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New cembrane diterpenoids from a Hainan soft coral Sinularia sp.

Yang B, Zhou X, Huang H, Yang XW, Liu J, Lin X, Li X, Peng Y, Liu Y - Mar Drugs (2012)

Bottom Line: Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp.Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites.Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Marine Bio-Resources Sustainable Utilization, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China. bingo525@163.com

ABSTRACT
Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp. Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites. Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

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Key HMBC correlations 1 and 5.
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marinedrugs-10-02023-f002: Key HMBC correlations 1 and 5.

Mentions: Compound 1 was isolated as a colorless oil. The HRESIMS of 1 established its molecular formula as C21H38O6, indicating three unsaturations. Resonances due to olefinic carbons (δC 133.9, 128.7), and one carboxyl (δC 178.9) in the 13C NMR spectrum accounted for two double-bond equivalents, indicating that 1 was a monocyclic compound (Table 1). Signals for a vinyl methyl at δ 1.68 (3H, s), one methoxy group at δ 3.68 (3H, s), a methyl doublet at δ 1.17 (3H, d, J = 7.0 Hz), and two tertiary oxygenated methyl groups at δ 1.15 (3H, s), and 1.08 (3H, s) were observed in the 1H NMR spectrum (Table 2). Carbon signals at δ 70.6, 71.0, 75.3, and 75.7, and two proton signals at δ 3.52, and 3.65 indicated the presence of two secondary and two tertiary hydroxyl groups. A signal at δ 5.43 attributed to an olefinic proton, together with a methyl carbon signal at δ 17.0, indicated the E configuration for this double bond. These data suggested that 1 was a rearranged cembrane. Key HMBC correlations from H3-20 to C-13, C-12, and C-11; H-11 to C-12, C-10, and C-20; H3-19 to C-7, C-8, and C-9; H-7 to C-9, C-6, and C-19; H3-18 to C-5, C-4, and C-3; and H-13 to C-14, and C-1 established the 14-membered ring structure of 1 (Figure 2). The isopropyl acid group was found based on the HMBC correlations observed from H3-21 to C-1, C-15, and C-16; H-15 to C-1, C-2, C-21, and C-16. Furthermore, the methoxyl substituent was shown to be connected to position C-16 on the basis of the HMBC correlation between the oxymethyl protons (δH 3.68) and the carbonyl carbon (δC 178.9). The NMR spectra of compound 1 were almost identical with those of sinuflexibilin [20] with the exception that the exo-methylene proton resonances of the latter were replaced by a methyl doublet. The stereochemistry of 1 was determined on the basis of the chemical shift and NOESY spectrum (Figure 3). NOE correlations from H-3 to H-1, H-11, H3-18 and from H-11 to H-20 indicated that all four hydroxy groups in 1 were β-oriented and H-1, H-3, H-11, H3-18, and CH3-20 were α-oriented with respect to this ring.


New cembrane diterpenoids from a Hainan soft coral Sinularia sp.

Yang B, Zhou X, Huang H, Yang XW, Liu J, Lin X, Li X, Peng Y, Liu Y - Mar Drugs (2012)

Key HMBC correlations 1 and 5.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475270&req=5

marinedrugs-10-02023-f002: Key HMBC correlations 1 and 5.
Mentions: Compound 1 was isolated as a colorless oil. The HRESIMS of 1 established its molecular formula as C21H38O6, indicating three unsaturations. Resonances due to olefinic carbons (δC 133.9, 128.7), and one carboxyl (δC 178.9) in the 13C NMR spectrum accounted for two double-bond equivalents, indicating that 1 was a monocyclic compound (Table 1). Signals for a vinyl methyl at δ 1.68 (3H, s), one methoxy group at δ 3.68 (3H, s), a methyl doublet at δ 1.17 (3H, d, J = 7.0 Hz), and two tertiary oxygenated methyl groups at δ 1.15 (3H, s), and 1.08 (3H, s) were observed in the 1H NMR spectrum (Table 2). Carbon signals at δ 70.6, 71.0, 75.3, and 75.7, and two proton signals at δ 3.52, and 3.65 indicated the presence of two secondary and two tertiary hydroxyl groups. A signal at δ 5.43 attributed to an olefinic proton, together with a methyl carbon signal at δ 17.0, indicated the E configuration for this double bond. These data suggested that 1 was a rearranged cembrane. Key HMBC correlations from H3-20 to C-13, C-12, and C-11; H-11 to C-12, C-10, and C-20; H3-19 to C-7, C-8, and C-9; H-7 to C-9, C-6, and C-19; H3-18 to C-5, C-4, and C-3; and H-13 to C-14, and C-1 established the 14-membered ring structure of 1 (Figure 2). The isopropyl acid group was found based on the HMBC correlations observed from H3-21 to C-1, C-15, and C-16; H-15 to C-1, C-2, C-21, and C-16. Furthermore, the methoxyl substituent was shown to be connected to position C-16 on the basis of the HMBC correlation between the oxymethyl protons (δH 3.68) and the carbonyl carbon (δC 178.9). The NMR spectra of compound 1 were almost identical with those of sinuflexibilin [20] with the exception that the exo-methylene proton resonances of the latter were replaced by a methyl doublet. The stereochemistry of 1 was determined on the basis of the chemical shift and NOESY spectrum (Figure 3). NOE correlations from H-3 to H-1, H-11, H3-18 and from H-11 to H-20 indicated that all four hydroxy groups in 1 were β-oriented and H-1, H-3, H-11, H3-18, and CH3-20 were α-oriented with respect to this ring.

Bottom Line: Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp.Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites.Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Marine Bio-Resources Sustainable Utilization, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China. bingo525@163.com

ABSTRACT
Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp. Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites. Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

Show MeSH
Related in: MedlinePlus