A new octaprenylhydroquinone from Sarcotragus spinosulus

Among the marine sponges, the genera Ircinia and Sarcotragus are the major source of polyprenylated compounds, both benzoquinones and benzohydroquinones [1, 2]. Biological studies conducted on hydroxylated 2-octaprenylhydroquinones have shown antioxidant activity [3], antifouling activity against Balanus amphitrite Darwin cyprids [4], and activity in the Artemia salina shrimp lethality and fish lethality assays [5]; a potential role in the pathogenesis of inflammatory processes has also been demonstrated [6]. In this work we have isolated three polyprenyl-1’,4’-hydroquinone derivates (heptaprenyl-1’,4’-hydroquinone, 1; octaprenyl-1’,4’-hydroquinone, 2; hydroxyoctaprenyl-1’,4’-hydroquinone, 3) from Sarcotragus spinolosus (family Irciniidae, order Dictyoceratida) collected at Baia di Porto Conte, Alghero (Italy). The methanolic extract of freeze-dryed animals has been partitioned using a modified Kupchan partition [7]; from the hexane-soluble fraction the three compounds have been purified by means of MPLC and semi-preparative HPLC and identified by UV and IR spectroscopy and 1D and 2D-NMR and HR-MS experiments. The NMR spectral data and the HR-MS data of 1 and 2 were consistent with literature data of heptaprenylhydroquinone [8, 9] and octaprenylhydroquinone [1, 5, 10] respectively. The NMR spectral data and the HR-MS spectrum of 3 suggested a 2-polyprenylhydroquinone skeleton, consistent with literature data [1, 10] for an hydroxylated compound and particularly with the data of a 2-octaprenylhydroquinone with the allylic primary hydroxyl group located on the second isoprene unit [10]. However this compound differs from 2’-[38-hydroxy]nonaprenyl-1’,4’-hydroquinone described by Abed et al. [10] for the length of the prenylated chain and from 2-octaprenyl-1,4-dihydroxybenzene hydroxylated on the fifth isoprene unit previously described by Cimino et al. [2] and Erdogan et al. [11] for the location of the hydroxyl group.