Isolation and structural elucidation of secondary metabolites obtained from the soft coral Sinularia candidula present in the Egyptian Red Sea

Abstract

The present study described the isolation and structural elucidation of five compounds (1 – 5) obtained from the Red Sea soft coral Sinularia candidula. Sinularia is a soft coral belonging to the phylum Cnidaria, class Alcyonaria, and family Alcyoniidae. Its taxonomic identification is largely based on the examination of the spicules, and a fairly reliable taxonomic key is available to guide species identification [1]. The presently investigated species yielded two sterols namely, Cholesterol (1), 24-methylene cholesterol (2), two oxygenated compounds namely chimyl alcohol (3), heptadecanoic acid (4), along with the ceramide (R)-2'-hydroxy-N-[(2S,3S,4R)-1,3,4-trihydroxypentacosan-2-yl] nonadecanamide (5). Their structures were elucidated by means of 1D and 2D NMR spectroscopic techniques. Cytotoxicity testing for Sinularia candidula extracts of different polarities was performed against HELA, HCT, MCF-7 and PC3 cell Lines [2], where the hexane-ethyl acetate (1:1) fraction revealed the highest percentage of inhibition by 73.77% and 78.92% against MCF-7 and PC3 cell lines, respectively, while the ethyl acetate fraction showed the highest percentage of inhibition by 67.29% against HCT cell line. This study also includes the investigation of lipoidal matter of the Red sea soft coral Sinularia candidula, where the hydrocarbons as well as the fatty acid contents were identified in both the unsaponifiable and saponifiable fractions of the total extract using GC/MS.