Med Chem Res DOI 10.1007/s00044-017-1876-z MEDICINAL CHEMISTR Y RESEARCH ORIGINAL RESEARCH Bioactive sterols and sesquiterpenes from the Red Sea soft coral Sinularia terspilli Rabab Mohammed 1 ● Mohamed M. Radwan 2,3 ● Guoyi Ma 2 ● Tarek A. Mohamed 4 ● Mohamed A. Seliem 5,6 ● Mena Thabet 6 ● Mahmoud A. ElSohly 7 Received: 20 September 2016 / Accepted: 11 March 2017 © Springer Science+Business Media New York 2017 Abstract The ethanolic extract of the Red Sea soft coral Sinularia terspilli was subjected to several chromatographic techniques resulting in the isolation of compounds 1–8 including (five sterols 1–5 and three sesquiterpenes 6–8). The isolated compounds have been identified by 1D and 2D NMR spectral analysis and by comparison with literature data. Different biological activities for the isolated com- pounds and some synthetic derivatives have been carried out. Compounds 4 and 5 exhibited strong cytotoxic activity against human leukemia cell lines HL60 and K562 with IC 50 values ranging from 2.0 to 25 nM. This is the first reported isolation of these metabolites from this soft coral species. Keywords Sterols ● Sinularia terspilli ● Anti-leukemic ● Anti-leishmanial ● Anti-malarial ● Anti-microbial Introduction The Red Sea represents one of the most promising areas as a source of medicinal natural products as it is considered as an area that has not been fully explored. The genus Sinu- laria has been shown to contain a wide variety of secondary metabolites, mainly diterpenoids, sesquiterpenoids, and steroids. Many of these constituents are structurally unique and exhibit interesting biological activities. Cytotoxic sterols and sesquiterpenoids were identified from a Formosan soft coral Sinularia sp. with ED 50 s ranging from 1.3–2.9 μg/mL (Sheu et al. 1999), (Zhang et al. 2006). Flexibilisolides, a group of diterpenoids were shown to exhibit moderate cytotoxic activity against HeLa and B16 cancer cell lines (Shih et al. 2012). Crassarines, a group of new cembranoids isolated and identified from the soft coral Sinularia crassa were found to significantly inhibit the expression of both pro-inflammatory iNOS and COX-2 proteins at 10 μM, respectively (Chao et al. 2011). The novel Sinutriangulin A, a diterpenoid from the soft coral Sinularia triangula was found to exhibit cytotoxicity toward human tumor cell lines CCRF-CEM and DLD-1 (Lu et al. 2011). Capilloquinol, an unprecedented farnesyl quinoid skeleton, was isolated from the Dongsha Atoll soft coral Sinularia capillosa; it was found to possess antiviral activity against human cytome- galovirus in vitro (Cheng et al. 2011). The Formosan soft coral Sinularia discrepans has shown to produce several anti-inflammatory cembranoids that displayed significant in vitro anti-inflammatory activity in LPS-stimulated * Mohamed M. Radwan mradwan@olemiss.edu 1 Faculty of Pharmacy, Beni-Suef University, Beni Suef, Egypt 2 National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 3867, USA 3 Department of Pharmacognosy, Faculty of Pharmacy, University of Alexandria, Alexandria, Egypt 4 National Institute of Oceanography and Fisheries, Red Sea Branch, Hurghada, Egypt 5 Department of Pharmacognosy, Faculty of pharmacy, Cairo University, Giza, Egypt 6 Department of Pharmacognosy, Misr University for Science and Technology, 6th of October City, Egypt 7 National Center for National Product Research and, Department of Pharmaceutics and drug delivery, School of Pharmacy, University of Mississippi, Oxford, MS 38677, USA Electronic supplementary material The online version of this article (doi:10.1007/s00044-017-1876-z) contains supplementary material, which is available to authorized users.