S.P.R. Thota, et al. /Journal of Natural Products, Vol. 8(2015): 05-08 Copyright © 2015, Journal of Natural Products, INDIA, Dr. Sudhanshu Tiwari, All rights reserved 5 ISSN 0974 – 5211 Occurrence of a rare gorgosterol type steroid in marine sponge Sigmadocia fibulata S.P.R. Thota, N.S. Sarma*, Y.L.N. Murthy School of Chemistry, Andhra University, Visakhapatnam-530003, India *Corresponding Author (Received 10 Sept. 2014; Revised 22 Sept. 2014-06 Jan. 2015; Accepted 07 January 2015) ABSTRACT A rare gorgosterol type sterol, 22, 23-methylene (22S, 23S) cholesterol (3) and three other compounds 1, 2 and 4 were isolated from the marine sponge Sigmadocia fibulata, for the first time. Their structures were elucidated by spectroscopic (IR, 2D NMR and Mass spectral) data. Keywords: Gorgosterol; Marine sponge; Sigmadocia fibulata. INTRODUCTION Over the last 50 years, a large number of new natural products, including sterols have been reported from marine sources (Blunt, et al., 2014). Many of them are vested with the potential for drug development and also structurally intriguing. Gorgosterol is a unique C 30 sterol with cyclopropane ring system substituted with two methyl groups in the sterol side chain. It was first isolated from the gorgonian Plexaura flexuosa (Bergmann, et al., 1962; Hale, et al., 1970). Related sterols having this side chain with one or two methyl substitutions of the cyclopropane ring have subsequently been isolated from several other gorgonians. Later, they have also been reported from other marine organisms such as starfish (Sheikh, et al., 1971), mollusks, and microalgae and fungi that symbiotically live in the zooxanthellae of hexacoral (hard coral) and octocoral (soft coral) species. Surprisingly, marine sponges, which also host symbiont colonies and produce a large variety of natural products, are scarcely reported (Delseth, et al., 2004) to produce gorgosterol type sterols. Continuing our interest on organisms occurring on Indian shores (Prakasa Rao, et al., 2010; Rambabu, et al., 1987; Sarma, et al., 1987), we report herein from the marine sponge Sigmadocia fibulata, a gorgosterol type sterol lacking methyl substitution of the cyclopropane ring system, namely 22, 23-methylene (22S, 23S) cholesterol 3 along with other known compounds, the sterol 1 and two non-sterol metabolites (2 and 4), for the first time. Previous work on this sponge reported steroid mixtures (Lo, et al., 2001), and peptides (Tan, et al., 2000). Also for the first time, we record herein the HR NMR and DEPT spectra for the gorgosterol type sterol 3. MATERIALS AND METHODS Experimental: Melting points were measured with Kumar apparatus and are uncorrected. The IR spectra were taken on a Perkin-Elmer Paragon spectrophotometer. The 1 H and 13 C NMR spectra were obtained on Bruker 300 and 600MHz Journal of Natural Products Volume 8 (2015) www.JournalofNaturalProducts.Com Research Paper