Anti-H5N1 virus metabolites from the Red Sea soft coral, Sinularia candidula

A novel polyhydroxylated sterol, 3β-25-dihydroxy-4-methyl-5α,8α-epidioxy-2-ketoergost-9-ene (1) along with three new ceramides, N-[(2S,3R,E)-1,3-dihydroxyhexacos-4-en-2-yl]icosanamide (2), N-[(2S,3S,4R)-1,3,4-trihydroxyhexacosan-2-yl]icosanamide (3), and (R)-2′-hydroxy-N-[(2S,3S,4R)-1,3,4-trihydroxypentacosan-2-yl] nonadecanamide (4) were isolated from the Red Sea soft coral, Sinularia candidula. Complete structure elucidation was achieved through extensive spectroscopic analysis including one- and two-dimensional nuclear magnetic resonance spectroscopy. Sinularia candidula extracts of different polarities as well as the isolated pure compounds were screened against the highly pathogenic H5N1 avian influenza strain using the plaque inhibition assay in MDCK. The results indicated that the extracts of the Red Sea soft coral Sinularia candidula possessed potent antiviral activity (100% inhibition at a concentration of 1 μg/mL). The isolates 1, 2, 3, and 4 showed reduction of virus titer by 55.16%, 48.81%, 10.43%, and 15.76% at a concentration of 1 ng/mL, respectively.