A new steroid from the Red Sea soft coral Lobophytum lobophytum

Chemical investigation of the soft coral Lobophytum lobophytum collected from the Red Sea led to the isolation of a new compound gorgostan-5,25-dien-3β-ol (1), and two known compounds gorgosterol (2), and alismol (3). Structures were elucidated by employing extensive NMR and HR-ESI-MS experiments.


Introduction
Soft coral isolated from diverse marine souces have proven to be a rich basis of biologically active secondary metabolites (Blunt et al. 2011). With the high concentration of marine diversity present in the Red Sea, this marine habitat represents one of the most promising areas of medicinal natural products (Hegazy et al. 2011).
Soft corals belonging to the genus Lobophytum (class Coelenterata, subclass Octocorallia, and family Alcyonaceae) are a source of macrocycliccembrane-type diterpenes and their cyclised derivatives, germacrenediterpene, steroids (Cheng et al. 2008;Lu et al. 2010;Hegazy et al. 2011;Minh et al. 2011;Govindam et al. 2012) and zoanthamine-type alkaloids (Fattorusso et al. 2008). Some of these metabolites have been shown to exhibit significant cytotoxic activity against the growth of various cancer cell lines (Cheng et al. 2008Hegazy et al. 2011;Quang et al. 2011) as well as anti-inflammatory (Chao et al. 2008;Lin et al. 2009;Lin et al. 2009;Lu et al. 2010;Quang et al. 2011) and/or antioxidant activity ). Here we report on chemical constituents of the species Lobophytum lobophytum which has not been previously chemically characterised.
The The stereochemistry of the side chain was determined by comparison of NMR data of 1 with those of gorgosterol (Tanaka et al. 1982;Elshamy et al. 2013), as well as by NOESY experiment. NOESY correlations in which identified alpha protons as 1 (d H 2.27) correlated with H-3 allowing for the beta hydroxyl assignment at C-3. From the above data, the structure of this compound was deduced as gorgostan-5,25-dien-3b-ol, a new natural product compound.

Experimental
3.1 General experimental procedures 1 H and 13 C NMR spectra were recorded in CDCl 3 on a JEOL ECA-600 spectrometer (JEOL, Kyoto Pharmaceutical university, Japan) (600 MHz for 1 H and 150 MHz for 13 C, respectively). All chemical shifts (d) are given in ppm units with reference to TMS as an internal standard and coupling constants (J) reported in Hz. HRESI-FT-MS experiments were performed on HR-ESI-FT-MS: Thermo Fisher Scientific LTQ Orbitrap XL mass spectrometer. Silica gel 60 (230 -400 mesh, Merck, Darmstadt, Germany) was used for purification and compounds monitored by TLC on pre-coated silica gel plates (Merck, Kieselgel 60 F 254 , 0.25 mm) after spraying with 10% H 2 SO 4 and heating.

Animal material
Soft coral L. lobophytum was collected from the Egyptian Red Sea off the coast of Hurghada in March, 2013.The soft coral was identified by Dr. M. Alhammady with a voucher specimen (03RS35) deposited in the National Institute of Oceanography and Fisheries, Marine Biological Station, Hurghada, Egypt.

Supplementary material
Supplementary material relating to this paper is available online at http://dx.doi.org/10.1080/ 14786419.2015.1046871.

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
This project was supported financially by the Science and Technology Development Fund (STDF), Egypt [grant number 1102].