New anti-inflammatory 4-methylated steroids from the Formosan soft coral Nephthea chabroli
Introduction
Soft corals of the genus Nephthea are rich in terpenoids and steroids [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. As part of our search for bioactive substances from marine organisms, chromatographic fractionation of the Formosan soft coral Nephthea chabroli Audouin (Nephtheidae) resulted in the isolation and characterization of eight new 4-methylated steroids, nebrosteroids A–H (1–8) Fig. 1.
Section snippets
General
Optical rotations were determined on a JASCO P1020 polarimeter. UV spectra were obtained on a Hitachi U-3210 spectrophotometer, and IR spectra were recorded on a JASCO FT/IR-4100 spectrophotometer. The NMR spectra were recorded on a Bruker Avance 300 NMR spectrometer at 300 MHz for 1H and 75 MHz for 13C or on a Varian Unity INOVA 500 FT-NMR at 500 MHz for 1H and 125 MHz for 13C, respectively, using TMS as internal standard. Chemical shifts are given in δ (ppm) and coupling constants in Hz. ESIMS
Results and discussion
Compound 1 had a molecular formula of C29H48O4 as established by HRESIMS and NMR spectroscopic data. The 1H NMR spectrum revealed the presence of two tertiary methyls (δH 1.15 and 1.34), three secondary methyls (δH 0.97, 1.01, and 1.03), and two oxymethines [δH 3.05 (1H, td, J = 10.4, 5.6 Hz), 4.45 (1H, br s)]. The presence of a vinylic methylene conjugated to a carbonyl group was revealed by NMR signals [(δH 5.91 and 5.67); δC 120.9 (CH2), 155.8 (qC), and 202.7 (qC)] (Table 1, Table 2). 13C NMR
Acknowledgments
Financial support was provided by the Ministry of Education (96C031703) and National Science Council of Taiwan (NSC96-2320-B-110-003-MY3) awarded to C.Y. Duh.
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