Abstract. Sea fan, a type of gorgonian coral, originating from Maluku, Indonesia, which local people have used as medicinal ingredients for generations. Gorgonian has anti-inflammatory, anti-cancer, analgesic, gastroprotective, anti-viral, anti-bacterial, and anti-fouling activities with secondary metabolites steroid found in abundance. Steroid significantly inhibits the estrogen receptor that triggers breast cancer. However, the activity of these metabolites on sea fan has not been studied. Determination of specific receptor with Swiss Target Prediction, then the interaction ability of steroid of sea fan from binding pocket using LigandScout 4.3, while ligand-protein interaction with Autodock Tools 1.5.6. Based on the
target prediction results, the steroid of sea fan significantly acts on the target class of estrogen receptor alpha (ER-α). Pharmacophores identification shows that steroid components can act as lead compounds to ER-α based on the pharmacophore fit scores are dinosterol; 4,24-dimethyl cholestanol; 4,24-dimethyl 22-dehydro cholestanol; 4-methyl 24-methylene cholestanol; and 4,24-dimethyl cholesta 7,22-dien-3ß-ol. The results of molecular docking showed only 4,24-dimethyl 22-dehydro cholestanol; 4,24-dimethyl cholesta 7,22-dien-3ß-ol; and 4,24-dimethyl cholestanol, which has the best binding affinity compared to tamoxifen as the reference ligand (drug). So, it can be concluded that steroids from the sea fan have the potential to inhibit ER-α.Keywords. sea fan, breast cancer, pharmacophore, in-silico