Evaluation of in vitro anticancer activity of sphaeropsidins A–C, fungal rearranged pimarane diterpenes, and semisynthetic derivatives Benjamin Lallemand a,1 , Marco Masi b,1 , Lucia Maddau c , Manuela De Lorenzi d , Ricard Dam d , Alessio Cimmino b , Laetitia Moreno y Banuls d , Anna Andolfi b , Robert Kiss d , Ve ´ ronique Mathieu d , Antonio Evidente b, * a Laboratoire de Chimie BioAnalytique, Toxicologie et Chimie Physique Applique ´e, Brussels, Belgium b Dipartimento di Scienze, del Suolo, della Pianta, dell’Ambiente e delle Produzioni Animali, Universita ` di Napoli Federico II, Portici, Italy c Dipartimento di Agraria, Universita ` di Sassari, Sassari, Italy d Laboratoire de Toxicologie, Faculte ´ de Pharmacie, Universite ´ Libre de Bruxelles (ULB), Brussels, Belgium 1. Introduction The fungi associated with the so-called ‘‘canker’’ disease of the Italian cypress (Cupressus sempervirens L.) and other species of Cupressus in the Mediterranean area belong to the genera Diplodia, Pestalotiopsis, Seiridium and Sphaeropsis (Solel et al., 1987; Madar et al., 1989, 1991; Swart and Wingfield, 1991; Swart et al., 1993; Graniti, 1998). They induce heavy loss of cypress forests and ornamental heritage, with consequent alteration of the typical landscape of some regions of Central Italy and other countries of the Mediterranean basin. The consequence of this disease is also very important economically, considering noteworthy losses in the nursery industry and loss of valuable cypress wood. These diseases are related to the production by fungi of several phytotoxins belonging to different chemical classes (Evidente et al., 2010). In particular, Diplodia cupressi (from Central Bureau of Schimmelcultures of Baarn, the Netherlands) produces at least six tri- and tetra-cyclic unrearranged pimaranes, namely, sphaeropsidins A–F (Sparapano et al., 2004), and two phytotoxic dimedone methyl ethers, sphaeropsidone and episphaeropsidone (Evidente et al., 1998). While the relationships between sphaeropsidin chemical structures and their phytotoxic and antimycotic activities have already been extensively studied (Sparapano et al., 2004; Weber et al., 2007), their anticancer activity has not yet been analyzed, at least to the best of our knowledge. Nevertheless, sphaeropsidin A (Weber et al., 2007; Wang et al., 2011) and 6-O-acetyl sphaeropsidin A (Wang et al., 2011) were already described to display interesting anti-cancer activities. We thus determined the IC 50 in vitro growth-inhibitory concentrations of sphaeropsidins A (1), B (7) and C (10) and of 10 of their semisynthetic derivatives (2–6, 8, 9 and 11–13) (see Fig. 1) using the MTT colorimetric assay (van Goietsenoven et al., 2010) in five human and one mouse cancer cell lines. Four compounds used to treat a large set of human cancers were included here as reference compounds, i.e. cisplatin, carboplatin, etoposide (VP16) and temozolomide. Sphaeropsidin A (1) remained the most potent compound under study (and as active as cisplatin and VP16, but more active than carboplatin and temozolomide). The physicochemical stability of sphaeropsidin A in methanol and in cell culture medium was analyzed over a 7-day period. Phytochemistry Letters 5 (2012) 770–775 A R T I C L E I N F O Article history: Received 24 May 2012 Received in revised form 25 July 2012 Accepted 19 August 2012 Available online 7 September 2012 Keywords: Diplodia cupressi Botryosphaeriaceae Sphaeropsidins Unrearranged pimarane diterpenes In vitro anticancer activity A B S T R A C T Sphaeropsidins A (1), B (7) and C (10), three fungal phytotoxins, unrearranged pimarane diterpenes produced by Diplodia cupressi and 10 semisynthetic derivatives were evaluated for their in vitro anticancer activities. Among these 13 compounds, sphaeropsidin A and two derivatives (2 and 6) thereof display 50% growth-inhibitory concentration in the low micromolar range for all cell lines analyzed. Structure activity relationship paralleled the phytopathogenic and antimicrobial ones except regarding the vinyl group at C-13 that does not seems to be required as it is for their antipathogenic activity. ß 2012 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +39 081 2539178; fax: +39 081 2539186. E-mail address: evidente@unina.it (A. Evidente). 1 The first two authors equally contributed to the work. Contents lists available at SciVerse ScienceDirect Phytochemistry Letters jo u rn al h om ep ag e: ww w.els evier.c o m/lo c ate/p hyt ol 1874-3900/$ – see front matter ß 2012 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.phytol.2012.08.011