3-12 to C-1, C-10, and C-11, respectively. The hy-droxy group was determined to be located at C-9 due to the HMBC correlations observed from H2-14 (d 5.09, s and 5.29, s) and H2-10 (d 2.02, m and 2.56, dd, J12.0, 4.0) to C-9 (d 74.8, CH). Thus, two methyl-containing double bonds and a hydroxy group were positioned at C-1/C-11, C-4/C-5 and C-9, respectively. The structure of 1 was thus establish-ed as a norhumulene. On the basis of above results, the struc-ture of 1 was established as 9-hydroxy-13-norhumulene-1E,4E,8(14)-triene.
Gibberosin O (2) was found to possess a molecular for-mula C21H32O4from the pseudomolecular ion peak appearing at m/z 371.2197 [MNa] in the HR-ESI-MS, correspond-ing to six degrees of unsaturation. The IR spectrum of
Novel Norhumulene and Xeniaphyllane-Derived Terpenoids from a
Formosan Soft Coral Sinularia gibberosa
Shin-Pin CHEN,aJui-Hsin SU,bHsiao-Chien YEH,cAtallah Fouad AHMED,aChang-Feng DAI,d
Yang-Chang WU,eand Jyh-Horng SHEU*,a,f
aDepartment of Marine Biotechnology and Resources, National Sun Yat-sen University; fAsia-Pacific Ocean Research
Center, National Sun Yat-sen University; Kaohsiung 804, Taiwan: bDepartment of Biological Science and Technology,
Mei-Ho Institute of Technology; 23 Pingguang Road, Neipu Hsiang, Pingtung 912, Taiwan: cDepartment of Planning and
Research, National Museum of Marine Biology and Aquarium; Pingtung 944, Taiwan: dInstitute of Oceanography,
National Taiwan University; Taipei 112, Taiwan: and eGraduate Institute of Natural Products, Kaohsiung Medical
University; Kaohsiung 807, Taiwan. Received September 24, 2008; accepted November 5, 2008
A novel skeletal norhumulene (1) and six xeniaphyllane-derived compounds, including norditerpenoids (2, 3) and diterpenoids (4—7), were isolated from the EtOAc extract of the Formosan soft coral Sinularia gibberosa. Their structures were elucidated by spectroscopic analysis. In vitro cytotoxic evaluation of the above metabolites revealed that 2 and 4 showed weak cytotoxicity toward a few cancer cell lines.
Key words diterpenoid; xeniaphyllane; Sinularia gibberosa; cytotoxic
© 2009 Pharmaceutical Society of Japan ∗ To whom correspondence should be addressed. e-mail: [email protected]
2 showed the presence of ester (1734 cm1) and ketone (1716 cm1) functionalities. This was further supported by the 13C-NMR signals appearing at d 170.8 (C), 213.3 (C), 216.8 (C), respectively. In the 1H-NMR spectrum, the signals at d 1.98 (1H, m), 2.41 (1H, m), 4.91 (1H, s) and 4.92 (1H, s) were found to be HMQC correlated with the carbon
sig-nals at d 47.0 (CH), 41.7 (CH) and 112.5 (CH2), respectively, indicating that 2 might be a b-caryophyllene-derived com-pound.1,2,5)The gross structure of 2 was successively estab-lished by the assistance of 1H–1H COSY and HMBC correla-tions as shown in Fig. 1. Accordingly, the C-5 and C-12 posi-tions of two keto-carbonyls 2 were interpreted by the HMBC
February 2009 163
Table 1. 13C-NMR Spectral Data of Compounds 1—7
C# 1a) 2b) 3c) 4b) 5b) 6a) 7b) 1 129.2 (CH)d) 47.0 (CH) 47.4 (CH) 46.9 (CH) 49.9 (CH) 44.5 (CH) 44.5 (CH) 2 25.4 (CH2) 27.5 (CH2) 27.4 (CH2) 27.4 (CH2) 27.5 (CH2) 26.8 (CH2) 30.5 (CH2) 3 39.0 (CH2) 30.2 (CH2) 30.0 (CH2) 30.1 (CH2) 30.5 (CH2) 29.8 (CH2) 39.6 (CH2) 4 132.8 (C) 48.3 (CH) 48.7 (CH) 48.2 (CH) 47.8 (CH) 47.5 (CH) 135.3 (C) 5 127.1 (CH) 216.8 (C) 217.4 (C) 216.8 (C) 217.1 (C) 217.2 (C) 124.5 (CH) 6 25.0 (CH2) 41.6 (CH2) 41.9 (CH2) 41.7 (CH2) 42.3 (CH2) 42.8 (CH2) 28.3 (CH2) 7 34.7 (CH2) 32.3 (CH2) 32.2 (CH2) 31.3 (CH2) 32.1 (CH2) 31.7 (CH2) 34.7 (CH2) 8 153.2 (C) 151.9 (C) 152.0 (C) 151.9 (C) 152.8 (C) 152.6 (C) 154.2 (C) 9 74.8 (CH) 41.7 (CH) 42.0 (CH) 41.6 (CH) 43.3 (CH) 43.0 (CH) 47.4 (CH) 10 49.9 (CH2) 34.0 (CH2) 34.2 (CH2) 34.1 (CH2) 36.9 (CH2) 33.4 (CH2) 34.0 (CH2) 11 130.4 (C) 48.1 (C) 48.2 (C) 48.2 (C) 36.6 (C) 40.5 (C) 41.2 (C) 12 16.7 (CH3) 213.3 (C) 213.3 (C) 213.6 (C) 36.9 (CH2) 77.6 (CH) 99.9 (C) 13 15.3 (CH3) 32.5 (CH2) 32.7 (CH2) 32.2 (CH2) 35.3 (CH2) 28.0 (CH2) 126.8 (CH) 14 109.5 (CH2) 29.5 (CH2) 29.3 (CH2) 34.8 (CH2) 215.1 (C) 126.1 (CH) 131.5 (CH) 15 70.3 (CH) 67.6 (CH) 81.4 (C) 40.8 (CH) 132.2 (C) 80.4 (C) 16 — — 25.7 (CH3) 18.4 (CH3) 63.0 (CH2) 19.4 (CH3) 17 20.1 (CH3) 23.9 (CH3) 25.7 (CH3) 18.4 (CH3) 21.5 (CH3) 66.8 (CH2) 18 17.0 (CH3) 17.1 (CH3) 17.0 (CH3) 19.3 (CH3) 16.3 (CH3) 16.8 (CH3) 19 112.5 (CH2) 112.7 (CH2) 112.5 (CH2) 111.6 (CH2) 112.1 (CH2) 112.6 (CH2) 20 16.4 (CH3) 16.5 (CH3) 16.3 (CH3) 16.5 (CH3) 16.0 (CH3) 16.3 (CH3) OAc 170.8 (C) 170.4 (C) 170.8 (C) 21.3 (CH3) 22.4 (CH3) 21.0 (CH3) OAc 171.1 (C) 21.1 (CH3)
a) Spectra recorded at 100 MHz in CDCl3at 25 °C. b) Spectra recorded at 125 MHz in CDCl3at 25 °C. c) Spectra recorded at 75 MHz in CDCl3at 25 °C. d) Attached protons were deduced by DEPT spectra.
Table 2. 1H-NMR Spectral Data of Compounds 1—7
H# 1a) 2b) 3c) 4b) 5b) 6a) 7b) 1 4.84 dd (10.0, 4.4)d) 1.98 m 1.99 m 2.00 m 1.47 m 1.62 m 2.58 dd (9.5, 9.5) 2a 2.02 m—2.14 m 1.73 m 1.76 m 1.78 m 1.60 m 1.56 m 1.63 m 2b 1.38 m 1.40 m 1.40 m 1.28 m 1.25 m 1.50 m 3a 1.98 m—2.03 m 1.65 m 1.66 m 1.66 m 1.66 m 1.63 m 1.98 m 3b 1.83 m 1.84 m 1.84 m 1.80 m 1.80 m 2.05 m 4 2.52 m 2.52 m 2.52 m 2.52 m 2.51 m 5 5.18 dd (8.4, 7.2) 5.37 dd (10.0, 9.5) 6a 2.24 m 2.50 m 2.50 m 2.48 m 2.50 m 2.49 m 2.02 m 6b 2.35 m 7a 1.76 m—2.35 m 2.44 m 2.45 m 2.46 m 2.47 m 2.46 m 2.25 m 7b 2.01 m 9 4.14 dd (10.4, 4.4) 2.41 m 2.42 m 2.42 m 2.40 m 2.41 m 2.32 q (9.5) 10a 2.02 m 2.03 m 2.05 m 1.95 m 1.55 m 1.49 m 2.23 dd (10.0, 9.5) 10b 2.56 dd (12.0, 4.0) 1.68 m 1.66 m 1.72 m 1.78 m 1.53 m 12 1.59 s 1.52 m 4.68 dd (9.2, 3.6) 13 1.49 s 2.35 m 2.35 m 2.38 m 2.31 m 2.16 m 5.87 d (10.5) 14 5.09 s; 5.29 s 1.77 m 1.76 m 1.94 m 5.32 dd (7.2, 6.8) 5.95 d (10.5) 15 4.88 m 3.79 m 2.63 septet (7.0) 16 1.45 s 1.10 d (7.0) 4.51 d (12.0); 4.60 d (12.0) 1.35 s 17 1.23 d (6.0) 1.25 d (6.3) 1.45 s 1.10 d (7.0) 1.73 s 3.59 d (12.5); 3.64 d (12.5) 18 1.18 s 1.20 s 1.21 s 0.95 s 1.01 s 1.11 s 19 4.91 s; 4.92 s 4.91 s; 4.92 s 4.91 s; 4.92 s 4.88 s; 4.89 s 4.88 s; 4.91s 4.86 s; 5.06 s 20 1.05 d (7.0) 1.05 d (6.9) 1.05 d (7.0) 1.03 d (7.0) 1.00 d (6.8) 1.60 s OAc 2.05 s 1.99 s 2.07 s OAc 2.13 s
a) Spectra recorded at 400 MHz in CDCl3at 25 °C. b) Spectra recorded at 500 MHz in CDCl3at 25 °C. c) Spectra recorded at 300 MHz in CDCl3at 25 °C. d) The J values (in Hz) in parentheses.
correlations observed from H-4 (d 2.52, m), H2-6 (d 2.50, m) and H3-20 (d 1.05, d, J7.0 Hz) to C-5 (d 216.8, C), and from H2-13 (d 2.35, m) and H3-18 (d 1.18, s) to C-12 (d 213.3, C). The acetoxy group was also determined to be lo-cated at C-15 due to the HMBC correlations observed from H2-14 (1.77, m) and H3-17 (d 1.23, d, J6.0 Hz) to C-15 (d 70.3, CH). Thus, the norxeniaphyllane framework of metabo-lite 2 and the lack of one methyl group at C-15 relative to other xeniaphyllane diterpenoids1,2,5)were suggested.
The relative stereochemistry of the four chiral centers at C-1, C-4, C-9, and C-11 in 2 was established on the basis of the NOE correlations (Fig. 2) observed in the NOESY spec-trum. Assuming the b orientation of H-9,1,2)it was found that H-9 exhibited NOE correlations with H-4, H-10b (d 1.68, m) and H3-18, but not with H-1 (d 1.98, m), and H3-20, while H-3a (d 1.65, m) displayed NOE interaction with H-1 and H3-20. These observations suggested that H-1, and H3-20 should be a-oriented. On the basis of the above findings and other detailed NOE interactions (Fig. 2), the relative structure of compound 2 was unambiguously established as (1S*,4S*,9R*,11S*)-15-acetoxy-16-norxeniaphylla-8(19)-en-5,12-dione.
Gibberosin P (3) had a molecular formula C19H30O3as es-tablished from its HR-ESI-MS (m/z 329.2093, [MNa]). The IR spectrum indicated the presence of hydroxy (3420 cm1) and carbonyl (1716 cm1) groups. The 1H- and 13 C-NMR spectroscopic data of 3 were quite similar to those of 2 except that the oxymethine carbon signal at d 70.3 (C-15) in
2 was found to be upfield shifted to 67.6 ppm in compound 3.
This was associated by the disappearance of the NMR sig-nals of acetate and the IR absorption band of the ester group in 3. Thus, compound 3 was elucidated as the deacetyl de-rivative of 2. The relative configurations at C-1, C-4, C-9, and C-11 in compound 3 were found to be identical to those of 2 due to the same NOE correlations displayed in NOESY spectra of 2 and 3. Compound 3 was thus identified as (1S*,4S*,9R*,11S*)-15-hydroxy-16-norxeniaphylla-8(19)-en-5,12-dione.
The molecular formula of gibberosin Q (4) was estab-lished as C22H34O4by HR-ESI-MS (m/z 385.2353 [MNa])
and NMR data (Tables 1, 2). As in the case of 2, the IR absorptions of 4 at 1734, and 1716 cm1also suggested the presence of ester and ketone moieties, respectively. The ester function was also represented by one acetoxy group from the NMR signals at dC 170.4 (C) and 22.4 (CH3); dH 1.99 (s). Comparison of the 13C-NMR spectroscopic data of com-pound 4 with those of comcom-pound 2 (Table 1) indicated that compound 4 has the same carbon skeleton from C-1 to C-14, while two tertiary methyl groups (dH 1.45, s, 6H; dC25.7, CH3, 2C) were found to be attached at C-15 in 4 by show-ing HMBC correlations from protons of these two methyls to C-14 and C-15. Thus, gibberosin Q (4) was identified as (1S*,4S*,9R*,11S*)-15-acetoxyxeniaphylla-8(9)-en-5,12-dione.
Gibberosin R (5) exhibited a pseudomolecular ion peak in the HR-ESI-MS at m/z 327.2301, appropriate for a molecular formula of C20H32O2. It differs from 4 in the absence of an acetoxy group as revealed from the disappearance of IR absorption band of ester function and NMR signals of ac-etate group. The carbon of the side chain carbonyl carbon (d 215.1, C) was found to be C-14 due to the HMBC correla-tions observed from H2-13 (d 2.31, m), H-15 (d 2.63, septet, J7.0 Hz), and H3-16 and H3-17 (d 1.10, d, J7.0 Hz) to the carbon signal at d 215.1. On the basis of the above findings, the molecular framework of compound 5 was determined as shown in Fig. 1. Furthermore, the analysis of the NOESY spectrum of 5 revealed 5 possesses the same relative configu-rations at C-1, C-4, C-5, C-9, and C-11 as those in 2—4. Thus, the relative structure of metabolite 5 was determined as (1S*,4S*,9R*,11S*)-xeniaphylla-8(19)-en-5,14-dione.
Gibberosin S (6) was found to possess a molecular for-mula C24H36O5, as indicated from its HR-ESI-MS at m/z 427.2462 [MNa]. It also exhibited IR absorptions at 1736 and 1717 cm1, suggesting the presence of ester and ketone moieties. Comparison of the 1H- and 13C-NMR data of com-pound 6 with those of 2—5 revealed that 6 is also a 5-oxoxe-niaphyllane with a trisubstituted double bond and two ace-toxy groups in the side chain. The HMBC correlations (Fig. 1) observed from H3-18 (d 1.01, s) to C-1 (d 44.5, CH), C-10 (d 33.4, CH2), C-11 (d 40.5, C) and an oxymethine carbon at d 77.6 (CH) assigned this oxymethine carbon as C-12. This finding together with the upfield shift of C-11 relative to
Fig. 1. Key 1H–1H COSY and HMBC Correlations for 1, 2 and 4—7
those of metabolites 2—4 (dC 48.1—48.2), and the down-field shift of C-11 relative to that of 5 (dC36.6), indicated the C-12 attachment of an acetoxy group. Furthermore, the pro-tons of an oxymethylene group in 6 (dH4.51 and 4.60, each 1H, d, J12.0 Hz) were found to exhibit HMBC correlations with the carbonyl carbon of another acetoxy group (dC170.8, C) and an olefinic carbon (dC 132.2, C, C-15), while this olefinic carbon was found to be correlated with the protons of an olefinic methyl (dH 1.73, s,). Therefore, the trisubsti-tuted double bond was positioned between C-14 and C-15 where an acetoxymethyl and a methyl were the substituents at C-15. The 1H–1H COSY correlations found from H-12 (d 4.68, dd, J9.2, 3.6 Hz) to H2-13 (d 2.16, m) and from H2-13 to the olefinic proton (d 5.32, dd, J7.2, 6.8 Hz, H-14) fur-ther supported the C-14/C-15 position of the double bond. This double bond was determined to have a Z geometry on the basis of the NOE interaction found between H-14 and H3-17. Furthermore, the analysis of the NOESY spectrum of
6 revealed the similar stereochemistries at C-1, C-9, C-10,
and C-11 as those in 2—5. Therefore, the relative structure of compound 6 was established as (1S*,4S*,9R*,11S*,14Z)-12,16-diacetoxyxeniaphylla-8(19),14-dien-5-one.
Sinugibberoside F (7) was found to possess a molecular formula C20H30O4 as established from its HR-ESI-MS (m/z 357.2044, [MNa]), implying six degrees of unsaturation. The IR spectrum indicated the presence of hydroxy (nmax 3420 cm1) group in the molecule. The 1H-NMR data (Table 2) revealed the presence of one upper field shifted methyl (d 1.11, s), one olefinic methyl (d 1.60, s) one trisubstituted double bond (d 5.37, dd, J10.0, 9.5 Hz), one 1,1-disubsti-tuted double bond (d 4.86, s and 5.06, s), and two 1H–1H COSY correlated ring-juncture methines (d 2.58, dd, J9.5, 9.5 Hz and 2.32, q, J9.5 Hz), characteristic for a caryophyl-lene moiety in 7.3)The 1H- and 13C-NMR data of 7 spectra were very similar to those of a known compound sinugib-beroside C (8),2) except that a trisubstituted epoxide at C-4/C-5 in 8 was replaced by a trisubstituted double bond (dH 5.37, dd, J10.0, 9.5 Hz, H-5; dC135.3, C, C-4; dC124.5, CH, C-5) in 7. The molecular framework of 7 was further es-tablished by the 1H–1H COSY and HMBC correlations as il-lustrated in Fig. 1. The E geometry of the 4,5-endocyclic double bond in 7 was indicated by the absence of NOE corre-lation between the olefinic methyl protons (d 1.60, s) at-tached at 4 and H-5 (d 5.37, dd) and the upfield shift of C-20 (d 16.3). Further NOE analysis revealed that 7 possessed the same relative configurations at C-1, C-9, C-11, C-12, and C-15 as those of the known metabolite 8.2) Based on the above results, the relative structure of 7 was determined as (1S*,9R*,11S*,12R*,15R*,4E)-12,15-epidioxy-xeniaphylla-4,8(19),13-trien-12,17-diol.
Cytotoxicity of metabolites 1—7 toward a limited panel of cancer cell lines was evaluated. Compound 2 was found to exhibit weak cytotoxicity toward Hep G2 (human hepatocel-lular carcinoma) and A549 (human lung carcinoma) cell lines with IC50’s of 18.7 and 19.5mg/ml, respectively. Also, metabolite 4 showed weak cytotoxicity (IC50 11.0mg/ml) toward A549 cells. Other metabolites were found to be inac-tive against the growth of the above three cancer cell lines.
Experimental
Optical rotations were measured on a Jasco DIP-1000 digital polarimeter. IR spectra were recorded on a JASCO FT-5300 infrared spectrophotometer.
NMR spectra were recorded on a Bruker AVANCE DPX 300 FT-NMR at 300 MHz for 1H and 75 MHz for 13C, or on a Varian Mercury Plus 400
FT-NMR at 400 MHz for 1H and 100 MHz for 13C, or on a Varian Unity INOVA
500 FT-NMR at 500 MHz for 1H and 125 MHz for 13C, in CDCl
3using TMS
as an internal standard. LR-MS and HR-MS were obtained by ESI on a Bruker APEX II mass spectrometer. Silica gel (Merck, 230—400 mesh) was used for column chromatography. Precoated silica gel plates (Merck, Kiesel-gel 60 F-254, 0.2 mm) were used for analytical TLC. High-performance liq-uid chromatography (HPLC) was performed on a Hitachi L-7100 apparatus equipped with a Bischoff refractive index detector and a Merck Hibar Si-60 column (250 mm21 mm, 7 mm).
Animal Material The soft coral Sinularia gibberosa was collected by hand using scuba off the coast of northeastern Taiwan, in May 2004, at a depth of 15—20 m, and was stored in a freezer until extraction. A voucher specimen was deposited in the Department of Marine Biotechnology and Resources, National Sun Yat-sen University (voucher no. SC-20040621-5).
Extraction and Isolation The bodies of S. gibberosa (1.3 kg fresh weight) were minced and extracted exhaustively with EtOAc, and the extract was concentrated under reduced pressure to give a dark brown viscous residue (15.4 g). The residue was fractionated by open column chromatogra-phy on silica gel using n-hexane and n-hexane–EtOAc mixture of increasing polarity to yield 32 fractions. Fraction 15, eluting with n-hexane/EtOAc (5 : 1), was further purified by silica gel column using n-hexane/EtOAc (5 : 1) to give compound 5 (1.2 mg). A combined mixture of fractions 17—19, eluting with n-hexane/EtOAc (5 : 1→4 : 1), was purified by normal phase HPLC using n-hexane/EtOAc (4 : 1) to give compounds 2 (1.5 mg) and 4 (12.4 mg), and then using n-hexane/acetone (5 : 1) to give compounds 1 (1.0 mg) and 6 (1.1 mg). Fraction 20, eluting with n-hexane/EtOAc (3 : 1), was further puri-fied by normal phase HPLC using n-hexane/acetone (5 : 1 to 3 : 1) to give compound 3 (3.8 mg). Fraction 22, eluting with n-hexane/EtOAc (1 : 1), was further purified by normal phase HPLC using n-hexane/acetone (2 : 1), to give compound 7 (1.9 mg).
Gibberosin N (1): Colorless oil; [a]D
2516.0 (c0.3, CHCl
3); IR (KBr)
nmax3423, 1653 cm1;
1H- and 13C-NMR data, see Tables 1 and 2; ESI-MS
m/z 189 ([MH2OH]); HR-ESI-MS m/z 189.1641 [MH2OH]
(Calcd for C14H21, 189.1643).
Gibberosin O (2): Colorless oil; [a]D
259.8 (c0.6, CHCl
3); IR (KBr)
nmax1734, 1716 cm1;
1H- and 13C-NMR data, see Tables 1 and 2;
ESI-MS m/z 371 ([MNa]); HR-ESI-MS m/z 371.2197 [MNa](Calcd for C21H32O4Na, 371.2198).
Gibberosin P (3): Colorless oil; [a]D
255.0 (c0.6, CHCl
3); IR (KBr)
nmax3420, 1716 cm1;
1H- and 13C-NMR data, see Tables 1 and 2;
ESI-MS m/z 329 ([MNa]); HR-ESI-MS m/z 329.2093 [MNa](Calcd for C19H30O3Na, 329.2092).
Gibberosin Q (4): Colorless oil; [a]D
254.8 (c1.2, CHCl
3); IR (KBr)
nmax1734, 1716 cm1;
1H- and 13C-NMR data, see Tables 1 and 2;
ESI-MS m/z 385 ([MNa]); HR-ESI-MS m/z 385.2353 [MNa](Calcd for C22H34O4Na, 385.2355).
Gibberosin R (5): Colorless oil; [a]D
2529.5 (c0.4, CHCl
3); IR (KBr)
nmax 1717 cm1;
1H- and 13C-NMR data, see Tables 1 and 2; ESI-MS
m/z 327 ([MNa]); HR-ESI-MS m/z 327.2301 [MNa] (Calcd for
C20H32O2Na, 327.2300).
Gibberosin S (6): Colorless oil; [a]D
2517.3 (c0.7, CHCl
3); IR (KBr)
nmax1736, 1717 cm1;
1H- and 13C-NMR data, see Tables 1 and 2;
ESI-MS m/z 427 ([MNa]); HR-ESI-MS m/z 427.2462 [MNa](Calcd for C24H36O5Na, 427.2460).
Sinugibberoside F (7): Clorless oil, [a]D
25 32.0 (c0.6, CHCl 3); IR
(neat) nmax 3420, 1647 cm1;
1H- and 13C-NMR data, see Tables 1 and
2; ESI-MS m/z 357 ([MNa]); HR-ESI-MS m/z 357.2044 (Calcd for C20H30O4Na, 357.2042).
Cytotoxicity Testing Cell lines were purchased from the American Type Culture Collection (ATCC). Cytotoxicity assays of the test compounds 1—7 were performed using the MTT [3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide] colorimetric method.6,7)
Acknowledgment Financial support was provided by Ministry of Edu-cation (96C031702) and National Science Council of Taiwan (NSC 95-2113-M-110-011-MY3) awarded to J.-H. Sheu.
References
1) Ahmed A. F., Su J.-H., Shiue R.-T., Pan X.-J., Kuo Y.-H., Sheu J.-H., J. Nat. Prod., 67, 592—597 (2004).
2) Chen S.-P., Ahmed A. F., Dai C.-F., Lu C.-K., Hu W.-P., Wang J.-J., Sheu J.-H., Tetrahedron, 62, 6802—6806 (2006).
3) Chen S.-P., Chao C.-H., Huang H.-C., Wu Y.-C., Lu C.-K., Dai C.-F., Sheu J.-H., Bull. Chem. Soc. Jpn., 79, 1547—1551 (2006).
4) Snider B. B., Shi Z., J. Am. Chem. Soc., 114, 1790—1800 (1992). 5) Groweiss A., Kashman Y., Tetrahedron, 39, 3385—3396 (1983). 6) Alley M. C., Scudiero D. A., Monks A., Hursey M. L., Czerwinski M.
J., Fine D. L., Abbott B. J., Mayo J. G., Shoemaker R. H., Boyd M. R., Cancer Res., 48, 589—601 (1988).
7) Scudiero D. A., Shoemaker R. H., Paull K. D., Monks A., Tierney S., Nofziger T. H., Currens M. J., Seniff D., Boyd M. R., Cancer Res., 48, 4827—4833 (1988).
