ORIGINAL PAPER Furano-sesquiterpene from soft coral, Sinularia kavarittiensis: induces apoptosis via the mitochondrial-mediated caspase- dependent pathway in THP-1, leukemia cell line S. K. Arepalli Æ V. Sridhar Æ J. Venkateswara Rao Æ P. Kavin Kennady Æ Y. Venkateswarlu Published online: 13 March 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Bioassay directed fractionation and purification led to the successful isolation of a furano sesquiterpene, Methyl 5-[(1E,5E)-2,6-Dimethyl octa-1,5,7-trienyl] furan- 3-carboxylate (MDTFC), a bioactive component from a soft coral, Sinularia kavarittiensis. Its structure was determined by analyzing 1 H, 13 C NMR and FAB-MS. The results show that MDTFC could efficiently and selectively inhibit the proliferation of several human cancer cell lines. Among all the cell lines, THP-1 was found to be most sensitive (IC 50 29.59 lM), whereas the peripheral blood mononuclear cells were least effected (IC 50 464.16 lM). The molecular mechanism of MDTFC mediated apoptosis was investigated for the first time. Induction of apoptosis in THP-1 cells was characterized by cell membrane blebbing, chromatin condensation, DNA fragmentation, and decrease in level of pro-caspases 3, 9 and increase in Bax/Bcl-2 ratio. Our results were further strengthened through cleavage of poly (ADP-ribose) polymerase, reduction of mitochondrial membrane potential (Wm) and cytosolic release of cytochrome c, which are key events during apoptosis. Moreover, phosphatidyl serine exposure and appearance of sub-G1 peak also demonstrated cell death, when analyzed by flow cytometry. DNA fragmentation was prevented moderately when pretreated with caspase-9 inhibitor (Z-LEHD-FMK) and largely with caspase-3 inhibitor (Z-DEVD-FMK). In summary, MDTFC mediated apoptosis involves mitochondria-dependent pathway and the present compound of marine origin might have a therapeutic value against human cancer cell lines and especially on leukemia cells. Keywords Apoptosis Á Sesquiterpenes Á Morphology Á Caspases Á Membrane potential Á Leukemia cells Introduction In search of new biologically active compounds, it has been found that some natural products and organisms are potential sources for chemical molecules having useful biological activity of great diversity. Most of the marine natural products, which are available today are not general cytotoxic agents but are rather targeted towards specific cellular or biochemical events and therefore, hold a strong potential as anti-microbial, anti-cancer or anti-inflamma- tory agents [1, 2]. These secondary metabolites or their derivatives are formed from invertebrates including soft corals, sponges, tunicates, mollusks or bryozoans, and are currently in advanced preclinical evaluation [3]. However, relatively few attempts have been made to explore resources of structurally unique chemistry for apoptotic mechanism. Apoptosis or programmed cell death plays a vital role in controlling cell number in many developmental and phys- iological stages, tissue homeostasis, and regulation of immune system [4], while inadequate apoptosis is an integral part of cancer development [5]. Agents, which S. K. Arepalli Á V. Sridhar Á J. Venkateswara Rao (&) Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad 500 607, India e-mail: jv@iict.res.in; jv@india.com P. Kavin Kennady Flow-Cytometry Facility, Centre for Cellular and Molecular Biology, Hyderabad 500 007, India Y. Venkateswarlu Natural Products Laboratory, Organic Division-I, Indian Institute of Chemical Technology, Hyderabad 500 607, India 123 Apoptosis (2009) 14:729–740 DOI 10.1007/s10495-009-0332-z